Effect of chemical aging on warpage for encapsulated packages — Characterization and simulation

The effect of curing process on the warpage of encapsulated electronic package is considered by using a coupled chemical-thermo-mechanical modeling methodology. A cure-dependent constitutive model that consists of a cure kinetics model, a curing and chemical aging induced shrinkage model and a degree of cure-dependent viscoelastic relaxation model was implemented in a numerical finite element model for warpage simulation. Effects of polymerization conversion and chemical aging on the warpage evolution of a bimaterial dummy package after molding and during the post-mold curing (PMC) process were investigated by using the proposed modeling methodology. Shadow Moiré warpage analyses were also performed to validate the numerical results. It was found from the warpage analyses that the chemical aging, while contributing little to the overall crosslinking during PMC, has a significant effect on package warpage. The coupled chemical-thermo-mechanical model can be applied for performing numerical optimization for packaging process and assembly reliability.