Low cycle creep-fatigue behaviors of Sn-4Ag/Cu solder joints

In this study, the creep-fatigue behaviors of the Sn-4Ag/Cu solder joints were investigated using in-situ tensile stage. The results reveal that the creep-fatigue process is composed by the strain hardening stage, steady deforming stage and accelerating fracture stage. During the initial few cycles, the strain increases rapidly because the solder is soft. After the strain hardening becomes saturated, the strain increases linearly with increasing cycles, strain concentration occurs in the solder close to the joint interfaces and generates the initial microcracks. When the microcracks connect to form long cracks, the failure accelerates and the specimens fracture along the joint interface shortly after that. Dislocation climb is predicated to be the major creep mechanism.