Wire Sweep

Wire sweep is the deformation or displacement of bonded wires caused by mold-flow forces during encapsulation - excessive sweep can create shorts and reliability failures.

What Is Wire sweep?

• Definition: Post-bond wire movement from intended loop path under dynamic molding pressure.
• Primary Drivers: Mold compound viscosity, flow direction, gate design, and loop geometry.
• Failure Outcomes: Wire-to-wire shorting, cracked necks, and bond-lift stress concentration.
• Process Stage: Most critical during transfer molding in plastic package assembly.

Why Wire sweep Matters

• Yield Loss: Sweep-related shorts are high-impact assembly defects.
• Reliability Risk: Swept wires may fail early under thermal cycling and vibration.
• Design Constraints: Loop spacing and pad layout must account for expected flow forces.
• Process Interaction: Molding conditions and wire profile are tightly coupled.
• Cost Impact: Sweep failures often occur late in flow, increasing scrap cost.

How It Is Used in Practice

• Loop Optimization: Control loop height, span, and stiffness to resist mold-flow displacement.
• Mold Tuning: Adjust gate location, fill rate, and compound rheology for lower flow stress.
• X-Ray Inspection: Monitor wire position shifts statistically across lots and package zones.

Wire sweep is a major assembly defect mechanism in molded wire-bond packages - controlling sweep requires coordinated loop design and molding process engineering.