Lifetime prediction and fracture behavior of shear cycled Cu/Sn–3.0Ag–0.5Cu/Cu joints under current stressing

Influences of shear amplitude and joint height on fatigue lifetime and fracture behavior of Cu/Sn–3.0Ag–0.5Cu/Cu joints with increasing current density were investigated. The results show that fatigue lifetime was shortened with increasing shear amplitude and current density but presented no joint height-dependency. A fatigue lifetime prediction model considering electric current stressing was proposed, and the predicted values were close to the experiment results. Additionally, when the current density increased, the fracture initially occurred in the solder matrix with a ductile mode, then shifted to partial at the solder/IMC layer interface with a ductile–brittle mixed mode, and finally migrated to complete at the solder/IMC layer interface with a brittle mode, showing a prominent ductile-to-brittle transition. These changes were mainly due to the sharply aggravated strain mismatch at the interface.