Plastic package has mainly been used in current IC package, and transfer mold is the mainstream of the molding technology. When high viscous mold resin flow into mold cavity during filling stage, bonded Au wire connected between chip and lead frame usually deform. This deformation is called ‘wire sweep’. Excessive wire sweep may cause defects such as electric short at semiconductor chip and wire. This paper describes effect of filler profiles involved mold resin on wire sweep.