To Extend Suhir Theory for Predicting Thermally-Induced Warpage of Flip-Chip Packages

The thermally-induced warpage control on the electronics packages is an important issue during their fabrication process and assembly. It needs a fundamental theory to provide an insight of mechanics to assist and further check the finite element and experimental results. The well-known, closed-form solution to thermal stresses of a die-substrate assembly has been proposed by Suhir in the mid-1980's. The solution has been corrected and extended in prediction of thermal stresses and deformations of die-substrate assembly. The solution was further applied to warpage prediction of flip-chip packages and closely compared with finite element and experimental results. However, a thorough evaluation of this theory for thermally-induced warpage (or deformation) of the packages has not been done yet. This study aims to take a close look into the theory again and validate it by finite element analysis and shadow moiré experiment. The shear- effect region will be proposed and its effect on curvature distribution over entire package length and corresponding warpage will be examined in terms of thickness and elastic modulus of underfill. The other parameters such as extended substrate, and fillets of underfill will be also studied. The limitation and feasibility of the Suhir solution to warpage prediction of flip-chip packages will be discussed in detail in this study.