corrosion of nickel cladded contact 1

[davidmoul]

Dear all,

I have a corrosion problem between a connector and a nickel cladded copper. The wire became all black, even if the connection is protected by a protection (shrinked on the wire).

The wire is brazed with silver on the connector. The application is a vacuum pump, so there is, theoretically, nothing to corrode the connection.

Does anyone have a clue on the phenomena that appears here?

you can see a picture of the connection attached to this file.

Thank you for your help,

 

[btrueblood]

That doesn't look anything like a vacuum pump...maybe you mean a pass-thru into a vacuum chamber?

Presumably the braze was done with a flux? It is likely that you have vaporized the flux residues to create the smut you are seeing. It may also be certain constituents of the braze alloy (cadmium? zinc?) or oxides or sulfides of those metals are boiling off...how hot does the connector get, and to what vacuum level are you pumping?

 

[davidmoul]

Firts of all, many thanks for your quick answer... You're right, that's a pass thru that came into the vacuum chamber of a turbomolecular pump.

In fact this problem has been seen only on certain pump coming back from our client... After the manufacturing process, there is no problem at all... And most of our product doesn't show that kind of problem...

This problem appear on a specific application, but we can't have any details on the process...

 

[btrueblood]

Hmm. They may have higher temperatures in the vacuum chamber, or have a high partial pressure of something corrosive (fluorine gas?) than your other users. Without knowing details of the braze alloy and flux you are using, and the end use environment, you (or they) are stuck.

Can you switch to solid wire, and strip it and pot it directly into a pass-thru (avoiding brazing or soldering)? Could you use a mechanically crimped connection on the inside, again to avoid braze/solder/fluxes?

 

[davidmoul]

In fact, these machines are used to manufacture semi-conductors, with gas containing fluorine.

I will check for the composition / way to solder the wires. Thank you for your help!