Abstract
While considerable amount of researches and investigations have been made on lead-free solder joint reliability, limited number of literatures are available on the effect of gold content on lead-free solder joint performance. The challenges of lead-free solder/gold metallization interdiffusion during high temperature application/test are: gold embrittlement, intermetallics growth, void formation, and tin-whisker formation. Tin whiskers causing system failures in earth and space-based applications have been reported. This paper illustrates a few case histories of such challenges. The results confirmed that the synergistic effects of void formation, intermetallic compounds formation due to the thick gold plating, and coefficient of thermal expansion mismatch between organic and ceramic substrates resulted in brittle fracture of the solder joint. The tin whisker formation was attributed to the compressive stress in the tin solder material, which was caused by diffusion of the end-cap metallization, formation of intermetallics, and thermal cycling of the soldered components.
