Flip chip solder joint fatigue analysis using 2D and 3D FE models

In this paper, the numerical and experimental study of solder joints of flip chip on board (FCOB) assembly with 63Sn/37Pb and 96.5Sn/3.5Ag solder bumps are reported. The impact of different finite element (FE) models on solder joint fatigue life was investigated. The five FE models used were 2D-plane strain, 2D-plane stress, 2D-axisymmetry, 3D-slice and 3D-octant. The solder joints were modeled with elastic-plastic-creep constitutive equations. To predict the solder joint fatigue life, the time-independent plastic strain and time-dependent creep strain parameters were used in conjunction with Engelmaier model for 63Sn/37Pb solder bumps and Kanchanomai model for 96.5Sn/3.5Ag solder bumps. The FCOB assemblies were subjected to temperature cycling condition of -40°C to 125°C to gather experimental solder joint fatigue data. The two-parameter Weibull analysis was used to determine the mean time to failure (MTTF) life. The modeling results show that the solder joint fatigue life predicted by the 2D-plane stress model is higher than the 2D-plane strain model. The solder joint fatigue life predicted by the 2D-axisymmetry, 3D-slice and 3D-octant models fall within the predicted life of the 2D-plane stress and 2D-plane strain models. The comparison between the modeling and the experimental results shown that Engelmaier model for 63Sn/37Pb solder bump tend to predict the solder joint fatigue life closed to the MTTF life, while the Kanchanomai model for 96.5Sn/3.5Ag solder bump tend to predict the solder joint fatigue life near to the 1^st failure.