Microstructural stability and mechanical properties of Sn-1Ag-0.5Cu solder alloy with 0.1 wt.% Al addition under high-temperature annealing

Effects of 0.1 wt.% Al addition on the microstructural stability and mechanical properties of the low-Ag-content Sn-1Ag-0.5Cu (SAC105) solder alloy under high-temperature aging were investigated. Addition of Al suppresses the formation of Cu6Sn5 intermetallic compound (IMC) particles and leads to the formation of large AlCu IMCs. Moreover, the Ag3Sn IMC particles become larger and less-packed in the interdendritic regions after the additions of Al. The addition of Al also leads to enlarge the primary β-Sn dendrites and diminish the interdendritic regions. The tensile test results indicate that the addition of Al significantly decreases the elastic modulus, yield strength, and total elongation. After 720 h and 24 h of aging at 100°C and 180°C, respectively, the Al-bearing SAC105 solder alloy exhibits more resistance to microstructural coarsening than the SAC105 solder alloy which in turn significantly reduces the mechanical properties degradation with aging.