JPS6344250B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing electrical contacts, particularly electrical contacts for reed switches widely used in switch circuits, control circuits, etc. in electronic equipment.

The intention is to replace the conventional switch function obtained by treating contacts with precious metals such as gold or rhodium to obtain the same or better switch function or contact life by plating base metals. be. This is because, with the recent sharp rise in the price of gold, the prices of precious metals other than gold have also tended to soar, and this is becoming a major factor in increasing costs in the manufacture of switches that use these precious metals as contacts.

Conventionally, the reed piece used in reed switch assembly has a structure as shown in the perspective view of the reed piece in Figure 1, in which a bar member 1 made of 52 alloy (an alloy of 52% nickel and 48% iron) is flattened. The tip part 2 is plated to improve its contact function, such as gold or composite plating of gold/nickel, gold/silver, etc., or no plating of rhodium known as platinum metal, and furthermore, plating with gold to achieve the above-mentioned plating. Alternatively, lead pieces were made by diffusing alloy plated bodies against 52 alloy in a hydrogen furnace. Although only a single lead piece is shown in the diagram, the reed switch is a so-called sealed contact in which the flat parts of the lead pieces are arranged in an overlapping state and are sealed and assembled in an inert gas atmosphere in a glass tube. It is.

However, the contact processing of a reed switch depends on the required contact load conditions and the switching operation life, and in order to economically obtain the switch function, conventional plating mainly made of precious metals, as described above, and interplating. 700℃~900℃ for layer
This was dealt with by diffusion treatment at a moderate temperature. Moreover, in order to use precious metals economically, only the contact surface at the tip of the reed piece is partially plated (from the dotted line in the figure to the tip), but the abnormal rise in gold prices has pushed up switch manufacturing costs and made it cheaper for users. The situation is becoming increasingly difficult to provide suitable switches.

An object of the present invention is to solve the above-mentioned problems, and this is accomplished by applying a plating layer mainly composed of nickel and a plating layer mainly composed of copper to the contact formation surface of a lead piece made of a magnetic material containing an iron component. This can be achieved by a method for manufacturing an electrical contact, which is characterized in that the electrical contacts are formed one after another, and then the lead piece including the contact forming surface is subjected to a diffusion treatment in a hydrogen furnace.

Of course, using this manufacturing method eliminates the need to use expensive precious metals as contact materials, and the iron component contained in the contact forming surface of the lead piece is mainly composed of nickel and copper during diffusion treatment in a hydrogen furnace. However, the intermediate nickel layer acts as a barrier and slows down the rate of diffusion into the copper plating layer on the surface. Then, before this iron component diffuses into the copper plating layer, nickel and copper are diffused, and as a result, the amount of iron component diffused to the surface of the plating layer is suppressed to a low level.

The following is an example, and shows the plating solution composition during plating and the production conditions at that time.

Nickel solution; (1) Nickel sulfamate: 330gr / Boric acid: 15gr / Ammonium chloride: 15gr / Additives: 1ml / (2) Solution temperature 55℃ (3) Current density 1 ampere / dm ² Copper plating solution : (1) Copper sulfate: 225gr / Sulfuric acid: 65gr / Additive: 2ml / (2) Solution temperature: 25℃ (3) Current density: 1 ampere/dm ² Additives in liquid under the above plating conditions ensure uniform plating thickness This was added to give the surface a glossy appearance. However, the liquid temperature and current density are both standard values. The thickness of the plating applied to the material corresponds to the life of the switch contact (the greater the thickness, the longer the life will be proportionally); for example, 0.5 μm of nickel and 2 μm of copper are treated. The reed pieces subjected to such treatment are then heated to 800°C in a hydrogen furnace.
The material is heat treated for 20 minutes to effect diffusion and form a stable contact surface. This diffusion temperature is just one example.

The results of a lifespan test comparing a switch in which a pair of lead contact pieces obtained in this way are enclosed and a switch in which a lead piece plated with a conventional or equivalent precious metal (1.5 μm of rhodium) is enclosed. It is shown in Figure 2.

Figure 2 shows the number of opening/closing operations based on Weibull probability paper as the horizontal axis (t), and the failure rate F(t) for the number of times t.
is expressed as the vertical axis.

In the figure, the switch A is a conventional switch, and the switch B is a switch for the composite plating/diffusion process of the present invention, and the number of tested switches is 20. Test contact -
5mA: pure resistance load, contact make rate 50%, switching conditions: 25Hz (AC drive), coil excitation ampere turns 75AT.

As can be inferred from the above test results, the present switch B shows no inferiority to the target conventional switch A, and in fact, it is known that it has a preferable life performance under relatively low level load conditions.

In addition, the copper on the surface can be expected to have the effect of lowering the stickiness of the switch and improving the switch's blocking performance, which is not found anywhere else.

According to the contact treatment of the present invention, since precious metals such as gold and rhodium are not used, inexpensive products can be provided, and the industrial effects thereof are significant.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a lead piece to which the present invention is applied;
FIG. 2 shows test results comparing the switch assembled according to the example with a conventional product. In the figure, 1 is a circular cross-section portion of the lead piece, 2 is a flat portion where the contact surface is formed, and the surface beyond the dotted line is the plating portion of the contact.

Claims (1)

[Claims] 1. A plating layer mainly composed of nickel and a plating layer mainly composed of copper are sequentially formed on the contact forming surface of a lead piece made of a magnetic material containing an iron component, and then the lead piece including the contact forming surface is heated with hydrogen. A method for manufacturing an electrical contact, characterized by carrying out a diffusion treatment in a furnace.