US2309081A - Electrically conductive device - Google Patents

Description

1943. N. Y. PRIESSMAILI EIAL 2,309,031

ELECTRICALLY CONDUCTIVE DEVICE Filed Oct. 1, 1941 NJ. PR/EssMA/v MENTOR; J. WHVTOCK ATTGRNEV I Patented Jan. 26, 1943 I UNITED STATES PATENT" OFFICE ELECTRICALLY CONDUOTIVE DEVICE Neil Y. Priessman, Short Hills, N. J.', andJohn Whytock, Garden City, N. Y., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application October 1, 1941, Serial No. 413,186

2 Claims.

This application relates to conductive devicesand more particularly to such devices which include dry rectifier discs or similar elements having semiconductive portions.

Conductive devices, comprising assemblies including several dry rectifier discs or similar elements, have heretofore been made by assembling the discs or other elements on bolts and the like or in housings or containers. Such assemblies while useful for many purposes are relatively expensive and, in some cases, too bulkyfor someapplications.

It has been proposed to assemble conductive devices of this character by means of solder. However, this. practice is subject to certain limitations because only a low melting point solder can be safely employed. Temperatures sufficiently high to melt ordinary solders are injurious to the semiconductive portion or to the junction between a conductive and asemiconductive por- A feature of this invention resides in"a combined terminal and clamping means which in conjunction with a relatively weak, low melting point solder assures a rugged conductive device of the type described. I

Other and further objects and features of this invention will be understood more clearlyand fully .from the following description of an illustrative embodiment thereof, taken in connection with the appended drawing in which:

Fig. 1 is an elevational view of a conductive assembly embodying the invention; and,

Fig. 2 is a view of the same assembly taken at right angles to that of Fig. 1.

Referring to the drawing in and II are dry rectifier discs, e. g., cuprous oxide-copper rec- The cuprous oxide surfaces of tifier disc units. the discs should be provided with a suitable adherent, low resistance, substantially non-rectifytion of the elements used. For example, since it is known that cuprous oxide-copper rectifiers age rapidly at temperatures in the order of 100 C. it is inadvisable to solder such rectiflers at temperatures much higher than this because of the probability of excessive ageing or other damage thereto.

The low melting point of very soft solderswhich may be safely employed for assembling conductive devices of the type under consideration, are of relatively low strength. For this reason the assembled devices may not be sufiiciently rugged to maintain their required electrical characteristics over a-reasonable period of time, under the' conditions to which such devices may be subjected.

An example of the type of use contemplated is afforded by the so-called click reducer" employed in telephone sets. These devices which may comprise a small stack of cuprous oxidecopper rectifier discs,.are often, designed "to be housed within the ordinary handset. In view of space limitations, the compact device that canbe-j' ing contact. Such a' co'ntact may-be made by electrolytically or otherwise reducing the surface of the oxide to copper, or by vapor deposition of a metal, such as gold or silver, on said surface.

This contact is commonly called a front contact as distinguished from the copper face of the disc which is designated as the back. In the device illustrated, the front.contacts each face in the same direction. A terminal member has a disc or ring-like portion l2 betweenthe discs l0 and H and a connector portion I 3 projecting there- 7 from. An insulated conductor It provided with a terminal l9 may be secured, as by soldering to the connector portion [3.

Another terminal member has a connector portion I5 at one end and at the other a'U-shaped portion comprising substantially parallel, contacting elements l6 and lf'|';'and a part l8 connecting l6 and I! together. The part I 8' is sufficiently resilient and elements l6 and I! are so spaced, that a clamping action is-zexerted upon the stack comprising discsill and II and termi let-portion l2. The elements l2, l6 and I! "may" be provided with a= central orifice 2|, as indicated for the element, IS in Fig. 1, for a purpose to be described. Low melting point solder is interposed between all mating surfaces of the device.

follows? The discs l0 and II should be masked or otherwise protected over their edges to avoid deposition of solder thereon; Masking may be accomplished by means of a suitable adhesive tape or a coating of varnish, lacquer or the like. One.

of the lacquers made from cellulose derivatives would be suitable. The discs may then beplaced One method of assembling such a device is as in contact-with either face of terminal portion I2 and the U-shaped terminal l6-Ili8 forced over the assembly to hold the parts together.

The assembled parts are dipped into a bath of.

low melting point solder after suitable preparatory treatment. The solder coats the exposed metal portions of the device and seeps into the spaces therebetween. This seepage is encouraged around the contacting portions of the terminal members 12, I6 and H by the orifices 2i therein.

The parts may also be assembled by depositing sufficient amounts of solder on each of the surfaces to be soldered together. The parts may then be assembled as above indicated and dipped in a bath of hot water, alcohol, oil or other suitable material to melt the solder and secure the parts together.

After removal of the device from the soldering bath, the solder solidifies upon cooling and a rugged assembly results. The tendency of the solder to expand during cooling is to some extent resisted by the resilient clamping action of the outer terminal. Thus, the thin layers of solder between the parts are kept relatively dense and the parts are held in intimate ,contact. Moreover, .due to the clamping action, there is less tendency for the solder layers to work loose during expansion. In some cases there is also a tendency for the cooling solder to pull the front contact away from the cuprous oxide surface. This is overcome by the clamping action. A slight expansion of the solder also somewhat increases the gripping action of the outer terminal.

In the finished device the clamping action of the outer terminal added to the adhesive effect of the solder holds the parts together in a relatively strong assembly. The additional effect of the clamping terminal makes the difierence between an assembly that might fail mechanically due to the weakness of the solder and one that will stand a considerable strain because of the joint action of the solder and said clamping terminal.

Although a specific illustrative embodiment of the invention has been disclosed, it is to be understood that said invention is not limited thereby but by the scope of the appended claims only.

What is claimed is:

1. A conductive device comprising two cuprous oxide-copper rectifier discs, a terminal member having a flat portion between said discs and in electrical connection with the copper face of one disc and the oxide face of the other, a second terminal having a U-shaped portion embracing said discs, said U-shaped portion comprising two fiat substantially parallel elements making contact respectively to the oxide face of said one disc and the copper face of said other disc and a resilient portion interconnecting said fiat elements to urge them toward said disc faces, and solder having a melting point below about C. adhering to all mating surfaces of said device, said U-shaped terminal portion exerting a clamping force that in conjunction with the adhesive action of the solder is suificient to assure a rugged, self-supporting device.

2. A conductive device comprising two dry rectifier discs, a terminal member having a flat,

ring-like portion between said discs and a connector portion extending therefrom, another J-shaped, terminal member, the long arm of which comprises a connector portion and the hooked portion of which includes two flat substantially parallel ring-like sections connected together by a resilient U-shaped portion that urges the two flat portions toward each other to clamp the discs and first-named terminal member therebetween, and solder having a melting point below a temperature that would adversely affect the rectifier discs, said solder interposed in thin films between all mating surfaces of said conductive device.

NEIL Y. PRIESSMAN. JOI-lIN WI-IYTOCK.

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