Isothermal Fatigue Damage Model for Lead-free Solder

This article presents an investigation of lead-free solder material 95.5Sn-3.9Ag-0.6Cu under isothermal fatigue loading. The effects of strain rate on hysteresis loop and fatigue life over the total strain range from 0.4 to 1% at room temperature are investigated. A fatigue damage model is established to characterize the isothermal fatigue behavior of the material with the theory of damage mechanics. A fatigue failure criterion is proposed based on the concept of damage accumulation in solder material. The model takes into account the effect of strain rate in the development of constitutive and damage evolution equations. The life prediction is compared with the testing data and has shown a good agreement.