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Stripping silver and nickel from PCBs

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We need to remove the nickel plate (immersion nickel) the finish down to the copper; what is the best chemistry to strip off the nickel from the copper leaving the copper body and key of the copper surface smooth and clean? We need to remove the silver plate (immersion silver) from copper also what is the best chemistry to strip off the silver and keep copper surface clean?

Thank you very much.

Yanlu Zhai
PCB mfgr. - Salt Lake City, Utah, USA

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September 22, 2010

hi, don't know if ill be of any help. I am but a humble plater. but when we need to strip nickel off copper based material we use a sulfuric dekote @70-90 deg[its normally electroless nickel off brass] but I'd guess its the same.
i forget the exact make up but its along the lines of 110g dekote base salt ,10ml dekote activator , 50 ml sulphuric acid conc. per litre [im sure you could verify this by goggling.]
i found its best to start with say 600ml of water add the acid then get to temp , add the base salt and mix till disolved , then the activator, and top up to 1 litre with water.

and for silver [99.999] on a copper base we'd use a sulphuric/nitric @50 deg

95% sulphuric acid conc. and 5% nitric acid

be sure to be well ventilated and take extreme care with the nitric sulphuric as splash's with it are extremely painful/dangerous.

i think this is what you were after if I read the question correctly , hope it helps.

leigh cox
- exeter devon uk