CA2051824A1 - Thermistor having a negative temperature coefficient in multi-layer technology - Google Patents
Thermistor having a negative temperature coefficient in multi-layer technologyInfo
- Publication number
- CA2051824A1 CA2051824A1 CA002051824A CA2051824A CA2051824A1 CA 2051824 A1 CA2051824 A1 CA 2051824A1 CA 002051824 A CA002051824 A CA 002051824A CA 2051824 A CA2051824 A CA 2051824A CA 2051824 A1 CA2051824 A1 CA 2051824A1
- Authority
- CA
- Canada
- Prior art keywords
- thermistor
- metal
- layer
- metal coats
- layers
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C1/00—Details
- H01C1/14—Terminals or tapping points or electrodes specially adapted for resistors; Arrangements of terminals or tapping points or electrodes on resistors
- H01C1/1413—Terminals or electrodes formed on resistive elements having negative temperature coefficient
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/04—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having negative temperature coefficient
- H01C7/041—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having negative temperature coefficient formed as one or more layers or coatings
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49082—Resistor making
- Y10T29/49085—Thermally variable
Abstract
ABSTRACT OF THE DISCLOSURE
A thermistor having negative temperature coefficient in multi-layer technology is formed of a cuboid, monolithic member sintered from a plurality of layers. The layers are formed of fine-particle ceramic material provided with alternating metal coats as internal electrodes and with external metallizations. The metal coats are applied by printing (silk screening) and contain at least one precious metal, particularly an element from the group Ag, Au, Pd, Pt, as a critical constituent.
A thermistor having negative temperature coefficient in multi-layer technology is formed of a cuboid, monolithic member sintered from a plurality of layers. The layers are formed of fine-particle ceramic material provided with alternating metal coats as internal electrodes and with external metallizations. The metal coats are applied by printing (silk screening) and contain at least one precious metal, particularly an element from the group Ag, Au, Pd, Pt, as a critical constituent.
Description
205~824 ~ACKGROUND OF THE INVENTION
The invention i9 directed to a ther~listor having a negative temperature coefficient in multi-layer technology.
There has been a need for some years to transfer multilayer (ML) technology, which has proven itself and has been known for a long time in the manufacture of ceramic multilayer capacitors, to other ceramic components as well. The transfer of a first modification of the ML technology onto varistors is known, for example, from European Patent 0 18g 087, incorporated herein. The varistor is thereby constructed of thin layers of varistor material having precious metal electrodes lying therebetween, these being respectively conducted out at an end side and being connected to one another with a metallization (solder area). The precious metal electrodes that have a relatively high melting point are applied onto the thin ceramic layers with silk screening and before the sintering process in this modification of the ML technology.
The transfer of ML technology onto temperature-dependent thermistors has hitherto been disclosed, not for thermistors having a negative temperature coefficient (NTC, high-temperature conductors), but only for PTC elements (posistors) and only within the framework of a second modification of the known ML technology (U.S. Patent 4,766,409, incorporated herein). In this modification, the ceramic member is alternately constructed of porous and dense ceramic layers, whereby metal alloys whose melting temperatures are considerably lower than the sintering temperature of the ceramic member are pressed into the cavities of the porous intermediate layers. The internal electrodes are thus produced after the sintering process by being pressed in and ~y subsequent solidification of the molten metal, whereby the penetration of the molten metal, the moistening of the ceramic material, and preventing the molten metal from flowing out again, raise a number 20~182~
of problems that, for example, are described in German Published Application 37 25 455, incorporated herein.
U.S. Patent 4,766,409 initially proceeds on the basis that ML technology is especially suitable for the realization of a PTC
thermistor having a resistance of only about 0.3 through 3 ohms on the basis of the parallel connection of many thin ceramic layers within a single component. Attempts to manufacture such a PTC
thermistor are disclosed in the Letters Patent, a refractory metal paste being applied onto the ceramic layers before the sintering by analogy to the most widespread ML ceramic capacitors. The metals having a high melting point that come into consideration (gold, platinum, palladium, silver-palladium alloy), however, did not lead to functioning internal electrodes since, according to the Letters Patent, barrier layers arose. It has in fact been known for a long time that complications involving non-conductive barrier layers at the ceramic surface metallized with precious metals can arise in PTC resistors, but not in NTC thermistors.
Due to the test results, the U.S. patent states that these refractory metals are unsuitable for internal electrodes of PTC
resistors. The U.S. Letters Patent subsequently points out that electrodes free of barrier layers which are composed of an indium-gallium alloy as well as of nickel or aluminum are known, but, as its own solution, proposes that internal electrodes of lead, tin, or of an alloy of these two metals, be pressed into porous intermediate layers of ceramic after the sintering. Such internal electrodes are in fact free of barrier layers. The metals employed, however, have poor moistening properties, for which reason additional protective measures to prevent the injected, molten metals from flowing out must be undertaken, these making the known PTC resistor even more complicated.
205~824 An object of the present invention is to specify a thermistor having a negative temperature coefficient in multi-layer technology that, on the one hand, guarantees a good bonding, i.e.
a connection having low electrical contact resistance between the internal electrodes and the ceramic surface, and that, on the other hand, is simply constructed and can be manufactured in a simplified way.
For achieving this object, an inventive thermistor of the type initially cited comprises the features:
a) a cuboid, monolithic member sintered of a plurality of layers composed of fine-particle ceramic material;
b) having metal coats arranged between the ceramic layers and serving as internal electrodes that are conducted to opposite lateral surfaces of the member in alternating fashion from layer to layer and having a solderable metallization respectively applied thereat and which are connected to one another in electrically conductive fashion;
c) whereby the metal coats are applied by printing (silk screening); and d) containing at least one precious metal, particularly an element from the group Ag, Au, Pd, Pt as a critical constituent.
The drawing figure illustrates a thermistor according to the invention having a negative temperature coefficient in multi-layer technology.
' The wired or unwired NTC thermistor chips of the invention can be mechanically loaded, have small dimensions (for example, 3.2 x 1.6 mm given a thickness of 1.3 mm), and having electrical 2 0 S 18 2 Ll resistances from 0.1 ohm through 1 mega ohm (at 25C). At the very most, values of resistance ~ust below 500 ohms can be realized with the conventional dry-pressing technology wherein a granulate is pressed to form a thermistor blank without layer structure, since the ceramic members would otherwise become too thin and too mechanically sensitive. The pressing technology, moreover, is complicated and expensive. Due to the parallel connection realized on the basis of the specific ML structure - and that goes beyond the structure of ceramic layers without internal electrodes arranged above one another that is also possible and especially suitable for the high-impedance range above approximately 3 k ohm - the NTC thermistors of the invention have the general advantage that their resistance can be set largely independently of their external dimensions.
It has been shown that functional NTC thermistors having an arbitrary number of internal electrodes composed of combinations or mixtures of alloys of the metals Ag, Al, Au, co, Cr, Cu, Fe, In, Ir, Mo, Ni, Pb, Pd, Pt, Sn, Ta, Ti, V, W, Zn, Zr can be produced, whereby the specific NTC ceramic composition is not critical.
Internal electrodes whose critical constituents are palladium and silver have often proven themselves in ML technology.
There is thus an interest to select a silver proportion above 50%
by weight for reasons of cost, due to the better elimination of heat arising in the inside of the monolithic block and in order to avoid migration. Internal electrodes composed in this way and applied before the sintering, however, would melt at the sintering temperatures of approximately 1200C which are usually necessary.
The sintering reactivity of the ceramic material,jhowever, is enhanced due to the selection of an especially fine-particle initial ceramic material such that a lower sintering temperature in the range of about 950 through 1150C is enabled. Such a fine-~' .
20~182~
particle initial material, for example, can be acquired bymechaniaal powder preparation methods, for instance liquid doping, that are inareasing in significance.
The manufacture of an NTC thermistor of the invention occurs in that a slip or suspension i8 produced in a known way from the initial material with the assistance of organic bonding materials, solvents, and softening agents as well. This slip or suspension is subsequently drawn out with a stripping technique to form an extremely thin film. A pattern composed of the approximately 2-3 ~ m thick internal metal coats, and composed of a silver-palladium compound having a silver part of 70 to 80% by weight, is applied with a known silk screening technique onto portions of the film produced in this way that have the approximate size of a postcard card. Thus, a corresponding number of such postcard-size films are stacked on top of one another such that the alternating offset of the metal coats results in the finished member. After a presæing process, finally the layer thermistor is separated in rough form from the film stack and is sintered at temperatures up to 1150C after undergoing the standard cycle of tempering and expelling the binder. Compared to known ML thermistors manufactured by impressing lead, with porous intermediate layers and special metallizations, the NTC thermistors manufactured in this way are less complicated.
The resulting thermistor of the invention is shown in the drawing figure generally at 1 in the form of a cuboid monolithic member. Ceramic layers 2 are shown with the internal electrode metal coats 3 applied thereto. A solderable metallization 4 is provided at sides connecting to every other internaljelectrode.
The sintered NTC thermistors can subsequently be provided with a solderable metallization by immersion, printing, sputtering, , .
~; vacuum metallization, or on the basis of electro-deposition, this solderable metallization also being potentially composed o~ the aforementioned metals. Finally, an optional enveloping of the surface of the thermistors with lacquers, epoxy resins or fluxes can also be implemented.
Although various minor changes and modifications might be proposed by those skilled in the art, it will be understood that we wish to include within the claims of the patent warranted hereon all such changes and modifications as reasonably come within our contribution to the art.
The invention i9 directed to a ther~listor having a negative temperature coefficient in multi-layer technology.
There has been a need for some years to transfer multilayer (ML) technology, which has proven itself and has been known for a long time in the manufacture of ceramic multilayer capacitors, to other ceramic components as well. The transfer of a first modification of the ML technology onto varistors is known, for example, from European Patent 0 18g 087, incorporated herein. The varistor is thereby constructed of thin layers of varistor material having precious metal electrodes lying therebetween, these being respectively conducted out at an end side and being connected to one another with a metallization (solder area). The precious metal electrodes that have a relatively high melting point are applied onto the thin ceramic layers with silk screening and before the sintering process in this modification of the ML technology.
The transfer of ML technology onto temperature-dependent thermistors has hitherto been disclosed, not for thermistors having a negative temperature coefficient (NTC, high-temperature conductors), but only for PTC elements (posistors) and only within the framework of a second modification of the known ML technology (U.S. Patent 4,766,409, incorporated herein). In this modification, the ceramic member is alternately constructed of porous and dense ceramic layers, whereby metal alloys whose melting temperatures are considerably lower than the sintering temperature of the ceramic member are pressed into the cavities of the porous intermediate layers. The internal electrodes are thus produced after the sintering process by being pressed in and ~y subsequent solidification of the molten metal, whereby the penetration of the molten metal, the moistening of the ceramic material, and preventing the molten metal from flowing out again, raise a number 20~182~
of problems that, for example, are described in German Published Application 37 25 455, incorporated herein.
U.S. Patent 4,766,409 initially proceeds on the basis that ML technology is especially suitable for the realization of a PTC
thermistor having a resistance of only about 0.3 through 3 ohms on the basis of the parallel connection of many thin ceramic layers within a single component. Attempts to manufacture such a PTC
thermistor are disclosed in the Letters Patent, a refractory metal paste being applied onto the ceramic layers before the sintering by analogy to the most widespread ML ceramic capacitors. The metals having a high melting point that come into consideration (gold, platinum, palladium, silver-palladium alloy), however, did not lead to functioning internal electrodes since, according to the Letters Patent, barrier layers arose. It has in fact been known for a long time that complications involving non-conductive barrier layers at the ceramic surface metallized with precious metals can arise in PTC resistors, but not in NTC thermistors.
Due to the test results, the U.S. patent states that these refractory metals are unsuitable for internal electrodes of PTC
resistors. The U.S. Letters Patent subsequently points out that electrodes free of barrier layers which are composed of an indium-gallium alloy as well as of nickel or aluminum are known, but, as its own solution, proposes that internal electrodes of lead, tin, or of an alloy of these two metals, be pressed into porous intermediate layers of ceramic after the sintering. Such internal electrodes are in fact free of barrier layers. The metals employed, however, have poor moistening properties, for which reason additional protective measures to prevent the injected, molten metals from flowing out must be undertaken, these making the known PTC resistor even more complicated.
205~824 An object of the present invention is to specify a thermistor having a negative temperature coefficient in multi-layer technology that, on the one hand, guarantees a good bonding, i.e.
a connection having low electrical contact resistance between the internal electrodes and the ceramic surface, and that, on the other hand, is simply constructed and can be manufactured in a simplified way.
For achieving this object, an inventive thermistor of the type initially cited comprises the features:
a) a cuboid, monolithic member sintered of a plurality of layers composed of fine-particle ceramic material;
b) having metal coats arranged between the ceramic layers and serving as internal electrodes that are conducted to opposite lateral surfaces of the member in alternating fashion from layer to layer and having a solderable metallization respectively applied thereat and which are connected to one another in electrically conductive fashion;
c) whereby the metal coats are applied by printing (silk screening); and d) containing at least one precious metal, particularly an element from the group Ag, Au, Pd, Pt as a critical constituent.
The drawing figure illustrates a thermistor according to the invention having a negative temperature coefficient in multi-layer technology.
' The wired or unwired NTC thermistor chips of the invention can be mechanically loaded, have small dimensions (for example, 3.2 x 1.6 mm given a thickness of 1.3 mm), and having electrical 2 0 S 18 2 Ll resistances from 0.1 ohm through 1 mega ohm (at 25C). At the very most, values of resistance ~ust below 500 ohms can be realized with the conventional dry-pressing technology wherein a granulate is pressed to form a thermistor blank without layer structure, since the ceramic members would otherwise become too thin and too mechanically sensitive. The pressing technology, moreover, is complicated and expensive. Due to the parallel connection realized on the basis of the specific ML structure - and that goes beyond the structure of ceramic layers without internal electrodes arranged above one another that is also possible and especially suitable for the high-impedance range above approximately 3 k ohm - the NTC thermistors of the invention have the general advantage that their resistance can be set largely independently of their external dimensions.
It has been shown that functional NTC thermistors having an arbitrary number of internal electrodes composed of combinations or mixtures of alloys of the metals Ag, Al, Au, co, Cr, Cu, Fe, In, Ir, Mo, Ni, Pb, Pd, Pt, Sn, Ta, Ti, V, W, Zn, Zr can be produced, whereby the specific NTC ceramic composition is not critical.
Internal electrodes whose critical constituents are palladium and silver have often proven themselves in ML technology.
There is thus an interest to select a silver proportion above 50%
by weight for reasons of cost, due to the better elimination of heat arising in the inside of the monolithic block and in order to avoid migration. Internal electrodes composed in this way and applied before the sintering, however, would melt at the sintering temperatures of approximately 1200C which are usually necessary.
The sintering reactivity of the ceramic material,jhowever, is enhanced due to the selection of an especially fine-particle initial ceramic material such that a lower sintering temperature in the range of about 950 through 1150C is enabled. Such a fine-~' .
20~182~
particle initial material, for example, can be acquired bymechaniaal powder preparation methods, for instance liquid doping, that are inareasing in significance.
The manufacture of an NTC thermistor of the invention occurs in that a slip or suspension i8 produced in a known way from the initial material with the assistance of organic bonding materials, solvents, and softening agents as well. This slip or suspension is subsequently drawn out with a stripping technique to form an extremely thin film. A pattern composed of the approximately 2-3 ~ m thick internal metal coats, and composed of a silver-palladium compound having a silver part of 70 to 80% by weight, is applied with a known silk screening technique onto portions of the film produced in this way that have the approximate size of a postcard card. Thus, a corresponding number of such postcard-size films are stacked on top of one another such that the alternating offset of the metal coats results in the finished member. After a presæing process, finally the layer thermistor is separated in rough form from the film stack and is sintered at temperatures up to 1150C after undergoing the standard cycle of tempering and expelling the binder. Compared to known ML thermistors manufactured by impressing lead, with porous intermediate layers and special metallizations, the NTC thermistors manufactured in this way are less complicated.
The resulting thermistor of the invention is shown in the drawing figure generally at 1 in the form of a cuboid monolithic member. Ceramic layers 2 are shown with the internal electrode metal coats 3 applied thereto. A solderable metallization 4 is provided at sides connecting to every other internaljelectrode.
The sintered NTC thermistors can subsequently be provided with a solderable metallization by immersion, printing, sputtering, , .
~; vacuum metallization, or on the basis of electro-deposition, this solderable metallization also being potentially composed o~ the aforementioned metals. Finally, an optional enveloping of the surface of the thermistors with lacquers, epoxy resins or fluxes can also be implemented.
Although various minor changes and modifications might be proposed by those skilled in the art, it will be understood that we wish to include within the claims of the patent warranted hereon all such changes and modifications as reasonably come within our contribution to the art.
Claims (7)
1. A thermistor having a negative temperature coefficient in multi-layer technology, comprising:
a cuboid, monolithic member sintered from a plurality of layers formed of fine-particle ceramic material;
metal coats printed on the ceramic layers and arranged between the ceramic layers and serving as internal electrodes which are conducted to opposite lateral surfaces of the member in alternating fashion from layer to layer and having a solderable metallization respectively applied thereat and being connected to one another in electrically conductive fashion; and the metal coats containing at least one precious metal as a critical constituent and selected from the group consisting of Ag, Au, Pd, Pt.
a cuboid, monolithic member sintered from a plurality of layers formed of fine-particle ceramic material;
metal coats printed on the ceramic layers and arranged between the ceramic layers and serving as internal electrodes which are conducted to opposite lateral surfaces of the member in alternating fashion from layer to layer and having a solderable metallization respectively applied thereat and being connected to one another in electrically conductive fashion; and the metal coats containing at least one precious metal as a critical constituent and selected from the group consisting of Ag, Au, Pd, Pt.
2. A thermistor according to claim 1 wherein the metal coats contain at least one element selected from the group Al, Pb as a further critical constituent.
3. A thermistor according to claim 1 wherein the metal coats contain Pd and Ag as a critical constituent with a silver part of more than 50% by weight.
4. A thermistor according to claim 3 wherein the silver part is between 70% and 80% by weight.
5. A thermistor according to claim 3 wherein the metal coats are approximately in a range of 2 to 3 µ m thick.
6. A thermistor according to claim 1 wherein the printed metal coats are silk screened metal coats.
7. A multi-layer thermistor having a negative temperature coefficient, comprising:
a cuboid, monolithic member formed from a plurality of layers formed of fine-particle ceramic material;
metal coats printed on the ceramic layers and arranged between the ceramic layers and serving as internal electrodes which are conducted to opposite lateral surfaces of the member in alternating fashion from layer to layer and having a metallization respectively in contact therewith and being connected to one another in electrically conductive fashion by said contact; and the metal coats containing at least one precious metal as a critical constituent and selected from the group consisting of Ag, Au, Pd, Pt.
a cuboid, monolithic member formed from a plurality of layers formed of fine-particle ceramic material;
metal coats printed on the ceramic layers and arranged between the ceramic layers and serving as internal electrodes which are conducted to opposite lateral surfaces of the member in alternating fashion from layer to layer and having a metallization respectively in contact therewith and being connected to one another in electrically conductive fashion by said contact; and the metal coats containing at least one precious metal as a critical constituent and selected from the group consisting of Ag, Au, Pd, Pt.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE(P4029988.0) | 1990-09-21 | ||
| DE4029988 | 1990-09-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2051824A1 true CA2051824A1 (en) | 1992-03-22 |
Family
ID=6414728
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002051824A Abandoned CA2051824A1 (en) | 1990-09-21 | 1991-09-19 | Thermistor having a negative temperature coefficient in multi-layer technology |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US5500996A (en) |
| EP (1) | EP0476657A1 (en) |
| CA (1) | CA2051824A1 (en) |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6023403A (en) | 1996-05-03 | 2000-02-08 | Littlefuse, Inc. | Surface mountable electrical device comprising a PTC and fusible element |
| DE19635276C2 (en) * | 1996-08-30 | 2003-04-24 | Epcos Ag | Electro-ceramic multilayer component and method for its production |
| EP0952591B1 (en) * | 1996-09-20 | 2005-02-16 | Matsushita Electric Industrial Co., Ltd. | Ptc thermistor |
| JPH1154301A (en) * | 1997-08-07 | 1999-02-26 | Murata Mfg Co Ltd | Chip thermister |
| US6282072B1 (en) | 1998-02-24 | 2001-08-28 | Littelfuse, Inc. | Electrical devices having a polymer PTC array |
| US20020125982A1 (en) * | 1998-07-28 | 2002-09-12 | Robert Swensen | Surface mount electrical device with multiple ptc elements |
| US6582647B1 (en) | 1998-10-01 | 2003-06-24 | Littelfuse, Inc. | Method for heat treating PTC devices |
| US6347175B1 (en) | 1999-07-14 | 2002-02-12 | Corning Incorporated | Solderable thin film |
| WO2001082314A1 (en) * | 2000-04-25 | 2001-11-01 | Epcos Ag | Electric component, method for the production thereof and use of the same |
| US6279811B1 (en) * | 2000-05-12 | 2001-08-28 | Mcgraw-Edison Company | Solder application technique |
| US6628498B2 (en) | 2000-08-28 | 2003-09-30 | Steven J. Whitney | Integrated electrostatic discharge and overcurrent device |
| US6498561B2 (en) * | 2001-01-26 | 2002-12-24 | Cornerstone Sensors, Inc. | Thermistor and method of manufacture |
| US7154736B2 (en) * | 2001-05-08 | 2006-12-26 | Epcos Ag | Ceramic multi-layer element and a method for the production thereof |
| US6759940B2 (en) * | 2002-01-10 | 2004-07-06 | Lamina Ceramics, Inc. | Temperature compensating device with integral sheet thermistors |
| EP1846740B1 (en) * | 2005-02-10 | 2010-09-08 | Ist Ag | Sensor connector conductor with reduced thermal conductance |
| US20090027821A1 (en) * | 2007-07-26 | 2009-01-29 | Littelfuse, Inc. | Integrated thermistor and metallic element device and method |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB545679A (en) * | 1939-06-23 | 1942-06-08 | Standard Telephones Cables Ltd | Resistance composition and method of making it |
| US2886476A (en) * | 1956-10-19 | 1959-05-12 | Du Pont | Resistors |
| GB1337929A (en) * | 1972-05-04 | 1973-11-21 | Standard Telephones Cables Ltd | Thermistors |
| US4189760A (en) * | 1973-05-13 | 1980-02-19 | Erie Technological Products, Inc. | Monolithic capacitor with non-noble metal electrodes and method of making the same |
| US4454495A (en) * | 1982-08-31 | 1984-06-12 | The United States Of America As Represented By The United States Department Of Energy | Layered ultra-thin coherent structures used as electrical resistors having low temperature coefficient of resistivity |
| DE3660342D1 (en) * | 1985-01-17 | 1988-07-28 | Siemens Ag | Voltage-dependent electric resistance (varistor) |
| US4766409A (en) * | 1985-11-25 | 1988-08-23 | Murata Manufacturing Co., Ltd. | Thermistor having a positive temperature coefficient of resistance |
| US4918421A (en) * | 1986-03-20 | 1990-04-17 | Lawless William N | Nonlinear resistor for low temperature operation |
| US4912450A (en) * | 1986-09-20 | 1990-03-27 | Murata Manufacturing Co., Ltd. | Thermistor and method of producing the same |
| DE3725455A1 (en) * | 1987-07-31 | 1989-02-09 | Siemens Ag | ELECTRICAL MULTI-LAYER COMPONENT WITH A SINTERED, MONOLITHIC CERAMIC BODY AND METHOD FOR PRODUCING THE ELECTRICAL MULTI-LAYER COMPONENT |
-
1991
- 1991-09-19 EP EP91115954A patent/EP0476657A1/en not_active Ceased
- 1991-09-19 CA CA002051824A patent/CA2051824A1/en not_active Abandoned
-
1993
- 1993-02-22 US US08/020,435 patent/US5500996A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0476657A1 (en) | 1992-03-25 |
| US5500996A (en) | 1996-03-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |