Time-Accurate, 3-D Computation of Wire Sweep During Plastic Encapsulation of Electronic Components

A computational technique is developed for accurate prediction of wire sweep during encapsulation of electronic components by transfer molding. The technique advances the current state-of-the-art by modeling the effects of the two-phase flow involved, the effects of the polymerization of the melt, and the effects of the time-dependence of the fluid and heat flows and of the wire stresses and deformations. The computational techniques used for separately computing the fluid and heat flows, for separately computing the structural-dynamic stresses and deformations, and for establishing two-way coupling between the separately computed “flow” and “structural” solutions are described. Validations comparing the computational predictions with the corresponding analytical solutions for reference cases with straight wires immersed in flowing liquids are presented and discussed. The validation results show close agreement with theory, and demonstrate the need for using large-deformation theory for computing wire deformations and stresses. Demonstrative results for the unsteady flowfield and wire sweep in a TO-220 package are also presented and discussed.