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Reworking gold plating

2003

We occasionally will get a low gold thickness on our parts. Rather than scrap the parts I would like to know if we can "rework" them by adding more gold to the existing gold. Is this an "accepted" practice? What is the "accepted" process flow? We soft (24k) gold plate for electronic applications.

Also, what is the best test for gold plating adhesion to copper or nickel?

Thanks,

John Hutchison
- Eau Claire, Wisconsin

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Hi John,

You can replate the components with a gold strike and then with your regular 24kt gold plating bath to required thickness. Activation will play an important role. Have a watch on it. Bend test and thermal shock at 250 °C will be good adhesion tests.

Venkat Raja
- Kitchener, Ontario, Canada
2003

On the subject of activation, I disagree with the previous response. Gold does not passivate. Passivation is a form of oxidation but gold is a noble metal and will not form oxides. It can adsorb foreign oxides which must be cleaned away as well as soils, oils, grease, etc. A good cleaning cycle will take care of this, then additional gold can be added after a conventional strike. About the other question, gold must not be plated on top of copper for it will interdiffuse and form an amalgam with Cu. A barrier of nickel or other suitable metal is required.

Guillermo Marrufo
Monterrey, NL, Mexico
2003