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Au Plating on Cu and on Ni

2006

My question is :
What's the difference if we plate Au on Cu and Au on Ni.There is a lot of improvement in defects if Ni is used underneath Au. Is it related to surface energy?
Also what is the effect of current density on grain size if grain refiner (Pb/As/Tl) is present?

Ajay Garg
Student - Minnesota, USA

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Hello Ajay,
The reason you have less defects plating gold over nickel is because nickel is a good diffusion inhibitor. The base metal or underplate generally will not migrate through the nickel into the gold. The important properties that gold lends itself to are maintained. In the plating industry nickel is widely used as a "barrier plate" for the aforementioned reasons. The type of grain refiner you mentioned is foreign to me, so I can't answer the second part of your question in full. Lower current densities in gold provide better grain structure, but the current can be increased slightly with the addition of a brightener. The current increase would depend on the concentration of the brightener. For rack plating gold with gold metal @ 1 oz/gal, adequate solution agitation, 10 asf is the norm. Good Luck!

Mark Baker
Process Engineer - Syracuse, New York
2006