How to Fix Stripping Gold

Q: We selectively strip gold from using a reel-to-reel process. Quite often, the gold that remains after the stripping process is dark in color similar to a brown gold. We have tried a number of different formulations with little success in solving the problem. Do you have any suggestions? 

A: The dark color may be caused by impurities that build up in the stripping solution. I assume you are using a cyanide based stripping solution. This type of solution tends to form dark polymeric-like materials as they age. The dark color could be a residue that is deposited on the surface during the stripping step. Temperature may also play a role here. A higher temperature may cause discoloration.

Q. What is the best way to strip immersion gold from electronic packages? 

A. Your best bet is to use a proprietary formulation for stripping the gold. These products are designed to dissolve the gold and protect any copper and nickel that may be on the surface of the parts. You can find vendors of stripping solutions at Products Finishing Supplier Database.

You should be aware that immersion golds have different characteristics depending on what the base metal is and how it has been prepared. The porosity of the deposit, the thickness of the deposit and the amount of alloying material in the deposit all will affect the rate of removal.