Creep and Fatigue Behavior of SnAg Solders With Lanthanum Doping

In this paper, extensive testing was conducted to study the effects of Lanthanum (La) doping on the creep and fatigue behavior of SnAg lead free solder alloys. Variables considered in this paper include doping amount, aging temperature, and aging time. The experimental data show that rare earth element (RE) doping increases SnAg solders creep resistance by about 15%. Meanwhile, RE doping does not affect thermal aging behavior of the solder alloy. A microstructure dependent Anand viscoplastic model is proposed to capture the RE doping effect on the creep behavior. Good agreement between the model predictions and experimental data are obtained. In addition, fatigue tests were performed with bulk specimen. It is found that La doping increases the fatigue life by about five times. The optimal doping level for better fatigue performance is around 0.1%.