Fatigue Failure in a Model SMD Joint

A model SMD test‐piece has been developed which permits mechanical stressing of a solder joint in a similar mode to that occurring in the process of thermal fatigue. The failure mechanisms in the 60Sn40Pb alloy studied have been in agreement with those frequently observed in thermal fatigue. Further, the fatigue life of model joints was found to increase with increasing solder volume whilst, upon ageing at room temperature, fatigue resistance decreased. These effects were attributed to microstructural changes occurring within the solder.