The effect of morphology coarseness on vibration fracture behavior of Pb-Sn solders under various aging conditions

This work investigates the characteristics of vibration fatigue under a res onant state for different aging conditions, and the microstructural variati on of Pb-Sn solder alloys. The major experimental parameters include natura l aging time and Pb-Sn composition. Examination of crack initiation and maj or crack formation behavior during a resonant vibration test shows that cra cks initiated at different sites of the Sn-Pb and Sn-Sn phase boundary on t he specimen's surface, and that some cracks then linked up with each other to form a major track that grew into the specimen. It is worth noticing tha t a stratum-type deformation occurred in the Ph-rich phase during the vibra tion 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 P b-Sn alloys. In addition, as greater Sn content increased the fraction of t he Sn-rich phase, it definitely improved vibration fracture resistance.