DE3203037A1 - CONTACT ELEMENT AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Description

SIEMENS AKTIENGESELLSCHAFT - $ - Our symbol Berlin and Munich VPA

82 P 1 0 5 7 DE

Contact element and process for its manufacture

The invention relates to a contact element which is on a preferably ferromagnetic carrier material has at least two contact layers galvanically applied one on top of the other, the outer layer of which is made of rhodium and the underlying second layer consists of a noble metal. The invention also relates to a method for producing such contact elements.

In multi-layer contacts for relays and the like, it is known, the actual contact layer made of gold or a gold alloy and then to reduce the tendency to cold welding with a thin layer of rhodium to be covered ("Electronics" 15/1981, page 58/59). To reduce the contact resistance through the rhodium layer If you do not increase it too much, this protective layer becomes smaller than 1 µm, usually on the order of 0.1 / µm thick chosen. The previously known rhodium-plated gold or gold alloy layers show in most cases of application satisfactory results in terms of contact resistance and the tendency to cold weld, but also because of the costs, improvements are desirable.

The object of the invention is therefore to provide a contact element with to create a noble metal contact layer and a rhodium coating, which is low even with high switching numbers Maintains contact resistance and does not tend to cold weld.

According to the invention, this object is achieved in that the noble metal layer consists of silver and the rhodium protective layer has a thickness between 0.2 µm and 2 µm.

Pr 1 Fra / 28.1.1982

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Those coated with silver and ultra-rhodium-plated according to the invention Even after a long service life, contact elements do not yet tend to cold welding or sticking while maintaining a largely constant low contact resistance. surprisingly is the contact resistance is even more constant than with correspondingly brightly rhodium-plated contact layers Gold or gold alloys. In addition, the contacts according to the invention have the additional Advantages resulting from the use of the contact material silver. So silver is essential cheaper than gold and also more resilient as a contact material.

Up to a layer thickness of about 2 lam of rhodium are rhodium-plated silver contacts lower resistance than pure rhodium contacts. Let particularly good results are achieved with a rhodium layer thickness between 0.3 / µm and 1 µm. The thickness of the silver layer is expediently between 1 and 10 µm, preferably 2 to 5 µm. Below the silver layer is expediently a nickel layer with a thickness of about 2 to 4 μm and possibly even less a copper layer in a thickness of 2 to 10 µm is provided to provide a diffusion barrier between the preferably ferromagnetic carrier material and to achieve the silver contact layer.

In the following, some test results are shown on the basis of Tables 1 and 2, which allow a comparison

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between the rhodium-plated silver layers according to the invention of relay contacts and correspondingly rhodium-plated Show gold-cobalt layers in terms of their contact resistance and their tendency to stick.

Table 1 shows the development of the contact resistance for the various contact layers:

Table 1 (3 experiments with 25 relays each)

Experimental 1 Contact material ,1. Rh Contact resistance. first spora No. 2 , 5 .. Rh (Continuous test without load) dische about 3 , 4 .. Rh 50% value violations (mil) from 50 mi2 to 10 ⁸ Number of operations Switching cycles '5-1O ⁶ 10 ⁵ AuCo / 0 <40 no over AuCo / 0 <30 violations Ag / 0 <35 to 10 ⁸ Switching cycles 0.2 µm
/ .. 1 um /
, .0.6 µm

When new , the contact resistance of all layers, i.e. both the rhodium-plated silver layers and the rhodium-plated gold-cobalt layers, were below 40 mil.The rhodium-plated silver layers with their contact resistance always remained below 50 mI2 until the end of the measurement during switching cycles, while this was with the gold-cobalt layers Value from 10 ^ switching cycles was sporadically exceeded.

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Tabel

Experimental 1 Contact material 0.2 µm Rh Tendency to stick New Endurance test without 25 relays) No. 2 I.
.. 1 um Rh State Last (de number of 3 ..0.6 µm Rh (from 80 additional Glue Relay) Glue (up to ver number away searcher) the Switching Glue number 15th 1 ^Β 2.5 x 10 3 AuCο / Ο, 1. 0 3.5'10 ⁷ 0 AuCo / 0.5. 0 no Ag / 0.4. Glue

The same batches as in Table 1 were used to investigate the tendency to stick (cold welding tendency). In the table, the contact material used is shown in the second column and the number of adhesive contacts when new is shown in the third column. For the measurement, the term "glue" or "sticky contact" was defined in such a way that the response value of the relay at the first response is 15 % or more excessive compared to normal operation.

It can be seen from Table 2 that the hot-rhodium-plated silver layers when new did not show any tendency to stick with any contact, whereas this was the case with the hot-rhodium-plated gold-cobalt layers in a relay. With the ultra-rhodium-plated silver layers, ^{no sticking occurred after 10 8} switching cycles until the end of the test, while with the ultra-rhodium-plated gold-cobalt layers over 2.5 * 10 switching cycles - especially with a thin rhodium layer - increased contact sticking was found.

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Overall, the test results show that the ultra-rhodium-plated silver contact layers according to the invention, Even with high numbers of switching cycles, both consistently low contact resistances and extremely high show a low tendency to stick compared to the examined gold-cobalt layers.

For the application of the silver contact layer, an electrolyte is expediently used which is largely free of brighteners and wetting agents and which is advantageously deposited using the wave electroplating technique. The rhodium, which expediently has a sulfur content of 4 to 7 wt.% Is produced in the other hand vorteihafterweise spray electroplating technology ( "jet plating"). As a result, the layer thickness of the protective layer can be achieved particularly precisely. It is also advantageous to heat-treat the contact element after the contact layers have been applied.

9 claims

Claims (9)

VPA 82 P 1 0 5 7 DE Claims ( My contact element, which has at least two contact layers galvanically applied one above the other on a preferably ferromagnetic carrier material, of which the outer layer consists of rhodium and the second layer underneath consists of a noble metal, characterized in that the rhodium layer has a thickness between 0.2 μm and 2 µm and the underlying noble metal layer consists of silver. 2. Contact element according to claim 1, characterized in that that the rhodium layer has a thickness between 0.3 and 1 μm. 3. Contact element according to claim 1 or 2, characterized in that the rhodium layer has a sulfur content of 4 to 7 wt.%. 4. Contact element according to one of claims 1 to 3, d a characterized in that the silver layer has a thickness of 1 to 10 µm, preferably 2 to 5 µm. 5. Contact element according to one of claims 1 to 4, characterized characterized in that below the silver layer a nickel layer with a thickness of 2 to 4 µm. 6. Contact element according to one of claims 1 to 5 _f, characterized in that an additional copper layer with a thickness of 2 to 10 µm is provided between the carrier material and the noble metal layer. 7. Method for producing a contact element according to -JT- VPA 82 P 1 0 5 7 DE Claim 1, characterized in that optionally coated with copper and / or nickel Carrier material one after the other the silver layer in bath or wave electroplating technology and then the rhodium layer is applied in spray electroplating technology. 8. The method according to claim 7, characterized in that that for the application of the silver layer a particularly pure electrolyte, which is largely is free of brighteners and wetting agents is used. 9. The method according to claim 7 or 8, characterized in that the contact element is tempered after the application of the contact layers.