Quantifying the effect of porosity on the evolution of deformation and damage in Sn-based solder joints by X-ray microtomography and microstructure-based finite element modeling

The presence of reflow porosity in Sn-based solder alloys is one of the key factors affecting their reliability and mechanical performance. In this study we have used X-ray microtomography to visualize the reflow porosity in a Pb-free solder joint and to reconstruct a three-dimensional model based on the exact geometry of the pores. Interrupted shear tests and subsequent tomography were conducted to image the joint at several stages of deformation. The initial reconstructed microstructure was used as a basis for a finite element (FE) model to simulate damage and predict failure of the single lap shear joint. Sphericity analysis was conducted to verify the accuracy of the FE results. The deformation predicted by the FE simulation incorporating the ductile damage model showed very good agreement with experimental observations. The model was also able to accurately predict the crack nucleation sites and propagation path.