QFN Packaging Process Explained: Step-by-Step Guide

Front of Line (FOL) – QFN Packaging Early Stage

1. Wafer Incoming Quality Assurance (IQC) – First Optical Inspection

  • Definition: Incoming wafers are inspected after unpacking to ensure quality before entering the production line.
  • QA vs QC: QC ensures products meet required standards; QA builds the system to guarantee continuous compliance, creating trust internally and externally.
  • Common IQC checks:
    • Diameter (visual)
    • Chipping (visual / caliper)
    • Edge cracks (caliper)
    • Pits & stains (visual)
    • Scratches (microscope / caliper)
    • Warpage & flatness (feeler gauge)
    • Thickness (thickness gauge)

2. Wafer Backgrinding (BG)

  • The wafer is mounted on a grinding chuck with vacuum suction.
  • A rotating grinding wheel thins the wafer backside to the required thickness while DI water removes debris.
  • Process:
    1. Apply protective tape on wafer front side.
    2. Grind backside.
    3. Remove tape and measure thickness.
  • Common issues: grinding marks, chipping, TTV (Total Thickness Variation), water ingress.
Wafer Backgrinding (BG)

3. Wafer Mounting (Dicing Tape Application)

Protective dicing tape applied before wafer sawing.

4. Wafer Dicing (Sawing)

  • Wafers are fixed on blue tape to prevent die scattering.
  • Diamond saw blade cuts along scribe lines.
  • Defects: chipping, saw lane shift.

5. Second Optical Inspection

  • Microscope inspection after wafer sawing to detect defective dies.

6. Die Attach (Die Bonding)

  • Die picked up and placed on lead frame pad with epoxy adhesive.

7. Epoxy Cure (Baking)

  • Curing in oven at 175°C for ~1 hour to remove stress.

8. Wire Bonding

  • Gold or copper wires connect die pads to lead frame leads.

9. Third Optical Inspection

  • Inspection after die attach and wire bonding.

End of Line (EOL) – QFN Packaging Back-End Process

10. Post-Mold Film Application

11. Molding (Encapsulation)

  • Epoxy mold compound injected into mold cavity to encapsulate die and wires.
  • Defects: voids, wire sweep, incomplete fill.

12. Post-Mold Cure

  • 175 ± 5°C for ~8 hours.
  • Purpose: strengthen structure, reduce stress.

13. Plating (Leadframe Electroplating)

  • Pre-cleaning, acid treatment, copper pre-plating, silver plating.
  • Defects: poor adhesion, burrs, incomplete plating.

14. Marking (Laser Engraving)

  • Product ID, company logo, lot code.

15. Package Singulation (Sawing / Cutting)

  • Packages cut into individual QFN units.

16. Final Optical Inspection

17. Packing & Shipment

  • Electrical test, taping & reel, final packaging.

Similar Posts