Gold Solderability Problems

Q: We occasionally have problems with dewetting of our pure gold plating during the soldering step. The parts we plate are thin, made of copper and have a sulfamate nickel strike on them. We perform regular maintenance on all of the plating baths used in our process. Do you have any suggestions on how we might solve this problem? J. M.

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A: There are a number of things that you should at least consider in trying to solve this problem. First of all, soldering can fail in two different modes: dewetting and non-wetting. Dewetting can be caused by a plate thickness that is too thin, impurities underneath the final coating or oxidation of the plated surface. Nonwetting is when the top layer, in this case gold, doesn’t wet or take solder.

Quite often the problem is with the solder itself. Solder does become contaminated and it should be changed on a regular basis.

Don’t forget about your cleaning steps. Cleaners do not last forever and have to be changed on a regular basis. You mentioned in your e-mail that you perform maintenance on all of your plating baths but you did not indicate how well you maintain control of your cleaners.

Last but not least, look at your rinsing steps. We tend to take for granted that rinsing is a “slam-dunk” process. In my experience, many plating operations create their own problems by not having good rinsing between process steps.