Warpage Analysis of Fan-Out Panel-Level Packaging Using Equivalent CTE

Abstract

In this study, we developed a simple method to obtain the equivalent coefficient of thermal expansion (CTE) by comparing the results of the finite element method (FEM) with the experimental results. This equivalent CTE was used to effectively describe the final mechanical/chemical shrinkage behavior after post-molding curing (PMC). During fan-out panel-level packaging, the chemical/molding shrinkage, curing and temperature cool down processes can cause excessive warpage of the panel structure. When this warpage becomes excessively large, the subsequent processing is substantially more difficult. Thus, it is important to be able to accurately predict structural warpage before manufacturing. FEMs are commonly used to estimate panel warpage during molding, however, the shrinkage behavior of the epoxy resin during molding and the material properties after curing are difficult to fit, and a much experimentation is usually required to obtain the temperature-dependent material properties of the molding compound and parameters required for the empirical equation, e.g., PVTC (Pressure Volume Temperature Cure). Furthermore, the simulation results from these empirical equations are often inconsistent with the experimental results. However, our results showed that under various geometric conditions, the equivalent CTE remained almost constant, and thus can be used in FEM as a reliable material property to predict the warpage after a panel PMC process.