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Trouble with free machining copper substrate

Has anyone heard of certain alloys of free machining copper having impurities (possibly tellurium)which can pollute a cyanide copper or cyanide silver plating tank? The part in question gets a tenth of electroless nickel, a tenth of copper, and 4 tenths of silver. We use a silver strike, and run all solutions at recommended levels. We have tried various dips between the copper and silver to rinse off any film or to give the copper an etch, but nothing seems to work. We have intermittent blistering of the silver layer with these parts, and blistering problems with other substrates after running these parts.

Keith Rosenblum
plating shop - St. Paul, Minnesota
1998

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1998

Your problem sounds like oil contamination. Maybe your cleaning process is not aggressive enough for the particular type of machining or stamping oil used on these parts.

You also indicated electroless nickel followed by copper then silver. Why this particular combination?

Bill Vins
microwave & cable assemblies - Mesa (what a place-a), Arizona

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1998

I would say that step one is to find out where the problem is happening. The copper EN interface or EN-copper plate or copper plate-silver strike or silver strike to silver plate.

Then find out the complete normal base metal analysis to see what could be a possible culpurt.

Why are you going copper base-EN-copper-silver vs copper-EN-silver?

Which tank can you dummy and make the problem go away?

James Watts
- Navarre, Florida