Process Parameters Analysis And Quality Evaluation Software Pevelopment Of Package On Package(PoP) Reflow Process

Reflow process of package-on-package (PoP) is the key process to the yield ofPoP production. We always wish that the temperature of BGA in PoP chips increasesand drops along the reflow profile. But in the practical production process, we can onlymeasure the temperature of chips’ surface with thermocouples, and can notimmediately monitor the temperature of BGA in the chips. Therefore, it is important tostudy the true reflow profile of the BGAin PoP chips.This paper firstly builds the one-dimensioned multiple-layered transient heattransfer partial differential equations with typical theory of heat transfer, definiteconditions are given and simulation calculation with MATLAB is done. The truereflow profile of BGA is finally given in this paper, and this paper points out that oneof the reasons of the “head in pillow effect” is the temperature difference betweenupper solder balls and bottom solder balls in reflow process. Then heat transfer,warpage and deformation, solder joints shapes, liquid bridges auto assembly, residualstress of solder joints and stress concentration of PoP chips are summarized in thispaper to build a system of quality evaluation for PoP reflow process.