JPH02216721A - Manufacture of electric contact point - Google Patents

Abstract

PURPOSE:To obtain an electric contact point of the same cost as that of an electric contact point of a palladium-nickel alloy and preferable lifetime characteristics by fixing a palladium-cobalt alloy including a specific amount of cobalt to a conductive substrate by electroplating directly or via conductive adherence layer. CONSTITUTION:A palladium-cobalt alloy including cobalt of 0.5 to 15wt.% is fixed to a conductive substrate by electroplating directly or via conductive adherence layer. Adhesion tendency of an electric contact point is reduced and its lifetime is extended since it is easy to control the composition of the alloy by electroplating and fix the alloy to the substrate thickly and cobalt as additive of the electric contact point has higher hardness. Therefore, contact electric resistance of the electric contact point is uniformed and its adhesion tendency is reduced so that its lifetime is extended and its cost is reduced.

Description

[Detailed Description of the Invention] [Summary] Regarding the manufacturing method of an electrical contact used in an inert atmosphere such as nitrogen gas, the cost is the same as that of an electrical contact made of palladium-nickel alloy, and the contact has excellent life characteristics. palladium containing 0.5wt% to 15wt% of cobalt.
[Industrial application field] The present invention particularly relates to the application of a cobalt alloy to a conductive substrate by electroplating either directly or through a conductive adhesive layer. For example, the present invention relates to a new method for manufacturing electrical contacts formed on reed switch reed pieces.

A reed switch, in which an electrical contact formed at the tip of one of at least a pair of reed pieces is sealed in a glass tube together with an inert gas, and the contacts face each other at an appropriate interval, can be used to remove dust, harmful gases, humidity, etc. in the atmosphere. A reed relay, which combines the reed switch with a driving means such as a permanent magnet, has the advantage of being smaller, lighter, and faster operating than an electromagnetic relay.

The electrical contacts used in such reed switches and the like are made of rhodium, ruthenium, gold, etc., but in recent years, palladium, which is cheaper than these, has been considered as an alternative material.

[Conventional technology]

Figure 3 is a cross-sectional view of a conventional reed switch equipped with electrical contacts (A) and an enlarged view of the electrical contacts (II+), and Figure 4 is an example of the composition of the electrical contact shown in Figure 3 in the thickness direction. FIG.

In FIG. 3, the reed switch 1 is 5270i (
A pair of lead pieces (substrate) made of 52% Ni, balance Fe
The middle part of each lead piece 2 is sealed to a glass tube 3, and the electrical contact 4 formed at the tip of each lead piece 2 and sealed together with an inert gas (for example, N2) 5 faces each other with an appropriate distance apart.

The electrical contact 4 is made by, for example, plating gold on the lead piece 2 and thermally diffusing the base material (5270I) and gold, and the composition in the thickness direction is as shown in FIG. Concentration (wt
%], when the horizontal axis is the depth from the surface of the electrical contact 4,
Gold (Au) gradually decreases from the surface of the electrical contact 4, while nickel (Ni) and iron (Fe) gradually increase. The amount and the content of nickel and ten irons become reversed.

[Problem to be solved by the invention]

When palladium, the cheapest of the platinum group metals, is used in electrical contacts instead of conventional rhodium, ruthenium, gold, etc.
Palladium is softer than rhodium or ruthenium, has a strong tendency to stick, and has a short lifespan. In order to overcome these difficulties, electrical contacts made of palladium alloys containing nickel or cobalt have been proposed, but electrical contacts made of such alloys are formed by sputtering palladium and nickel or cobalt alternately or simultaneously. It was something.

In conventional alloy electrical contacts made by sputtering, it is difficult to control the content of nickel or cobalt. There was a problem in that the productivity was low when forming the film to a thickness of several μm.

[Means to solve the problem]

The method for manufacturing an electrical contact of the present invention, which aims to solve the above problems, involves electroplating a palladium-cobalt alloy containing 0.5 wt% to 15-1% cobalt on a conductive substrate directly or through a conductive adhesive layer. It is characterized by being deposited at.

[Effect]

According to the above method, alloys produced by electroplating are easier to control composition and thickness (deposition) than those produced by sputtering, and as an additive for electrical contacts, cobalt has a higher hardness than nickel, so it tends to stick. This is advantageous in that it can reduce the amount of damage and extend the lifespan.

Therefore, a reed switch using the electrical contact made by the method of the present invention has a uniform electrical contact resistance, a reduced tendency to stick, has a long life, and can be provided at a low cost.

〔Example〕

EMBODIMENT OF THE INVENTION Below, the electrical contact which becomes an Example of the method of this invention is demonstrated using drawing.

FIG. 1 is a sectional view (A) of a reed switch equipped with an electric contact according to an embodiment of the present invention, and an enlarged view (I) of the electric contact.
I).

In FIG. 1, in which the same reference numerals are used for common parts as in FIG. The electrical contacts 12 formed at the tip of the cap 2 and sealed together with an inert gas 5 such as N2 are separated by an appropriate amount and face each other in the thickness direction.

The electrical contact 12 is formed by electroplating a palladium-cobalt alloy using a palladium complex compound such as sulfuric acid, nitric acid, nitrous acid, hydrochloric acid, or iodine, and a cobalt compound such as sulfuric acid, nitric acid, or hydrochloric acid. In this example, the plating solution was Pb (NOx) t (Nu, I) t as Pb...15g/1CoSOa as Co...
...2 g/1 included, current density as plating condition...5 A/d11z liquid temperature... 40'CPH・・
・・・・・・・・・・・・・・・ 8.

The table below shows the microknoop hardness (HMK) and surface contact electrical resistance of the electroplated layer of palladium-cobalt alloy (Pd-Co) containing 8 wt% cobalt according to the present invention. , palladium-nickel alloy containing 20-t% nickel (Pd-Ni
) compared with those of the plating layer.

As is clear from the table, the palladium-cobalt alloy plating layer has higher hardness than the palladium plating layer and the palladium-nickel alloy plating layer, and its surface contact resistance is slightly inferior to that of the palladium plating layer. This is almost equivalent to a palladium-nickel alloy plating layer.

FIG. 2 is a diagram in which actually measured values of surface hardness and surface contact electrical resistance of an electrical contact made by the method of the present invention are plotted and the plots are connected by a solid line or a broken line.

In Figure 2, the vertical axis is surface hardness (HMK) or surface resistance (Xo, 1 mΩ), and the horizontal axis is cobalt content (wt
%), and the hardness characteristics shown by the solid line in the figure rapidly decrease when the cobalt content reaches about 0.5 wt%, and the surface resistance characteristics shown by the broken line in the figure decrease when the cobalt content reaches about 15 wt%.
The increase becomes noticeable above t%.

From FIG. 2, the electrical contact made by the method of the present invention is 600HMK.
Cobalt content that ensures a certain degree of hardness and a surface resistance of about 30111Ω or less, that is, 0.5wt% to 1% of cobalt.
5 wt% palladium-cobalt alloy, such electrical contacts can ensure adequate hardness to reduce the tendency to stick and contact resistance applicable to conventional electrical contacts (eg reed switches).

In the embodiment shown in FIG. 1, the electrical contact 12 is attached directly to the lead piece 2, but in order to increase the adhesion to the lead piece 2, it may be attached via an adhesive layer made of gold or palladium. It is practical to do so.

Further, the electrical contact 12 according to the method of the present invention may be subjected to appropriate heat treatment,
It should be noted that even higher hardness (approximately 700) can be achieved by heating at 200''C for approximately 15 minutes in the air, for example.

〔Effect of the invention〕

As explained above, the electrical contacts formed by electroplating of palladium-cobalt alloy according to the present invention have higher hardness than electrical contacts of palladium-nickel alloy, so they have a lower tendency to stick and have a longer life. It is easier to form the reed switch thicker than the reed switch, and it is excellent in mass production. When the method of the present invention is applied to a reed switch, it has the effect of extending the life of the switch and making it possible to provide the switch at a low cost.

[Brief explanation of the drawing]

Fig. 1 shows a reed switch equipped with an electrical contact according to an embodiment of the present invention, Fig. 2 shows the surface hardness characteristics and surface resistance characteristics of an electrical contact obtained by the method of the present invention, and Fig. 3 shows a conventional electrical contact. FIG. 4 is an example of the composition of the electrical contact shown in FIG. 3. In the figure, 2 indicates a lead piece, and 12 indicates an electrical contact. (b) Da (b) □v? Soaring 4 times

Claims (1)

[Claims] Palladium containing 0.5wt% to 15wt% of cobalt
A method for producing an electrical contact, comprising depositing a cobalt alloy on a conductive substrate by electroplating either directly or via a conductive adhesive layer.