wire sag
**Wire Sag** is a wire bonding defect where the wire loop droops below its intended trajectory, risking contact with the die surface or other wires.
## What Is Wire Sag?
- **Cause**: Excessive loop height, inadequate wire tension, thermal softening
- **Risk**: Short circuits if wire touches die surface or adjacent wires
- **Detection**: Optical inspection, X-ray for encapsulated packages
- **Specification**: Minimum clearance typically 50-100μm above die
## Why Wire Sag Matters
Modern packages stack multiple die layers with minimal vertical clearance. Sagging wires can cause catastrophic shorts or intermittent failures under thermal cycling.
```svg
```
**Prevention Methods**:
- Optimize loop profile parameters
- Control bonding temperature precisely
- Use appropriate wire diameter for span length
- Verify wire tensioner settings daily