Effects of Material Properties on Top PoP Package Warpage

摘要

In recent years, Package on Package (PoP) is an increasing high density package solution for package stacking technologyrnin various device manufacturing applications. Especially, top package with stacked memory packaging system connected to arnbottom logic packaging system via solder joint is representative PoP configuration. To guarantee the assembly yield andrnreliability of the solder joint between the top package and bottom package, mechanical compliance between these two packagesrnis crucial during package stacking. Therefore package warpage needs to be understood and controlled to meet the assemblyrnyield target. As the complexity of the package configuration increases by thinner package thickness, higher number of stackingrndies and large package size, the warpage control within the target requirement is very challenging, especially when the materialrnbehaviors of substrate, die, molding compound and die attach film are different and also changing as a function of temperature.rnTherefore, the material property of key component in top PoP package plays a crucial role in warpage performance. Amongrnkey components, the thermo-mechanical properties of molding compounds is very important and mainly determine the warpagernlevel of the Top package at room temperature and the warpage behaviors during the reflow high temperature profile for thernboard level assembly with bottom package. Among various material properties, the chemical cure shrinkage, coefficient ofrnthermal expansion and storage modulus for the molding compounds are determining factors on the temperature dependantrnwarpage control of top PoP package. In this paper, the effects of various molding compound material properties on warpagernare studied through comprehensive experiment and modeling work. The findings and results provide some clues and guidelinernfor material property selection for warpage control in Top PoP package, which influence the PoP assembly yield and reliability.