US3016506A

US3016506A - Semi-conductive element

Info

Publication number: US3016506A
Application number: US5952A
Authority: US
Inventors: Rakowski Alexander Joseph; Rollins James Edgar; Jr John Conrad Zenobia
Original assignee: Specialties Development Corp
Current assignee: Specialties Development Corp
Priority date: 1960-02-01
Filing date: 1960-02-01
Publication date: 1962-01-09
Anticipated expiration: 1979-01-09
Also published as: GB909767A

Description

Jan. 9, 1962 A. J. RAKOWSKI ETAL 3,016,506

SEMI-CONDUCTIVE ELEMENT Filed Feb. 1, 1960 ATTORNEY Fatenteel Jan. 9, lQiiZ 3,016,506 SEMLQONDUTHVE ELEMENT Alexander ph Plalrewslri, Towaeo, .l'ames Prollins, Newark, and .l'ohn Conrad Zenobia, Sin, Helleville, NJL, assignors to Specialties Development @orporation, llelleviile, NJL, a. corporation or New .lersey Filed Feb. 1, 1960, Ser. No. 5,952 1 (Ilaim. (Cl. 333 212) The present invention relates to semi-conductive elements such as thermistors, and, more particularly, to the composition of the body of resistance material and the terminal wires for the body.

Previously, it has been found that such elements having desirable voltage insensitivity characteristics can be reproduced with predictable resistance values by placing a resistance material on platinum terminal wires. With the increased demand and uses for thermistor elements, it is desirable to reduce the cost thereof as greatly as possible. While certain improvements have been made in that direction, the relatively high cost of platinum wires has hindered further reduction in costs.

In an attempt to use less expensive terminal wires, such as wires formed of an alloy sold by The International Nickel Company, Inc., under the trademark lnconel and consisting essentially of between about 6% and about 17% by weight of iron, between about 11% and about 18% by weight of chromium and the balance nickel at a minimum of 70% by weight, it was found that the resistance material became voltage sensitive to the extent that it did not provide a satisfactory tremistor elements where a change in its resistance in excess of about 20% could not be tolerated.

Accordingly, an object of the present invention is to provide a resistance material which is sufficiently voltage insensitive to enable the same to be used with wires much less expensive than platinum wires and produce a satisfactory thermistor element.

Another object is to accomplish the foregoing in a simple, practical and economical manner.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claim, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice. I

In accordance with the present invention, it has been found the foregoing objects can be accomplished by producing a semi-conductor such as a thermistor element comprising a body formed of a resistance material consisting essentially of between about 50% and about 80% by weight of manganese dioxide and between about 50% and about 20% by weight of cobaltic oxide; and spaced parallel conductive terminal wires formed of Inconel.

In the drawing, the single figure is a greatly enlarged longitudinal sectional view of a semi-conductor such as a thermistor element embodying the present invention.

Referring to the drawing in detail, the element shown by Way of example comprises a cylindrical body or bead 10 having a. pair of spaced apart parallel terminal wires 11 embedded therein. This element has the following dimensions:

in. Body length 0.0625 Body diameter 0.0625 'Wire diameter 0.0100 Space between wires 0.0100

Suchelements are adapted to be used in networks with a potential of about one volt normally applied thereto.

2 EXAMPLE I An element having the foregoing dimensions was con- 'structed by forming the body 10 of thoroughly admixed line particles consisting essentially of 75% by weight of manganese dioxide and 25% by weight cobaltic oxide and by embedding wires ll therein formed of an alloy consisting essentially of 75% by weight nickel, 15% by weight chromium and by weight iron. The body 10 was fired to adhere the same onto the wires.

The element was tested by applying measured potentials only for a short duration to prevent appreciable self-heating effects, and measuring the resistance of the element with a bridge or a null detector.

The following readings were taken:

Table I Potential Percent Resist nce Percent Test N o. In Volts Change In In K Ohms Change In Potential Resistance 0. 3 70 295 plus 3.2. 0.6 40 293 plus 2.5. 1. 0 286 1. 5 50 280 minus 2.1. 2. 2 120 271 minus 5.2. 3.0 200 256 minus 10.5. 4. 5 350 236 minus 17.5. 6.0 500 225 minus 21.

EXAMPLE II For comparative purposes, an element was similarly constructed by forming the body of a mixture consisting essentially of 90% by weight of manganese oxide and 10% by weight of cupric oxide and embedding platinum wires therein. The element was similarly tested and the following readings were taken:

Table II Potential Percent Resistance Percent Test No. In Volts Change In In K Ohms Change In Potential Resistance 1..- 0. 3 70 20. 5 plus 1.4. 2 0.6 40 29. 3 plus 0.7.

1.0 29.1 1. 5 29.0 minus 0.4. 2. 2 120 28. 8 minus 1.0. 3.0 200 28. 5 minus 2.1. a. 5 350 27. 9 minus 4.1. 6.0 500 27. 5 minus 5.5.

These readings indicate that the element in accordance 50 with the present invention compares favorably with a manganese dtoxide-cupric oxide body on platinum wires where about a 20% change in resistance can be tolerated when the normal voltage increases about 500%.

EXAMPLE in Another element was similarly constructed by forming the body of a mixture of the material used in Example H and embedding wires therein formed of the same alloy used in Example I. This element was similarly tested and the following readings were taken:

with Example 111 is so voltage sensitive that its resistance decreases about 20% when the normal voltage increases only 200%.

Further cursory tests were made with materials respectively consisting essentially of 50% by weight of manganese dioxide and 50% by weight of cobaltic oxide; and 80% by weight of manganese dioxide and 20% by weight of cobaltic oxide. it was found that elements having a body. of such compositions and lncone wire embedded therein were sufficicntly voltage insensitive to enable the same to be used as thermistors.

Itwas further found that the compositions of the higher eobaltie oxide content exhibited greater voltage insensitivity than those of the lower cobaltic oxide content. However, the bodies formed of compositions having a 20% to 30% by weight cobal-tic oxide content have better structural characteristics.

The expressionfivoltage insensitivity and expressions of similar context mean that the resistance of the body material does not materially increase or decrease as the voltage applied across the terminal wires respectively decreases or increases. This effect is independent of changes in resistance due to the thermal coefiieient of resistivity of the element.

From the foregoing description, it will be seen that the present invention provides a thermistor body composition which permits the use of low cost terminal wires without causing undue voltage sensitivity.

It will be understood that the details and examples I hereinbefore set forth are illustrative only and that the invention as broadly described and claimed is in no way limited thereby.

A semi-conductor comprising a body formed of a re- References Cited inthe file of this patent UNiTED STATES PATENTS 2,329,511 Christensen Sept. 14, 1943 2,407,288 Kleimack et al. Sept. 10, 1946 2,414,793 Becker et al. Ian. 28, 1947 2,720,573 Lundquist Get. 11, 1956 2,871,197 Maclntyre et al. Jan. 27, 1959 2,936,434 1960 Postal May 10,