Application of viscoelastic model for simulating process-induced warpage of ball grid array packages

Warpage evolution of an overmolded BGA package either under uniform temperature excursion or during post-mold curing process is analyzed by using finite element simulation with a cure-dependent viscoelastic model for the molding compound. Additional finite element analyses are performed to compare molding compound constitutive behavior (temperature-dependent elastic or viscoelastic) on the package warpage prediction. Through shadow Moire¿ experimental validation, it is observed that the prediction with viscoelastic constitutive model agrees well to the measured values; while the elastic model overestimates package warpage.