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.