Warpage mechanism of single-sided molded package studied with viscoelastic analysis

This paper presents simulation results of the warpage of single-sided molded packages studied by the finite element method. We calculated the warpage of model packages using elastic and viscoelastic analysis, and discussed the generating mechanism. The amount of the warpage of the single-sided molded package is mainly dominated by two factors. One is the difference of the coefficient of thermal expansion (CTE) between the molding compound and the substrate, and the other is the stress relaxation due to the viscoelasticity of the molding compound. The influence of the stress relaxation appears strongly when the glass transition temperature (Tg) exists between the cure temperature and the room temperature. It is necessary to take care of these factors in order to design package so as not to cause the warpage.