Indentation Creep Properties Evolution of Lead-Free Solder Joints Subjected to Thermal Cycling

Abstract

Solder interconnections undergo thermomechanical stress when exposed to temperature changes. This leads to the evolution of the microstructure and the degradation of mechanical properties, causing component failure. Doped lead-free solders have substituted traditional SnPb solders for harsh applications. These alloys have been found to improve the mechanical and thermal fatigue properties of solder joints. However, few studies have investigated the evolution of the creep properties of lead-free solder joints in thermal cycling tests. This paper examines the creep properties of newly developed solder alloys during thermal cycling. The study focused on three solder alloys: SAC305, SAC-3Bi, and Sn63Pb37. The tested component was 15 x 15 mm CABGA208. The thermal cycling profile ranged between -40°C and +125 °C with a ramp rate of 10 °C/min and a dwell time of 15 min at extreme temperatures. A microindentation test was performed for individual solder joints using a cylindrical flat tip at room temperature. Three different loads were applied, with three replicates at 0, 100, 250, and 650 cycles for each test combination. The results showed that the dopped solder alloys demonstrated a decrease in creep rate until 250 cycles. However, SnPb and SAC305 alloys were found to deform more when the number of cycles increased.