Abstract: The process of delamination and crack in TQFP during the reflow and the effect of PECVD SiNx thin films on moisture-resistance properties of TQFP were studied. The experiments revealed that the content of moisture in TQFP is the main cause of delamination and crack, and the interface between silver paste and molding compound, die pad and molding compound are the weakest positions where delamination initiates and extends. PECVD SiNx thin films can decrease the moisture content of TQFP effectively, and prevent the delamination and crack to certain extent, and the thicker the films, the lower the moisture content.