A mathematical model has been developed to describe the extrusion die flow of reactive electronic packaging materials. This model assumes that the flow is 1-D in the manifold of the die, but the flow obeys the 2-D Hele–Shaw model in the slot section. A realistic viscosity expression that includes the effects of chemical reaction and heat transfer has been adopted. A linearly tapered coat-hanger die was selected for illustration and the packaging material was chosen to be the epoxy system. Some example calculations are presented to illustrate the effects of several parameters on the flow distribution. Two optimization approaches were adopted to improve the uniformity of the flow; both the Taguchi method and the method of inserting a specially designed choker bar are applicable. However, using a choker bar appears to be more effective and flexible.