JPH04160200A - Production of electric contact material - Google Patents

Abstract

PURPOSE:To suppress the adhesion and wear of silver and to obtain an electric contact material which has an excellent sliding characteristic and electrically connecting characteristic by forming a plating layer of tin on the surface of the silver layer on a contact base material, then subjecting the layer to a heating treatment to diffuse the magnetic silver and tin layer. CONSTITUTION:The surface of the contact base material consisting of a copper alloy, etc., is coated with the silver layer, and further, the tin plating layer is formed thereon. This material is heated in a nonoxidative atmosphere to diffuse the silver layer and the tin layer to form a silver-tin alloy. The material, the outermost layer of which is the silver-tin alloy, is subjected to drawing or rolling.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing an electrical contact material, and more particularly, to a method for manufacturing an electrical contact material that has excellent sliding properties and electrical connectivity.

(Prior Art) Materials made by coating the surface of various metal wires with silver or silver alloys have not only the characteristics of the metal wires that are the base material, but also the corrosion resistance of silver or silver alloys. Soldering also exhibits properties such as stability and electrical connectivity, so it has been used for various purposes.

For example, a material made by coating the surface of a copper alloy strip with a silver layer with a thickness of 0.5 to 20 μm has the excellent mechanical properties of copper alloy, as well as the excellent corrosion resistance, solderability, and electrical properties of silver. It is known as an economical, high-performance conductor that also exhibits connectivity, etc., and is widely used as a material for contact parts and leads in the electrical and electronic equipment fields.

By the way, among these materials, for example, a switch is constructed by combining a fixed contact and a movable contact, but both of these contacts are made of a material whose base material is coated with the above-mentioned silver or silver alloy. Usually used.

(Problem to be solved by the invention) However, the switch made of the above-mentioned contact material,
As the number of contacts between the contacts increases, the switch function begins to deteriorate due to a decrease in switch actuation force and an increase in contact resistance between the contacts. In the end, the life of the switch becomes short.

This phenomenon is caused by adhesive wear of the silver or silver alloy at the contact surfaces of both contacts. In other words, the operating force of the switch decreases due to the progress of adhesion due to contact between both contacts.
Furthermore, the contact resistance increases when the silver layer or silver alloy layer on the contact surface peels off and the base material is exposed.

As a method for preventing such adhesive wear between both contacts, Au-Ag, Pd-Ag, AgPd-
It is known to construct the surface of the contact with a dissimilar metal such as Ag.

However, since such a method uses the above-mentioned expensive precious metals, the cost of the contact material increases significantly, and the applications of the contact must be limited to an extremely narrow range.

On the other hand, electrical contact materials are required to have stable electrical connectivity. In order to stabilize this electrical connectivity, the contact material must be able to suppress the contact resistance between the two contacts to a low level both at the initial stage of contact and after the passage of time, and to have sliding properties on the contact surface. Characteristics such as good corrosion resistance, low wear and tear, and excellent corrosion resistance are required.

The present invention aims to solve the above-mentioned problems and provide a method for inexpensively manufacturing an electrical contact material that does not cause adhesive wear between contacts and can realize stable electrical connectivity. .

(Means for Solving the Problems) In order to achieve the above object, in the present invention, a soot plating layer is formed on the surface of the silver layer of a contact base material coated with a silver layer, and then a non-oxidized Provided is a method for producing an electrical contact material, which comprises heating in a neutral atmosphere to perform a diffusion treatment between the silver layer and the tinned layer, and then performing drawing or rolling.

First, the contact base material to which the method of the present invention is applied includes, for example, copper and various copper alloys; composite materials formed by coating the surface of materials such as steel and aluminum with copper or copper alloy; , nickel or iron, or their alloys;
etc. can be given.

The shape of the contact base material is not particularly limited, and may be, for example, a wire, a strip, a bar, a tube, or the like.

The surface of this substrate is coated with a silver layer. The silver layer may be formed by, for example, a commonly used electroplating method or a cladding method. Furthermore, if the thickness of the silver layer is too thin, the base material will be exposed even by slight wear and the contact resistance will increase, so it is usually preferable that the thickness of the silver layer be 0.5 μm or more. More preferably, it is 1 to 10 μm.

In the present invention, a tin plating layer is first formed on the silver layer by, for example, electroplating.

If the thickness of this plating layer is too thin, the amount of Ag-3n alloy produced during the diffusion treatment described below will decrease, reducing the adhesive wear suppressing effect, so the thickness should be 0.01 μm.
It is preferable that it is more than m.

Further, it is preferable to select the thickness of Sn and the heat treatment conditions so that the amount of Sn in the Ag-8n alloy is 1 to 10% by weight.

The material on which the tin plating layer is formed in this way is then heated in a non-oxidizing atmosphere and subjected to this treatment, thereby creating a gap between the surface part of the silver layer or all of the silver layer and the tin plating layer. A diffusion reaction takes place, producing an Ag-8n alloy that exhibits the effect of suppressing adhesive wear.

The non-oxidizing atmosphere at this time may be, for example, nitrogen, argon, hydrogen, or the like. Further, the heating temperature may be approximately 300° C. or higher in order to produce the above-mentioned alloy, but the upper limit thereof is set to be lower than the melting point of silver. Furthermore, the treatment time may be changed depending on the heating temperature, but it is approximately 10
More than seconds.

This material, whose outermost layer is made of Ag-5n alloy, is then subjected to drawing processing (if the material is a wire, bar, or tube) or rolling processing (if the material is a strip).

Through this processing, the alloyed silver is work hardened.

As a result, the wear resistance of the obtained material is further improved.

If the processing rate at this time is too low, the improvement in wear resistance due to work hardening will not be noticeable, so the processing rate is preferably 3% or more.

(Embodiments of the invention) Examples 1 to 9. Comparative Examples 1 to 3 A brass plate with a thickness of 0.3 mm, a width of 30 mm, and a length of 100 mm was subjected to a surface cleaning treatment of alkaline degreasing, water washing, pickling, and water washing, and silver strike plating was applied to the surface. A silver layer and a tinned layer having the thickness shown in Table 1 were successively formed by electroplating.

Then, after washing with water and drying, the brass plate was subjected to a diffusion treatment in a nitrogen atmosphere furnace under the conditions shown in Table 1, and further subjected to rolling processing at the processing rate shown in Table 1.

The coefficient of dynamic friction and micro-abrasion contact resistance of the obtained material were measured according to the following specifications.

Dynamic friction coefficient: Silver bar with head radius 5mm, load Log
, sliding distance 10mm, number of sliding 500 times.

Micro-movement abrasion contact resistance: Silver bar with head radius 5 mm, load 50 g, current IA, sliding distance 0.1-1, number of sliding 200,000 times.

The above results are collectively shown in Table 1.

(The following is a blank space) (Effects of the invention) As is clear from the above explanation, the adhesive wear of silver is suppressed in the material produced by the method of the present invention, and its electrical connectivity is also good and stable. .

Therefore, the method of the present invention has extremely great industrial value as a method for producing electrical contact materials with excellent characteristics without using expensive precious metals.

Claims (1)

[Claims] After forming a tin plating layer on the surface of the silver layer of the contact base material coated with a silver layer, heating in a non-oxidizing atmosphere to perform a diffusion treatment between the silver layer and the tin plating layer, and then drawing. A method for producing an electrical contact material, which comprises processing or rolling.