Abstract:

This paper discusses the corrosion process of immersion silver (ImAg) board finish on printed circuit boards subjected to elemental sulfur environments in the presence of high-sulfur content clay and moisture. The tests induced various types of metal migration processes and corrosion products.Migration phenomena ranged from short dendrites of Ag₂S, Cu₂S, and CuS, which grew fromImAg surface edges without solder masks, to long dendrites of Cu₂S growing from ImAg surface edges with solder masks that had copper traces beneath them.

Index Terms—Clay test, elemental sulfur environment, immersion silver (ImAg), printed circuit boards (PCBs).

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