US3793604A - High strength electrical lead for disk type thermistors - Google Patents

High strength electrical lead for disk type thermistors Download PDF

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Publication number
US3793604A
US3793604A US00348946A US3793604DA US3793604A US 3793604 A US3793604 A US 3793604A US 00348946 A US00348946 A US 00348946A US 3793604D A US3793604D A US 3793604DA US 3793604 A US3793604 A US 3793604A
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lead
wire
thermistor
face
coating
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US00348946A
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G Duggan
J Dow
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GTE Sylvania Inc
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GTE Sylvania Inc
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    • 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
    • H01C1/144—Terminals or tapping points or electrodes specially adapted for resistors; Arrangements of terminals or tapping points or electrodes on resistors the terminals or tapping points being welded or soldered

Definitions

  • a lead-in wire is soldered to each metallic coating, each lead-in wire extending beyond the edge of the thermistor in a plane generally parallel to the face thereof.
  • Each lead-in wire is shaped so that the solder bond between the lead-in wire and the metallic coating does not extend to the periphery of the thermistor.
  • Thermistors are relatively simple, two-terminal semiconductor devices the electrical resistance of which varies in a known retraceable manner with temperature. They are'commonly manufactured invarious shapes, such as rods, disks, washers, beads and molded.
  • This invention relates to disk type thermistors and particularly to such thermistors having generally radial lead-in wires.
  • a lead-in wire is laid across the face of the thermistor and soldered thereto. The solder bond therebetween extends from the inner end of the lead-in wire to the periphery of the thermistor, the lead-in wire extending therebeyond.
  • the peel strength is determined by measuring the amountof force required to rupture the bond between the wire and the disk face. The force is applied to the wire outside the periphery of the disk and in a direction substantially parallel to the axis of the disc, the effect being to peel the wire up from the face of the disk.
  • the peel strength of such lead-in wires can be substantially increased by the use of a lead-in wire bent in such a manner that the solder bond between the-wire and disk face does not extend to the periphery of the disk. That is to say, at about the point where the lead-in wire extends beyond the periphery of the disk, the wire should be sufficiently above the surface of the disk so that a solder fillet therebetween does not extend to the periphery of the disk.
  • FIGURE in the drawing is a perspective view of a thermistor in accordance with this invention.
  • thermistor l was a disk type barium titanate thermistor, made by the usual process of blending thermistor material in powder form, pressing the powder into a disk shape and then firing the disk at an elevated temperature, above about l,000 C.
  • the fire disk had a diameter of 9% inch and a thickness of 125 mils.
  • a conductive metallic coating 2 was then applied in known manner to each face of the disk to provide an ohmic contact,
  • a coating is made of a powdered metal, such as silver, aluminum or copper, dispersed in a liquid vehicle.
  • the coating also contains a small amount of inorganic binder, such as glass frit.
  • the thermistor is fired at a temperature above the melting point of the glass frit to provide a good bond between the condcutive coating and the thermistor surface. It is necessary that coating 2 provide good ohmic contact and be readily wettable by solder.
  • coating 2 consist of two coatings, the first coating selected to provide ohmic contact and a good bond to the thermistor surface and the second coating selected to bond well to the first coating and also provide better solderability than the first coating.
  • the first coating could contain silver or aluminum in an amount that provides good ohmic contact to the barium titanate.
  • the second coating could contain a higher percentage of metal, e.g. silver, to provide better solderability.
  • Lead-in wire 3 was made of 25 mil tinned copper wire and had an overall length of about 1% inches.
  • segment 4 of lead-in wire 3 that was soldered to coating 2 was straight and had a length of A inch. Segment 4 was positioned on the face of the thermistor so that acute angle bend 5 in lead-in wire 3 raised lead-in wire 3 sufficiently above the surface of the thermistor that solder fillet 6 did not extend to the periphery of the thermistor.
  • lead-in wire 3 should be elevated above the face of the thermistor, at its periphery, at least about double the wire diameter of lead-in wire 3. Both lead-in wires 3, one on each face of the thermistor, were bent so that the space between them, at their outer ends, was about equal to the thickness of the thermistor.
  • Lead-in wires 3 were soldered to thermistor I by the process shown in US. Pat. No. 3,721,003, where both lead-in wires 3 constituted a prebent single wire which was cut after soldering. Prior to soldering, the thermistor, held between the lead-in wires, was dipped into a liquid flux and was then dipped in molten solder. In this example the solder was 96.5% tin 3.5% silver having a melting point of about 221 C. The solder formed a fillet all around segment 4 and securely bonded lead-in wire 3 to coating 2'.
  • Disk thermistors in accordance with this invention had a lead-in wire peel strength at least 50% greater than that of similar prior art thermistors, where the solder bond between the lead-in wire and the thermistor extend to the periphery of the disk.
  • a barium titanate disk type thermistor having a solderable coating securely bonded to each face thereof and a separate bent lead-in wire fastened with solder to each of said coatings, the solder bond between said coating and said lead-in wire extending across the face of the thermistor but not as far as the periphery thereof, each of said lead-in wires having a bend so as to be elevated above the face of the thermistor at the periphery thereof by a distance at least about double the thickness of the lead-in wire, a peelstrength-improving solder fillet between said thermistor face and said lead-in wire at said bend of the lead-in wire and each of said lead-in wires having additional bends so that their outer ends are substantially parallel and spaced apart about the thickness of the thermistor.

Abstract

A disk type thermistor has a conductive metallic coating bonded to each face thereof. A lead-in wire is soldered to each metallic coating, each lead-in wire extending beyond the edge of the thermistor in a plane generally parallel to the face thereof. Each lead-in wire is shaped so that the solder bond between the lead-in wire and the metallic coating does not extend to the periphery of the thermistor.

Description

United States Patent [1 1 Duggan et al.
[451 Feb. 19, 1974 HIGH STRENGTH ELECTRICAL LEAD FOR DISK TYPE THERMISTORS [75] Inventors: George L. Duggan, Bedford; Judith A. Dow, Danvers, both of Mass.
[73] Assignee: GTE Sylvania Incorporated,
' Danver s, Mass.
[22] Filed: 'Apr. 9, 1973 [21] Appl. N0.: 348,946
[52] US. Cl 338/22 R, 338/324, 338/329 [51] Int. Cl H0lc 7/04 [58] Field of Search 338/22 R, 22 SD, 23, 25, 28,
[56] References Cited UNITED STATES PATENTS 3,547,835 12/1970 Short 338/22 SD 2,720,573 10/1955 Lundquist 338/22 R 3,452,314 6/1969 Sapoff et a1 338/22 3,182,118 5/1965 DeProost et a1. 338/322 X 3,381,081 4/1968 Schalliol 338/329 X 2,418,460 4/1947 Buehler 338/322 Primary Examiner-C. L. Albritton Attorney, Agent, or Firm.lames Theodosopoulos [57] ABSTRACT A disk type thermistor has a conductive metallic coating bonded to each face thereof. A lead-in wire is soldered to each metallic coating, each lead-in wire extending beyond the edge of the thermistor in a plane generally parallel to the face thereof. Each lead-in wire is shaped so that the solder bond between the lead-in wire and the metallic coating does not extend to the periphery of the thermistor.
1 Claim, 1 Drawing Figure HIGH STRENGTH ELECTRICAL LEAD FOR DISK TYPE THERMISTORS SUMMARY OF THE INVENTION Thermistors are relatively simple, two-terminal semiconductor devices the electrical resistance of which varies in a known retraceable manner with temperature. They are'commonly manufactured invarious shapes, such as rods, disks, washers, beads and molded.
This invention relates to disk type thermistors and particularly to such thermistors having generally radial lead-in wires. In such thermistors a lead-in wire is laid across the face of the thermistor and soldered thereto. The solder bond therebetween extends from the inner end of the lead-in wire to the periphery of the thermistor, the lead-in wire extending therebeyond.
We have found that such a construction does not produce an adequately strong lead-in wire bond in those situations where the peel strength requirement of the lead-in wire is quite high. The peel strength is determined by measuring the amountof force required to rupture the bond between the wire and the disk face. The force is applied to the wire outside the periphery of the disk and in a direction substantially parallel to the axis of the disc, the effect being to peel the wire up from the face of the disk.
We have found that the peel strength of such lead-in wires can be substantially increased by the use of a lead-in wire bent in such a manner that the solder bond between the-wire and disk face does not extend to the periphery of the disk. That is to say, at about the point where the lead-in wire extends beyond the periphery of the disk, the wire should be sufficiently above the surface of the disk so that a solder fillet therebetween does not extend to the periphery of the disk.
The single FIGURE in the drawing is a perspective view of a thermistor in accordance with this invention.
In one embodiment of this invention, thermistor l was a disk type barium titanate thermistor, made by the usual process of blending thermistor material in powder form, pressing the powder into a disk shape and then firing the disk at an elevated temperature, above about l,000 C. In this example, the fire disk had a diameter of 9% inch and a thickness of 125 mils.
A conductive metallic coating 2 was then applied in known manner to each face of the disk to provide an ohmic contact, Such a coating is made of a powdered metal, such as silver, aluminum or copper, dispersed in a liquid vehicle. The coating also contains a small amount of inorganic binder, such as glass frit. After coating 2 has dried, the thermistor is fired at a temperature above the melting point of the glass frit to provide a good bond between the condcutive coating and the thermistor surface. It is necessary that coating 2 provide good ohmic contact and be readily wettable by solder.
In some cases it may be desirable that coating 2 consist of two coatings, the first coating selected to provide ohmic contact and a good bond to the thermistor surface and the second coating selected to bond well to the first coating and also provide better solderability than the first coating. In such a case, the first coating could contain silver or aluminum in an amount that provides good ohmic contact to the barium titanate. The second coating could contain a higher percentage of metal, e.g. silver, to provide better solderability.
Lead-in wire 3 was made of 25 mil tinned copper wire and had an overall length of about 1% inches. The end, segment 4, of lead-in wire 3 that was soldered to coating 2 was straight and had a length of A inch. Segment 4 was positioned on the face of the thermistor so that acute angle bend 5 in lead-in wire 3 raised lead-in wire 3 sufficiently above the surface of the thermistor that solder fillet 6 did not extend to the periphery of the thermistor. We have found that in order to prevent solder fillet 6 from extending to the periphery of the thermistor, lead-in wire 3 should be elevated above the face of the thermistor, at its periphery, at least about double the wire diameter of lead-in wire 3. Both lead-in wires 3, one on each face of the thermistor, were bent so that the space between them, at their outer ends, was about equal to the thickness of the thermistor.
Lead-in wires 3 were soldered to thermistor I by the process shown in US. Pat. No. 3,721,003, where both lead-in wires 3 constituted a prebent single wire which was cut after soldering. Prior to soldering, the thermistor, held between the lead-in wires, was dipped into a liquid flux and was then dipped in molten solder. In this example the solder was 96.5% tin 3.5% silver having a melting point of about 221 C. The solder formed a fillet all around segment 4 and securely bonded lead-in wire 3 to coating 2'.
Disk thermistors in accordance with this invention had a lead-in wire peel strength at least 50% greater than that of similar prior art thermistors, where the solder bond between the lead-in wire and the thermistor extend to the periphery of the disk.
We claim:
1. A barium titanate disk type thermistor having a solderable coating securely bonded to each face thereof and a separate bent lead-in wire fastened with solder to each of said coatings, the solder bond between said coating and said lead-in wire extending across the face of the thermistor but not as far as the periphery thereof, each of said lead-in wires having a bend so as to be elevated above the face of the thermistor at the periphery thereof by a distance at least about double the thickness of the lead-in wire, a peelstrength-improving solder fillet between said thermistor face and said lead-in wire at said bend of the lead-in wire and each of said lead-in wires having additional bends so that their outer ends are substantially parallel and spaced apart about the thickness of the thermistor.

Claims (1)

1. A barium titanate disk type thermistor having a solderable coating securely bonded to each face thereof and a separate bent lead-in wire fastened with solder to each of said coatings, the solder bond between said coating and said lead-in wire extending across the face of the thermistor but not as far as the periphery thereof, each of said lead-in wires having a bend so as to be elevated above the face of the thermistor at the periphery thereof by a distance at least about double the thickness of the lead-in wire, a peel-strength-improving solder fillet between said thermistor face and said lead-in wire at said bend of the lead-in wire and each of said lead-in wires having additional bends so that their outer ends are substantially parallel and spaced apart about the thickness of the thermistor.
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Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4058701A (en) * 1974-05-14 1977-11-15 Schoeller & Co. Elektrotechnische Fabrik Gmbh & Co. Glow element arrangement for electric cigarette lighters
EP0001750A1 (en) * 1977-10-27 1979-05-16 Siemens Aktiengesellschaft Method for affixing a terminal conductor onto an electrical PTC resistor
EP0193854A1 (en) * 1985-03-07 1986-09-10 Siemens Aktiengesellschaft Electrical resistance having a negative temperature coefficient, and production process therefor
US4685025A (en) * 1985-03-14 1987-08-04 Raychem Corporation Conductive polymer circuit protection devices having improved electrodes
EP0243602A1 (en) * 1986-04-23 1987-11-04 Siemens Aktiengesellschaft Electric component having a higher solidity versus temperature variations and current pulses, especially a varistor
US4730102A (en) * 1986-09-15 1988-03-08 Gte Products Corporation Electroceramic heating devices
US4746784A (en) * 1985-06-11 1988-05-24 Littelfuse-Tracor, B.V. Method of attaching a lead to a metal end cap of a safety fuse
US4827634A (en) * 1984-08-29 1989-05-09 Murata Manufacturing Co., Ltd. Three-terminal capacitor
US5117089A (en) * 1990-04-02 1992-05-26 Emerson Electric Co. Structural support for hermetic terminal assembly heater apparatus
US5557251A (en) * 1993-03-29 1996-09-17 Murata Manufacturing Co., Ltd. Thermistor with electrodes for preventing inter-electrode migration
US6150918A (en) * 1995-05-03 2000-11-21 Bc Components Holdings B.V. Degaussing unit comprising one or two thermistors
US6177857B1 (en) * 1995-01-26 2001-01-23 Murata Manufacturing Co., Ltd. Thermistor device
US20040218329A1 (en) * 2003-05-02 2004-11-04 Tyco Electronics Corporation Circuit protection device
US7075407B1 (en) * 1999-04-09 2006-07-11 Murata Manufacturing Co., Ltd. Temperature sensor
US7164341B2 (en) * 2000-10-24 2007-01-16 Murata Manufacturing Co., Ltd. Surface-mountable PTC thermistor and mounting method thereof
DE102017116381A1 (en) * 2017-07-20 2019-01-24 Tdk Electronics Ag Electrical component with solder connection
US10488062B2 (en) 2016-07-22 2019-11-26 Ademco Inc. Geofence plus schedule for a building controller
US10534331B2 (en) 2013-12-11 2020-01-14 Ademco Inc. Building automation system with geo-fencing
US10895883B2 (en) 2016-08-26 2021-01-19 Ademco Inc. HVAC controller with a temperature sensor mounted on a flex circuit

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2418460A (en) * 1943-12-31 1947-04-08 Bell Telephone Labor Inc Resistor
US2720573A (en) * 1951-06-27 1955-10-11 Dick O R Lundqvist Thermistor disks
US3182118A (en) * 1962-04-19 1965-05-04 Philips Corp Method of providing contacts on semiconductive ceramic bodies of n-type oxidic material and contacts produced thereby
US3381081A (en) * 1965-04-16 1968-04-30 Cts Corp Electrical connection and method of making the same
US3452314A (en) * 1967-05-22 1969-06-24 Victory Eng Corp Low noise thermistor assembly and method
US3547835A (en) * 1969-06-09 1970-12-15 Du Pont Processes of producing and applying silver compositions,and products therefrom

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2418460A (en) * 1943-12-31 1947-04-08 Bell Telephone Labor Inc Resistor
US2720573A (en) * 1951-06-27 1955-10-11 Dick O R Lundqvist Thermistor disks
US3182118A (en) * 1962-04-19 1965-05-04 Philips Corp Method of providing contacts on semiconductive ceramic bodies of n-type oxidic material and contacts produced thereby
US3381081A (en) * 1965-04-16 1968-04-30 Cts Corp Electrical connection and method of making the same
US3452314A (en) * 1967-05-22 1969-06-24 Victory Eng Corp Low noise thermistor assembly and method
US3547835A (en) * 1969-06-09 1970-12-15 Du Pont Processes of producing and applying silver compositions,and products therefrom

Cited By (32)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4058701A (en) * 1974-05-14 1977-11-15 Schoeller & Co. Elektrotechnische Fabrik Gmbh & Co. Glow element arrangement for electric cigarette lighters
EP0001750A1 (en) * 1977-10-27 1979-05-16 Siemens Aktiengesellschaft Method for affixing a terminal conductor onto an electrical PTC resistor
US4827634A (en) * 1984-08-29 1989-05-09 Murata Manufacturing Co., Ltd. Three-terminal capacitor
EP0193854A1 (en) * 1985-03-07 1986-09-10 Siemens Aktiengesellschaft Electrical resistance having a negative temperature coefficient, and production process therefor
US4695818A (en) * 1985-03-07 1987-09-22 Siemens Aktiengesellschaft Electrical resistor with a negative temperature coefficient for incremental resistance values and method for manufacturing same
US4685025A (en) * 1985-03-14 1987-08-04 Raychem Corporation Conductive polymer circuit protection devices having improved electrodes
US4746784A (en) * 1985-06-11 1988-05-24 Littelfuse-Tracor, B.V. Method of attaching a lead to a metal end cap of a safety fuse
US4714910A (en) * 1986-04-23 1987-12-22 Siemens Aktiengesellschaft Electrical component having high strength given stressing due to temperature change and due to surge currents, particularly a varistor
EP0243602A1 (en) * 1986-04-23 1987-11-04 Siemens Aktiengesellschaft Electric component having a higher solidity versus temperature variations and current pulses, especially a varistor
US4730102A (en) * 1986-09-15 1988-03-08 Gte Products Corporation Electroceramic heating devices
US5117089A (en) * 1990-04-02 1992-05-26 Emerson Electric Co. Structural support for hermetic terminal assembly heater apparatus
US5557251A (en) * 1993-03-29 1996-09-17 Murata Manufacturing Co., Ltd. Thermistor with electrodes for preventing inter-electrode migration
US6177857B1 (en) * 1995-01-26 2001-01-23 Murata Manufacturing Co., Ltd. Thermistor device
US6150918A (en) * 1995-05-03 2000-11-21 Bc Components Holdings B.V. Degaussing unit comprising one or two thermistors
US20060208848A1 (en) * 1999-04-09 2006-09-21 Murata Manufacturing Co., Ltd. Method of producing temperature sensor and mounting same to a circuit board
US7075407B1 (en) * 1999-04-09 2006-07-11 Murata Manufacturing Co., Ltd. Temperature sensor
US7193498B2 (en) 1999-04-09 2007-03-20 Murata Manufacturing Co., Ltd. Method of producing temperature sensor and mounting same to a circuit board
US7164341B2 (en) * 2000-10-24 2007-01-16 Murata Manufacturing Co., Ltd. Surface-mountable PTC thermistor and mounting method thereof
US20040218329A1 (en) * 2003-05-02 2004-11-04 Tyco Electronics Corporation Circuit protection device
US7148785B2 (en) * 2003-05-02 2006-12-12 Tyco Electronics Corporation Circuit protection device
US10534331B2 (en) 2013-12-11 2020-01-14 Ademco Inc. Building automation system with geo-fencing
US10591877B2 (en) 2013-12-11 2020-03-17 Ademco Inc. Building automation remote control device with an in-application tour
US10649418B2 (en) 2013-12-11 2020-05-12 Ademco Inc. Building automation controller with configurable audio/visual cues
US10712718B2 (en) 2013-12-11 2020-07-14 Ademco Inc. Building automation remote control device with in-application messaging
US10768589B2 (en) 2013-12-11 2020-09-08 Ademco Inc. Building automation system with geo-fencing
US10488062B2 (en) 2016-07-22 2019-11-26 Ademco Inc. Geofence plus schedule for a building controller
US10895883B2 (en) 2016-08-26 2021-01-19 Ademco Inc. HVAC controller with a temperature sensor mounted on a flex circuit
WO2019016076A1 (en) * 2017-07-20 2019-01-24 Tdk Electronics Ag Electrical component having a solder connection
DE102017116381A1 (en) * 2017-07-20 2019-01-24 Tdk Electronics Ag Electrical component with solder connection
CN110914929A (en) * 2017-07-20 2020-03-24 Tdk电子股份有限公司 Electrical component with soldered connection
US10770204B2 (en) 2017-07-20 2020-09-08 Tdk Electronics Ag Electrical device with soldered joint
CN110914929B (en) * 2017-07-20 2022-07-29 Tdk电子股份有限公司 Electrical component with soldered connection

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