The assembly of plastic electronic package requires a sequence of process steps. Every
process step induces thermal residual deformation and stresses on the assembled components,
which cause mechanical effects on the subsequent process step. In this study, both processing and
non-processing models with and without considering the effect of chemical shrinkage on molding
compound are built to simulate the package warpage and stresses in assembly. The processing
model, a nonlinear model with element birth and death used to activate and deactivate the
processing materials, can more realistically simulate a series of assembly processes in a plastic
package. Due to negligence of the intermediate step, the package warpage and stresses predicted by
non-processing model are in significant error.