In the semiconductor packaging process, Cover Tape peeling or bursting (where the cover tape detaches from the carrier tape or fails to seal properly) is a critical issue that directly impacts the First Pass Yield (FPY). This can lead to component leakage, machine downtime, and potential damage to the chips.
The following is an analysis of the root causes and corresponding solutions:
I. Root Cause Analysis
Cover tape bursting is generally caused by unstable Peel Strength or excessive Mechanical Stress, categorized into four dimensions:
1. Improper Equipment Parameter Settings
Insufficient Sealing Pressure: If the pressure rollers or heating blocks don’t apply enough force, the adhesive layer between the cover tape and carrier tape won’t fuse completely.
Low or Fluctuating Sealing Temperature: Heat-activated tapes require a specific activation temperature. Insufficient heat causes “false sealing,” while excessive heat can warp or embrittle the carrier tape.
Mismatched Sealing Time/Speed: If the packaging speed is too high, the dwell time in the heating zone is insufficient for a secure bond.
2. Material Compatibility Issues
Adhesive Failure: The pressure-sensitive (PSA) or heat-activated adhesive (HSA) on the back of the tape may be expired, damp, or unevenly coated.
Polarity Incompatibility: The chemical materials of the carrier tape (usually PS, PC, or PET) and the cover tape may not bond well due to surface energy differences.
Dimensional Deviation: A mismatch between the cover tape width and the sealing tracks of the carrier tape leads to off-center sealing.
3. Environmental and Physical Factors
Electrostatic Interference: High ESD generated during peeling can cause electrostatic repulsion, forcing the tape to “pop” open during downstream processes.
Contamination: Dust, oil, or debris on the sealing tracks hinders direct contact between the tapes.
4. Winding Stress
Excessive Winding Tension: If the finished reel is wound too tightly, the accumulated internal stress can cause the edges of the cover tape to burst open over time.
II. Solutions and Preventive Measures
1. Optimize Sealing Parameters (DOE)
Use a Design of Experiments (DOE) to find the “Sweet Spot” between pressure, temperature, and speed:
Temperature Control: Periodically calibrate sealing blades with thermocouples to ensure the actual temperature stays within ±5℃ of the set point.
Pressure Adjustment: Ensure the pressure rollers are balanced on both sides to prevent one-sided sealing weakness.
2. Material Qualification and Testing
Peel Strength Test: Follow the EIA-481 standard to ensure peel strength remains between 0.1N and 1.3N (10g to 130g).
Compatibility Verification: When switching suppliers, perform a 72-hour aging test (e.g., $60℃/ 90% ) to check for edge lifting.
3. Equipment Maintenance
Cleaning: Use Isopropyl Alcohol (IPA) every shift to clean the sealing blades/blocks and remove adhesive residue or carbonized particles.
Track Alignment: Ensure the carrier tape runs on a smooth, flat trajectory without vertical vibration.
4. Environment and Storage
Humidity Control: Maintain workshop humidity between 40% – 60% to minimize static buildup.
Winding Tension: Adjust the take-up motor torque to follow a “tight inside, loose outside” principle to prevent physical squeezing.
III. Quick Troubleshooting Guide
| Phenomenon | Likely Cause | Recommended Action |
| Localized Bursting | Uneven heat or nicked sealing blade | Inspect and replace sealing blade/block |
| Full Strip Detachment | Low temp or excessive speed | Increase temperature or reduce speed |
| Bursting after 24 hours | Excessive tension or aged adhesive | Reduce winding tension; check expiry date |
| Tape/Carrier Tearing | Sealing temperature too high | Lower the sealing temperature |