Effects of aging temperature on tensile and fatigue behavior of Sn-3.0Ag-0.5Cu solder joints

Thermal aging effects on the tensile and fatigue properties of Sn-3.0Ag-0.5Cu (wt%, SAC305) solder joint are investigated. Three series of experiments were conducted at different temperatures, including uniaxial tension experiments for specimens after aging for 24 and 72 h, and low cycle fatigue experiments for specimens after aging for 72 h. The tensile strength and fatigue life of SAC305 solder joint were analyzed statistically by using a modified Weibull distribution model, which takes the thermal aging effect into account and the results agrees well with the experimental data. The maximum tensile strength after aging for 24 h was obtained by aging at room temperature. After aging for 72 h, the maximum tensile strength and longest fatigue life were obtained by aging at the cryogenic temperature. With elevated aging temperatures, the tensile strength and fatigue life decrease. Microstructure observations on the solder joints reveal that with reducing of aging temperatures, the Ag₃Sn phase gradually grows and occupies more volume while Cu₆Sn₅ phase occupies less volume. The high content of Ag₃Sn phase can embrittle the solder joint and dominate the tensile failure.