Influence of aging treatment on deformation behavior of 96.5Sn3.5Ag lead-free solder alloy during in situ tensile tests

This study investigates the influence of aging treatment on deformation behavior of 96.5Sn3.5Ag eutectic solder alloys with lower strain rate (<10−3 s−1) during tensile tests under the scanning electron microscope. Results showed that because of the existence of Ag3Sn intermetallic particles and the special microstructure of β-Sn phases in Sn3.5Ag solder, grain boundary sliding was not the dominant mechanism any longer for this Pb-free solder. While the interaction of dislocations with the relatively rigid Ag3Sn particles began to dominate. For the as-cast specimen, accompanied by partial intragranular cracks, intergranular fracture along the grain boundaries in Sn–Ag eutectic structure or the interphase boundaries between Sn-rich dendrites and Sn–Ag eutectic phases occurred primarily in early tensile stage. However, the boundary behavior was limited by the large Ag3Sn particles presented along the Sn-rich dendrites boundaries after aging. Plastic flow was observed in large area, and cracks propagated in a transgranular manner across the Sn-dendrites and Sn–Ag eutectic structure.