DE1564069C2 - Composite material for electrical contacts - Google Patents

Description

Palladium-silver alloys have long been used for electrical contacts in almost all areas of low-voltage technology used, especially when high requirements have to be met in terms of switching reliability. Usually this will be only the parts that come directly into question for making contact are made of these alloys and these with a base made of non-noble Base metal connected by plating, for example with a base made of copper or its Alloys or other base metals and base metal alloys.

Also the base metals of the 8th group of the periodic table, e.g. iron and nickel and their Alloys and alloys that contain these metals as essential components can be found as materials for the base metal base of these so-called bimetal contacts.

These known composite materials made of a base metal base and a contact pad made of palladium-silver alloys, which are connected by plating, show considerable disadvantages in practical processing when a base made of the base metals of the 8th group of the Periodic Table is iron, nickel or their alloys or alloys in which the metals mentioned are an essential component ^; represent, is used and strong thermal and mechanical stresses are unavoidable. These difficulties and disadvantages primarily occur when such parts ^{are heated to high temperatures, for example above 800 °} C., and are then subjected to mechanical stress, such as bending. .

It is known per se to the person skilled in the art that pure silver can be found without difficulty the base metal materials in question can be plated and that the composite material then can be heated up to the vicinity of the silver melting point without the material in any Manner is adversely affected or shows damage.

This also applies to the plating to the same extent; from pure palladium to the listed base metals the 8th group of the Periodic Table or the alloys of these base metals; because even these composite materials can easily be exposed to high thermal and mechanical loads during further processing. This However, conditions change decisively when palladium-silver alloys are used for production used by composites that

consist of 20 to 80%, preferably 30 to 60% palladium and the remainder silver. In this case, when the composite materials are further processed into electrical contacts, even when they are heated to temperatures of 800 ° C and above, without. ₇ subsequent mechanical stress very often cracks in the cladding layer, which in certain circumstances can even lead to the complete detachment of the contact surface, but at least the operational

ao question the security of contacts.

The present invention is based on the object of the above-mentioned disadvantages Composite materials from base metals of the 8th group of the periodic table or their alloys with a plating layer -, made of palladium-silver alloys turn off or restrict as much as possible so that this. Materials even with prolonged intensive loads both in thermal and mechanical relation retain their excellent properties.

The surprising solution to this problem is that according to the invention 'between the base layer and the contact layer an intermediate layer made of platinum, palladium or alloys of these Metals such as palladium-iridium 70/30, palladium-gold 50/50 or alloys in addition to the precious metals Contain up to 10% iron, cobalt and / or nickel, such as palladium-nickel 95/5 or platinum-nickel 90/10 is arranged. Interlayers of 10 to 50 μm are particularly favorable, preferably 25 to 40 μm thick. . .

The composite material according to the invention thus consists of:

1. the load-bearing base layer made of iron, nickel or alloys of these metals, in which these The main component or at least an essential component are.

2. an 'intermediate layer made of platinum, palladium or alloys of these metals, ■. ■' ■. _;

3. the noble metal contact layer, known per se, made of binary palladium-silver alloys a palladium content of 20 to 80%, preferably from 30 to 60%. -; - · .- ■

The load-bearing base layer can, for example, be pure, .. Be nickel or one of the iron-nickel alloys known per se: consist; also cupro, Nickel can be used.

In particular, pure platinum, pure palladium, palladium-iridium have proven to be the material for the intermediate layer 70/30 and gold-palladium 50/50 proven. However, alloys can also be used for the intermediate layer are used, in addition to the noble metals mentioned, up to 10% iron and / or nickel contain. Examples of such alloys are palladium-nickel 95/5 and platinum-nickel 90/10.

The particular advantages of arranging the individual layers in the composite material for elec-

3 4

Irish contacts according to the invention consist of bonding the base layer and noble metal contact the previously observed disadvantages of the composite layer even after high processing temperatures materials such as crack formation between the base metal and the subsequent mechanical stress on the top layer and possible falling of the deck hold remains. In this way a higher coating becomes no longer occur and a firm sales reliability of the electrical contacts is achieved.

Claims (2)

Patent claims: 1. Composite material for electrical contacts with a base layer made of iron, nickel or alloys these metals, such as iron-nickel alloys or cupro-nickel alloys, and a contact layer made of a palladium-silver alloy with 20 to 80%>, preferably 30 up to 60% palladium and the remainder silver, characterized in that between the base layer and the contact layer an intermediate layer made of platinum, palladium or alloys these metals, such as palladium-iridium 70/30, palladium-gold 50/50, or alloys in addition to the precious metals contain up to 10% iron, cobalt and / or nickel, such as palladium-nickel 95/5 or platinum-nickel 90/10. 2. Composite according to. Claim 1, characterized in that the intermediate layer 10 to 50 μΐη ,. preferably 25 to 40 μm thick.