Thermal Fatigue Life of Sn-2Ag Solder Bump with Small Al Addition

Recently, in accordance with environmental demands, Pb-free solders are being widely used. Our research was done to further promote the use of Pb-free solders. We tried to improve the thermal fatigue life by adding a small amount of Al to conventional Sn-Ag Pb-free solders. Ceramic ball grid arrays (C-BGAs), whose uses will increase in the future, were selected as the most crucial issue in thermal fatigue. Moreover, we used Sn-Ag solder as the mother solder alloy, to which we added a 0.1 and 0.05% wt. of Al. There were two kinds of fatigue fracture. In the first, the crack propagates inside the solder bump, and in the second, the crack propagates near the jointed solder and substrate interface. The fatigue life showed considerable improvement for the first mode, but no improvement for the second.