Effects of fillers on wire sweep in semiconductor chip encapsulation

Epoxy molding-compounds which are used in semiconductor chip encapsulation by transfer molding are filled with high concentrations of silica particles whose dimensions are comparable to the diameter of the bonding wire. This study is aimed at investigating the effects of solid fillers on wire deformation during encapsulation. Experiments were performed to measure wire deformation due to the flow of a mixture of liquid and solid fillers. Wire deformation was determined by measuring the change in electrical resistance of the wire when it deformed and relating the change in electrical resistance to wire deformation. Next, the wire deformation was calculated based on the viscous drag force of the fluid on the wire. A theoretical estimate of the magnitude of the wire deformation due to direct particle collision was made which indicated that this is negligible compared with that due to the viscous drag force. The experimental wire deformation values were in good agreement with wire deformation values calculated based on the viscous drag force of the fluid