Micro-Mechanics of Fatigue Damage in Pb-Sn Solder Due to Vibration and Thermal Cycling

Abstract

This paper presents a micro-mechanistic approach for modeling fatigue damage initiation due to cyclic plasticity and cyclic creep in eutectic Pb-Sn solder. The issue of damage evolution is deferred to a future paper. Fatigue damage model due to cyclic plasticity is modeled with dislocation mechanics. A conceptual framework is provided to quantify the influence of temperature on fatigue damage due to cyclic plasticity. Damage mechanics due to cyclic creep is modeled with a void nucleation model based on micro-structural stress fields. Micro-structural stress states are estimated under viscoplastic phenomena like grain boundary sliding and its blocking at second phase particles, and diffusional creep relaxation. A conceptual framework is provided to quantify the creep-fatigue damage due to thermo-mechanical cycling.