US20050248353A1 - Electrical testing of prited circuit boards employing a multiplicity of non-contact stimulator electrodes - Google Patents
Electrical testing of prited circuit boards employing a multiplicity of non-contact stimulator electrodes Download PDFInfo
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- US20050248353A1 US20050248353A1 US10/660,356 US66035603A US2005248353A1 US 20050248353 A1 US20050248353 A1 US 20050248353A1 US 66035603 A US66035603 A US 66035603A US 2005248353 A1 US2005248353 A1 US 2005248353A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/28—Testing of electronic circuits, e.g. by signal tracer
- G01R31/2801—Testing of printed circuits, backplanes, motherboards, hybrid circuits or carriers for multichip packages [MCP]
- G01R31/2805—Bare printed circuit boards
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/28—Testing of electronic circuits, e.g. by signal tracer
- G01R31/302—Contactless testing
- G01R31/312—Contactless testing by capacitive methods
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/28—Testing of electronic circuits, e.g. by signal tracer
- G01R31/2801—Testing of printed circuits, backplanes, motherboards, hybrid circuits or carriers for multichip packages [MCP]
- G01R31/2818—Testing of printed circuits, backplanes, motherboards, hybrid circuits or carriers for multichip packages [MCP] using test structures on, or modifications of, the card under test, made for the purpose of testing, e.g. additional components or connectors
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- General Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Tests Of Electronic Circuits (AREA)
- Measuring Leads Or Probes (AREA)
- Measurement And Recording Of Electrical Phenomena And Electrical Characteristics Of The Living Body (AREA)
- Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
Abstract
Apparatus for the electrical testing of electrical circuits including at least one array of non-contact stimulator electrodes having a multiplicity of individually controlled stimulator electrodes arranged to be linearly disposed adjacent a first side of an electrical circuit to be tested; a signal generator coupled to the at least one array arranged to supply an electrical stimulation signal to each of the stimulator electrodes; and at least two non-contact sensor electrodes, each having dimensions sufficiently large to overlay part of a conductor on the electrical circuit to be tested.
Description
- The present invention relates to equipment and methods for testing the electrical integrity of electrical circuits, and more particularly to equipment and methods for the non-contact electrical testing of printed circuit boards (“TCBs”), chip carriers and similar electrical circuits having conductors of various configurations.
- Electrical circuits, such as PCBs and chip carriers, are generally tested after manufacture to determine whether or not all of the conductors and other electrically conductive elements in the circuit are in their designated positions and to ensure that they are not unintentionally cut, shorted or otherwise have an undesired continuity or lack thereof. The conductors of electrical circuits are normally interconnected to define nets.
- Conventional methods and apparatus for electrically testing electrical circuits typically employ some kind of physical-contact with the nets. For example, in moving probe apparatus, a pair of probes may be physically moved by an X-Y mechanism into and out of contact with terminals of various nets. Because nets are tested sequentially by moving the probes from net to net, moving probe testing is a relatively slow method for electrically testing complicated electrical circuits.
- Another method for electrically testing electrical circuits employs a so-called “bed-of-nails” testing fixture. A bed-of-nails fixture typically includes a large number of pins, which are positioned so that when a circuit to be tested is pressed thereagainst, the pins come into electrical contact with pads at the terminal ends of each net to establish electrical contact therewith. The conductivity of each net is subsequently measured. Although an electrical circuit can be tested much faster on an existing bed-of-nails fixture than by using a moving probe, bed-of-nails testing requires a dedicated fixture to be constructed for each electrical circuit configuration. As a result, bed-of-nails testing is, overall, a time consuming and costly solution.
- Electrical testing methods which rely on physical contact with an electrical circuit to be tested, such as the moving probe and bed-of-nails methods described above, suffer from at least two additional fundamental disadvantages: First, as the size of pads at the terminal ends of conductors on electrical circuits decreases and their density increases, it becomes increasingly difficult to obtain adequate electrical contact therewith. Second, physical contact between conductor pads and the probes or pins may damage the pads.
- To overcome these difficulties, a number of non-contact electrical testing methods have been proposed. One non-contact printed circuit board testing method is described in U.S. Pat. No. 5,218,294, issued to Soiferman. The patent describes stimulating a PCB under test with an AC signal through power and ground lines or layers, or in a non-contact manner by employing a near-field active antenna. The resulting stimulation generates an electromagnetic field which characterizes the PCB under test. The electromagnetic field proximate to the PCB under test is measured in a non-contact manner and compared to the electromagnetic field of a known faultless circuit board to determine whether the PCB under test is defective.
- U.S. Pat. No. 5,517,110, also issued to Soiferman, describes non-contact stimulation of a PCB by a pair of stimulators located adjacent to the PCB on one side thereof A resulting electromagnetic field is detected using a sensor array located between the stimulators on the same side of the PCB.
- U.S. Pat. No. 5,424,633, issued to Soiferman describes a spiral loop antenna useful in the electrical testing of PCBs, as well as electrical testing in which an electromagnetic field is applied to a first side of a PCB under test by a non contact stimulator and an array of non-contact sensors on an opposite side of the PCB is operative to measure an electromagnetic field that is characteristic of the PCB when stimulation is applied. This system is able to electrically test nets that have terminal points on opposite sides of a PCB and relatively thin PCBs that do not have internal metal layers.
- The present invention seeks to provide improved methods and apparatus for non-contact electrical testing of electrical circuits such as PCBs. For the purpose of the description and claims which follow, an electrical circuit being tested is referred to as a “board under test” or “BUT”.
- One aspect of a preferred embodiment of the present invention provides for the non-contact electrical testing of BUTs, such as PCBs, that have nets which begin and terminate on the same side thereof, and that have other nets which begin and terminate on opposite sides thereof.
- Another aspect of a preferred embodiment of the present invention provides for the non-contact electrical testing of BUTs, such as PCBs, that have internal metal layers and conductors that cross through or between the metal layers.
- In accordance with a preferred embodiment of the invention, non-contact electrical testing of BUTS, such as PCBs, that have nets which begin and terminate on the same side as well as nets which begin and terminate on opposite sides is performed generally simultaneously. One side of a BUT is stimulated with an AC electric field at a first frequency and the other side of the BUT is stimulated with an AC electric field at a second frequency. Potentials induced by the different frequency stimulation in conductors on the BUT are measured and separated according to frequency.
- It is readily appreciated that by applying stimulation to both sides of the BUT that results in separable potentials that are identified with stimulation applied to one side or the other of BUT, the electric continuity in different types of conductors on a BUT can be tested simultaneously.
- In accordance with a still further aspect of the present invention, a pattern of potentials on a BUT is analyzed and compared to a pattern characteristic of an electrical circuit known to be not defective.
- There is thus provided in accordance with a preferred embodiment of the present invention an apparatus for electrical testing of an electrical circuit having first and second side surfaces and including a plurality of conductors, the apparatus including at least one stimulation electrode disposed adjacent at least one of the first and second side surfaces of the electrical circuit and being operative to apply thereto a stimulation electromagnetic field in a non-contact manner, at least one sensing electrode disposed adjacent at least one of the first and second side surfaces of the electrical circuit and being operative to sense a resulting electromagnetic field produced by application of the stimulation. electromagnetic field at various locations thereon in a non-contact manner, wherein at least one of the at least one simulation electrode and the at least one sensing electrode includes at least two electrodes at least one of which is disposed adjacent each of the first and second side surfaces of the electrical circuit.
- Further in accordance with a preferred embodiment of the present invention the at least one stimulation electrode includes at least first and second simulation electrodes disposed adjacent respective ones of the first and second side surfaces of the electrical circuit.
- Still further in accordance with a preferred embodiment of the present invention the at least one sensing electrode includes at least first and second sensing electrodes disposed adjacent respective ones of the first and second side surfaces of the electrical circuit.
- Further in accordance with a preferred embodiment of the present invention there is provided at least one stimulation signal generator providing at least one stimulation signal to the at least one stimulation electrode.
- Additionally in accordance with a preferred embodiment of the present invention the at least one stimulation signal generator provides stimulation signals to a plurality of stimulation electrodes in a manner such that signals induced in the electrical circuit by individual ones of the stimulation electrodes may be distinguished from each other, and preferably also includes at least one separating detector for receiving from the at least one sensing electrode signals induced in the electrical circuit by individual ones of the stimulation electrodes and distinguishes the signals from each other.
- Additionally the apparatus for electrical testing of an electrical circuit also includes a signal analyzer operative to analyze at least one signal received from the at least one sensing electrode and a comparator receiving at least one signal derived from the resulting electromagnetic field and operative to compare the at least one signal with a reference.
- Preferably the apparatus for electrical testing of an electrical circuit also includes a defect report generator providing a defect report relating to the electrical circuit based on the output of the comparator.
- Additionally in accordance with a preferred embodiment of the present invention the at least one stimulation electrode includes first and second stimulation electrodes arranged to be disposed alongside a first side of the electrical circuit and a third stimulation electrode arranged to be disposed alongside a second side of the electrical circuit. Preferably the at least one sensing electrode includes a linear array of sensing electrodes.
- Still further in accordance with a preferred embodiment of the present invention the linear array is disposed intermediate the first and second stimulation electrodes.
- Additionally or alternatively the at least one stimulation electrode includes a linear array of stimulation electrodes.
- Preferably the at least one sensing electrode includes first and second sensing electrodes arranged to be disposed alongside a first side of the electrical circuit and a third sensing electrode arranged to be disposed alongside a second side of the electrical circuit.
- Further in accordance with a preferred embodiment of the present invention the at least one sensing electrode includes first and second sensing electrodes arranged to be disposed alongside a first side of the electrical circuit.
- Still further in accordance with a preferred embodiment of the present invention the linear array is disposed intermediate the first and second stimulation electrodes.
- Moreover in accordance with a preferred embodiment of the present invention the at least one signal generator provides signals having different frequencies to different ones of the stimulation electrodes, and the at least one signal generator provides multiplexed signals to different ones of the stimulation electrodes.
- Preferably the at least one stimulation electrode includes a plurality of individually controllable sections.
- There is also provided in accordance with a preferred embodiment of the present invention a method for electrical testing of an electrical circuit having first and second side surfaces and including a plurality of conductors, the method including the steps of applying an electromagnetic field in a non-contact manner to at least one of first and second side surfaces of the electrical circuit and sensing a resulting electromagnetic field in a non-contact manner at various locations along at least one of the first and second side surfaces of the electrical circuit, wherein at least one of the applying and sensing steps employs non-contact electrodes disposed along both the first and second side surfaces of the electrical circuit.
- Further in accordance with a preferred embodiment of the present invention the applying step includes employing at least first and second simulation electrodes disposed adjacent respective ones of the first and second side surfaces of the electrical circuit to apply at least one electromagnetic field thereto.
- Preferably the sensing step includes employing at least first and second sensing electrodes disposed adjacent respective ones of the first and second side surfaces of the electrical circuit to sense the resulting electromagnetic field.
- Still further in accordance with a preferred embodiment of the present invention at least one stimulation signal and is generated and provided to at least one stimulation electrode.
- Additionally in accordance with a preferred embodiment of the present invention the generating step includes providing stimulation signals to a plurality of stimulation electrodes in a manner such that signals induced in the electrical circuit by individual ones of the stimulation electrodes may be distinguished from each other. Additionally or alternatively the method also includes receiving signals induced in the electrical circuit by individual stimulation electrodes and distinguishing the signals from each other.
- Preferably the method electrical testing of an electrical circuit also includes analyzing at least one signal induced in the electrical circuit,
- Moreover according to a preferred embodiment, the present invention also includes receiving at least one signal derived from the resulting electromagnetic field and comparing the at least one signal with a reference. Preferably the step also includes providing a defect report relating to the electrical circuit based on the comparing step.
- Additionally according to a preferred embodiment of the present invention the applying step employs first and second stimulation electrodes disposed alongside a first side of the electrical circuit and a third stimulation electrode disposed alongside a second side of the electrical circuit.
- Still further according to a preferred embodiment of the present invention the sensing step employs a linear array of sensing electrodes. The linear array may also be disposed intermediate first and second stimulation electrodes.
- Additionally according to a preferred embodiment of the present invention the applying step employs a linear array of stimulation electrodes. Furthermore the linear array is disposed intermediate first and second stimulation electrodes.
- Preferably the sensing step employs first and second sensing electrodes disposed alongside a first side of the electrical circuit and a third sensing electrode disposed alongside a second side of the electrical circuit. Additionally or alternatively the sensing step employs first and second sensing electrodes disposed alongside a first side of the electrical circuit.
- Preferably the method for electrical testing of an electrical circuit includes a generating step in which signals having different frequencies are provided to different ones of the stimulation electrodes. Additionally or alternatively the generating step includes providing multiplexed signals to different ones of the stimulation electrodes.
- Still further in accordance with a preferred embodiment of the present invention the applying step employs at least one stimulation electrode including a plurality of individually controllable sections.
- Additionally according to a preferred embodiment of the present invention also includes the step of grounding an intermediate metal layer in the electrical circuit.
- Moreover in accordance with a preferred embodiment of the present invention the sensing step includes sensing potentials on one side of the electrical circuit and sensing potentials on the opposite side of the electrical circuit.
- There is also provided in accordance with yet another preferred embodiment of the present invention a method for electrical testing of a multi-layered electrical circuit having first and second side surfaces and including a plurality of conductors, the method including the steps of grounding an intermediate metal layer in the electrical circuit, inducing potentials into at least some of the conductors of the electrical circuit, and sensing a resulting electromagnetic field in a non-contact manner at various locations along at least the first side surface thereof to obtain electromagnetic field data characteristic of the electrical circuit.
- Further in accordance with a preferred embodiment of the present invention also includes sensing a resulting electromagnetic field at various locations along at least the second side surface thereof to obtain electromagnetic field data characteristic of the electrical circuit.
- Still further in accordance with a preferred embodiment of the present invention the electromagnetic field data is for the potential in conductors including the electrical circuit. Furthermore, the inducing step may include inducing potentials on both a first side and a second side of the electrical circuit.
- Additionally in accordance with a preferred embodiment of the present invention the inducing step includes inducing potentials on the first side of the electrical circuit which are differentiable from potentials induced on the second side of the circuit.
- Moreover in accordance with a preferred embodiment of the present invention the inducing step includes inducing potentials which are differentiable by frequency.
- Still further in accordance with a preferred embodiment, the present invention provides a method for electrical testing of a multi-layered electrical circuit wherein the inducing step includes inducing potentials which are multiplexed.
- Moreover in accordance with a preferred embodiment of the present invention the sensing step includes sensing electromagnetic field data on one side of the electrical circuit. Preferably the sensing step further includes distinguishing the electromagnetic field resulting from potentials induced on the first side of the electrical circuit from the electromagnetic field resulting from potentials induced on the second side of the electrical circuit.
- Further in accordance with a preferred embodiment of the present invention the inducing step includes inducing potentials on a first side of the electrical circuit.
- Additionally or alternatively the inducing step employs a plurality of stimulators, and each stimulator induces potentials which are differentiable by frequency. Preferably the inducing step employs a plurality of stimulators, and each stimulator induces potentials which are multiplexed.
- Additionally in accordance with a preferred embodiment of the present invention the sensing step employs at least a first sensor and a second sensor arranged along a first side of the electrical circuit. Preferably the sensing step additionally employs a third sensor located along a second side of the electrical circuit.
- Moreover in accordance with a preferred embodiment of the present invention also includes correlating electromagnetic field data sensed by the sensors to a stimulator. Additionally or alternatively a preferred embodiment of the present invention also includes determining electrical continuity of at least some of the conductors by comparing the electromagnetic field data to reference electromagnetic field data characteristic of a desired electrical circuit.
- Still further in accordance with a preferred embodiment of the present invention the inducing step is carried out in a non-contact manner.
- There is further provided in accordance with a preferred embodiment of the present invention a method for electrical testing of a multi-layered electrical circuit having first and second side surfaces and including a plurality of conductors, the method including the steps of stimulating the electric circuit to induce in proximity thereto an electromagnetic field, acquiring electromagnetic field data in a non-contact manner at various locations along the first side surface, acquiring electromagnetic field data in a non-contact manner at various locations along the second side surface, and determining electrical continuity characteristics of the conductors by analysis of electromagnetic field data for the first side surface and by analysis of electromagnetic field data for the second side surface.
- Preferably in the method for electrical testing of a preferred embodiment of the present invention, the analysis steps employs reference data which is characteristic of an electrical circuit having known structure.
- Still further in accordance with a preferred embodiment of the present invention the electrical circuit is a multi-layered circuit which includes at least one intermediate layer which is substantially completely metalized, and the method includes grounding the at least one substantially completely metalized layer.
- There is further provided in accordance with a preferred embodiment of the present invention a method for electrical testing of an electrical circuit having a plurality of electrically conductive elements, the method including the steps of applying a first electromagnetic field to the electrical circuit with at least one stimulator located near but not contacting the article on a first side thereof, applying a second electromagnetic field to the article at generally the same time as the first electromagnetic field with at least one stimulator located near but not contacting the article on a second side thereof, and separately detecting first and second potentials induced on the electrically conductive elements of the article by the first and second electromagnetic fields, respectively.
- Further in accordance with a preferred embodiment of the present invention the first and second steps of applying an electromagnetic field include the steps of generating electromagnetic signals of first and second frequencies, respectively.
- Still further in accordance with a preferred embodiment of the present invention the step or separately detecting includes the step of sensing the potentials with at least one sensor located near the first side of the article. Preferably the method further includes the step of scanning by at least one sensor.
- Additionally according to a preferred embodiment of the present invention the step of scanning includes the step of scanning in a first scanning direction and followed by the step of scanning in a second scanning direction which is substantially perpendicular to the first scanning direction. Additionally or alternatively the step of scanning includes the step of scanning the article in a first position followed by the step of scanning the article in a second position which is upside-down from the first position.
- Preferably the method further including step of grounding internal metal layers of the article.
- There is also provided in accordance with a preferred embodiment of the present invention an apparatus for electrically testing an article having an electric circuit therein formed of a plurality of conductors, in which the apparatus includes (i) a first electromagnetic field generator applying a first electromagnetic field to the article, wherein the first field generator includes at least one stimulator located near but not in contact with a first side of the article, and (ii) a second electromagnetic field generator applying a second electromagnetic field to the article, wherein the second field generator includes at least one stimulator located near but not in contact with a second side of the article, wherein the second side is opposite the first side, and (iii) a sensor operative to separately detect first and second potentials induced on the conductors by the first and second electromagnetic fields, respectively.
- Further in accordance with a preferred embodiment of the present invention the sensor includes an array of sensors adjacent to the at least one stimulator of the first field generator. Preferably the first field generator generates an electromagnetic field at a first frequency, and the second field generator generates an electromagnetic field at a second frequency. Additionally or alternatively in the apparatus for electrically testing an article, the first field generator includes a first stimulator and a second stimulator operative to generate the electromagnetic field.
- Additionally according to a preferred embodiment of the present invention the first stimulator and second stimulator each generate a field which are 180 degrees out of phase with respect to each other. Preferably the stimulators are made of a plurality of strip-shaped elements.
- Still further in accordance with a preferred embodiment of the present invention the strip-shaped elements extend obliquely relative to the array of sensors.
- Additionally or alternatively at least one of the stimulators is made of a plurality of patch-shaped stimulators.
- There is also provided in accordance with a preferred embodiment of the present invention a method for electrically testing an article having a plurality of conductors therein, which preferably includes the steps of subjecting a first side of the article to an electromagnetic field with at least one stimulator in close but not in contact arrangement with a first side of the article, scanning the side of the article in at least two partially orthogonal directions with a not in contact sensor, sensing potentials induced on the conductors by the electromagnetic field, and analyzing the potentials to determine the existence of defects in the elements.
- Still further in accordance with a preferred embodiment of the present invention the method also includes the additional steps of subjecting a second side of the article to a second electromagnetic field with a second stimulator in close but not in contact arrangement with the second side, scanning the side of the article in at least two at least partially orthogonal directions with a not in contact sensor and sensing the induction of potentials induced on the elements by the second electromagnetic field, and analyzing the potentials induced by the second electromagnetic field to determine the existence of defects in the elements.
- Additionally according to a preferred embodiment of the present invention the article is subjected to the first and second electromagnetic fields at generally the same time. Preferably the electromagnetic fields are propagated at different frequencies. Additionally or alternatively the article includes a metal layer, and the metal layer is grounded.
- Moreover according to a preferred embodiment of the present invention the article is subjected to the first and second electromagnetic fields one after the other.
- There is also provided in accordance with a preferred embodiment of the present invention a method for the electrical testing of an article having a plurality of electrically conductive elements and internal conductive layers, the method including the steps of subjecting the article to an electromagnetic field with at least one stimulator in close but not in contact arrangement with at least one side of the article, grounding the internal conductive layers of the article, scanning the at least one side of the article with a not in contact sensor and sensing the induction of potentials induced on the elements by the electromagnetic field, and analyzing the potentials to determine the existence of defects in the elements.
- These and other features and advantages of the present invention will become apparent from the ensuing detailed description of the preferred embodiments, given by way of example only, when taken in conjunction with the drawings, in which:
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FIG. 1 is a simplified pictorial illustration of non-contact electrical testing apparatus, constructed and operative in accordance with a first preferred embodiment of the present invention; -
FIG. 2 is a schematic cross-sectional illustration of a simplified BUT together with stimulators and sensors in accordance with a preferred embodiment of the present invention, taken along line II-II inFIG. 1 ; -
FIG. 3 is a schematic circuit diagram of an exemplary circuit useful as part of a separating detector forming part of the hardware ofFIG. 1 ; -
FIGS. 4A and 4B are simplified illustrations of unbroken and broken conductors extending entirely along a first surface of a BUT in spatial registration with a diagrams of potentials sensed thereon; -
FIGS. 5A and 5B are simplified illustrations of unbroken and broken conductors extending entirely along a second surface of a BUT in spatial registration with diagrams of potentials sensed thereon; -
FIGS. 6A-6D are simplified illustrations of unbroken and broken conductors having a portion extending along a first surface of a BUT, a portion extending through intermediate parts thereof, and a portion extending along a second surface thereof, in spatial registration with diagrams of potentials sensed thereon; -
FIGS. 7A-7D are simplified illustrations of the unbroken and broken conductors shown inFIGS. 6A-6D , but in upside-down testing orientation, in spatial registration with diagrams of potentials sensed thereon; -
FIGS. 8A-8C are simplified illustrations of unbroken and broken conductors having a portion extending along a first surface of a BUT, a portion extending through intermediate parts thereof, and another portion extending along the first surface thereof, in spatial registration with diagrams of potentials sensed thereon; -
FIGS. 9A-9C are simplified illustrations of the unbroken and broken conductors shown inFIGS. 8A-8C , but in upside-down testing orientation, in spatial registration with diagrams of potentials sensed thereon; -
FIGS. 10A-10B are simplified illustrations of two non-shorted and two shorted conductors in spatial registration with diagrams of potentials sensed thereon; -
FIGS. 11A-11B are simplified illustrations of the two non-shorted and shorted conductors shown inFIGS. 10A-10B but in upside-down testing orientation, in spatial registration with diagrams of potentials sensed thereon; -
FIGS. 12 and 13 schematic illustrations of two alternative stimulator configurations; -
FIG. 14 is a simplified pictorial illustration of non-contact electrical testing apparatus, constructed and operative in accordance with a second preferred embodiment of the present invention; and -
FIG. 15 is a schematic circuit diagram of an exemplary circuit useful as part of a separating detector forming part of the hardware ofFIG. 14 . - Reference is now made to
FIG. 1 which is a schematic illustration of non-contact electrical testing apparatus, constructed and operative in accordance with a preferred embodiment of the present invention.Testing apparatus 10 is operative to perform non-contact electrical testing of electrical circuits, such as are found on aBUT 12, having a multiplicity ofelectrical conductors 13. Although the present invention is generally described in the context of non-contact electrical testing of printed circuit boards, it is readily appreciated that the methods and apparatus disclosed herein are generally applicable to the non-contact electrical testing of other electrical circuits including, for example, chip carriers, ball grid array substrates, multi-chip modules, hybrid circuit substrates and printed circuit boards loaded with electronic components. Reference herein to BUTs shall be deemed to additionally refer to other suitable similar forms of electrical circuits. - In a preferred embodiment of the invention,
testing apparatus 10 includes twofirst side stimulators first signal generator 18 supplying first AC electrical stimulation signals tostimulator electrodes side stimulator electrode 20, hereinafter referred to asstimulator 20, is disposed to be adjacent to an opposite side of the BUT 12 and asecond signal generator 22 provides second AC electrical stimulation signals thereto. An array ofsensor electrodes 24, preferably comprising a plurality ofindividual sensors 25 arranged along a line, is preferably disposed betweenstimulators first side stimulators sensors 25 are configured in as described in U.S. Pat. No. 5,517,110, incorporated herein by reference. - A separating
detector 26 receives the outputs of eachsensor 25 and supplies them to asignal analyzer 28 which outputs to a comparator andreport generator 30. As used herein, the terms “first side stimulators” 14 and 16 and “second side stimulator” 20 relate to their respective locations as shown inFIG. 1 . It is readily appreciated by those skilled in the art that the important factor relating to the position of the stimulators is that the two sets of stimulators are on geometrically opposing sides of BUT 12. It is not of consequence which stimulators are above or below BUT 12. - Preferably, the AC signals provided by
first generator 18 andsecond generator 22 respectively are different. For example, the AC signals provided byfirst generator 18 tofirst side stimulators second generator 22 forsecond side stimulator 20 are at a second frequency F2. Preferably,first signal generator 18 provides signals to respectivefirst side stimulators - It is readily appreciated that instead of distinguishing the AC signals by frequency, the signals provided by
first generator 18 andsecond generator 22 may be at the same frequency but distinguished from each other by suitable known signal separation techniques. - When energized by the AC electrical stimulation signals, first and second
first side stimulators second side stimulator 20 generate electromagnetic fields which stimulate BUT 12 and induce measurable potentials onconductors 13 of BUT 12. Eachsensor 25 inarray 24 senses the potential induced in the conductors. Preferably, the potentials are sensed bysensors 25 by capacitive coupling. Alternatively any other suitable sensing technique may be employed. - Preferably, the AC electrical simulation signals have a frequency in the range of 10 KHz to 20 MHz, and more preferably about 1 MHz.
First side stimulators - In a preferred embodiment of the present invention, BUT 12 and
second side stimulator 20, which is preferably sufficiently large to underlie all of BUT 12, are moved linearlypast sensor array 24 andstimulators stimulator 20 may be held stationary whilesensor array 24 andstimulators sensor array 24. - As is readily appreciated, the potentials induced in
conductors 13 are distinguishable from each other to the extent that the stimuli which induce these potentials are distinguishable from each other, for example by frequency or by multiplexing. - By employing information indicating potentials at various locations on BUT 12 sensed by
sensors 25,signal analyzer 28 generates a precise representation characteristic of potentials inconductors 13 on aBUT 12, which indicates, inter alia, conductor continuity and which includes information regarding shorts and breaks in conductors constituting defects. - The representation provided by
signal analyzer 28 to comparator andreport generator 30 enables provision of adefect report 34 indicating defective electrical continuity inconductors 13 of BUT 12 (FIG. 1 ), such as missing continuity where continuity is expected (opens and cuts in conductors) and excess continuity where not expected (shorts between conductors). The defect report preferably is generated by comparing the representation supplied bysignal analyzer 28 with areference 32 representing a non-defective printed circuit board having the same design. - Reference is now made to
FIG. 2 , which is a schematic cross-sectional illustration of a typical arrangement ofconductors 13 of a simplified BUT 12 together withstimulators 14. 16 and 20 and sensors 25 (FIG. 1 ). In the illustrated example BUT 12 has afirst surface 40 and asecond surface 42, opposite tofirst surface 40, and comprises severalelectrical conductors 13, including: - (I) a
conductor 50 located entirely alongfirst surface 40; - (II) a
conductor 52 located entirely alongsecond surface 42; - (III) a
first metal plane 54 located intermediate first andsecond surfaces - (IV) a
second metal plane 56 located intermediatefirst metal plane 54 andsecond surface 42, which is preferably grounded during testing; - (V) a
conductor 58, including afirst portion 60 extending alongsecond surface 42 and being connected through a plated viahole 62 to asecond portion 64 located intermediatefirst metal plane 54 andsecond metal plane 56, which is in turn connected through a plated viahole 66 to athird portion 68, which extends alongfirst surface 40; - (VI) a
conductor 70, including afirst portion 72 extending alongfirst surface 40 and being connected through a plated viahole 74 to asecond portion 76 located intermediatefirst metal plane 54 andsecond metal plane 56, which is in turn connected through a plated viahole 78 to athird portion 80, which extends alongfirst surface 40. - It is appreciated that the there may be only a single metal plane or a multiplicity of metal planes, for example grounding planes, power planes or shielding, in a BUT. Conventionally, metal layers are not grounded, so that when a BUT is stimulated, a complex pattern of superimposed potentials of the ungrounded metal layer and conductors is produced. However, if a metal layer separating the first and second surfaces of the BUT is grounded, a potential is not induced in the metal layer. Moreover, the metal layer normally isolates sensors from measuring potentials in conductors in a non-contact manner on those portions of the conductors which are situated across the grounded metal layer from the sensor.
- As described in greater detail hereinbelow with reference to
FIGS. 4A-11B ,first side stimulators first metal plane 54 and alongfirst surface 40 adjacent thereto, such asconductors FIG. 2 . Similarlysecond side stimulator 20 stimulates conductors having portions that extend belowmetal plane 56 and alongsecond surface 42, such asconductors FIG. 2 . It is a particular feature of a preferred embodiment of the present invention that by stimulating on both sides of the BUT, all conductors having at least one portion that is not sandwiched between two internal metal layers are stimulated and potentials thereon are sensed. - It is appreciated that
sensors 25 are able to sense potentials on conductor portions extending alongfirst surface 40 or therebelow down to groundedfirst metal plane 54.Sensors 25 are not able to sense potential on other conductor portions. In general, the BUT is preferably grounded when performing electrical testing in various layers comprising a multi-layered BUT. Thus, normally following testing of a BUT in the orientation illustrated inFIG. 2 , the BUT is turned upside down and tested again, withsensors 25 adjacentsecond surface 42. When BUT 12 is in this orientation,sensors 25 are able to sense potentials on conductor portions extending alongsecond surface 42 or therebelow down tosecond metal plane 56. It is appreciated that potentials on conductor portions lying intermediatesecond metal plane 56 andfirst metal plane 54 normally cannot be sensed in a non contact manner when thesecond metal plane 56 andfirst metal plane 54 are grounded. - It is also appreciated potentials on conductors which extend entirely in a direction perpendicular to the scanning direction indicated in
FIG. 2 may not be adequately sensed. For this reason, normally following testing of a BUT in the orientation illustrated inFIG. 2 , the BUT is rotated by 90 degrees and tested again, such that all of the conductors are rotated by 90 degrees with respect to the scanning direction. It is thus appreciated that full testing of a BUT 12 preferably involves four passes through the apparatus ofFIG. 1 . - Reference is now made to
FIG. 3 , which is a schematic circuit diagram of a preferred embodiment of aseparating circuit 127 in separating detector 26 (FIG. 1 ). An output fromsensor 25 is supplied to anamplifier 128, which outputs to first andsecond mixers signal generators FIG. 1 ). The outputs ofmixers mixers sensor 25 and a an undesirable AC out-band signal obtained as result from mixing of the components of the frequencies F1 and F2. TheLPFs analyzer 28, preferably via an AID converter (not shown). Preferably, a separatingcircuit 127 may be provided for eachsensor 25 inarray 24, however, it is appreciated that signals fromsensors 25 may be multiplexed to a lesser number of separatingcircuits 127. - The
first side stimulators sensor 25 at any particular sampling location is the sum of the potentials induced in theconductors 13 bystimulators first side stimulators first side stimulators - Reference is now made to
FIG. 4A which shows electrical potentials, sensed by a sensor 25 (FIG. 2 ) lying abovefirst surface 40 of a BUT 12, induced in a typical conductor, such asconductor 50 shown inFIG.2 , which extends alongfirst surface 40, by an electromagnetic field generated byfirst side stimulators second side stimulator 20 in the arrangement ofFIG. 2 . InFIG. 4A , at least one groundedmetal layer 90, such as a ground plane or a power plane, extends between first andsecond surfaces -
FIG. 4A includes a representation ofconductor 50 arranged in spatial registration with a first diagram 100 of the potential thereon, induced bystimulators sensor 25, as a function of the position alongconductor 50 of the midpoint betweenstimulators FIG. 2 and a second diagram 102 of the potential onconductor 50 induced bystimulator 20 as a function of the position alongconductor 50 of asensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 100 that as the
conductor 50 is scanned in the scanning direction bystimulators conductor 50 induced bystimulators - It is also seen in diagram 102 that as the
conductor 50 is scanned in the scanning direction by asensor 25 lying abovefirst surface 40, the potential on theconductor 50 induced bystimulator 20 remains zero inasmuch asconductor 50 is not stimulated bystimulator 20 since it extends only alongfirst surface 40, which is isolated fromstimulator 20 adjacent tosecond surface 42 by at least one groundedmetal layer 90. - It is appreciated that
conductor 50 shown inFIG. 4A is continuous and has no breaks therealong. - Reference is now made to
FIG. 4B , which is identical toFIG. 4A but relates to aconductor 150, identical toconductor 50, except in that it has a break at a location “i” therealong.FIG. 4B shows electrical potentials induced inconductor 150, extending alongfirst surface 40 of a BUT 12 in the environment ofFIG. 2 , by an electromagnetic field generated byfirst side stimulators second side stimulator 20 in the arrangement ofFIG. 2 . InFIG. 4B , at least one groundedmetal layer 190, such as a ground plane or a power plane, extends between first andsecond surfaces -
FIG. 4B includes a representation ofconductor 150 arranged in spatial registration with a first diagram 104 of the potential thereon induced bystimulators sensor 25 as a function of the position alongconductor 150 of the midpoint betweenstimulators FIG. 2 and a second diagram 106 of the potential onconductor 150 induced bystimulator 20 as a function of the position alongconductor 150 ofsensor 25 along the scanning direction shown inFIG. 2 . - It is seen that as the
conductor 150 is scanned in the scanning direction bystimulators conductor 150 induced bystimulators conductor 150 induced bystimulators conductor 150. It is appreciated that there is a clear and measurable difference in the potential pattern produced inbroken conductor 150 as compared with that incontinuous conductor 50. - It is also seen from diagram 106 that as the
conductor 150 is scanned in the scanning direction by asensor 25, the potential on theconductor 150 induced bystimulator 20 remains zero inasmuch asconductor 150 is not stimulated bystimulator 20 since it extends only alongfirst surface 40 which is isolated fromsecond surface 42 by at least one groundedmetal layer 190. Thus inasmuch asconductor 150 does not include any portion extending below grounded metal plane, thestimulator 20 does not have any effect in detecting a break inconductor 150. - Reference is now made to
FIG. 5A which shows potentials, sensed by a sensor 25 (FIG. 2 ) lying abovefirst surface 40, induced in a typical conductor, such asconductor 52 shown inFIG. 2 , which extends alongsecond surface 42 of BUT 12, by an electromagnetic field generated byfirst side stimulators second side stimulator 20 in the arrangement ofFIG. 2 . - In the embodiment of
FIG. 5A , at least one groundedmetal layer 200, such as a ground plane or a power plane, extends between first andsecond surfaces -
FIG. 5A includes a representation ofconductor 52 arranged in spatial registration with a first diagram 210 of the potential thereon induced bystimulators conductor 52 of the midpoint betweenstimulators FIG. 2 and a second diagram 212 of the potential onconductor 52 induced bystimulator 20 as a function of the position alongconductor 52 ofsensor 25 along the scanning direction shown inFIG. 2 . - It is seen that as the
conductor 52 is scanned in the scanning direction bystimulators conductor 52 induced bystimulators conductor 52 is not stimulated bystimulators second surface 42, which is isolated fromstimulators metal layer 200. - It is also seen that as the
conductor 52 is scanned in the scanning direction bysensor 25 lying abovefirst surface 40, the potential on theconductor 52 as sensed bysensor 25 remains zero inasmuch asconductor 52 does not have any portion that extends above groundedmetal layer 200. - It is appreciated that in order for the system of
FIG. 2 to test a conductor such asconductor 52 for continuity, BUT 12 must be turned upside down and tested again, in which case its characteristics are the same as those ofconductor 50 shown inFIG. 4A . - Reference is now made to
FIG. 5B , which is identical toFIG. 5A but relates to aconductor 252, identical toconductor 52, except in that it has a break at a location “j” therealong.FIG. 5B shows electrical potentials induced inconductor 252 in the environment ofFIG. 2 , extending alongfirst surface 42 of BUT 12, by an electromagnetic field generated byfirst side stimulators second side stimulator 20 in the arrangement ofFIG. 2 . InFIG. 5B , at least one groundedmetal layer 300, such as a ground plane or a power plane, extends between first andsecond surfaces -
FIG. 5B includes a representation ofconductor 252 arranged in spatial registration with a first diagram 314 of the potential thereon, sensed by asensor 25 lying abovefirst surface 40, induced bystimulators conductor 252 of the midpoint betweenstimulators FIG. 2 and a second diagram 316 of the potential onconductor 252 induced bystimulator 20 as a function of the position alongconductor 252 ofsensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 314 that as the
conductor 252 is scanned in the scanning direction bystimulators conductor 252 induced bystimulators conductor 252 is not stimulated bystimulators second surface 42, which is isolated fromfirst surface 40 by at least one groundedmetal layer 300. - It is also seen in diagram 316 that as the
conductor 252 is scanned in the scanning direction bysensor 25 lying abovefirst surface 40, the potential on theconductor 252 as sensed bysensor 25 remains zero inasmuch asconductor 252 does not have any portion that extends above groundedmetal layer 300. - It is appreciated that in order for the system of
FIG. 2 to test a conductor such asconductor 252 for continuity, BUT 12 must be turned upside down and tested again, in which case its characteristics are the same as those ofconductor 52 shown inFIG. 4B . - It is thus appreciated that the system of the embodiment of
FIG. 2 does not provide any information regarding breaks in conductors which lie entirely alongsecond surface 42 or entirely below groundedmetal layer 300, unless the BUT is turned upside down and tested again. - Reference is now made to
FIG. 6A which shows electrical potentials induced in a typical conductor, such asconductor 58 which includesfirst portion 60 which extends alongsecond surface 42,second portion 64 located intermediate a groundedmetal layer 400 andfirst surface 40, andthird portion 68, which extends alongfirst surface 40 of BUT 12. The electrical potentials are induced by an electromagnetic field generated byfirst side stimulators second side stimulator 20 in the arrangement ofFIG. 2 and are sensed by asensor 25 lying abovefirst surface 40. -
FIG. 6A includes a representation ofconductor 58, which does not have any breaks therealong, arranged in spatial registration with a first diagram 420 of the potential thereon induced bystimulators conductor 58 of the midpoint betweenstimulators FIG. 2 and a second diagram 422 of the potential onconductor 58 induced bystimulator 20 as a function of the position alongconductor 58 of asensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 420 that as the
conductor 58 is scanned in the scanning direction bystimulators conductor 58 induced bystimulators conductor 58 extends below groundedmetal layer 400. Whensensor 25 in the arrangement ofFIG. 2 reachessecond portion 64, which extends above groundedmetal layer 400 but belowfirst surface 40, the sensed potential goes quickly from a zero value up to a first positive value and then upon reaching the end ofsecond portion 64 decreases to a second positive value which is less than the first positive value. Upon reachingthird portion 68, the sensed potential increases quickly to a third positive value, which is greater than the first positive value, and then goes to a negative value, the amplitude which is greater than the amplitude of the third positive value, and thereafter returns quickly to zero. It is appreciated that when the midpoint of thestimulators second portion 64, the maximum strength of the potential sensed is less than the maximum strength of the potential sensed when the midpoint of thestimulators third portion 68, thus contributing to the difference in relative amplitudes. - Turning now to diagram 422, it is seen that inasmuch as
conductor 58 includesfirst portion 60 which is located onsecond side 42 adjacent to second side stimulator 20 (FIG. 2 ), a potential is induced inconductor 58 bystimulator 20 along the entire length ofconductor 58. As seen in diagram 422, becausesensor 25 only measures the potential induced on theconductor 58 when thesensor 25 is adjacent to those portions thereof which are above groundedmetal layer 400, whensensor 25 is overfirst section 60 no potential is sensed. Potential is sensed whensensor 25 is situated oversecond portion 64 and overthird portion 68, however becausesecond portion 64 is located at a relatively greater distance fromsensor 25 the amplitude of the sensed potential is less than the amplitude sensed whensensor 25 is situated overthird section 68. - Reference is now made to
FIG. 6B , which is identical toFIG. 6A but relates to aconductor 458, identical toconductor 58, except in that it has a break at a location “i” therealong.FIG. 6B shows electrical potentials induced inconductor 458 in the environment ofFIGS. 2 .Conductor 458 includes afirst portion 460 which extends alongsecond surface 42, asecond portion 464 located intermediate a groundedmetal layer 500 andfirst surface 40, and athird portion 468, which extends alongfirst surface 40 and has a break therein at location “i” as shown. An electromagnetic field is generated byfirst side stimulators second side stimulator 20 in the arrangement ofFIG. 2 and electrical potential onconductor 458 is sensed by sensor 25 (FIG. 2 ) which lies abovefirst surface 40. -
FIG. 6B includes a representation ofconductor 458 arranged in spatial registration with a first diagram 530 of the potential thereon induced bystimulators conductor 458 of the midpoint betweenstimulators FIG. 2 and a second diagram 532 of the potential onconductor 458 induced bystimulator 20 as a function of the position alongconductor 458 of asensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 530 that as the
conductor 458 is scanned in the scanning direction bystimulators conductor 458 induced bystimulators conductor 458 extends below groundedmetal layer 500. Whensensor 25 in the arrangement ofFIG. 2 reachessecond portion 464, which extends above groundedmetal layer 500, the sensed potential goes quickly from a zero value up to a first positive value and then at the end ofsecond portion 464 decreases to a second positive value, the value which is less than the first positive value. Upon reachingthird portion 468, the sensed potential increases quickly to a third positive value, which is greater than the second positive value, and then goes to a negative value and thereafter returns quickly to zero at location “i”. From location “i”, in the scanning direction, the potential on theconductor 458 induced bystimulators conductor 458. - It is appreciated that there is a clear and measurable difference in the potential pattern produced in
broken conductor 458 as compared with that produced incontinuous conductor 58. - Turning now to diagram 532, it is see that inasmuch as
conductor 458 includesfirst portion 460 which is located onsecond side 42 adjacent tosecond side stimulator 20 as shown in the arrangement ofFIG. 2 , a potential is induced inconductor 458 along its length until break at location “k”. As seen in diagram 532, becausesensor 25 only senses the potential induced on theconductor 458 when it is adjacent to the portions thereof which are above groundedmetal layer 500, whensensor 25 is situated overfirst section 460 no potential is sensed. Potential is sensed whensensor 25 is situated oversecond portion 464 and overthird portion 468 until location “k”. Because of electrical discontinuity due to the break at location “k”, for the section ofthird portion 468 following the break in the scanning direction, which is not connected to any portion of theconductor 458 extending below groundedmetal layer 500, no potential is induced. - Reference is now made to
FIG. 6C , which is identical toFIG. 6A but relates to aconductor 558, identical toconductor 58, except in that it has a break at a location “l” therealong.FIG. 6C shows electrical potentials induced inconductor 558 in the environment ofFIG. 2 .Conductor 558 includes afirst portion 560 which extends alongsecond surface 42, a second portion.564 located intermediate a groundedmetal layer 600 andfirst surface 40, and athird portion 568, which extends alongfirst surface 40.First portion 560 has a break therein as shown. An electromagnetic field is generated byfirst side stimulators second side stimulator 20 in the arrangement ofFIG. 2 and electrical potential onconductor 558 is sensed by sensor 25 (FIG. 2 ) which lies abovefirst surface 40. -
FIG. 6C includes a representation ofconductor 558 arranged in spatial registration with a first diagram 630 of the potential thereon induced bystimulators conductor 558 of the midpoint betweenstimulators FIG. 2 and a second diagram 632 of the potential onconductor 558 induced bystimulator 20 as a function of the position alongconductor 558 of asensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 630 that as the
conductor 558 is scanned in the scanning direction bystimulators conductor 558 induced bystimulators conductor 558 extends below groundedmetal layer 600, Whensensor 25 in the arrangement ofFIG. 2 reachessecond portion 564, which extends above groundedmetal layer 600 but belowfirst surface 40, the sensed potential goes quickly from a zero value up to a first positive value and then upon reaching the end ofsecond portion 564 the potential decreases to a second positive value which is less than the first positive value. Upon reachingthird portion 568, the sensed potential increases quickly to a third positive value and then goes to a negative value, the amplitude which is greater than the amplitude of the third positive value, and thereafter returns quickly to zero. It is appreciated that because the break at location “l” is infirst portion 560 which lies below groundedmetal layer 600, the only information about the presence of a break infirst portion 560 is provided by the amplitude of the potential sensed at the second andthird portions - Turning now to diagram 632, it is see that inasmuch as
conductor 558 includesfirst portion 560 which is located onsecond side 42 adjacent to second side stimulator as shown in the arrangement ofFIG. 2 , despite the break at location “l”, some potential is induced inconductor 558 along its length from break until the end of the conductor. As seen in diagram 632, becausesensor 25 only measures the potential induced on theconductor 58 when it is adjacent to those portions thereof which are above groundedmetal layer 600, whensensor 25 is situated overfirst section 560 no potential is sensed. Potential is sensed whensensor 25 is situated oversecond portion 564 andthird portion 568, however because of the break at location “i” reduces the effective size offirst portion 560 stimulated bystimulator 20, less potential is induced inconductor 568, as compared to the potential induced in correspondingunbroken conductor 58. It is appreciated that the difference may be small and difficult to measure. - Reference is now made to
FIG. 6D , which is identical toFIG. 6A but relates to aconductor 658, identical toconductor 58, except in that it has a break at a location “m” therealong.FIG. 6D shows electrical potentials induced inconductor 658 in the environment ofFIG. 2 .Conductor 658 includes afirst portion 660 which extends alongsecond surface 42 below a groundedmetal layer 700, asecond portion 664 located intermediate groundedmetal layer 700 andfirst surface 40, and athird portion 668, which extends alongfirst surface 40. A break is shown at location “m” insecond portion 664. An electromagnetic field is generated byfirst side stimulators second side stimulator 20 in the arrangement ofFIG. 2 and electrical potential onconductor 658 is sensed by sensor 25 (FIG. 2 ) which lies abovefirst surface 40. -
FIG. 6D includes a representation ofconductor 658 arranged in spatial registration with a first diagram 730 of the potential thereon induced bystimulators conductor 658 of the midpoint betweenstimulators FIG. 2 and a second diagram 732 of the potential onconductor 658 induced bystimulator 20 as a function of the position alongconductor 658 of asensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 730 that as the
conductor 658 is scanned in the scanning direction bystimulators conductor 658 induced bystimulators first portion 660 ofconductor 658 extends below groundedmetal layer 700. Whensensor 25 in the arrangement ofFIG. 2 reachessecond portion 664, which extends above groundedmetal layer 700, the sensed potential goes quickly from a zero value up to a relatively small first positive value decreases to a relatively small negative value the amplitude of which is generally the same as the first positive value quickly increases to 0 at the break at location m. From location “m” in the scanning direction, the sensed potential quickly increases to a second relatively small third positive value, and then decreases to a third positive value at the end ofsecond portion 664. From the beginning of thethird portion 668 in the scanning direction, the sensed potential quickly increases to a fourth positive value, and decreases to a negative value, the amplitude of which is greater than the fourth positive value, and then quickly increases to zero at the end ofconductor 658. - It is appreciated that there is a clear and measurable difference in the potential pattern produced in
broken conductor 658 as compared with the potential pattern produced incontinuous conductor 58. - Turning now to diagram 732, it is seen that inasmuch as
conductor 658 includesfirst portion 660 which is located onsecond side 42 adjacent tosecond side stimulator 20 as shown in the arrangement ofFIG. 2 , a potential is induced inconductor 658 along its length until break at location “m”. As seen in diagram 732, becausesensor 25 only measures the potential induced on theconductor 658 when the sensor is adjacent to those portions which are above groundedmetal layer 700, whensensor 25 is situated overfirst section 660 no potential is sensed. Potential is sensed whensensor 25 is situated oversecond portion 664 until location “m”. Because of the electrical discontinuity due to the break at location “m”, for the second section ofsecond portion 664 in the environment ofFIG. 2 following the break at location “m” in the scanning direction and forthird portion 668, neither of which have any part extending below groundedmetal layer 700, no potential is induced. - It is appreciated that there is a clear and measurable difference in the potential pattern produced in
broken conductor 658 as compared withcontinuous conductor 58. - Reference is now made to
FIG. 7A , which includes a representation of aconductor 58 shown inFIG. 6A in which BUT 12 is turned upside down for additional testing.Sensor 25 in the arrangement ofFIG. 2 now lie abovesecond surface 42 of BUT 12. -
FIG. 7A shows electrical potentials induced inconductor 58 which, as indicated hereinabove with reference toFIG. 6A , includesfirst portion 60 which extends alongsecond surface 42,second portion 64 located intermediate groundedmetal layer 400 andfirst surface 40, andthird portion 68, which extends alongfirst surface 40. The electrical potentials are induced by an electromagnetic field generated byfirst side stimulators second surface 42, andsecond side stimulator 20, which now lies belowfirst surface 40, and are sensed by asensor 25 lying abovefirst surface 42. -
FIG. 7A includes a representation ofconductor 58, which does not have any breaks therealong, arranged in spatial registration with a first diagram 740 of the potential thereon induced bystimulators conductor 58 of the midpoint betweenstimulators FIG. 2 and a second diagram 742 of the potential onconductor 58 induced bystimulator 20 as a function of the position alongconductor 58 ofsensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 740 that as the
conductor 58 is scanned in the scanning direction bystimulators conductor 58 induced bystimulators first portion 60, and quickly returns to a zero value. Inasmuch assecond portion 64 andthird portion 68 are below groundedmetal layer 400, the potential remains at a zero value. - As
conductor 58 includesthird portion 64 which is located onfirst side 40, now adjacent tosecond side stimulator 20 as shown in the arrangement ofFIG. 2 , a potential is induced inconductor 58 bystimulator 20 along the entire length ofconductor 58. As seen in diagram 740, becausesensor 25 only measures the potential induced on theconductor 58 when thesensor 25 is adjacent to those portions which are above groundedmetal layer 400, a potential is sensed overfirst portion 60. Whensensor 25 is oversecond portion 64 andthird portion 68, no potential is sensed. - Reference is now made to
FIG. 7B , which includes a representation ofbroken conductor 458 shown inFIG. 6B except that it is turned upside down for additional testing such thatsensors 25 in the arrangement ofFIG. 2 now lie abovesecond surface 42. -
FIG. 7B shows the electrical potential induced inconductor 458 which is identical toconductor 58 inFIG. 7A except that it includes a break at position “k”. As indicated hereinabove with reference toFIG. 7A ,conductor 458 includesfirst portion 460 which extends alongsecond surface 42,second portion 464 located intermediate a groundedmetal layer 500 andfirst surface 40, andthird portion 468, which extends alongfirst surface 40 of BUT 12. The break at a location “k” is situated inthird portion 468. The electrical potential is induced by an electromagnetic field generated byfirst side stimulators second surface 42, andsecond side stimulator 20, which now lies belowfirst surface 40, and are sensed bysensor 25 lying abovesecond surface 42. -
FIG. 7B includes a representation ofconductor 458, arranged in spatial registration with a first diagram 744 of the potential thereon induced bystimulators conductor 458 of the midpoint betweenstimulators FIG. 2 and a second diagram 746 of the potential onconductor 458 induced bystimulator 20 as a function of the position alongconductor 458 ofsensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 744 that as the
conductor 458 is scanned in the scanning direction bystimulators conductor 458 induced bystimulators first portion 460. Inasmuch assecond portion 464 andthird portion 468 are below groundedmetal layer 500, the potential of these portions sensed bysensor 25 remains at a zero value. - Turning now to diagram 746, it is seen that inasmuch as
conductor 458 includessecond portion 464 which is located beneathmetal plane 600 andthird portion 468 which is located onfirst side 40, now adjacent tosecond side stimulator 20 as shown in the arrangement ofFIG. 2 , a potential is induced inconductor 458 bystimulator 20 along the entire length ofconductor 458. However, because of the break at location “k”, the potential is somewhat reduced relative to the potential induced by unbroken third portion 68 (FIG. 7A ). - As seen in diagram 746, because
sensor 25 only measures the potential induced on theconductor 458 when the sensor is adjacent to those portions which are above groundedmetal layer 500, a somewhat reduced potential is sensed overfirst portion 460, however whensensor 25 is oversecond portion 464 andthird portion 468, no potential is sensed. It is appreciated that there may be only small differences in the potential induced bystimulator 20 in the configurations ofFIG. 7A andFIG. 7B respectively, and that it may be difficult to differentiate between these differences. - It is appreciated that when tested in the “upside-down” orientation of
FIGS. 7A and 7B the difference in the potential patterns produced inbroken conductor 458 as compared with the potential patterns induced incontinuous conductor 58, namely the amplitude of the potential induced bystimulator 20, may be difficult to measure. - Reference is now made to
FIG. 7C , which includes a representation ofconductor 558 shown inFIG. 6C except that it is turned “upside-down” such thatsensor 25 in the arrangement ofFIG. 2 now lies abovesecond surface 42 of BUT 12. -
FIG. 7C shows the electrical potential induced inconductor 558 which is identical toconductor 58 inFIG. 7A except that it includes a break at position “1”. As indicated hereinabove with reference toFIG. 7A ,conductor 558 includes afirst portion 560 which extends alongsecond surface 42, asecond portion 564 located intermediate a groundedmetal layer 600 andfirst surface 40, and athird portion 568, which extends alongfirst surface 40. A break at a location “l” is situated infirst portion 560. The electrical potentials are induced by an electromagnetic field generated byfirst side stimulators second surface 42, and bysecond side stimulator 20, which now lies belowfirst surface 40, and are sensed bysensor 25 lying abovefirst surface 42. -
FIG. 7C includes a representation ofconductor 558 arranged in spatial registration with a first diagram 748 of the potential thereon induced bystimulators conductor 558 of the midpoint betweenstimulators FIG. 2 and a second diagram 750 of the potential onconductor 558 induced bystimulator 20 as a function of the position alongconductor 558 of asensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 748 that as the
conductor 558 is scanned in the scanning direction bystimulators conductor 558 induced bystimulators FIG. 2 , the potential on theconductor 558 induced bystimulators first portion 560. Inasmuch assecond portion 564 andthird portion 568 are below groundedmetal layer 600, the measured potential thereon remains at a zero value. - Turning now to diagram 750, it is see that inasmuch as
conductor 558 includessecond portion 564 and athird portion 568 which are beneath groundedmetal layer 600, now adjacent tosecond side stimulator 20 as shown in the arrangement ofFIG. 2 , a potential is induced inconductor 558 bystimulator 20. However, as seen in diagram 750, because of a break at location “l”, from the beginning offirst portion 560 in the scanning direction ofFIG. 2 until the break at location “l”, no potential is induced bybottom stimulator 20. Becausesensor 25 only measures the potential induced on theconductor 558 when adjacent to those portions which are above groundedmetal layer 600, a potential is only sensed overfirst portion 560 from the break at location “l” in the scanning direction ofFIG. 2 until the end offirst portion 560. Whensensor 25 is oversecond portion 564 andthird portion 568, which are beneath groundedmetal layer 600, no potential is sensed. - It is appreciated that there are a clear and measurable differences in the potential patterns produced in
broken conductor 558 as compared with the potential patterns produced incontinuous conductor 58, as sensed bysensor 25. - Reference is now made to
FIG. 7D , which includes a representation ofconductor 658 shown inFIG. 6D except that it is turned “upside-down” such thatsensor 25 in the arrangement ofFIG. 2 now lies abovesecond surface 42 of BUT 12. -
FIG. 7D shows the electrical potential induced inconductor 658, which is identical toconductor 58 inFIG. 7A except that it includes a break at location “m”. As indicated hereinabove with reference toFIG. 7A ,conductor 658 includes afirst portion 660 which extends alongsecond surface 42, asecond portion 664 located intermediate a groundedmetal layer 600 andfirst surface 40, and athird portion 668, which extends alongfirst surface 40. A break at a location “m” is shown insecond portion 664. An electromagnetic field is generated byfirst side stimulators second side stimulator 20 in the arrangement ofFIG. 2 and electrical potential onconductor 658 is sensed by sensor 25 (FIG. 2 ) which lies abovefirst surface 40. -
FIG. 7D includes a representation ofconductor 658 arranged in spatial registration with a first diagram 752 of the potential thereon induced bystimulators conductor 658 of the midpoint betweenstimulators FIG. 2 and a second diagram 754 of the potential onconductor 658 induced bystimulator 20 as a function of the position alongconductor 658 ofsensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 752 that as the
conductor 658 is scanned in the scanning direction bystimulators conductor 658 induced bystimulators first portion 660. Inasmuch assecond portion 664 andthird portion 668 are below groundedmetal layer 600, the measured potential remains at a zero value. - Turning to diagram 754, it is seen that
conductor 658 includessecond portion 664 which is beneathmetal plane 600 andthird portion 664 which is located onfirst surface 40, now adjacent tosecond side stimulator 20 as shown in the arrangement ofFIG. 2 . A break is shown at location “m” insecond portion 664. A relatively small potential is induced inconductor 658 bystimulator 20 along the first section ofsecond portion 664 in the scanning direction ofFIG. 2 , and this relatively small potential is sensed bysensor 25 when adjacent tofirst portion 660. A potential is also induced in the second section ofsecond portion 664 in the scanning direction shown inFIG. 2 , and inthird portion 668, however whensensor 25 is over these portions, which are beneath groundedmetal layer 600, no potential is sensed thereby. - It is appreciated that when
conductor 658 ofFIG. 6D is tested in the “upside-down” orientation ofFIG. 7D , the difference in the potential patterns produced inbroken conductor 658 as compared with the potential patterns produced incontinuous conductor 58 in the orientation ofFIG. 7A , namely the amplitude of the potential induced bystimulator 20, may be difficult to measure. - Reference is now made to
FIG. 8A which shows electrical potentials induced in a typical conductor, such as aconductor 770 which includes afirst portion 772 which extends alongfirst surface 40, asecond portion 776 located intermediate a groundedmetal layer 800 andsecond surface 42, and athird portion 780, which extends alongfirst surface 40 of BUT 12. The electrical potentials are induced by an electromagnetic field generated byfirst side stimulators second side stimulator 20 in the arrangement ofFIG. 2 and are sensed bysensor 25 lying abovefirst surface 40. -
FIG. 8A includes a representation ofconductor 770, which does not have any breaks therealong, arranged in spatial registration with a first diagram 830 of the potential thereon induced bystimulators conductor 770 of the midpoint betweenstimulators FIG. 2 and a second diagram 832 of the potential onconductor 770 induced bystimulator 20 as a function of the position alongconductor 770 ofsensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 830 that as the
conductor 770 is scanned in the scanning direction bystimulators conductor 770 induced bystimulators first portion 772 and decreases to zero at the end offirst portion 772. Inasmuch assecond portion 776 is beneath groundedmetal layer 800, no potential is sensed whilesensor 25 is oversecond portion 776, and the potential value remains zero. - Progressing in the scanning direction indicated in
FIG. 2 , assensor 25 reachesthird portion 780, the potential decreases to a negative value and then goes to zero at the end ofthird portion 780. - Turning to diagram 832, it is seen that inasmuch as
conductor 770 includessecond portion 776 which is located beneath groundedmetal layer 800 adjacent tosecond side stimulator 20 as shown in the arrangement ofFIG. 2 , a relatively small potential is induced inconductor 770 bystimulator 20 along the entire length ofconductor 770. As seen in diagram 832, becausesensor 25 only measures the potential induced on theconductor 770 whensensor 25 is adjacent to those portions which are above groundedmetal layer 800, whensensor 25 is overfirst portion 772 andthird portion 780, a relatively small potential is sensed. Inasmuch assecond portion 776 is situated beneath groundedmetal layer 800, no potential is sensed whensensor 25 is situated oversecond portion 776 of BUT 12. - Reference is now made to
FIG. 8B , which is identical toFIG. 8A but relates to aconductor 870, identical toconductor 70, except in that it has a break at a location “n” therealong.FIG. 85B shows electrical potentials induced inconductor 870 in the environment ofFIG. 2 .Conductor 870 includes afirst portion 872 which extends alongfirst surface 40, and has a break as shown, asecond portion 876 located intermediate a groundedmetal layer 900 andsecond surface 42, and athird portion 880, which extends alongfirst surface 40. The electrical potentials are induced by an electromagnetic field generated byfirst side stimulators second side stimulator 20 in the arrangement ofFIG. 2 and are sensed bysensor 25 lying abovefirst surface 40. -
FIG. 8B includes a representation ofconductor 870 arranged in spatial registration with a first diagram 930 of the potential thereon induced bystimulators conductor 870 of asensor 25 situated betweenstimulators FIG. 2 and a second diagram 932 of the potential onconductor 870 induced bystimulator 20 as a function of the position alongconductor 870 ofsensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 930 that as the
conductor 870 is scanned in the scanning direction bystimulators conductor 870 induced bystimulators FIG. 2 , the potential onconductor 870 quickly goes to a second positive value, and decreases to a third positive value and quickly returns to zero at the end offirst portion 872. Inasmuch assecond portion 876 is beneath groundedmetal layer 900, no potential is sensed whilesensor 25 is oversecond portion 776, and the potential value remains zero. At the beginning ofthird portion 880, in the scan direction ofFIG. 2 , the potential quickly goes to the third positive value, then decreases to a negative value and quickly increases to zero at the end ofthird portion 880. - Turning to diagram 932, it is seen that inasmuch as
conductor 870 includessecond portion 876 which is located beneath groundedmetal layer 900 adjacent tosecond side stimulator 20 as shown in the arrangement ofFIG. 2 , a relatively small potential is induced inconductor 870 bystimulator 20 alongconductor 870 from the break at location “n” until the end ofthird portion 880. As seen in diagram 832, because of the electrical discontinuity resulting from the break at location “n”, no potential is induced infirst portion 872 up to break at location “n” along the scanning direction.Sensor 25 measures the potential induced on theconductor 870 when it is adjacent to those portions which are above groundedmetal layer 900. Whensensor 25 is overfirst portion 872, after location “n” in the scanning direction, andthird portion 880, a relatively small potential is sensed. Inasmuch assecond portion 876 is situated beneath groundedmetal layer 900, no potential is sensed whensensor 25 is situated oversecond portion 876 of BUT 12. - Reference is now made to
FIG. 8C , which is identical toFIG. 8A but relates to aconductor 970, identical toconductor 770, except in that it has a break at a location “o” therealong.FIG. 8C shows electrical potentials induced inconductor 970 in the environment ofFIG. 2 .Conductor 970 includes afirst portion 972 which extends alongfirst surface 40, asecond portion 976 located intermediate a groundedmetal layer 1000 andsecond surface 42, and has a break at location “o” as shown, and athird portion 980, which extends alongfirst surface 40. The electrical potentials are induced by an electromagnetic field generated byfirst side stimulators second side stimulator 20 in the arrangement ofFIG. 2 and are sensed bysensor 25 lying abovefirst surface 40. -
FIG. 8C includes a representation ofconductor 970 arranged in spatial registration with a first diagram 1030 of the potential thereon induced bystimulators conductor 970 of the midpoint betweenstimulators FIG. 2 and a second diagram 1032 of the potential onconductor 970 induced bystimulator 20 as a function of the position alongconductor 970 of asensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 1030 that as the
conductor 970 is scanned in the scanning direction bystimulators conductor 970 induced bystimulators first portion 972, decreases to a negative value and quickly returns to zero at the end offirst portion 972. Inasmuch assecond portion 976 is beneath groundedmetal layer 1000, no potential is sensed whilesensor 25 is oversecond portion 976, and the potential value remains zero. Progressing in the scanning direction indicated inFIG. 2 , assensor 25 reachesthird portion 980, the potential quickly goes to a positive value at beginning ofthird portion 980, decreases to a negative value and quickly returns to zero at the end ofthird portion 980. - Turning to diagram 1032, it is see that inasmuch as
conductor 970 includessecond portion 976 which is located beneath groundedmetal layer 1000 adjacent tosecond side stimulator 20 as shown in the arrangement ofFIG. 2 , a relatively small potential is induced inconductor 970 bystimulator 20 along the conductor on either side of break at location “o”. As seen in diagram 1032, becausesensor 25 only measures the potential induced on theconductor 970 when the sensor is adjacent to those portions of the conductor which are above groundedmetal layer 1000, whensensor 25 is overfirst portion 972 andthird portion 980, a relatively small potential is sensed. Inasmuch assecond portion 976 is situated beneath groundedmetal layer 1000, no potential is sensed whensensor 25 is situated oversecond portion 976. - Reference is now made to
FIG. 9A , which includes a representation of aconductor 770 shown inFIG. 8A in which BUT 12 is turned “upside-down” for additional testing.Sensors 25 in the arrangement ofFIG. 2 now lie abovesecond surface 42 of BUT 12. -
FIG. 9A shows electrical potentials induced inconductor 770 which, as indicated hereinabove with reference toFIG. 8A , includesfirst portion 772 which extends alongfirst surface 40,second portion 776 located intermediate groundedmetal layer 800 andsecond surface 42, andthird portion 780, which extends alongfirst surface 40 of BUT 12. The electrical potentials are induced by an electromagnetic field generated byfirst side stimulators second surface 42, andsecond side stimulator 20, which now lies belowfirst surface 40, and are sensed bysensor 25 lying abovesecond surface 42. -
FIG. 9A includes a representation ofconductor 770, which does not have any breaks therealong, arranged in spatial registration with a first diagram 1040 of the potential thereon induced bystimulators conductor 770 ofsensor 25 situated betweenstimulators FIG. 2 and a second diagram 1042 of the potential onconductor 770 induced bystimulator 20 as a function of the position alongconductor 770 ofsensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 1040 that as the
conductor 770 is scanned in the scanning direction bystimulators first portion 772 is located beneath groundedmetal layer 800, the potential onconductor 770 sensed bysensor 25 when it is abovefirst portion 772 is zero. Whensensor 25 reachessecond portion 776 the value for the potential sensed quickly goes to a positive value, decreases to a negative value and quickly returns to zero at the end ofsecond portion 776. It is appreciated that potential induced inconductor 770 and sensed when sensor is oversecond portion 776 is attenuated becausesecond portion 776 is located below, and not on,second surface 42. From the beginning ofthird portion 780 the sensed value for the potential is zero inasmuch asthird portion 780 is beneath the groundedmetal layer 800. - Turning to diagram 1042, it is seen that inasmuch as
conductor 770 includesfirst portion 772 andthird portion 780 located onfirst side 40, now adjacent tosecond side stimulator 20 as shown in the arrangement ofFIG. 2 , a potential is induced inconductor 770 bystimulator 20 along its entire length. As seen in diagram 1042, becausesensor 25 only measures the a potential induced onconductor 770 when it is adjacent to those portions thereof which are above groundedmetal layer 800, potential is sensed only oversecond portion 776, however this potential is relatively small becausesecond portion 776 is situated below, and not on,second surface 42. Whensensor 25 is overfirst portion 772 andthird portion 780, no potential is sensed because these portions are below groundedmetal layer 800. - Reference is now made to
FIG. 9B , which includes a representation of aconductor 870 shown inFIG. 8B except that it is turned “upside-down” such thatsensors 25 in the arrangement ofFIG. 2 now lie abovesecond surface 42 of BUT 12. -
FIG. 9B shows the electrical potential induced inconductor 870 which is identical toconductor 770 inFIG. 9A except that it includes a break at position “n” therealong. As indicated hereinabove with reference toFIG. 9A ,conductor 870 includes afirst portion 872 which extends alongfirst surface 40 and has a break therein at location “n” as shown, asecond portion 876 located intermediate groundedmetal layer 800 andsecond surface 42, and athird portion 880, which extends alongfirst surface 40. The electrical potentials are induced by an electromagnetic field generated byfirst side stimulators second surface 42, andsecond side stimulator 20, which now lies belowfirst surface 40, and are sensed bysensor 25 lying abovesecond surface 42. -
FIG. 9B includes a representation ofconductor 870, arranged in spatial registration with a first diagram 1044 of the potential thereon induced bystimulators conductor 870 of the midpoint betweenstimulators FIG. 2 and a second diagram 1046 of the potential onconductor 870 induced bystimulator 20 as a function of the position alongconductor 870 ofsensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 1044 that as the
conductor 870 is scanned in the scanning direction bystimulators first portion 872 is located beneath groundedmetal layer 800, the potential onconductor 870 sensed bysensor 25 when it is abovefirst portion 872 is zero. Whensensor 25 reachessecond portion 876 the value for the potential sensed quickly goes to a positive value decreases to a negative value and quickly returns to zero at the end ofsecond portion 876. It is appreciated that potential induced inconductor 870 and sensed when sensor is oversecond portion 876 is attenuated becausesecond portion 876 is located below, and not on, saidsecond surface 42. From the beginning ofthird portion 880 the sensed value for the potential is zero inasmuch as third portion is beneath the grounded metal layer. - Turning now to diagram 1046, it is seen that inasmuch as
conductor 870 includesfirst portion 872 andthird portion 880 located onfirst side 40, now adjacent tosecond side stimulator 20 as shown in the arrangement ofFIG. 2 , a potential is induced inconductor 870 bystimulator 20. As seen in diagram 1046, becausesensor 25 only measures the potential induced onconductor 870 when adjacent to those portions which are above groundedmetal layer 800, potential is sensed only oversecond portion 876, however this potential is relatively small becausesecond portion 876 is situated below, and not on,second surface 42, and is further attenuated because the length offirst portion 872 contributing to the potential onconductor 870 is shortened due to break at location “n”. Whensensor 25 is overfirst portion 872 andthird portion 880, no potential is sensed because these portions are below groundedmetal layer 800. - Reference is now made to
FIG. 9C , which includes a representation of aconductor 970 shown inFIG. 8C except that it is turned “upside-down” such thatsensor 25 in the arrangement ofFIG. 2 now lies abovesecond surface 42 of BUT 12. -
FIG. 9C shows the electrical potential induced inconductor 970 which is identical toconductor 770 inFIG. 9A except that it includes a break at position “o”. As indicated hereinabove with reference toFIG. 9A ,conductor 970 includesfirst portion 972 which extends alongfirst surface 40,second portion 976 located intermediate groundedmetal layer 1000 andsecond surface 42, and has break therein at location “o” as shown, andthird portion 980, which extends alongfirst surface 40. The electrical potentials are induced by an electromagnetic field generated byfirst side stimulators second surface 42, andsecond side stimulator 20, which now lies belowfirst surface 40, and are sensed bysensor 25 lying abovesecond surface 42. -
FIG. 9C includes a representation ofconductor 970 arranged in spatial registration with a first diagram 1048 of the potential thereon induced bystimulators conductor 970 of the midpoint betweenstimulators FIG. 2 and a second diagram 1050 of the potential onconductor 970 induced bystimulator 20 as a function of the position alongconductor 970 ofsensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 1048 that as the
conductor 970 is scanned in the scanning direction bystimulators first portion 972 is located beneath groundedmetal layer 1000, the potential onconductor 970 sensed bysensor 25 when the sensor is abovefirst portion 972 is zero. Whensensor 25 reachessecond portion 976 the value for the potential sensed quickly goes to a positive value decreases to a negative value and quickly returns to zero at the break at location “o”. From break at location “o” in the scanning direction as indicated inFIG. 2 , the potential sensed quickly returns to a positive value, decreases to a negative value and quickly returns to zero at the end ofsecond portion 976. From the beginning ofthird portion 980 the sensed value for the potential is zero inasmuch asthird portion 980 is beneath the groundedmetal layer 1000. - Turning now to diagram 1050, it is seen that inasmuch as
conductor 970 includesfirst portion 972 andthird portion 980 located onfirst side 40, now adjacent tosecond side stimulator 20 as shown in the arrangement ofFIG. 2 , a potential is induced inconductor 970 bystimulator 20 along either side of break at location “o”. As seen in diagram 1050, becausesensor 25 only measures the potential induced onconductor 970 when adjacent to those portions which are above groundedmetal layer 1000, the potential is sensed only oversecond portion 976, however this potential is relatively small becausesecond portion 976 is situated below, and not on,second surface 42. From the beginning ofsecond portion 976 in the direction indicated inFIG. 2 , the potential sensed quickly increases to a first positive value and quickly decreases at location “o” of the break, and thereafter again quickly increases to a positive value and quickly returns to zero at the end ofsecond portion 976. It is appreciated that the extent to which the potential patterns on either side of the break at location “o” are differentiable one from the other is a function of the size of the break. Inasmuch assensor 25 is overfirst portion 972 andthird portion 980, no potential is sensed because these portions are below groundedmetal layer 1000. - Reference is now made to
FIGS. 10A, 10B , 11A and 11B which are illustrative of the operation of the apparatus ofFIG. 1 to detect shorts between conductors on aBUT 1052 in the environment shown inFIG. 2 . - Reference is now made to
FIG. 10A which shows electrical potentials induced in typical conductors, such asconductors FIG. 2 . Aconductor 1058 includes afirst portion 1060 which extends along asecond surface 1042 of BUT 1052, a viahole 1062 connecting betweenfirst portion 1060 and asecond portion 1064, which is located intermediate groundedmetal layers third portion 1068 which extends along afirst surface 1040 of BUT 1052. Aconductor 1070 includes afirst portion 1072 which extends alongfirst surface 1040, asecond portion 1076 located intermediate groundedmetal layers hole 1078 connection betweensecond portion 1076 and athird portion 1080, which extends alongfirst surface 1040. The electrical potentials are induced by an electromagnetic field generated byfirst side stimulators second side stimulator 20 in the arrangement ofFIG. 2 and are sensed bysensor 25 lying abovefirst surface 1040. -
FIG. 10A includes a representation ofconductors conductors stimulators conductors stimulators FIG. 2 and a second diagram 1132 of the potential onconductors stimulator 20 as a function of the position along the conductors ofsensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 1130 that as
conductors stimulators conductor 1070 induced bystimulators first portion 1072 and decreases to zero at the end offirst portion 1072. Inasmuch assecond portion 1076 lies beneath groundedmetal layer 1054, no potential is sensed whilesensor 25 is oversecond portion 1076, and the potential value remains zero. Progressing in the scanning direction indicated inFIG. 2 , assensor 25 reachesthird portion 1080, the potential decreases from zero to a negative value and then quickly goes to zero at the end ofthird portion 1080. Further progressing in the scanning direction ofFIG. 2 , inasmuch assecond portion 1064 ofconductor 1058 is beneath groundedmetal layer 1054, the zero value is maintained untilsensor 25 reachesthird portion 1068 ofconductor 1058, at which point it quickly increases to a positive value, then decreases to a negative value and quickly increases to zero at the end ofconductor 1068. - Turning to diagram 1132, it is see that inasmuch as only
first portion 1060 ofconductor 1058 and no portion ofconductor 1070 is located beneath both groundedmetal layers stimulator 20 induces a potential only onconductor 1058, as seen in diagram 1132. - Reference is now made to
FIG. 10B , which is identical toFIG. 10A except thatconductors FIG. 10B shows electrical potentials induced inconductor 1158 in the environment ofFIG. 2 . As noted above,conductor 1158 includes afirst portion 1160 which extends alongsecond surface 1042, a viahole 1162 connecting betweenfirst portion 1160 andsecond portion 1164 which is located intermediate groundedmetal layers third portion 1168 which extends along afirst surface 1040.Conductor 1170 includes afirst portion 1172 which extends alongfirst surface 1040, asecond portion 1176 located intermediate groundedmetal layers hole 1178 connecting betweensecond portion 1176 andthird portion 1180, which extends alongfirst surface 1040.Conductors hole 1162 ofconductor 1158 and viahole 1178 ofconductor 1170. - The electrical potentials are induced by an electromagnetic field generated by
first side stimulators second side stimulator 20 in the arrangement ofFIG. 2 and are sensed bysensor 25 lying abovefirst surface 1040. -
FIG. 10B includes a representation ofconductors stimulators stimulators FIG. 2 and a second diagram 1236 of the potential onconductors stimulator 20 as a function of the position along the conductors ofsensor 25 along the scanning direction shown inFIG. 2 . - Reference is now made to
FIG. 11A , which includes a representation ofconductors FIG. 10A and in which BUT 12 is turned “upside-down” for additional testing.Sensor 25 in the arrangement ofFIG. 2 now lies abovesecond surface 1042 of BUT 1052. -
FIG. 11A shows electrical potentials induced inconductors FIG. 10A ,conductor 1058 includesfirst portion 1060 which extends alongsecond surface 1042, a viahole 1062 connecting betweenfirst portion 106 andsecond portion 1064, located between groundedmetal planes third portion 1068 which extends alongfirst surface 1040.Conductor 1070 includesfirst portion 1072 which extends alongfirst surface 1040,second portion 1076 located between groundedmetal planes hole 1078 connectingsecond portion 1076 andthird portion 1080, which extends alongfirst surface 1040. The electrical potentials are induced by an electromagnetic field generated byfirst side stimulators second side stimulator 20 in the arrangement ofFIG. 2 and are sensed by asensor 25 lying abovesecond surface 1042. -
FIG. 11A includes a representation of non-broken andnon-shorted conductors conductors sensor 25, induced bystimulators stimulators FIG. 2 , and a second diagram 1240 of the potential onconductors stimulator 20 as a function of the position along the conductors ofsensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 1238 that as
conductors stimulators conductor 1070 induced bystimulators sensor 25, quickly goes to a positive value at beginning offirst portion 1060, decreases to a negative value, and at the end offirst portion 1060 quickly increases to zero. It is seen that inasmuch assecond portion 1064 andthird portion 1068 ofconductor 1058, are situated below groundedmetal layer 1054, no potential is sensed with respect to potential induced bystimulators second portion 1064 andthird portion 1068. It is also seen that inasmuch asconductor 1070 is situated entirely below groundedmetal layer 1054, it is not stimulated bystimulators - Turning now to diagram 1240, it is seen that inasmuch as
conductor 1058 includesthird portion 1068 which is below groundedmetal layer 1056,conductor 1058 is stimulated bystimulator 20. When BUT 1052 is scanned in the scanning direction, whensensor 25 is overfirst section 1060 the potential induced bystimulator 20 is sensed bysensor 25. Inasmuch assecond portion 1064 andthird portion 1068 ofconductor 1058, are beneath groundedmetal layer 1054,sensor 25 does not sense potentials when over these portions. Inasmuch as all ofconductor 1070 is beneath groundedmetal layer 1054, the potential induced onconductor 1070 is not sensed bysensor 25. - Reference is now made to
FIG. 11B , which is identical toFIG. 10B , but refers to testing of BUT 1052 in “upside-down” orientation for testing as shown inFIG. 11A .FIG. 11B shows electrical potentials induced inconductors FIG. 10B ,conductor 1158 includesfirst portion 1160 which extends alongsecond surface 1042, a viahole 1162 connecting betweenfirst portion 1160 andsecond portion 1164, located between groundedmetal planes third portion 1168 which extends alongfirst surface 1040 of BUT 1052.Conductor 1170 includesfirst portion 1172 which extends alongfirst surface 1040,second portion 1176 located between groundedmetal planes hole 1178 connecting betweensecond portion 1176 andthird portion 1180, which extends alongfirst surface 1040. A short exists between viahole 1162 ofconductor 1158 and viahole 1178 ofconductor 1170 at location “t”. The electrical potentials are induced by an electromagnetic field generated byfirst side stimulators second side stimulator 20 in the arrangement ofFIG. 2 and are sensed by asensor 25 lying abovesecond surface 1042. -
FIG. 11B includes a representation ofconductors stimulators stimulators FIG. 2 and a second diagram 1244 of the potential onconductors stimulator 20 as a function of the position along the conductors of asensor 25 along the scanning direction shown inFIG. 2 . - It is seen in diagram 1242 that as
conductors stimulators conductor 1158 induced bystimulators sensor 25, quickly goes to a positive value at beginning offirst portion 1160, decreases to a negative value, and at the end offirst portion 1160 quickly increases to zero. It is seen that inasmuch assecond portion 1164 andthird portion 1168 ofconductor 1158 are situated below groundedmetal layer 1156, no potential is sensed with respect to potential induced bystimulators second portion 1164 andthird portion 1168. It is also seen that inasmuch asconductor 1170 is situated entirely below groundedmetal layer 1154, it is not stimulated bystimulators - Turning now to diagram 1244, it is seen that inasmuch as
conductor 1158 includesthird portion 1168, which is below groundedmetal layer 1154,conductor 1158 is stimulated bystimulator 20. As BUT 1052 is scanned along the scanning direction, whensensor 25 is overfirst section 1160 the potential induced bystimulator 20 is sensed. Inasmuch assecond portion 1164 andthird portion 1168 ofconductor 1158, are beneath groundedmetal layer 1156,sensor 25 does not sense potentials when it is over these portions. Inasmuch, as all ofconductor 1170 is beneath groundedmetal layer 1154, the potential induced onconductor 1170 is not sensed bysensor 25. - It is appreciated that when testing BUT 1054 in “upside-down” orientation, the potential patterns produced by shorted
conductors non-shorted conductors BUT 1054, it is necessary to perform electrical testing in “right-side-up” orientation wherein, as seen inFIG. 10B shortedconductors non-shorted conductors FIG. 10A . - It is generally appreciated that the foregoing examples of test results for various BUT configurations are not intended to encompass all testable BUT configurations and defects, but rather they are intended to provide illustrative examples of testing possibilities. Thus, in order to achieve fully robust non-contact electrical testing, such as electrical testing able to test for defects located in-between and across internal metal layers in BUTs, BUTs are preferably non-contact electrically tested using the aforementioned apparatus and methods by applying stimulation and sensing, including applying stimulation to the same side of the BUT from one or more sensors to induce potentials in the conductors; applying stimulation to the opposite side of the BUT from one or more sensors also to induce potentials in conductors, and applying stimulation and/or testing to both sides of the BUT simultaneously and/or sequentially. If, as is preferable, stimulation is applied simultaneously to both sides of the BUT, the stimulation is applied so as to induce potentials which, when the electromagnetic field in proximity to the BUT is sensed, it is possible to distinguish between potentials induced by stimulators adjacent to the first side of the BUT and potentials induced by stimulators adjacent to the second side of the BUT.
- For example stimulators may be operated on both opposite sides of a BUT while the BUT is sensed by sensors on one or both sides thereof. Stimulation on opposite sides of a BUT may take place concurrently and/or sequentially. Stimulation on both sides of the BUT may be at different frequencies or multiplexed. The same or different sequence of stimulation may be used for testing a BUT in mutually “upside-down” orientations, and the BUT may be tested sequentially in substantially orthogonal directions.
- The inventors have found that the present invention results not only in a time savings by preferably providing simultaneous performance of non-contact testing steps which previously could only have been performed sequentially, but additionally significantly increases the detectability of faults in BUTs and reduces false alarms.
- One particular advantage of the present invention lies in the fact that by using sensors each of which simultaneously detects potentials induced by multiple, separable electromagnetic stimuli, the potential patterns generated are automatically spatially registered thus generally obviating the need for further spatial registration. As a result, distribution patterns of potentials received in respect of stimulation provided on the same side of the BUT as on which the potentials are sensed are easily correlated with distribution patterns of potentials received in respect of stimulation provided on the opposite side of the BUT from that on which the potentials are sensed.
- Reference is now made to
FIGS. 12 and 13 , which are schematic illustrations of two alternative preferred configurations offirst side stimulators second side stimulator 20. The configurations illustrated inFIGS. 12 and 13 are designed to reduce interference difficulties, such as capacitance interference as may be caused by conductors which cross through metal layers such asfirst metal layer 54 and second metal layer 56 (FIG. 2 ). - Referring to
FIG. 12 , it is seen that astimulator 1310 is preferably sectioned into a plurality of mutually aligned linear stimulation strips 1312, which are oriented perpendicular orientation to the scanning direction along which a BUT, such as BUT 12 shown inFIG. 2 , is scanned. - Turning now to
FIG. 13 , astimulator 1320 may be partitioned into a multiplicity ofindividual stimulator patches 1322, each patch being a separate individually controllable antenna. As is readily appreciated, strips 1312 ofstimulator 1310, as shown inFIG. 12 , andstimulation patches 1322 ofstimulator 1320 as shown inFIG. 13 are preferably provided with AC stimulation signals of different frequencies or multiplexed inputs, in order to enable separation of potentials induced byindividual strips 1312 orpatches 1322 respectively. - Reference is now made to
FIG. 14 which is an alternative configuration of non-contact electrical testing apparatus constructed and operative in accordance with a preferred embodiment of the present invention. The apparatus ofFIG. 14 may be similar to that shown inFIG. 1 and differs therefrom in the arrangement of the stimulators and the sensors. - As seen in
FIG. 14 , there is providedtesting apparatus 1410, which is operative to perform non-contact electrical testing of electrical circuits, such as are found on BUT 12, having a multiplicity ofelectrical conductors 13.Testing apparatus 1410 comprises an array ofstimulator electrodes 1414, including a multiplicity of individually controlled stimulators 1416 linearly disposed adjacent to a first side of BUT 12. Asignal generator 1417 supplies an electrical stimulation signal to each of the stimulators 1416. Preferably the stimulation signals are at different frequencies, or multiplexed. - First side sensor electrodes, hereinafter referred to as
sensors array 1414 to lie adjacent a first side of BUT 12. A second side sensor electrode, hereinafter referred to assensor 1422, is arranged to underlie BUT 12 on a side thereof oppositefirst side sensors sensors - A separating
detector 1426 receives the outputs of eachsensor signal analyzer 1428 which outputs to a comparator andreport generator 1430. - As noted hereinabove, the AC signals provided by
signal generator 1417 to each stimulator 1416 instimulator array 1414 are preferably different. This may be accomplished either by providing signals of different frequencies or alternatively by multiplexing or other known signal differentiation methods. - When energized by the AC electrical stimulation signals, stimulators 1416 generate localized electromagnetic fields which stimulate various conductors on BUT 12. It is appreciated that each stimulator induces a characteristically different measurable potential.
Sensors separating detector 1426, which is operative to separate out each of the potentials. - In a preferred embodiment of the present invention, BUT 12 and
second side sensor 1422 are moved linearlypast stimulator array 1414 andsensors sensor 1422 may be held stationary whilestimulator array 1414 andsensors stimulator array 1414. - As in the apparatus described with respect to
FIG. 1 , by employing information indicating potentials at various locations on BUT 12 sensed bysensors signal analyzer 1428 generates a precise representation characteristic of potentials inconductors 13 on BUT 12, which indicates, inter alia, conductor continuity and which includes information regarding shorts and breaks in conductors, which constitute defects. - The representation provided by
signal analyzer 1428 to comparator andreport generator 1430 enables provision of a defect report 1431 indicating defective electrical continuity inconductors 13 of BUT 12. - Turning now to
FIG. 15 , there is shown a schematic circuit diagram of a preferred embodiment of a separating circuitry 1440 useful in separating detector 1426 (FIG. 14 ). Outputs from each oftop side sensors second amplifiers differential amplifier 1446. - The output of
differential amplifier 1446 is provided to amixer 1448 which also receives a signal input fromsignal generator 1417 and outputs to a low-pass filter (LPF) 1450, operative to remove undesirable AC out-band signal portions. The output ofLPF 1450 is a DC voltage representative of the potential sensed on BUT 12 by asensor sensor - An output from
bottom side sensor 1422 is supplied to anamplifier 1452 which outputs to amixer 1454, which also receives a signal input fromsignal generator 1417. The output ofmixer 1454 is provided to a low-pass filter (LPF) 1456, operative to remove undesirable AC out-band signal portions. The output ofLPF 1456 is a DC voltage representative of the amplitude of the signal input of a potential at a predetermined frequency sensed on BUT 12 bysensor 1422. - It is readily appreciated that separate circuits may be provided for each of the frequencies at which stimulators 1416 stimulate BUT 12, or a lesser number of circuits may be employed, in which event multiplexing of signals to sensors 1416 is required.
- It will be appreciated by persons skilled in the art that the present invention is not limited by what has been specifically described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of various features described hereinabove as well as modifications and variations thereof which would occur to a person skilled in the art upon reading the foregoing description and which are not in the prior art.
Claims (26)
1-82. (canceled)
83. Apparatus for electrically testing electrical circuits comprising:
at least one array of non-contact stimulator electrodes including a multiplicity of individually controlled stimulator electrodes arranged to be linearly disposed adjacent a first side of an electrical circuit to be tested;
a signal generator coupled to said at least one array arranged to supply an electrical stimulation signal to each of the stimulator electrodes; and
at least two non-contact sensor electrodes, each sensor electrode having dimensions sufficiently large to overlay part of a conductor on said electrical circuit to be tested.
84. Apparatus as claimed in claim 83 , wherein said at least one of said two non-contact sensor electrodes is arranged to lie on a second side of said electrical circuit to be tested, opposite to said first side.
85. Apparatus as claimed in claim 83 , wherein said sensor electrodes are operative to correlate a signal to a particular non-contact stimulator electrode to provide spatial information.
86. Apparatus as claimed in claim 83 , wherein at least some of said electrical stimulation signals are at different frequencies.
87. Apparatus as claimed in claim 83 wherein said electrical stimulation signals are multiplexed.
88. Apparatus as claimed in claim 83 , wherein said at least two non-contact sensor electrodes are arranged to lie adjacent said at least one array of non-contact stimulator electrodes.
89. Apparatus as claimed in claim 88 , wherein said at least two non-contact sensor electrodes are arranged to lie on opposite side of said at least one array of non-contact stimulator electrodes.
90. Apparatus as claimed in claim 83 , wherein said at least two non-contact sensor electrodes includes at least one sensor electrode arranged to lie adjacent a second side of said electrical circuit to be tested, said second side being opposite said first side.
91. Apparatus as claimed in claim 83 , further comprising:
a separating detector arranged to receive an output from each of said non-contact sensor electrodes and being operative to correlate a signal to a particular non-contact sensor electrode;
a signal analyzer operative to receive said outputs and to analyze the outputs;
a comparator operative to compare said outputs to an expected signal; and
a report generator at least reporting the presence of defects in said electrical circuit to be tested.
92. Apparatus as claimed in claim 91 , wherein said defects included defects selected from a group of defects including: faulty conductor continuity, shorts between conductors, and breaks in conductors.
93. Apparatus as claimed in claim 83 , wherein said non-contact stimulator electrodes are configured to generate localized electromagnetic fields each stimulating different conductors on said electrical circuit to be tested.
94. Apparatus as claimed in claim 83 , wherein said non-contact stimulator electrodes are arranged to be scanned over said electrical circuit to be tested.
95. Apparatus as claimed in claim 83 , wherein said non-contact sensor electrodes are at least as large as said electrical circuit to be tested.
96. A method for electrically testing electrical circuits, comprising:
stimulating conductors on an electrical circuit to be tested with a multiplicity of individually controlled stimulator electrodes linearly arranged adjacent a first side of said electrical circuit to be tested;
supplying an electrical stimulation signal to each of the stimulator electrodes; and
sensing a response to said stimulating with at least two non-contact sensor electrodes, each sensor having dimensions sufficiently large to overlay part of a conductor on said electrical circuit to be tested.
97. The method as claimed in claim 96 , further comprising correlating a signal to a particular non-contact stimulator electrode to provide spatial information.
98. The method as claimed in claim 97 , wherein said correlating comprises operating said stimulator electrodes at different frequencies.
99. The method as claimed in claim 97 , wherein said correlating comprises multiplexing said electrical stimulation signals.
100. The method as claimed in claim 96 , wherein sensing comprises sensing said response on said first side of said electrical circuit to be tested.
101. The method as claimed in claim 100 , wherein said sensing comprises sensing said response on opposite sides of said multiplicity of said non-contact stimulator electrodes.
102. The method as claimed in claim 96 , wherein sensing comprises sensing said response on a second side of said electrical circuit to be tested, said second side being opposite said first side.
103. The method as claimed in claim 96 , further comprising:
associating a signal with a particular non-contact sensor electrode;
analyzing outputs of said sensors;
comparing compare said outputs to an expected signal; and
reporting the presence of electrical defects in said electrical circuit to be tested.
104. The method as claimed in claim 103 , wherein said defects included defects selected from a group of defects including: faulty conductor continuity, shorts between conductors, and breaks in conductors.
105. The method as claimed in claim 96 , wherein stimulating comprises generating localized electromagnetic field stimulating a different conductor on said electrical circuit to be tested.
106. The method as claimed in claim 96 , further comprising scanning said non-contact stimulator electrodes over said electrical circuit to be tested.
107. The method claimed in claim 96 , wherein said non-contact sensor electrodes are at least as large as said electrical circuit to be tested.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US10/660,356 US20050248353A1 (en) | 1998-06-16 | 2003-09-11 | Electrical testing of prited circuit boards employing a multiplicity of non-contact stimulator electrodes |
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
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IL124961 | 1998-06-16 | ||
IL124961A IL124961A (en) | 1998-06-16 | 1998-06-16 | Contactless test method and system |
US09/719,753 US6630832B1 (en) | 1998-06-16 | 1999-06-16 | Method and apparatus for the electrical testing of printed circuit boards employing intermediate layer grounding |
PCT/IL1999/000333 WO1999065287A2 (en) | 1998-06-16 | 1999-06-16 | Non-contact test method and apparatus |
US10/660,356 US20050248353A1 (en) | 1998-06-16 | 2003-09-11 | Electrical testing of prited circuit boards employing a multiplicity of non-contact stimulator electrodes |
Related Parent Applications (2)
Application Number | Title | Priority Date | Filing Date |
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PCT/IL1999/000333 Continuation WO1999065287A2 (en) | 1998-06-16 | 1999-06-16 | Non-contact test method and apparatus |
US09/719,753 Continuation US6630832B1 (en) | 1998-06-16 | 1999-06-16 | Method and apparatus for the electrical testing of printed circuit boards employing intermediate layer grounding |
Publications (1)
Publication Number | Publication Date |
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US20050248353A1 true US20050248353A1 (en) | 2005-11-10 |
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ID=11071639
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US09/719,753 Expired - Fee Related US6630832B1 (en) | 1998-06-16 | 1999-06-16 | Method and apparatus for the electrical testing of printed circuit boards employing intermediate layer grounding |
US10/660,356 Abandoned US20050248353A1 (en) | 1998-06-16 | 2003-09-11 | Electrical testing of prited circuit boards employing a multiplicity of non-contact stimulator electrodes |
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US09/719,753 Expired - Fee Related US6630832B1 (en) | 1998-06-16 | 1999-06-16 | Method and apparatus for the electrical testing of printed circuit boards employing intermediate layer grounding |
Country Status (6)
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US (2) | US6630832B1 (en) |
CN (2) | CN1312911A (en) |
AU (1) | AU4388099A (en) |
IL (2) | IL124961A (en) |
TW (1) | TW496963B (en) |
WO (1) | WO1999065287A2 (en) |
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Also Published As
Publication number | Publication date |
---|---|
IL140145A0 (en) | 2002-02-10 |
CN1312911A (en) | 2001-09-12 |
US6630832B1 (en) | 2003-10-07 |
IL124961A0 (en) | 1999-01-26 |
IL140145A (en) | 2005-09-25 |
AU4388099A (en) | 2000-01-05 |
IL124961A (en) | 2006-10-05 |
WO1999065287A3 (en) | 2000-02-10 |
TW496963B (en) | 2002-08-01 |
CN1560647A (en) | 2005-01-05 |
WO1999065287A2 (en) | 1999-12-23 |
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