Identification of curing kinetics of epoxy molding compounds and mold flow analysis for assessment of die-shift defects

Fan-out processes are widely used in advanced packaging technologies to accommodate broader size variations and functional combinations of dies deployed on reconstituted wafers. However, such a process generates numerous mechanical loadings during the molding and curing phases. Without careful planning, failures such as “die shift” and “fly die” are frequently reported, which cause serious problems for subsequent processing. Among these issues, shear stress generation during molding, which is dominated by the resulted pressure distribution and increase in the viscosity of molding compound due to curing, has been recognized as a major controlling factor for defects of die shift and fly die. Prompted by the need to predict defects beforehand, this work presents an accurate 3D model for mold flow analysis by accounting for the curing kinetics. In conjunction with finite element structural analysis, the die shift induced by mold flow is estimated, and the results compare favorably with fabrication plant observations.