transfer molding

**Transfer molding** is the **molding process where preheated encapsulant is forced from a pot through runners into package cavities** - it is the dominant encapsulation method in many semiconductor assembly lines. **What Is Transfer molding?** - **Definition**: A plunger applies pressure to transfer compound into closed mold cavities around devices. - **Flow Path**: Compound moves through runner and gate systems designed for balanced filling. - **Cure Behavior**: Material crosslinks in-cavity under controlled thermal conditions. - **Production Fit**: Supports strip and multi-cavity processing for high-volume packaging. **Why Transfer molding Matters** - **Throughput**: Enables efficient encapsulation of many units per cycle. - **Process Maturity**: Long industrial history with robust tooling and controls. - **Quality Control**: Well-characterized flow dynamics support repeatable package outcomes. - **Cost Efficiency**: Optimized mold tooling lowers per-unit packaging cost. - **Defect Sensitivity**: Imbalanced flow can cause voids, wire sweep, and short shots. **How It Is Used in Practice** - **Runner Design**: Optimize gate and runner geometry for uniform cavity fill timing. - **Pressure Profiling**: Use staged pressure curves to reduce wire movement and trapped air. - **Maintenance**: Keep mold tooling clean to maintain consistent flow behavior. Transfer molding is **the primary encapsulation method for mainstream semiconductor package production** - transfer molding reliability depends on balanced flow design and disciplined process monitoring.