US3788997A - Resistance material and electrical resistor made therefrom - Google Patents

Resistance material and electrical resistor made therefrom Download PDF

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US3788997A
US3788997A US00209139A US3788997DA US3788997A US 3788997 A US3788997 A US 3788997A US 00209139 A US00209139 A US 00209139A US 3788997D A US3788997D A US 3788997DA US 3788997 A US3788997 A US 3788997A
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resistance material
titanium
resistance
tantalum carbide
resistor
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US00209139A
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G Mackenzie
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Northrop Grumman Space and Mission Systems Corp
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TRW Inc
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
    • H01C17/06—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base
    • H01C17/065—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base by thick film techniques, e.g. serigraphy
    • H01C17/06506—Precursor compositions therefor, e.g. pastes, inks, glass frits
    • H01C17/06513—Precursor compositions therefor, e.g. pastes, inks, glass frits characterised by the resistive component
    • H01C17/0652—Precursor compositions therefor, e.g. pastes, inks, glass frits characterised by the resistive component containing carbon or carbides

Definitions

  • a resistance material including a mixture of a glass frit and finely divided particles of tantalum carbide and titanium.
  • the resistance material is adapted to be applied to and fired on a substrate to form an electrical resistor which will readily fuse or open when subjected to an overload to prevent excessive overheating of the resistor.
  • SPECIFICATION comprises a mixture of a glassfrit and finely divided particles of a conductive material.
  • the mixture is applied to the, surface of a ceramic substrate and fired.
  • a film ofglass having the particles of the conductive material dispersed throughout the glass film.
  • the resistance material film is generally in the form of an elongated, narrow path.
  • the resistance material film is generally coated with a plastic material to protect it from mechanical damage and from. moisture and other contaminates in the atmosphere.
  • the invention accordingly comprises a composition of matter and the product formed therewith possessing the characteristics, properties and relation of constituents which will be exemplified in the composition hereinafter described, and the scope of the invention will be indicated in the claims.
  • the drawing is a cross-sectional view, on a highly exaggerated scale, of a portion of a resistor made from the resistance material of the present invention.
  • the vitreous enamel resistance material of the present invention comprises a mixture of a glass frit and finely divided particles of a mixture of tantalum carbide (TaC) and titanium (Ti).
  • finely divided particles it is meant an average particle size of not greater than about 5 microns.
  • the mixture of the tantalum carbide and titanium is present in the resistance material in the amount of 10% to by weight.
  • the ratio of the tantalum carbide to titanium in the resistance material may be varied depending on the resistivity and temperature coefiicient of resistance desired for the resistance material. Increasing the amount of the tantalum carbide with respect to the amount of titanium inthe resistance material will increase the resistivity and will make the temperature coeflicient of resistance more positive.
  • a desired temperature coefiicient of resistance canbe obtained at a desired resistivity of the resistance material.
  • the glass frit used in the resistance material of the present invention may be of any well known composition which has a softening point below that of the tantalum carbide and titanium.
  • the glass frits preferably used are the borosilicate frits, such as lead borosilicate frit, bis muth, cadmium, barium, calcium or other alkaline earth borosilicate frits.
  • the preparation of such glass frits is well known and consists, for example, of melting together the constituents of the glass in the form of the oxides of the constituents, and pouring such molten composition into water to form the frit.
  • the batch ingredients may, of course, be any compound that will yield the desired oxides under the usual conditions of frit production.
  • boric oxide will be obtained from boric aicd
  • barium oxide will be produced from barium carbonate, etc.
  • the coarse frit is preferably milled in a ball mill with water to reduce the particle size of the frit andto obtain 'a'frit'bf'subs'tantially uniform size.
  • tantalum carbide and titanium are each pre-milled to produce each of those materials in'p'owdered form of the desired particle size.
  • the tantalum carbide, titanium and glass frit in the desired proportionsto achieve a resistance material of the desired resistivity and temperature coefiicient of resistance are then throughly mixed together, such as by ball milling in water or an organic medium such as butyl carbitol acetate.
  • the viscosity of the mixture- is adjusted such as by removing or adding the liquid medium, to the proper viscosity for the desired manner of. applying the resistance material to make a resistor.
  • the resistance material is applied in a uniform thickness on the surface of a ceramic body.
  • the ceramic body may be comprised of any ceramic material which can withstand the firing temperature of the resistance material composition.
  • the ceramic body may be glass, alumina, steatite, porcelain, barium titanate or the like.
  • the resistance material may be coated on the ceramic body by brushing, dipping, spraying or screen stencil application.
  • the ceramic body and resistance material coating is then fired in a conventional furnace at a temperature at which the glass frit softens but less than the melting temperature of the tantalum carbide and titanium.
  • the resistance material is preferably fired in a nonoxidizing atmosphere, such as argon, helium or nitrogen.
  • the vitreous enamel hardens to bond the resistance material to the ceramic body.
  • the titanium reacts with the glass of the frit to form semiconducting suboxides of titanium, TiOx.
  • the conducting particles in the fired resistance material are tantalum carbide and the titanium oxide.
  • the titanium particles are not completely converted to the suboxides and relic titanium structures remain in the material.
  • the starting material can also include the suboxides of titanium in place of part or all of the titanium metal to produce the resistors with the desired characteristics.
  • Resistor 10 comprises a ceramic body 12 having a layer 14 of the resistance material coated on a surface thereof.
  • the resistance material layer 14 comprises a glass matrix 16 having the tantalum carbide particles 18 and the TiO particles 20 embedded in and dispersed throughout the glass matrix 16.
  • Table I shows, the electrical characteristics, i.e. resistance and temperature coeflicient of resistance, of a number of resistors of the present invention having various total amounts of the tantalum carbide and titanium and various ratios of the tantalum carbide to titanium.
  • the resistors were made in the manner described above, and the firing temperature and time are also shown in Table I.
  • Table II shows the electrical characteristics of 'a miniber of resistors of the present invention made with glass frits of diiferent compositions.
  • the total amount of tantalum carbide and titanium is 67% TABLE II Firing conditions Temp. coefl. of Resistrelistance Temp. Time, ance, Glass frit o 01 min. sz n 0. +15o 0.
  • the resistors of the present invention have very good flammability characteristics in that they do not excessively overheat when subjected to an overload. This good flammability characteristic is the result of the resistors quickly converting to a high resistance condition when subjected to an overload. For example, the resistors will fuse to an open circuit condition within approximately two seconds when subjected to 40 watts, and the fusing condition occurs more quickly as the wattage increases.
  • vitreous enamel resistance material and resistor made therefrom which can be provided over a wide range of resistance values, is relatively stable with regard to temperature, and has good flammability characteristics so that it'will not catch fire when subjected to an overload.
  • a vitreous enamel resistance composition adapted to be applied'to and fired on a substrate to form an electri: cal resistor consisting essentially of a glass frit and finely divided particles of tantalum carbide and particles containing titanium, the tantalum carbide and particles containing titanium being present in'the amount of between by weight and the ratio of tantalum carbide to titanium is 21:1 by volume.
  • the firing conditions are shown in Table I 10% and 75% by weight.
  • An electrical resistor having good flammability characteristics comprising a ceramic body having on a surface thereof a coating of a vitreous enamel resistor composition consisting essentially of finely divided particles of tantalum carbide and particles containing titanium embedded in 'aglass matrix the tantalum carbide and titanium containing particles being present in the amount of between 10% and 75% by weight.
  • An electrical resistor in accordance with claim 5 in which the tantalum carbide and titanium are present in the resistor composition in the amount of between 45% and 70% by weigh 8.
  • An electrical resistor in accordance with claim 7 2,693,521 11/1954 Alexander 117--22 in which the particles containing titanium include particles 3,277,020 10/1966 Rao 252-51 of an oxide of titanium. 3,001,893 9/1961 Kreuchen 11722 3,088,921 5/1963 Heischman 252-51 References Cited 5 ST P L. Primary Examiner 3,441,516 4/1969 Milligan et a1. 106-49 ESPOSITO, AssistantExaminer 3,394,087 7/1968 Huang et a1.

Abstract

A RESISTANCE MATERIAL INCLUDING A MIXTURE OF A GLASS FRIT AND FINELY DIVIDED PARTICLES OF TANTALUM CARBIDE AND TITANIUM. THE RESISTANCE MATERIAL IS ADAPTED TO BE APPLIED TO AND FIRED ON A SUBSTRATE TO FORM AN ELECTRICAL RESISTOR WHICH WILL READILY FUSE OR OPEN WHEN SUBJECTED TO AN OVERLOAD TO PREVENT EXCESSIVE OVERHEATING OF THE RESISTOR.

Description

Jan. 29, 1974 G. D. M KENZlE 3,788,997
RESISTANCE MATERIAL AND ELECTRICAL RESISTOR MADE THEREFROM 20 7/ TA N/UM oxms PARTICLES l4-RES/STANCEL 1 7 MATERIAL Filed Dec. 17, 1971 I8- TANTALUM CARBIDE PARTICLES l6- GLASS MATRIX INVENITOR GEORGE 0. MAC KENZ/E gMXMM ATTOR/VE'Y "United States Patent RESISTANCE MATERIAL AND ELECTRICAL RESISTOR MADE THEREFROM George D. MacKenzie, Maple Glen, Pa., assignor to TRW, Inc., Cleveland, Ohio Filed Dec. 17, 1971, Ser. No. 209,139 Int. Cl. B44d 1/02; H01b 5/04 US. Cl. 252-635 8 Claims ABSTRACT OF THE DISCLOSURE A resistance material including a mixture of a glass frit and finely divided particles of tantalum carbide and titanium. The resistance material is adapted to be applied to and fired on a substrate to form an electrical resistor which will readily fuse or open when subjected to an overload to prevent excessive overheating of the resistor.
SPECIFICATION comprises a mixture of a glassfrit and finely divided particles of a conductive material. The mixture is applied to the, surface of a ceramic substrate and fired. When cooled, there is provideda film ofglass having the particles of the conductive material dispersed throughout the glass film. To provide a resistor of a desired resistance value, the resistance material film is generally in the form of an elongated, narrow path. Also, the resistance material film is generally coated with a plastic material to protect it from mechanical damage and from. moisture and other contaminates in the atmosphere.
, In the use of such vitreous enamel resistors a problem has arisen when the resistors are subjected to overload conditions. All resistors, including those made with vitreous enamel resistance materials, heat up when placed under a load in use. The higher the'load the hotter. the resistors will become. It has been found that resistors 'made with the vitreous enamel resistance materials when subjected to overload conditions heat up to such an extent that they can cause the protective coatings or other flammable material near the resistor to catch fire. To prevent i such a dangerous condition from occurring, it would be sistor made therefrom'which can be made over a wide range-of resistance-values with stable resistance characteristics and which will not excessively overheat when subjected to an overload condition.
It is a furtherobject ofthe present invention to provide a vitreous enamel resistancematerial and aresistor made therefrom which will fuse or open to a high resistance condition when subjected to an overload condition, so as to prevent excessive overheating of the resistor.
Other objects will appear hereinafter.
The invention accordingly comprises a composition of matter and the product formed therewith possessing the characteristics, properties and relation of constituents which will be exemplified in the composition hereinafter described, and the scope of the invention will be indicated in the claims.
The drawing is a cross-sectional view, on a highly exaggerated scale, of a portion of a resistor made from the resistance material of the present invention.
In general, the vitreous enamel resistance material of the present invention comprises a mixture of a glass frit and finely divided particles of a mixture of tantalum carbide (TaC) and titanium (Ti). By finely divided particles it is meant an average particle size of not greater than about 5 microns. The mixture of the tantalum carbide and titanium is present in the resistance material in the amount of 10% to by weight. The ratio of the tantalum carbide to titanium in the resistance material may be varied depending on the resistivity and temperature coefiicient of resistance desired for the resistance material. Increasing the amount of the tantalum carbide with respect to the amount of titanium inthe resistance material will increase the resistivity and will make the temperature coeflicient of resistance more positive. Thus, by adjusting the ratio of the amount of tantalum carbide to the amount of titanium and varying the amount of the conductive mixture in the resistance material, a desired temperature coefiicient of resistance canbe obtained at a desired resistivity of the resistance material.
The glass frit used in the resistance material of the present invention may be of any well known composition which has a softening point below that of the tantalum carbide and titanium. The glass frits preferably used are the borosilicate frits, such as lead borosilicate frit, bis muth, cadmium, barium, calcium or other alkaline earth borosilicate frits. The preparation of such glass frits is well known and consists, for example, of melting together the constituents of the glass in the form of the oxides of the constituents, and pouring such molten composition into water to form the frit. The batch ingredients may, of course, be any compound that will yield the desired oxides under the usual conditions of frit production. For example, boric oxide will be obtained from boric aicd, barium oxide will be produced from barium carbonate, etc. The coarse frit is preferably milled in a ball mill with water to reduce the particle size of the frit andto obtain 'a'frit'bf'subs'tantially uniform size.
To make the resistance material of the present invention, commercially available tantalum carbide and titanium are each pre-milled to produce each of those materials in'p'owdered form of the desired particle size. The tantalum carbide, titanium and glass frit in the desired proportionsto achieve a resistance material of the desired resistivity and temperature coefiicient of resistance are then throughly mixed together, such as by ball milling in water or an organic medium such as butyl carbitol acetate. After the ingredients are blended, the viscosity of the mixture-is adjusted such as by removing or adding the liquid medium, to the proper viscosity for the desired manner of. applying the resistance material to make a resistor.
To make a resistor with the resistance material of the present invention, the resistance material is applied in a uniform thickness on the surface of a ceramic body. The ceramic body may be comprised of any ceramic material which can withstand the firing temperature of the resistance material composition. For example, the ceramic body may be glass, alumina, steatite, porcelain, barium titanate or the like. The resistance material may be coated on the ceramic body by brushing, dipping, spraying or screen stencil application. The ceramic body and resistance material coating is then fired in a conventional furnace at a temperature at which the glass frit softens but less than the melting temperature of the tantalum carbide and titanium. The resistance material is preferably fired in a nonoxidizing atmosphere, such as argon, helium or nitrogen. When the ceramic body and resistance material are cooled, the vitreous enamel hardens to bond the resistance material to the ceramic body. When the resistance material is fired, the titanium reacts with the glass of the frit to form semiconducting suboxides of titanium, TiOx. Thus, the conducting particles in the fired resistance material are tantalum carbide and the titanium oxide. In many cases, the titanium particles are not completely converted to the suboxides and relic titanium structures remain in the material. The starting material can also include the suboxides of titanium in place of part or all of the titanium metal to produce the resistors with the desired characteristics.
Referring to the drawing, there is shown a resistor, generally designated as 10, made from the resistance material of the present invention. Resistor 10 comprises a ceramic body 12 having a layer 14 of the resistance material coated on a surface thereof. The resistance material layer 14 comprises a glass matrix 16 having the tantalum carbide particles 18 and the TiO particles 20 embedded in and dispersed throughout the glass matrix 16.
Table I shows, the electrical characteristics, i.e. resistance and temperature coeflicient of resistance, of a number of resistors of the present invention having various total amounts of the tantalum carbide and titanium and various ratios of the tantalum carbide to titanium. The resistors were made in the manner described above, and the firing temperature and time are also shown in Table I.
TABLE I Temp. coefi. of Weight Firing conditions resistance, percent Resistp.p.m./ O. of TaG TaC/Ti Temp., Time, ance, and Ti (volume) C. min. fl/El 55 C. +150 0.
1/1 1, 150 30 89 682 507 1/1 1, 100 30 20. 5K 1, 215 846 1/1 1, 100 30 5. M 4, 233 2, 110 2/1 1, 150 60 5. +150 +130 2/1 1, 100 14 +73 +66 2/1 1, 150 30 6 +89 +83 1/1 1, 100 30 100 76 1/1 1, 150 30 9 ----144 -112 2/1 1, 100 30 56 i154 2. 5/1 1, 100 30 100 =l=30 :|:23 3/1 1, 100 30 495 3:16 :|=9
From Table I it appears that the optimum range of tantalum carbide and titanium is between 45% and 70% by weight of the composition for producing minimized temperature coefiicient of resistance characteristics for the resistors.
Table II shows the electrical characteristics of 'a miniber of resistors of the present invention made with glass frits of diiferent compositions. In each of these resistors the total amount of tantalum carbide and titanium is 67% TABLE II Firing conditions Temp. coefl. of Resistrelistance Temp. Time, ance, Glass frit o 01 min. sz n 0. +15o 0.
Ma nesimn borosilicite 1, 100 30 14 +73 +66 28 13 E23 E22 b silicate--. 1, 100 b d l f f? 1, 150 30 18 -174 188 Banum boroalumk 1, 100 30 24 -718 459 1, 150 37 817 581 The resistors of the present invention have very good flammability characteristics in that they do not excessively overheat when subjected to an overload. This good flammability characteristic is the result of the resistors quickly converting to a high resistance condition when subjected to an overload. For example, the resistors will fuse to an open circuit condition within approximately two seconds when subjected to 40 watts, and the fusing condition occurs more quickly as the wattage increases. Thus, there is provided by the present invention a vitreous enamel resistance material and resistor made therefrom which can be provided over a wide range of resistance values, is relatively stable with regard to temperature, and has good flammability characteristics so that it'will not catch fire when subjected to an overload.
It should be understood that the examples of the resistors and resistance materials of the present invention shown in Tables I and II are given merely to illustrate certain details of the invention, and are not to be taken as in any way limiting the invention thereto; The present invention may be embodied in other specific forms Without departing from the spirit or essential attributes thereof, and, accordingly, reference should be made to the append ing claims, rather than to the foregoing specification,'as indicating the scope of the invention.
I claim: I
1. A vitreous enamel resistance composition adapted to be applied'to and fired on a substrate to form an electri: cal resistor consisting essentially of a glass frit and finely divided particles of tantalum carbide and particles containing titanium, the tantalum carbide and particles containing titanium being present in'the amount of between by weight and the ratio of tantalum carbide to titanium is 21:1 by volume. The firing conditions are shown in Table I 10% and 75% by weight. I
2. A vitreous enamel resistance composition in accordance with claim 1 in which the particles containing titanium include particles of an oxide of titanium.
3. A vitreous enamel resistance composition in accordance with claim 1 in which the tantalum carbide and titanium are present in the amount of between 45% and 70% by weight.
4. A vitreous enamel resistance composition in accordance with claim 3 in which the particles containing titanium include particles of an oxide of titanium.
5. An electrical resistor having good flammability characteristics comprising a ceramic body having on a surface thereof a coating of a vitreous enamel resistor composition consisting essentially of finely divided particles of tantalum carbide and particles containing titanium embedded in 'aglass matrix the tantalum carbide and titanium containing particles being present in the amount of between 10% and 75% by weight.
6. An electrical resistor in accordance with claim 5 in which .the particles containing titanium include particles of an oxide of titanium. I
7. An electrical resistor in accordance with claim 5 in which the tantalum carbide and titanium are present in the resistor composition in the amount of between 45% and 70% by weigh 8. An electrical resistor in accordance with claim 7 2,693,521 11/1954 Alexander 117--22 in which the particles containing titanium include particles 3,277,020 10/1966 Rao 252-51 of an oxide of titanium. 3,001,893 9/1961 Kreuchen 11722 3,088,921 5/1963 Heischman 252-51 References Cited 5 ST P L. Primary Examiner 3,441,516 4/1969 Milligan et a1. 106-49 ESPOSITO, AssistantExaminer 3,394,087 7/1968 Huang et a1. 10648 3,180,841 4/1965 Murphy 252 516 2,851,376 9/1958 Adlassnig 106-48 10648, 49; 117-421; 252-516 3,503,801 3/1971 Huang et a1. 117-221
US00209139A 1971-12-17 1971-12-17 Resistance material and electrical resistor made therefrom Expired - Lifetime US3788997A (en)

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AU (1) AU461020B2 (en)
CA (1) CA950057A (en)
DE (1) DE7237312U (en)
DK (1) DK135357B (en)
FR (1) FR2163438B1 (en)
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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3912668A (en) * 1974-06-17 1975-10-14 Ibm Conductive paint formulations with very low electrical impedance in the Z-direction containing a metal carbide
US4084974A (en) * 1977-07-22 1978-04-18 Corning Glass Works Method of making light-absorbing glass-ceramic articles
US4272411A (en) * 1979-03-08 1981-06-09 Electric Power Research Institute Metal oxide varistor and method
US4724021A (en) * 1986-07-23 1988-02-09 E. I. Du Pont De Nemours And Company Method for making porous bottom-layer dielectric composite structure
US5248452A (en) * 1989-07-11 1993-09-28 Ngk Insulators, Ltd. Process for manufacturing a voltage non-linear resistor
US5250281A (en) * 1989-07-11 1993-10-05 Ngk Insulators, Ltd. Process for manufacturing a voltage non-linear resistor and a zinc oxide material to be used therefor
US5269971A (en) * 1989-07-11 1993-12-14 Ngk Insulators, Ltd. Starting material for use in manufacturing a voltage non-linear resistor

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4205298A (en) * 1978-11-20 1980-05-27 Trw Inc. Resistor material, resistor made therefrom and method of making the same
US4299887A (en) * 1979-05-07 1981-11-10 Trw, Inc. Temperature sensitive electrical element, and method and material for making the same
US4655965A (en) * 1985-02-25 1987-04-07 Cts Corporation Base metal resistive paints
DE3625087A1 (en) * 1986-07-24 1988-01-28 Ego Elektro Blanc & Fischer ELECTRIC COMPONENT

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3912668A (en) * 1974-06-17 1975-10-14 Ibm Conductive paint formulations with very low electrical impedance in the Z-direction containing a metal carbide
US4084974A (en) * 1977-07-22 1978-04-18 Corning Glass Works Method of making light-absorbing glass-ceramic articles
US4272411A (en) * 1979-03-08 1981-06-09 Electric Power Research Institute Metal oxide varistor and method
US4724021A (en) * 1986-07-23 1988-02-09 E. I. Du Pont De Nemours And Company Method for making porous bottom-layer dielectric composite structure
US5248452A (en) * 1989-07-11 1993-09-28 Ngk Insulators, Ltd. Process for manufacturing a voltage non-linear resistor
US5250281A (en) * 1989-07-11 1993-10-05 Ngk Insulators, Ltd. Process for manufacturing a voltage non-linear resistor and a zinc oxide material to be used therefor
US5269971A (en) * 1989-07-11 1993-12-14 Ngk Insulators, Ltd. Starting material for use in manufacturing a voltage non-linear resistor

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DE2249817A1 (en) 1973-07-05
JPS4867798A (en) 1973-09-17
GB1410210A (en) 1975-10-15
DE7237312U (en) 1977-04-21
DK135357C (en) 1977-09-26
AU4623072A (en) 1974-03-07
DE2249817B2 (en) 1976-05-13
SE390297B (en) 1976-12-13
DK135357B (en) 1977-04-12
JPS5219677B2 (en) 1977-05-30
CA950057A (en) 1974-06-25
IT975165B (en) 1974-07-20
AU461020B2 (en) 1975-05-15
FR2163438A1 (en) 1973-07-27
FR2163438B1 (en) 1976-04-23

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