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Publication numberUS2220961 A
Publication typeGrant
Publication dateNov 12, 1940
Filing dateNov 6, 1937
Priority dateNov 6, 1937
Publication numberUS 2220961 A, US 2220961A, US-A-2220961, US2220961 A, US2220961A
InventorsKern Emerson W
Original AssigneeBell Telephone Labor Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Soldering alloy
US 2220961 A
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Description  (OCR text may contain errors)

Patented Nov. 12, 1940 UNITED STATES soLDERiNG-ALLov Emerson W. Kern, New York, N. Y., assignor to Bell Telephone. Laboratories, Incorporated, New York, N. Yr, a corporation of New York No Drawing. Application November 6, 1937,

Serial No. 173,149 U 2 Claims.

This invention relates to alloys and their use and more particularly to alloys which are suitable for soldering to thin metal objects, such as metallic films or coatings and fine wires.

Heretofore difiiculty has been experienced in soldering metal bodies to thin metallic films or coatings or fine wires with the soldering alloys known to the art. It has been found to be particularly difficult to solder a metallic member to a thin metal film or coating, for example, of silver or gold, and such an attempt often has resulted in the destruction of the thin metal surface. Various expedients have been employed to prevent the destruction of the thin metal but none have been wholly satisfactory.

The primary object of the invention is to prevent the destruction of thin metallic films or fine Wires by soldering operations.

Another object of the invention is to inhibit solution of the film or Wire component in the solder.

A further object of the invention is to form alloys for soldering which do not attack the surface to which a metal is soldered.

Other and further objects and features of the invention will be apparent from the following description of certain exemplary embodiments thereof.

A feature of the invention is an improved method of soldering a metal object to a thin metallic coating, film, or filament by first saturating or partially saturating the solder with the same metal as that of the thin metal part, thereby preventing destruction thereof by absorption in the solder.

A study of the pertinent phase diagrams in connection with successful operations with certain soldering alloys indicates that there is a group of low melting point metals (under 350 degrees C.) in which a second group of higher melting point metals (above 700 degrees C.) are only slightly soluble and dissolve without destroying the fluidity of the metals of the first group. Exemplary of the first group are: lead, tin, bismuth, thallium and cadmium; and of the second group: silver, gold, platinum, copper and nickel. It, therefore, appears that where it is desired to solder to thin bodies of metal of the higher-melting-point group, a successful operation results when the solder comprises one or more metals of the low-melting-point group saturated or partially saturated with the same metal as that of the thin body.

In carrying out the teachings of this invention it has been found that by saturating a lead solder at working temperature with silver, the above-described difficulties are overcome. By the use of a saturated solution of the lead-silver alloy, the solution of the thin film of silver at the working temperature of the solder is prevented. 5 A lead-silver solder having a 7 per cent silver content may be employed to solder to a thin film of silver without dissolving the thin film. However, when the concentration of the silver is below 1 per cent, the solder dissolves the thin 19 film.

In the case of a tin-silver solder at the working temperature of the solder, the phase diagram shows a tin-silver compound of the composition AgsSn. Experiments with a 7 per cent silver-tin solder, at which composition silver is in the form of the above compound, indicate that the solution of the thin film of silver is inhibited to such an extent that the alloy could be satisfactorily used for soldering to thin silver films. so

It appears that the above-noted difficulty in the use of ordinary solder is due to the thin silver surface being absorbed by the molten solder. In the lead-silver solder of this invention, since it is already substantially saturated with 2 silver, the silver surface does not flow into the solder, and in the case of the tin-silver solder, the rate of solution is so inhibited by bringing the silver into equilibrium with the tin-silver compound that successful soldering operations result.

Advantages in certain cases have been found by employing an alloy solder of lead and tin in the approximate ratio of 5 to 4 with from 1 to 13 per cent silver. The proper amount of silver 35 is a variable determined by the temperature at which the soldering is performed. A particular composition which produces good results for soldering a wire to a silver film is lead 50 parts, tin 40 parts and silver 10 parts. With this compo- 40 sition the soldering is done without destroying or harming the film.

Where it is desired to solder thin filaments or films of gold, alloys similar to those used for silver give good results. A lead-tin alloy having the lead and tin in the ratio of approximately 5 to 4 and the gold ranging from 1 to 13 per cent of the whole is satisfactory. Gold forms compounds with lead and tin as may be shown by 50 reference to phase diagrams. Once the solution has been saturated with gold, further rate of solution of the gold is inhibited so that a successful soldering operation may be performed. Using an alloy of lead 49.7 per cent, tin 39.8 per la cent and gold 10.5 per cent, a gold filament was soldered without harm to a gold film.

In soldering to thin films or filaments of copper similar means and methods may be employed. A suitable lead or tin or lead-tin solder is saturated or partially saturated with copper at or near the soldering temperature and the resulting alloy used to solder to the thin copper body. The proportions of copper may be varied from 1 to 13 per cent with satisfactory results.

A thin film of copper has been successfully soldered by employing a lead-copper solution (eutectic 2 per cent copper) as the solder. The thin film of copper was not harmed in this operation. However, when lead alone was used as the solder, the film was damaged by the copper going into solution in the lead.

In soldering to thin films of platinum in accordance with this invention, a lead-platinum solder with the platinum in the range of from 1 to 13 per cent, is suitable. Employing a solder comprising 94 per cent lead and 6 per cent platinum in soldering to a thin film of platinum on glass, a satisfactory joint is obtained without harm to the film.

While the invention has been described with respect to several specific illustrative embodiments thereof, it is to be understood that it is not limited thereto but by the scope of the appended claims only.

What is claimed is:

1. A soldering composition composed of from 3 to 13 per cent of silver, 54 to 48 per cent lead and 43 to 39 per cent tin.

2. A soldering composition for use on a surface of gold, silver, or platinum, composed of 54 to 48 per cent lead, 43 to 39 per cent tin and 3 to 13 per cent of a metal corresponding to the surface to which the composition is to be applied.

EMERSON W. KERN.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2496052 *Mar 11, 1948Jan 31, 1950Lindsay Wire Weaving CompanySeam for woven wire fabric
US2585752 *May 26, 1948Feb 12, 1952Sprague Electric CoProduction of discontinuous, conducting coatings upon insulating surfaces
US2607981 *Aug 6, 1948Aug 26, 1952Gen ElectricQuartz to metal seal
US2611040 *Jun 23, 1947Sep 16, 1952Brunetti CledoNonplanar printed circuits and structural unit
US2671844 *Jul 26, 1951Mar 9, 1954Laubmeyer Guenther WTin solder
US2735050 *Oct 23, 1952Feb 14, 1956 Liquid soldering process and articles
US2838390 *Jun 1, 1954Jun 10, 1958Sylvania Electric ProdMethod of making metal-to-ceramic seals
US2856281 *Oct 5, 1954Oct 14, 1958Solar Aircraft CoHigh temperature brazing alloys
US2856681 *Aug 8, 1955Oct 21, 1958Texas Instruments IncMethod of fixing leads to silicon and article resulting therefrom
US3059329 *Oct 15, 1958Oct 23, 1962North American Philips Company IncMethod of soldering molybdenum foil
US3073269 *Dec 24, 1957Jan 15, 1963Gen ElectricMetallic brazing mixture
US3119172 *May 15, 1959Jan 28, 1964Martin N HallerMethod of making an electrical connection
US3225438 *Nov 22, 1960Dec 28, 1965Hughes Aircraft CoMethod of making alloy connections to semiconductor bodies
US3467765 *Oct 4, 1965Sep 16, 1969Contemporary Research IncSolder composition
US3523358 *Sep 26, 1967Aug 11, 1970Philips CorpProcess for producing a vacuum tight supra-conducting joint by diffusion soldering
US4268585 *Jun 1, 1978May 19, 1981Licentia Patent-Verwaltungs-G.M.B.H.Gold-tin intermediate layer, printed circuits
US4816219 *Jun 12, 1987Mar 28, 1989Nihon Speriasha Co., Ltd.Tin, bismuth, gallium, lead
DE975878C *Apr 29, 1941Nov 15, 1962Siemens AgVerfahren zur Verloetung duenner Edelmetallschichten mit anderen Metallteilen
DE976718C *Jan 8, 1955Mar 19, 1964Siemens AgVerfahren zum Anloeten elektrischer Anschluesse an eine Metallauflage, die auf einemim wesentlichen einkristallinen Halbleiter aufgebracht ist
DE1050450B *Apr 30, 1956Feb 12, 1959Westinghouse Electric CorpVerfahren zur Herstellung einer Silizium-Halbleiteranordnung mit Legierungselektroden
DE1165972B *Jul 15, 1959Mar 19, 1964Philips PatentverwaltungWeichlot auf Basis von Blei-Kadmium
DE1173769B *May 6, 1955Jul 9, 1964Dr Guenther LaubmeyerVerfahren zur Verringerung des Lotangriffes auf kupferne Loetwerkzeuge beim Loeten mit einem Weichlot
EP0638656A1 *Feb 3, 1993Feb 15, 1995World Metal Co., Ltd.Alloy to be plated, its plating method and plating solution
Classifications
U.S. Classification420/566, 219/85.2, 219/85.1, 228/262.6
International ClassificationB23K35/26
Cooperative ClassificationB23K35/268
European ClassificationB23K35/26E