Fatigue crack growth behavior in Sn-Pb eutectic solder/copper joint under mode I loading

Fatigue crack growth (FCG) behavior along 63Sn-37Pb solder/copper interface was investigated using a solder-jointed plate specimen with a single-edge crack under opening tensile loading (mode I). Finite element analysis was conducted for evaluating stress intensity factor (K) and J-integral (J) of the crack tip. Under frequency of 10 Hz and stress ratio of 0.1, the fatigue crack propagation rate could be characterized successfully by either stress intensity factor range (ΔK) or J-integral range (ΔJ). A fatigue crack propagated in transgranular manner through Pb-rich phases and Sn-rich phases near the solder-copper interface. With increasing crack length, the size of plastic zone at the crack tip and the von Mises stress along the solder-copper interface increased, which resulted in the interfacial debonding near the crack tip. The critical crack length (a/W) and adhesive strength for interfacial debonding were 0.46 and 20.2 MPa, respectively.