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Copper Migration through Ni and Au surface under high humidity

Copper migration mechanism:

I would like to understand more about copper migration (corrosion).

The problem I am facing is that the coaxial connector body which is made of BeCU (beryllium copper) and plated with 30-70 micro inch of Ni. On top of Ni, there is 30-50 micro inches of Au. However when subjected to high humidity such as 70 to 85 %RH, the surface start to see the brownish spots. This is very ugly. Please tell me how to solve this problem.

Max Teh
- Sonoma, California, USA

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This is not some fancy copper migration phenomena, it's plain old corrosion because the plating is so thin that it's porous. Increase the nickel thickness by a factor of 10 or so then let us know what happens :-)
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

While a factor of 10 I am sure will eliminate the problem, a thickness of 150 you in. should be sufficient. I have seen this problem before as many customers want to keep the nickel thickness to a minimum when the parts will be subsequently formed or bent, otherwise the nickel will crack. the best solution is to plate the part after forming if it is possible.

Richard Breslin
Starflex, Inc - Lowell, Massachusetts