Effect of Evolution of High Strain Rate Properties on Plastic-Work of SAC305 Alloy with 100°C Aging for Periods up to 240-days

Abstract

In the industries related to aerospace applications, medical applications and in oil/gas exploration, the electronic components may have to face very cold to extreme high surrounding temperatures. In addition, these electronic packages and assemblies can be exposed to vibrations, shocks and impacts. In such severe surrounding, electronic components may face strain rates of 1 to 100 per seconds and low surrounding temperature down to -65°C. The records are not existing for lead-free solder alloys tested at extreme surrounding temperature and at high strain rates, with isothermal aging. Previous published results for SAC305 lead-free solder alloys is limited to low strain rates and high operating temperatures. In this paper, lead-free solder alloy SAC305 has been tested and studied at extreme surrounding temperature starting from -65°C up to 200°C, with high strain rates, with isothermal aging at 100°C for up to 240 days. The prepared SAC305 lead-free alloy specimen after reflowing, were stored for thermal aging and then tested at strain rates of 10, 35, 50, and 75 per sec. at multiple operating temperatures ranging from -65°C to 200°C. Stress-strain curves are generated for various operating temperatures and for the range of strain rates. The experimental data has been fit to the Anand Viscoplasticity model for SAC305 and the Anand constants are established by predicting the measured stress-strain behavior for the various surrounding temperatures and high strain rates, for aging durations up to 240 days (i.e. 8 months). Also, FE analysis has been carried out for drop/shock events for BGA package assembly with PCB. Hysteresis stress-strain curves and plastic work density curves are generated for various aging conditions for SAC305 solder ball joints.