A three-dimensional modeling of wire sweep incorporating resin cure

Abstract

In this paper, a fully three-dimensional (3-D) model is introduced for the simulation of wire sweep during cavity filling in transfer molding of integrated circuit (IC) packages. This includes the composite-segment-functions method for defining spatial wirebond geometry, a singularity numerical integration procedure for calculating flow-induced forces on general 3-D wirebonds and a penalty finite element technique for simulating 3-D flow of molding compound in the mold cavity. The wire sweep of a 26-leaded IC package under various processing conditions was investigated. The wirebond deformation was studied in terms of wirebond orientation, local velocity field, local temperature, degree of cure, molding compound viscosity, etc. The effects of the process conditions, such as curing time, transfer rate and molding temperature, on wire sweep were also investigated. The effect of the location of the gate of the cavity was also studied and found to have a profound effect on the pattern of wire sweep. © 1998 IEEE.