Effects of Curing and Chemical Aging on Warpage—Characterization and Simulation

In this paper, the effect of the curing process on the warpage of an encapsulated electronic package is considered by using a coupled chemical-thermomechanical modeling methodology. A cure-dependent constitutive model that consists of a cure-kinetic model, a curing- and chemical-aging-induced shrinkage model, and a degree of cure-dependent viscoelastic relaxation model was developed and 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 postmold 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 cross linking during the PMC, has a significant effect on the package warpage. The coupled chemical-thermomechanical model can be applied for performing numerical optimization for the packaging process and the assembly reliability.