stitch bond

**Stitch bond** is the **second wire-bond connection formed by pressing wire onto substrate or lead without forming a free-air ball** - it completes the electrical path after the first bond in many wire-bond flows. **What Is Stitch bond?** - **Definition**: Tail-end bond created using ultrasonic force and tool pressure on the destination pad or lead. - **Sequence Role**: Typically follows first bond and loop formation in ball-bond processes. - **Quality Features**: Heel shape, stitch length, and intermetallic development determine robustness. - **Failure Modes**: Weak stitch can cause lift-off, high resistance, or intermittent opens. **Why Stitch bond Matters** - **Electrical Continuity**: Reliable stitch bonds are required for stable signal and power delivery. - **Mechanical Strength**: Second-bond integrity resists encapsulation and thermal-cycle stress. - **Yield Control**: Stitch defects are a common source of assembly fallout. - **Process Consistency**: Uniform stitch formation supports predictable package performance. - **Reliability**: Long-term bond survival depends on proper stitch morphology and metallurgy. **How It Is Used in Practice** - **Parameter Tuning**: Optimize ultrasonic power, force, and time for destination metallurgy. - **Visual Inspection**: Check stitch footprint, deformation, and heel cracks with microscopy. - **Strength Testing**: Use pull-test failure mode analysis to validate stitch robustness. Stitch bond is **a critical second-bond element in wire interconnect formation** - stitch-bond quality strongly influences assembly yield and lifetime stability.