Prediction of process-induced warpage of IC packages encapsulated with thermosetting polymers

One critical issue for manufacturing of map-molded packages is the warpage induced during the molding process. A cure-dependent viscoelastic constitutive model has been established to describe the evolution of material properties during the curing process of a thermosetting polymer. The evolution of the rubbery moduli is described by a model based on scaling analysis and is measured with a new method. The relaxation behavior of the transient part is described by the cure-dependent relaxation amplitude and reduced relaxation times which are based on the time-conversion superposition principle. The cure-dependent parameters are characterized by using an combinational approach of DMA and DSC measurements. The predictions agree well with the experimental results. FEM is conducted for QFN map molding processes, and prediction of the warpage induced during the curing process and the cooling down is made. The results show that warpage induced during the curing process has a significant contribution on the total warpage. Furthermore, when decreasing the number of maps, the contribution of curing-induced warpage significantly increases.