C*-parameter approach to low cycle fatigue crack growth of solders

Time-dependent fracture parameter (C*) and elasto-plastic fracture parameter (J-integral) have been used to correlate low cycle fatigue (LCF) crack growth behavior of Pb-free solder (96.5Sn/3.5Ag) and Pb-containing solder (63Sn/37Pb) under various frequencies (10^-3 - 10^-1 Hz) and temperatures (20, 85, 120°C). The results showed that J-integral would not characterize the LCF crack growth of 96.5Sn/3.5Ag under various frequencies and temperatures. However, C* was successfully correlated with the LCF crack growth rate of 96.5Sn/3.5Ag and 63Sn/37Pb. The plots of da_c/dt and C* for various frequencies and temperatures were located on a common straight line and in a narrow scatter band. It was confirmed that the LCF process of both solders is dominated by time-dependent mechanism.