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Dull tin plating blisters in solder bath

I've been trying to dull tin plate some CRS pieces for soldering purpose. However, when the part is heated up thru solder bath in order to receive the solder, the dull tin layer starts "bubbling", leaving a very bad finish. It is necessary for our process that the surface of the part after soldering remain smooth. We've gone to several platers, and all methods utilized have the same result. FYI, I am plating the parts with copper before plating it with dull tin.

Abdul Rahman Ismail
- Malaysia
2006

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2006

My guess is that you have a problem with the cleaning cycle. To find out, bake a few parts at the same temp that the solder tank is at. Allow to cool and I bet that you will see hundreds of tiny blisters.
A strange thing in plating is you can over clean and over etch steel parts that will cause blisters that look just like parts that were not cleaned or etched enough.
This bit me really bad while developing a tin-cadmium plating bath and with a tin-diffused cadmium plating of 4340 test panels.

James Watts
- Navarre, Florida