JPS604266B2 - Copper alloy for contact materials and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel alloy for contact materials that does not cause cold welding, and a method for manufacturing the same.

In particular, the present invention relates to a contact material that does not cause cold welding by plating a copper alloy with tin or a tin-containing alloy and then subjecting it to heat treatment. Tin has excellent corrosion resistance and solderability, and is widely used in consumer electronic devices as a metal for surface contacts, so-called tin plating. It won't come off unless you apply a certain amount of force.

This phenomenon is called cold welding, and conventionally, in fields where the occurrence of cold welding is a serious problem, plating with expensive metals such as gold, silver, Rh, and Pd has been applied.

Therefore, we searched for a method that does not cause cold welding even when plating with tin or a tin-containing alloy, and as a result we have arrived at the present invention. That is, the present invention provides plating with tin or a tin-containing alloy either directly on a copper alloy or after plating with a copper base, and then by heating and melting and/or heating at a temperature below the melting point of the plating material. The present invention provides a contact material which hardens the surface and prevents cold welding by forming an outer diffusion layer substantially made of a tin-copper compound.

Various types of copper alloys, such as phosphor bronze, brass, nickel silver, beryllium steel, and titanium steel, are used as steel alloys for contacts, but the present invention uses these copper alloys either directly or after being plated with a copper undercoating. Alternatively, plating with a tin-containing alloy is applied. The tin-containing alloy used for plating includes tin containing one or more types of solder materials such as lead, indium, antimony, aluminum, and zinc. The plating method may be electrolytic plating, electroless plating, or, in the case of tin or a tin-containing alloy, hot-dip plating, and is not limited to the plating bath composition.

There is no particular limit to the thickness of copper underplating and tin plating, but
When performing copper underplating, the product of the heat treatment is a copper-tin compound, which is initially mainly composed of Cu6,S spread.
The thickness of the copper undercoating and tin or tin-containing alloy plating is determined by considering the composition of Cu3Sn, which is the final product, and adjusting the ratio of copper to tin based on the elemental ratio. (0u/Sn): (3'1) or less is preferable.

Even when copper underplating is not performed, copper in the copper alloy and tin in the plating layer diffuse to form C&Sn5 and Cu3Sn. It is sufficient that most of the tin component in the tin or tin alloy plated with the contact material of the present invention forms a copper-tin compound, and it is not necessary that most of the compound be Cu. The heat treatment conditions after melting or electrolytically plating tin or tin-containing alloys include, in the case of heating and melting, for example, if the upper plating layer has a thickness of 0.5 mm or less, in many cases no further heat treatment is required and the surface is A diffusion layer consisting essentially of tin-copper is produced.

However, the thermal conditions for hot melt plating and heat melting are not determined for the purpose of generating intermetallic compounds. Thermal conditions are determined for the purpose of producing gloss, so whether or not further heat treatment is necessary to generate the diffusion layer consisting essentially of tin and copper, which is the object of the present invention, is a matter of individual concern. The plating method and plating conditions must be considered and selected, and the upper plating layer must be uniformly 0.
．． It cannot be determined that further heat treatment is not required if the temperature is less than 5 degrees. The heat treatment conditions at a temperature below the melting point of tin or a tin-containing alloy are largely influenced by, for example, the thickness of the upper plating layer, but a practical temperature range is from 150° C. to below the melting point. Although it is preferable that the heating atmosphere be non-oxidizing, heating in the atmosphere is of course possible. When heated in the atmosphere, oxides are formed on the surface, but the oxide film can be easily removed by washing with a 5 to 1 vol% sulfuric acid aqueous solution after the heat treatment, and does not pose any problem. Through these heat treatments, the surface of the material in which a diffusion layer consisting essentially of tin and copper is formed as an outer layer becomes extremely hard.While the Pickers hardness of phosphor bronze matrix for springs is 260 or less, is 3
50 to 450, and has excellent abrasion resistance.

The material of the present invention has a bush resistance value of 3 to 6 Q, which is a required property as a service material, which is slightly higher than the after-melting resistance value of tin plating, which is 3 mQ in the same test method. However, there are no practical problems. Furthermore, even in application fields where sliding occurs, since the surface is extremely hard, the bale melting resistance value is stable during sliding, and therefore has the advantage of generating less noise. Examples will be described below.

Example 1 A phosphor bronze strip for a spring was subjected to alkaline degreasing, electrolytic degreasing, pickling and neutralization, and then tin plating with a tin sulfate rating of 0.5 pu.

The tin sulfate rating and plating conditions are as follows. After holding the thus tinned strip at 600° C. for 5 seconds in a burner direct-fired heating furnace, The water linen was dried with warm air.

When this strip was examined by X-ray diffraction, it was confirmed that the surface state consisted of a faint amount of 8-tin and a large portion of C ratio Sn5. The welding resistance value of this strip was 3 skins. Next, a piece with the size of 1 x 1 x 1 inch was cut out from this strip, two pieces were stacked together, and LK9/secret melting pressure was applied and kept for 30 days, but no cold welding occurred. Example 2 Plated under the same conditions as Example 1 (however, the plating thickness was 1.5 mm)
) The molten tin-plated strip was heated in an argon atmosphere at 160°C for 2 hours.

No 8-tin was detected in this strip by X-ray diffraction, and the contact resistance was 5.
．． 5 skin was ○. Further, in the test conducted under the same conditions as in Example 1, no cold welding occurred. Example 3 Yellow steel strip containing 35% zinc was degreased with alkali.
After electrolytic degreasing and acid wash neutralization, copper underplating was carried out with tin sulfuric acid rating of 0.5 French, and tin plating was carried out under the same conditions as in Example 1.
The five coated strips were heated at 15,000 for 4 hours in an argon atmosphere.

This strip was examined by X-ray diffraction, but no 3-tin was detected, and the contact resistance was 5.6 (○).

Further, in the test conducted under the same conditions as in Example 1, no cold welding occurred.

Claims (1)

[Claims] 1. A copper alloy for contact materials that does not cause cold welding and has a diffusion layer made of a tin-copper compound as an outer layer. 2 After plating copper alloy with tin or tin-containing alloy,
A method for producing a copper alloy for contact materials that does not cause cold welding by heating at a temperature below the melting point of the melting and/or plating material to generate a diffusion layer substantially consisting of a tin-copper compound in the outer layer.