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Publication numberUS3503801 A
Publication typeGrant
Publication dateMar 31, 1970
Filing dateNov 29, 1967
Priority dateNov 29, 1967
Publication numberUS 3503801 A, US 3503801A, US-A-3503801, US3503801 A, US3503801A
InventorsHuang Cornelius Y D, Merz Kenneth M
Original AssigneeTrw Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Vitreous enamel resistance material and resistor made therefrom
US 3503801 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

March 31, 1970 c. Y. n. HUANG ETAL 3,

VITREQUS ENAMEL RESISTANCE MATERIAL-AND RESISTOR MADE THEREFRQM Filed NOV. 29, 1967 /4 RES/STANCE /5 MATERIAL ME TA 1. BUR/D E PART/C155 /2 CERAMIC SUBSTRATE 0 IN VEN TORS- CORNEL/US K0. HUANG KENNETH M. MERZ A TTORN' Y United States Patent 3,503,801 VITREOUS ENAMEL RESISTANCE MATERIAL AND RESISTOR MADE THEREFROM Cornelius Y. D. Huang, Bala Cynwyd, and Kenneth M.

Merz, Malvern, Pa., assignors to TRW Inc., a corporation of Ohio Filed Nov. 29, 1967, Ser. N 0. 686,592 Int. Cl. H01c 7/00 US. Cl. 117-221 2 Claims ABSTRACT OF THE DISCLOSURE A vitreous enamel resistance material comprising a mixture of a vitreous glass frit and fine particles of a metal boride of the transition elements of Groups IV, V and VI of the periodic chart. The metal boride may be chromium boride (CrB zirconium boride (ZrB molybdenum boride (MoB tantalum boride (TaB or titanium boride (TiBg). The metal boride is present in the vitreous enamel resistance material in the proportions of, by weight, 10% to 35% for chromium boride, to 50% for zirconium boride, 20% to 50% for molybdenum boride, 35% to 65% for tantalum boride and 20% to 50% for titanium boride. An electrical resistor is made with the vitreous enamel resistor material of the present invention by coating a ceramic substrate with the vitreous enamel resistance material and firing the coated substrate at a temperature sufiicient to melt the glass frit of the vitreous enamel resistance material. Upon cooling, the glass hardens so that the resultant resistor comprises the substrate having on the surface thereof a film of glass with the metal boride particles embedded in and dispersed throughout the glass film.

BACKGROUND A type of electrical resistance material which has recently come into commercial use is a vitreous enamel resistance material which comprises a mixture of a glass frit and finely divided particles of an electrical conductive material. The vitreous enamel resistance material is coated on the surface of a substrate of an electrical insulating material, usually a ceramic, and fired to melt the glass frit. When cooled, there is provided a film of glass having the conductive particles dispersed therein. Terminations are connected to the film to permit the resultant resistor to be connected in the desired circuit.

The materials which have been generally used for the conductive particles are the noble metals. Although the noble metals provide vitreous enamel resistance materials which have satisfactory electrical characteristics, they have the disadvantage that they are expensive. Thus, the resistors made from the vitreous enamel resistance materials containing the noble metals are expensive to manufacture. Therefore, it would be desirable to have a vitreous enamel electrical resistance material which utilizes a relatively inexpensive conductive material so as to provide an electrical resistor which is relatively inexpensive to manufacture. In addition, the conductive material used must be capable of providing a resistance material having a wide range of resistance values and which has relatively good electrical characteristics over the entire range of the resistance values. Such electrical characteristics include temperature coefficient of resistance, voltage coefficient, stability under load, etc.

SUMMARY It is an object of the present invention to provide a novel vitreous enamel resistance material utilizing a relatively inexpensive conductive material.-

It is another object of the present invention to provide "Ice an electrical resistor utilizing a novel vitreous enamel resistance material.

It is a further object of the present invention to provide a vitreous enamel electrical resistor having a relatively wide range of resistance values, which has relatively good electrical characteristics over the entire range of resistance values and which is relatively inexpensive to manufacture.

It is a still further object of the present invention to provide a vitreous enamel resistance material comprising a mixture of a glass frit and finely divided particles of a metal boride selected from the group consisting of molybdenum boride, titanium boride, zirconium boride, chromium boride and tantalum boride.

Other objects will appear hereinafter.

The invention accordingly comprises a composition of matter and 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.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a cross-sectional view, on a highly exaggerated scale, of a resistor produced in accordance with the present invention.

DESCRIPTION OF INVENTION In general, the vitreous enamel resistance material of the present invention comprises a mixture of a vitreous glass frit and fine particles of a metal boride of the transition elements of Groups IV, V and VI of the periodic chart. The metal boride can be molybdenum (MoB titanium boride (TiB zirconium boride (ZrB chr0- mium boride (CrB or tantalum boride (TaB In the vitreous enamel resistance material of the present invention, the metal boride of the above-stated group is present in the proportion of, by weight, 20% to 50% for molybdenum boride, 20% to 50% for titanium boride, 20% to 50% for zirconium boride, 10% to 35% for chromium boride, and 35% to 65 for tantalum boride.

The glass frit used in the resistance material of the present invention may be of any well-known composition which has a melting temperature below that of the refractory metal boride. The glass frits most preferably used are the borosilicate frits, such as lead borosilicate frit, bismuth, cadmium, barium, calcium or other alkaline earth borosilicate frits. The preparation of such glass frits is well-known and consists, for example, in 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 acid, silicon dioxide will be produced from flint, barium oxide will be produced from barium carbonate, etc. The glass is preferably milled in a ball-mill with water to reduce the particle size of the frit and to obtain a frit of substantially uniform size.

To make the resistance material of the present invention, the glass frit and refractory metal boride are broken down, such as by ball-milling, to a substantially uniform particle size. An average particle size of between 1 to 2 microns has been found to be preferable. The glass frit and refractory metal boride powder are thoroughly mixed together, such as by ball-milling in water or an organic medium, such as butyl carbitol acetate or a mixture of butyl carbitol acetate and toluol. The mixture is then adjusted to the proper viscosity for the desired manner of applying the resistance material to a substrate by either adding or removing the liquid medium of the material.

To make a resistor with the resistance material of the present invention, the resistance material is applied to a uniform thickness on the surface of a substrate. The substrate may be a body of any material which can withstand the firing temperature of the resistance material composition. The substrate is generally a body of a ceramic, such as glass, porcelain, refractory, barium titinate, or the like. The resistance material may be applied on the substrate by brushing, dipping, spraying or screen stencil application; The substrate with the resistance material coating is then fired in a conventional furnace at a temperature at which the glass frit becomes molten. For resistance materials of the present invention, it has been found preferable to fire the coated substrate in an inert atmosphere, such as argon, helium, nitrogen or a mixture of nitrogen and hydrogen, to achieve a resistor of better stability. When the coated substrate is cooled, the vitreous enamel hardens to bond the resistance material to the substrate.

As shown in the drawing, the resultant resistor of the present invention is generally designated as Resistor 10 comprises the ceramic substrate 12 having a layer 14 of the resistance material of the present invention coated and fixed thereon. The resistance material layer 14 comprises the glass 16 and the finely divided particles 18 of the metal boride embedded within and dispersed throughout the glass 16.

EXAMPLE I A plurality of resistance materials of the present invention were made in which the conductive material was molybdenum boride in the various amounts shown in Table I and the glass frit was a barium, titanium, aluminum borosilicate glass. Each of the resistance materials was'made by mixing together the glass frit and molybdenum boride particles in a ball-mill in butyl carbitol acetate. Resistors were made with each of the resistance materials by coating cylindrical ceramic bodies with the resistance material and firing the coated ceramic bodies in a furnace at approximately 900 C for thirty minutes. The resistors were fired in a nitrogen atmosphere. A number of resistors of each of the compositions were made, and the average resistance values and temperature coefiicient of resistance of the resulting resistors of. each group are shown in Table I.

A plurality of resistance materials of the present invention were made in which the conductive material was zirconium boride in the various amounts shown in Table II and the glass frit was a barium, titanium, aluminum borosilicate glass. Each of the resistance materials was made in the same manner as the resistance materials of Example I, and resistors were made with each of the resistance materials in the same manner as described in Example I. The resistors were fired at 1050" C. in a nitrogen atmosphere for thirty minutes and the average resistance values and temperature coefficient of resistance for each group of the resultant resistors are indicated in Table 11.

TABLE II Temperature Coef. of

Zirconium resistance (percent per C.)

boride Glass frit (percent by (percent by Resistance +25 C. to +25 C. to weight) weight) (ohms/El) 150 C. 55 C.

EXAMPLE III A plurality of resistance materials of the present invention were made in which the conductive material was chromium boride in the various amounts shown in Table III and the glass frit was a barium, titanium, aluminum borosilicate glass. Each of the resistance materials was made in the same manner as the resistance materials of Example I, and resistors were made with each of the resistance materials in the same manner as described in Example I. The resistors were fired at 850 C. in a nitrogen atmosphere for thirty minutes and the average resistance values and temperature coefiicient of resistance for each group of the resultant resistors are indicated in Table III.

A plurality of resistance materials of the present invention were made in which the conductive material was tantalum boride in the various amounts shown in Table IV and the glass frit was a barium, titanium, aluminum borosilicate glass. Each of the resistance materials was made in the same manner as the resistance materials of Example I, and resistors were made with each of the resistance materials in the same manner as described in Example I. The resistors were fired at 1050 C. in a nitrogen atmosphere for thirty minutes and the average resistance values and temperature coefficient of resistance for each group of the resultant resistors are indicated in Table IV.

A plurality of resistance materials of the present invention were made in which the conductive material was titanium boride in the various amounts shown in Table V and the glass frit was a barium, titanium, aluminum borosilicate glass. Each of the resistance materials was made in the same manner as the resistance materials of Example I, and resistors were made with each of the resistance materials in the same manner as described in Example I. The resistors were fired in a nitrogen atmosphere for thirty minutes with resistors containing 20% and 25% titanium boride being fired at a temperature of 1150 C. and the resistors containing 30% titanium boride being fired at 1100 C. The average resistance values and temperature coefficient of resistors for each group of the resultant resistors are indicated in Table V.

TABLE V Temperature Coei. of Titanium resistance (percent per C.) boride Glass frit (percent by (percent by Resistznce +25 C. to +25 C. to weight) weight) (ohms/E!) +150 C. 55 C.

It should be understood that the examples of the resistors and resistance materials of the present invention shown in Tables I through V 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 appending claims, rather than to the foregoing specification as indicating the scope of the invention.

We claim:

1. A vitreous enamel resistor composition adapted to be applied to and fired on a substrate to form an electrical resistor comprising a mixture of a glass frit and a finely divided metal boride selected from the group consisting of chromium boride, zirconium boride, molybdenum boride, tantalum boride and titanium boride,

wherein the metal boride is present in the proportions of, by weight, 10% to for chromium boride, 20% to for zirconium boride, 20% to 50% for molybdenum boride, 35% to for tantalum boride and 20% to 50% for titanium boride.

2. A vitreous enamel resistor composition in accordance with claim 1 in which the resistor composition is coated and fired on the surface of a ceramic body to provide a glass film having the metal boride particles embedded in and dispersed throughout the glass film.

References Cited UNITED STATES PATENTS 2,822,302 2/1958 McCaughna 1l7-221 WILLIAM L. JARVIS, Primary Examiner US. Cl. X.R.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2822302 *Jan 16, 1956Feb 4, 1958Radio Mfg Company IncNon-emissive electrode
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3943168 *Nov 13, 1974Mar 9, 1976E. I. Du Pont De Nemours And CompanyConductor compositions comprising nickel borides
US4016447 *Aug 8, 1975Apr 5, 1977E. I. Du Pont De Nemours And CompanyDielectric substrate bearing nickel boride conductor
US4039997 *Apr 2, 1976Aug 2, 1977Trw Inc.Resistance material and resistor made therefrom
US4093771 *Oct 29, 1976Jun 6, 1978NasaReaction cured glass and glass coatings
US4101799 *Sep 8, 1976Jul 18, 1978U.S. Philips CorporationHigh-pressure gas discharge lamp
US4271236 *Oct 29, 1979Jun 2, 1981E. I. Du Pont De Nemours And CompanyAir fireable end termination compositions for multilayer capacitors based on nickel borides
US4296309 *May 15, 1978Oct 20, 1981Canon Kabushiki KaishaThermal head
US4545881 *Nov 16, 1983Oct 8, 1985Canon Kabushiki KaishaReactive sputtering of elemental metal and diborane to form metal boride layer
US4645621 *Dec 17, 1984Feb 24, 1987E. I. Du Pont De Nemours And CompanyThick film for firing in low oxygen nitrides, oxynitrides, nonreducing glass blends
US4652397 *Dec 17, 1984Mar 24, 1987E. I. Du Pont De Nemours And CompanyResistor compositions
US4657699 *Dec 17, 1984Apr 14, 1987E. I. Du Pont De Nemours And CompanyThick films of semiconductive materials and glass in an organic medium
US5196915 *Nov 17, 1989Mar 23, 1993Hitachi, Ltd.Semiconductor device
US5518778 *Mar 16, 1995May 21, 1996Aerospatiale Societe Nationale IndustrielleSingle-layer high temperature coating on a ceramic substrate and its production
EP0134037A2 *Aug 18, 1984Mar 13, 1985E.I. Du Pont De Nemours And CompanyHexaboride resistor composition
Classifications
U.S. Classification428/427, 252/507, 338/308, 65/60.51, 252/520.22, 252/521.4
International ClassificationC23C30/00, H01C17/06, H01C17/065
Cooperative ClassificationC23C30/00, H01C17/06566
European ClassificationC23C30/00, H01C17/065B2L