Abstract
This work investigates the characteristics of vibration fatigue under a resonant state for different aging conditions, and the microstructural variation of Pb–Sn solder alloys. The major experimental parameters include natural aging time and Pb–Sn composition. Examination of crack initiation and major crack formation behavior during a resonant vibration test shows that cracks initiated at different sites of the Sn–Pb and Sn–Sn phase boundary on the specimen’s surface, and that some cracks then linked up with each other to form a major crack that grew into the specimen. It is worth noticing that a stratum-type deformation occurred in the Pb-rich phase during the vibration deformation process because of the high frequency fatigue deformation of Pb–Sn eutectic alloys. In addition, coarsening was found to develop with natural aging time, and a decrease in deflection amplitude occurred during vibration tests. The investigation used heat treatment to provide further insight into the coarsening effect on the resonant fracture resistance of Pb–Sn alloys. In addition, as greater Sn content increased the fraction of the Sn-rich phase, it definitely improved vibration fracture resistance.
