Chemical Reaction

Good afternoon all, I am looking for help from you folks to find a place that can do metalurgical analysis on components and contamination. We are an OEM and just recently received back from the customer several units that failed in the field after a short period of time. These units were built with water soluble SNpb paste and washed with aqueous batch cleaner. These units to the naked eye and under high power magnification look to be spotless, not a drop of flux residue to be seen. The Boards after production are conformal coated with FINE-L-Kote coating and then proceed to test after dry. When the PCB's were returned to us, the PCB's and all the components looked perfect except for one 0603 transorb. This particular transorb had some kind of growth growing across it, to the point that it was shorted. Has anyone ever seen anything like this before?

It happens to be the same component on all the boards. The component is a lead free component, believed to be palladium with other ingredients, according to the spec. This component also has battery voltage on it all the time. The growth looks like either a chemical reation to the coating or it is electroplating itself. If anyone could shed some light on this problem, it would be greatly appreciated. Regards, Brad

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