Study of package warp behavior for high-performance flip-chip BGA

To meet the future needs of high pin count and high performance, the LSI die and package size of flip-chip BGA (FC-BGA) devices have become larger. As a result, package warpage due to mismatch of the coefficients of thermal expansion among the construction materials has become a more serious problem for package reliability. In this paper, package warpage is successfully measured by a 3-D surface profile method in the temperature range from −55 to 230 °C. Furthermore, the package warpage of FC-BGA was investigated to clarify the effect of the thermomechanical properties of the underfill resin. Based on the results, we constructed a model of the mechanism of package warpage. This paper proposes an optimized underfill resin that can achieve low package warpage and a long fatigue life of the solder bump. The future trends in underfill resin will be to have properties of extremely low elastic modulus and non-linear properties such as creep.