Life-Prediction of SAC305/Bi-based Hybrid Solder Joint Considering Bi-Diffused Layers with Gradual Bi Concentrations

Abstract

Reliability of SAC-LTS hybrid joints is assessed. Two tasks are conducted to achieve the goal. The first task involves determination of the Bi concentration dependent constitutive properties. A simple solder assembly is fabricated to examine the distribution of Bi concentration within a hybrid solder joint. Based on the distribution results, specimens with known Bi concentrations are fabricated and tested at various temperatures to obtain the constants of the Anand model as a function of Bi concentration. In the second task, an FEM model is developed to simulate various layers with different Bi concentrations in the hybrid joint. The well-known energy-based fatigue model is implemented to predict the cycles to failure. The prediction is compared with actual thermal shock testing data, and the results are discussed.