Enhancing predictability of thermal warpage by applying temperature-dependent Poisson's ratio of epoxy molding compound

Abstract

The warpage behavior of electronic packages has become complicated in recent years owing to the miniaturization and heterogeneous integration technologies. Therefore, stress analyses through warpage simulations have become increasingly challenging. Understanding the thermo-mechanical behavior of epoxy-based packaging materials enhances the predictability of warpage simulation and helps in designing mechanically reliable electronic packages. However, the necessity and importance of an accurate database of thermo-elastic properties, especially the temperature dependency of Poisson's ratio, still has been overlooked for warpage prediction. In this study, the warpage prediction accuracy of a molded wafer was dramatically improved by measuring and applying the temperature dependency of elastic modulus and Poisson's ratio. If the temperature dependency of Poisson's ratio and elastic modulus is not considered, the warpage prediction error increases by 4.3 and 8.1 times for the 25 °C and 250 °C warpage, respectively. Surprisingly, even without considering only the temperature dependency of Poisson's ratio, the prediction error increased by 3.3 and 4.4 times for the 25 °C and 250 °C warpage, respectively. These results indicate that Poisson's ratio significantly affects the coefficient of thermal expansion-induced warpage behavior in the form of the biaxial modulus.

Keywords

• Poisson's ratio
• Warpage
• Epoxy molding compound
• Thermo-elastic properties
• Digital image correlation
• Finite element analysis