Environmental Conditions Impacts on PB-Free Solder Joint Reliability

Understanding the sensitivity of PB-free solder joint reliability on various environmental conditions, such as corrosive gas, low temperature, and high temperature/high humidity environment, becomes a crititcal topic while deploying Pb-free products in various markets and applications. In this study, several sets of test vehicles consisting of various types of packages are pretreated with corrosive gas, salt spray, low temperature storage, and humidity/temperature soak. They were then subjected to temperature cycle test to study their solder joint reliability. Test vehicles using eutectic Sn/Pb solder were also tested side-by-side with the Pb-free siblings as a reference. The results have shown, under certain conditions, these pre-treatments degrade the cycle life of Pb-free solder joints on the tested packages. In this paper, the extent of degradation, the microstructural evolutions, and dependency of the degradation on package types and solder alloys are discussed.