Investigation on high temperature mechanical fatigue failure behavior of SnAgCu/Cu solder joint

In this paper, high temperature mechanical fatigue tests on SnAgCu/Cu solder joints were carried out under three test temperatures (100, 125, 150 °C). Failure mechanism was analyzed through observation of micro-crack evolution and fracture morphology. The results show that the deformation curve of solder joint under high temperature mechanical fatigue tests can be divided into three stages: strain hardening stage, stable deformation stage and accelerated failure stage, which is similar to the curve under creep test condition. In addition, the cyclic life decreases rapidly with increasing temperature. Deformation field in the solder joint is non-uniform and shear strain concentration occurs in solder close to the intermetallic compound (IMC) layer. Micro-crack initiates at the corner of the solder joint and then tend to propagate along interface between Cu substrate and solder. The fracture morphology under three temperatures all exhibits ductile fracture mode and the failure path transforms from cutting through the top of Cu6Sn5 to propagation in solder matrix close to IMC layer with increasing temperature.