Study of underfill resin properties for high performance flip-chip BGA package

For the future trend of high pin count and high performance, the LSI die and a package size of FC-BGA have been larger. Therefore the package warpage due to mismatch of the CTEs (Coefficient Thermal Expansion) among the constructive materials has been more serious for package reliability. In this paper, the package warpage is successfully measured by 3-D surface profile method in the temperature range from 25°C to 230°C. And the package warpage of FC-BGA was investigated on the effect of thermomechanical properties of underfill resin. Based on this result, we constructed the mechanism model of package warpage. The optimized underfill resin to realize low package warpage and long fatigue life of solder bump is proposed. The future trend of underfill resin is to have the properties of extreme low elastic modulus and non-linear properties such as creep.