Contamination limits for Electroless Au bath?

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Dear All,

I face some problems with my electroless Au appearance. It looks patchy and the speed of plating is slow. We did a carbon treat on the Au bath. The speed did pick up but the appearance still looks patchy.

I checked for Cu and Fe contamination and found that Cu is 0.6ppm an Fe is 57 ppm. So I am wondering what is the control limit for Cu and Fe contamination?

Fayth Tan
Chemist - Singapore