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Dirty rinsewater staining NiAu plated parts?

Since some days we have some Brown spots on NiAu finishing after washing.
Tests have prove as the problem is the water using to rinse the PCB.
Nevertheless the water quality is controlled by a conductivity meter as 1µs/cm.

Someone know this problem?
Some one know the solution?

Franchomme Herve
sub contractor - France
July 1, 2009

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July , 2009

Hi, Franchomme. My suspicion is that your test was wrong and the problem is that the nickel and gold are not thick enough and pore-free enough.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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Franchomme, Ted could be right, so check the thickness of your deposits. However, if the thickness is OK, try investing in a water treatment plant that will solve your rinsewater issues. Rinsing is the most critical stage in any successful metal finishing operation and every opportunity for making it the best available should be taken - do not reduce the effectiveness of your rinsing, otherwise it will ruin your operations!

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
July 3, 2009

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July 14, 2009

Frachomme,
Ted and Trevor have covered the most likely causes for your problem. My company has experienced problems similar to your's and we were using reverse osmosis water for our rinse. It wasn't good enough so we installed mixed-bed ion exchange columns and spray guns for our rinsing and it has eliminated the staining of our gold on nickel coatings. At the point of use the ion exchange columns are producing water in the .1 - .07 microsiemen range

Tim Hamlett, CEF
- West Palm Beach, Florida, USA