FLOW MODELING OF PQFP DURING TRANSFER MOLDING

This paper addresses the use of Finite Element Method (FEM) and Finite Difference Method (FDM) for flow modeling of plastic quad flat package (PQFP) during automated transfer molding. The use of such numerical methods, together with the analytical model, can predict accurately the filling profile, melt-front advancement and wire sweep of PQFP during the molding process. This work adopted a more utilitarian engineering assumption for the flow modeling of the molding process compared with other published work. Factors considered for the prediction are the ram-speed profile for filling and melt front advancement, while for wire sweep the die and basic leadframe structure are included. With these improved assumptions the numerical results obtained for filling, melt front advancement and wire sweep agree well with experimental measurements. Also, a Sweep Indicator (SWI) model is developed that indicates potential zones of extensive wire sweep. This improved modeling methodology can lead to better and more cost-effective designs of molds used for encapsulation of plastic integrated circuits. Such use of computer aided engineering (CAE) helps to address reliability problems such as wire sweep in integrated circuits before production. It allows for process optimization of the molding parameters.