Isothermal low cycle fatigue tests of Sn/3.5Ag/0.75Cu and 63Sn/37Pb solder joints under mixed-mode loading cases

To give a proper and accurate estimation of the fatigue life of solder joints, a mechanical fatigue test method under mixed-mode loading is proposed. The loading phase is controlled by the angle of loading direction. Experiments are conducted with 63Sn/37Pb and Sn/3.5Ag/0.75Cu solder joints. The isothermal mechanical low cycle fatigue tests were performed under several loading phases. Constant displacement controlled tests are performed using a micromechanical test apparatus. Failure patterns of the fatigue tests are observed and discussed. Morrow energy model was examined and found to be a proper low cycle fatigue model for solder joints.