Wire Deflection
Lateral displacement occurs when the fine bonding wires of a semiconductor package are forced out of their original positions during plastic encapsulation. This wirebond sweep is driven by the viscous drag of the molding compound flowing into the mold cavity. It can lead to electrical short circuits between adjacent wire loops or cause wire necking at the bond heel.
Encapsulation Pressure
Flow dynamics of the epoxy molding compound during the transfer molding process dictate the magnitude of the force acting on the wire loops. When wirebond sweep exceeds acceptable limits, the thin gold or copper wires are swept closer together, increasing the risk of intermittent contacts during thermal expansion. Controlling the molding temperature and mold injection speed helps to reduce the viscosity of the epoxy.
This optimization decreases the drag force, protecting the delicate interconnects from bending or breaking and reducing manufacturing defect rates.
Radiographic Inspection
Real-time X-ray systems scan the finished microelectronic packages to verify internal wire alignment and calculate loop deflection. Technicians measure the percentage of lateral movement relative to the total wire length to ensure compliance with military or industrial standards. If the calculated wire deflection exceeds ten percent of the span, the molding parameters must be adjusted to prevent electrical failures.
