FEA Modeling of FCOB assembly Warpage and Stresses Due To Underfill Encapsulation and Thermal Cycling loading

摘要

FEA modeling investigations were conducted to study the residual bending stresses in a Flip-Chip-On-Board (FCOB) assembly during the underfill encapsulation curing process, generated in the package due to mismatches in the coefficients of thermal expansion (CTE) of the various materials in the assembly. The effect of silicon die and FR4 thickness was examined in relation to the bending stresses in the silicon die. Three different underfill encapsulant mechanical properties were examined for a specific FEA model. Elasto-plastic and creep deformation behavior of solder was simulated under thermal cycling conditions to study the equivalent plastic and creep strain behavior in the solder joints.