Building Accuracies in Finite Element Models for Life Prediction of Solder Joints

With the rapid transition to Pb free solder in electronic industry, reliability of solder joints and life prediction has seen a renewed interest. Using the knowledge gained from modeling SnPb solder, a number of life prediction models have been suggested for SnAgCu based solder joints. These models are determined utilizing certain modeling assumptions and material behavior. Assuming accuracy in test data, the methodology used for calculating the strain or energy density is a significant source of error which limits the application of life prediction model. Since measuring inelastic strain or energy density in a tiny solder joint is not practical, these values are usually calculated using analytical or numerical approach. All simulation approaches use some assumptions, which can impact the accuracy of life prediction model. For finite element analysis, these assumptions include factors such as the level of structural details, 2-D or 3-D representation, mesh density, boundary conditions, and material models used. This paper presents how these factors affect the accuracy and efficiency of finite element based simulations when applied for solder joint life prediction. The modeling approaches previously published for temperature cycling and drop/impact loading by the author have been reviewed and enhanced by using advanced simulation techniques. The effect of meshing, material properties, and solder behavior under slow and fast loading conditions are investigated.