Comparative study on the reliability of SnPbSb solder joint under common thermal cycling and extreme thermal shocking

The increasingly severe temperature has always been a problem for the solder joint applied in the future novel electrical devices. The reliability evolution of solder joint in these conditions is necessary for the design of electrical packaging materials. In this paper, a common thermal cycling test of - 65 to 150 celcius and an extreme thermal shocking test of - 196 to 150 celcius were carried out on Sn50Pb49Sb1/Cu solder joint. The interfacial behavior of the solder joint, as well as the corresponding mechanical performance, was analyzed. In the thermal cycling test, the coarsening behavior of Cu6Sn5 layer and the formation of a new Cu3Sn layer were detected. After 400 cycles of thermal cycling, the shear force of solder joint was decreased by 31.55%, but the ductile fracture was hardly changed. The reliability of solder joint was more sensitive to the extreme thermal shocking. Besides the coarsening behavior of IMC layer, the micro-crack formation induced by thermal stress was obtained in Cu6Sn5 layer. These micro-cracks became the crack source and gave a further decrement of the shear strength. After 400 cycles of extreme thermal shocking, the shear force of solder joint was reduced by 50.43%, giving a ductile/brittle mixed fracture.