In this study, we evaluated the strain distribution in flip chip (FC) packages by the FEM analyses and the digital image correlation method (DICM) measurement. The evaluation was carried out for four types of FC packages which consisted of two types of buildup (BU) resin and two types of underfill (UF) resin. The results show that the lower coefficient of thermal expansion (CTE) of resin reduced thermal strain around solder bumps. We also compared the DICM measurement with the FEM analyses. This comparison shows that the concentrated region of shear strain obtained by the FEM was the reverse of that obtained by the DICM in packages with OF-1 that has higher CTE. We found out the higher Poisson's ratio of OF-1 at higher temperature may change the distribution of shear strain around a solder bump. The distribution of shear strain around a solder bump analyzed by the FEM with the higher Poisson's ratio (=0.48) of OF-1 resin approached that measured by the DICM.
