An investigation of Sn pest in pure Sn and Sn-based solders

Five solders Sn–0.7Cu, Sn–3.4Ag–0.8Cu, Sn–3.5Ag, Sn–36Pb–2Ag, and pure Sn, and two mobile phone boards were tested at low temperatures for tin pest. The samples were stored at −196 °C for 50 h, −40 °C for 4 years, and finally −17 °C for 1.5 years. Tin pest was observed in pure tin but not in any of the solder alloys or the boards tested. It is suggested that the mechanical properties of tin-based solders play a key role in tin pest formation. Any factor that strengthens the materials can increase the resistance to tin pest. Influential factors such as solder composition, test temperature, and types of alloys are discussed.