Warpage simulation and DOE analysis with application in package-on-package development

The current paper talks about warpage modeling and validation, DOE analysis and approximation model derivation, and solving of actual warpage problem. Warpage of actual PoP (Package-on-Package), both the top and bottom packages, is investigated extensively through modeling and experimental measurement. It is found that the current warpage modeling method using average CTE and linear elastic analysis yields acceptable accuracy. Full factorial DOE analysis using ANSYS, EXCEL and JMP is performed to analyze the impact of design and material on warpage of both bottom and top packages. Surprisingly it is observed from DOE analysis that die size has completely different impact on warpage for top and bottom package. An actual problem, where a PoP top package exhibits large crying mode warpage, is quickly solved with the established warpage analysis method.