US2447979A - Copper base alloy for metal evaporation - Google Patents

Description

F. R.H ENsE| Erm. 2,447,979

COPPER BASE ALLOY FOR METAL EYAPORATION Aug. 24, 1948.

Filed July e. 1944 .T0 Mrz/UM PUMP P/mq/v/ 60,465

Hrm/P NEY Patented Aug. 24, 1948 COPPER BASE ALLOY FOR METAL EVAPORATION Franz R. Hensel and Earl I. Larsen, Indianapolis, Ind., assignors to P. R. Mallory & Co., Inc., Indianapolis, Ind., a corporation of Delaware Application July 6, 1944, Serial No. 543,634

2V Claims. (Cl. 75-153) This invention relates to improvements in metal evaporation.

An object of the invention is to improve the evaporation of copper and its alloys.

Other objects of the invention will be apparent from the description and claims.

Figure 1 is a sectional elevation of a metal evaporation apparatus;

Figure 2 is a fragmentary cross-section of the tungsten filament coated with the metal to be evaporated; and

Figure 3 shows a wire loop of the metal.

The vaporization process for depositing silver, copper and other metals has been known for some time and used commercially to some extent. The processing as applied to silver is described in considerable detail in the book Silver in Industry edited by Lawrence Addicks (Reinhold 1940), pages 291 to 296.

In carrying out the process the metal to be evaporated is usually hung on a tungsten filament as small loops of wire. Electric current is then passed through the lament to heat it and the wire loops are melted and the fused metal clings to the filament and evaporates as the heating is continued. One diiiiculty which has been encountered with silver and copper has been the failure of these metals to wet the tungsten sufciently to cling to it during the vaporization process. The metal tends to ball up and drop olf the filament before it can be evaporated. It also sometimes tends to spatter during evaporation, probably due to the accumulation of the liquid metal in large globules.

We have now discovered that this difficulty can be overcome in the case of copper and satisfactory wetting of the tungsten filament obtained by adding a small percentage of lithium to copper or its alloys. For example, an alloy of Per cent Lithium .05

Platinum 5.00 Copper Balance 2 or iron may be present in percentages ranging from .001 to .5%.

Referring to the drawing, Figure 1 shows a metal vaporization apparatus comprising a bell jar I0 resting on a pump plate II with a rubber gasket I 2 between them to afford a gas seal. The bell jar is connected to a vacuum pump through pipe I3 and a Pirani gauge I4 may be provided to measure the degree of vacuum obtained.

The articles to be coated with a thin film of copper such as glass plates or mirror blanks I5 are mounted on the inside wall of a cylindrical container I6 supported within the bell jar. The tungsten filament I'I is mounted axially within the container and connected to insulated terminals I8 and I9.

The copper alloy to be evaporated is hung on the spiral tungsten filament as little wire loops 23 (Fig. 3) so that when the filament heats up the loops will melt and cling to the filament.

Figure 2 is a fragmentary cross-section of the tungsten filament II coated with the fused alloy 2 I of copper preparatory to evaporation.

While speciflc embodiments of the invention have been described, it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed is:

1. An alloy loop for metal evaporation formed of an alloy composed of .001 to 1% lithium, .25 to 20% of a metal selected from the group consisting of platinum and palladium and the balance copper.

2. An alloy wire for metal evaporation composed of about .05% lithium, 5% platinum and the balance copper.

FRANZ R. HENSEL. EARL I. LARSEN.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,291,106 Payne Jan. 14, 1919 1,923,955 Smith Aug. 22, 1933 2,178,233 Klatzow Oct. 31, 1939 2,196,302 Hensel et al. Apr. 9, 1940 2,213,312 Hensel Sept. 3, 1940 2,330,062 Lempert Sept. 21, 1943 2,413,604 Colbert et al Dec. 31, 1946 2,413,606 Colbert et al Dec. 31, 1946

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