Numerical prediction of residual stresses evolving during packaging of ICs

This paper comprises a numerical constitutive model for evaluating residual stresses generated during encapsulation of integrated circuits. Residual stress is a consequence of molding process which can be divided in cure and thermal induced parts. Cure originated stress had been mostly neglected in literature and a special attention had always been given to detection of thermal induced stresses. In this study, both encapsulation resulted stresses are studied independently and a numerical methodology has been developed based on the applied boundary conditions during each stage of molding and the established process dependent mechanical models. A two dimensional numerical model is implemented in a commercially available software package. The numerically predicted stress results are experimentally validated by implementing a piezoresistive stress measuring chip in a transfer molding process.