JPH0412570B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method of manufacturing an electrical contact made of a silver-cadmium oxide alloy. (hereinafter referred to as contact) (Prior art and its problems) Silver-cadmium oxide alloys have excellent welding resistance and wear resistance, and stable contact resistance, so they can be used in a wide range of applications from low voltage and small current to high voltage and large current. Widely used in range. Recently, with the miniaturization of relays, efforts have been made to reduce contact force and separation force, narrow the contact gap, and downsize the contacts. On the other hand, high reliability is required for contact reliability, and in particular, the problem of contact resistance has been widely discussed. Regarding contact resistance, the initial value is especially important, and the contact force has a large influence on the contact resistance.As mentioned at the beginning, a decrease in the contact force with miniaturization means that the contact resistance increases. This means that these problems are being exacerbated even further. Currently, there are methods to deal with these problems, such as gold-silver 5-20% alloy coating, plating, and acid treatment, but gold-silver 5-20% alloy coating is disadvantageous in terms of cost and electricity. Some contacts cannot be processed due to their shape, and may have a negative impact on adhesive resistance. In the case of plating, there is a problem of pinhole, and to solve this problem, 2~3μ
It is necessary to make the film thicker, which is disadvantageous in terms of cost. In the case of acid treatment, in order to form a complete silver layer on the surface, it is necessary to perform a considerably strong acid or heat treatment with a strong acid, and as a result, the surface of the contact becomes rough, making it unsuitable for use. (Objects and Structure of the Invention) As a result of intensive research to meet such demands, the present invention exposes cadmium oxide in a silver-cadmium oxide alloy to the surface by heat treatment, and then removes the exposed cadmium oxide by acid treatment. A complete silver layer can be uniformly formed on the surface layer,
It was found that the initial value of contact resistance, which is particularly problematic, is very stable. Regarding heat treatment temperature
At temperatures below 450°C, the movement of Ag in the silver matrix is insufficient, making it difficult for cadmium oxide to be exposed on the surface, resulting in too much time and poor productivity. On the other hand, if the temperature exceeds 700℃, the sublimation of cadmium oxide will proceed rapidly and the variation in the thickness of the silver layer will increase, making it difficult to form a silver layer with a constant thickness.
~700℃ range. Next, contacts manufactured by the manufacturing method according to the present invention and the conventional manufacturing method will be explained. (Example and conventional example) Head diameter 5 mm, head height 1.0 mm, leg diameter 2.5 mm, leg length 2.5
mm fixed contact, head diameter 4 mm, head height 1.1 mm, leg diameter
We obtained a movable contact with a diameter of 2.8 mm, a leg length of 1.6 mm, and a spherical head of 5R. The contact points are Ag− as shown in the left column of the table below.
A composite riveted contact was manufactured using a CdO alloy contact material for the upper half of the contact head and copper was used for the rest.
After heat treatment for 30 minutes, acid treatment was performed with 10% H ₂ SO ₄ . However, by incorporating the contacts of these embodiments and conventional examples into a hinge type relay, the initial contact resistance can be reduced.
When measured with YHP4328A milliohm meter,
The results shown in the right column of the table were obtained.

【table】

[Table] As is clear from the above, it can be said that the product of the present invention has a lower initial contact resistance and is more stable than the conventional product. In addition, when comparing the surfaces of the conventional example and the example, a complete silver layer was formed on the surface of the example up to 1800 Å, but the concentration of cadmium oxide on the surface of the conventional example was about the same as the component composition. It turns out that it is. (Effects of the Invention) As can be seen from the above explanation, the method of manufacturing an electrical contact of the present invention has a very stable initial contact resistance, and can be said to be an epoch-making method that can replace conventional manufacturing methods.

Claims (1)

[Claims] 1. An electrical contact characterized by subjecting an electrical contact material made of a silver-cadmium oxide alloy to heat treatment at 450 to 700°C in a nitrogen gas atmosphere, followed by acid treatment to form a silver layer on the surface layer of the electrical contact. manufacturing method.