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

Abstract Since Ag 3 Sn 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 Ag 3 Sn 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 Ag 3 Sn 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 Ag 3 Sn and large primary Ag 3 Sn plates accelerated crack growth and thus degraded the ductility and vibration fracture resistance particularly when the damping effect was removed.