loop height control

**Loop height control** is the **process of setting and maintaining bonded wire loop vertical profile within specified limits for clearance and reliability** - it is critical for avoiding sweep, shorts, and mechanical stress failures. **What Is Loop height control?** - **Definition**: Wire-bond profile management covering first bond rise, loop apex, and second bond descent. - **Control Inputs**: Bond program trajectories, wire properties, and tool dynamics. - **Specification Scope**: Defined by package cavity height, neighboring wires, and mold-flow constraints. - **Measurement Methods**: 2D/3D optical metrology and sampled X-ray verification. **Why Loop height control Matters** - **Clearance Assurance**: Incorrect loop height can cause mold contact or inter-wire interference. - **Sweep Resistance**: Optimized loop shape improves stability during encapsulation flow. - **Reliability**: Profile consistency reduces fatigue stress and neck-crack risk. - **Yield Control**: Loop outliers are common drivers of assembly escapes and rework. - **Scalable Manufacturing**: Stable loop control supports high-volume repeatability. **How It Is Used in Practice** - **Program Calibration**: Tune bond trajectory parameters per wire type and package geometry. - **Tool Health Monitoring**: Track capillary wear and machine dynamics affecting loop repeatability. - **SPC Deployment**: Apply loop-height control charts and automated excursion responses. Loop height control is **a central process-control axis in wire-bond assembly** - tight loop-height governance improves both package yield and lifetime reliability.