Crystallization, morphology and distribution of Ag3Sn in Sn–Ag–Cu alloys and their influence on the vibration fracture properties

Since Ag3Sn phase plays a decided role in the performance of Sn–Ag–Cu solders, this study varied the solidification rate and Ag content to clarify the formation, morphology and distribution of Ag3Sn in Sn–Ag–Cu alloys, as well as their influence on the tensile properties and vibration fracture resistance under different vibration conditions. Results show that a less packed distribution of Ag3Sn in the eutectic regions and a larger area of β-Sn dendrites contributed to a higher damping capacity and thus a greater vibration life under constant force conditions. Acicular eutectic Ag3Sn and large primary Ag3Sn plates accelerated crack growth and thus degraded the ductility and vibration fracture resistance particularly when the damping effect was removed.