Common Wirebonding Defects in IC Packaging and Solutions | QFN Packages Reliability Guide

Common Wirebonding Defects in IC Packaging and Solutions | QFN Packages Reliability Guide

Translated Content

Common Wirebonding Problems and Corrective Actions in IC Packaging

Wirebonding is a critical step in semiconductor packaging, including QFN packages and other leadframe-based designs. However, common process issues may occur, affecting bond quality and long-term device reliability. Below we summarize typical wirebonding problems, their influencing factors, and recommended corrective measures.

1. Ball Over-Squeeze

Causes:

  • Excessive ultrasonic power.
  • Excessive bonding pressure.
  • Overheating.
  • Excessive initial bonding force (25–30 g).
  • CV setting too high.
  • Ball or wire size too small.
  • Using worn, damaged, or incorrect type of capillary.
  • Chip height variation causing early contact.

Solutions:

  • Reduce ultrasonic power and/or bonding time.
  • Reduce bonding pressure.
  • Lower preheat and bonding area temperature.
  • Reduce initial bonding pressure (25–30 g).
  • Adjust CV to proper level.
  • Use correct wire size.
  • Replace the capillary.
  • Re-teach bonding height (use Bond Height Re-learn tool).

2. Ball Under-Squeeze

Causes:

  • Low bonding pressure, temperature, ultrasonic power, or contact.
  • Oversized ball or wire.
  • Worn, damaged, or incorrect capillary.
  • Incorrect wire diameter.
  • Incorrect calibration (USG or bonding force calibration).
  • CV too low.

Solutions:

  • Increase bonding parameters as needed.
  • Correct FAB (Free Air Ball) size or install proper wire diameter.
  • Replace capillary.
  • Match wire diameter with capillary size.
  • Perform USG and bonding pressure calibration.
  • Increase CV.

3. Abnormal Ball Formation

Causes:

  • Improper or dirty tensioner.
  • Worn, damaged, or incorrect capillary.
  • Dirty or damaged wire clamp gem.
  • Undetected NSOL (Non-Stick On Lead) from previous wire.
  • Damaged or dirty glass capillary tube.
  • Misaligned glass tube, wire clamp, or capillary.
  • Contaminated or incorrect wire type.
  • Incorrect ball/wire size settings.
  • Improper secondary bond termination.

Solutions:

  • Ensure tensioner LED is on. Adjust or clean tensioner and air path.
  • Replace capillary.
  • Clean or replace clamp gem.
  • Replace or clean glass capillary tube with ultrasonic alcohol bath.
  • Re-align wire clamp and capillary.
  • Replace with correct wire (avoid contamination by touching wire).
  • Input correct wire diameter and FAB size. Reduce EFO current.
  • Re-optimize secondary bonding process.

4. Wire Tail After Secondary Bond

Causes:

  • Temperature too high.
  • Dirty, damaged, or incorrect capillary.
  • Secondary bond too close to lead edge.
  • Bonding current or pressure too low.
  • Incorrect wire elongation.

Solutions:

  • Lower heating temperature.
  • Replace capillary.
  • Re-teach bond position.
  • Increase bonding parameters.
  • Select 3%–6% wire elongation.

5. Ball Slip

Causes:

  • XY servo miscalibration.
  • Loose bonding head parts.
  • Improper clamping of workpiece.
  • Loose or misaligned Z encoder.
  • Incorrect bond height teaching.
  • CV too high.
  • Excessive ultrasonic power.

Solutions:

  • Perform XY servo calibration.
  • Tighten bonding head.
  • Calibrate workpiece clamp.
  • Re-teach MHS step; check heater block vacuum.
  • Adjust encoder head or replace if damaged.
  • Re-teach bonding height.
  • Lower CV or tail speed.
  • Reduce USG or increase pressure.

6. Poor Wire Feeding or Sensor Fault

Causes:

  • Gas path blocked or dirty.
  • Insufficient air pressure.
  • Optical fiber not aligned properly.
  • Damaged fiber equipment.
  • Loose wire spool fixture.

Solutions:

  • Clean air path and fiber tip.
  • Adjust air pressure.
  • Ensure optical fiber projects as a ring (not a dot).
  • Reconfigure fiber amplifier connections.
  • Replace damaged fiber equipment.
  • Tighten wire spool fixture screws.

Conclusion

Wirebonding defects such as ball over-squeeze, abnormal ball formation, wire tailing, or wire feed failures are common but preventable issues in IC packaging. By optimizing process parameters, maintaining equipment, and selecting the correct materials, manufacturers can significantly improve yield and reliability in QFN packages and other semiconductor packaging solutions.

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