Eliminating Burr Formation to Improve Hole Entry Cleanliness in High Speed PCB Drilling

In advanced PCB manufacturing, precision at the hole entry is critical. Even when drill endurance is optimized, many fabricators continue to face burr formation, raised ridges of copper or resin left around the hole edge. Though often overlooked at first glance, burrs are one of the most disruptive drilling defects, undermining lamination stack quality, plating reliability, and compliance with IPC Class 3 standards.

Why Burrs Are a Hidden Risk

Burrs form when drilling conditions cause material to deform rather than shear away. Typical triggers include dulling drill edges, friction induced heat softening resin, and inadequate chip evacuation that forces debris outward at the entry rim. The result is an uneven raised edge. 

The consequences ripple across the entire PCB build:

• Disrupted plating: uneven entry surfaces cause non uniform copper deposition
• Stacking interference: raised rims prevent flush lamination and precise alignment
• Weak bonding: contaminants trapped under burrs reduce adhesion strength
• Escalating costs: boards with excessive burrs require rework or end up scrapped

In compact multi layer designs where tolerances are tight, even burrs above 30 µm can compromise yield. Entry cleanliness is not cosmetic, it is fundamental to long term board reliability.

Rainbow TAC: Engineered for Burr Suppression

NTI Nanofilm’s Rainbow-TAC, built on proprietary Filtered taC Coating Technology with FCVA, is purpose designed to minimize burr formation at the hole entry. Rather than focusing only on extending tool life, Rainbow-TAC directly addresses the physical and thermal conditions that generate burrs.

• Crisp Cutting Edges Maintained
  With hardness near 50 GPa (~5000Hv), the filtered tetra amorphous carbon (taC) layer preserves drill geometry across long production runs, ensuring copper and resin are cut cleanly rather than smeared.
• Heat and Friction
  Under Control A friction coefficient below 0.1 keeps drilling temperatures stable. Resin remains firm, preventing the softened flow that typically produces raised ridges at hole entry.
• Durable Coating Integrity
  FCVA deposition creates a dense, adherent coating that resists delamination or surface cracks. Unlike conventional films that degrade mid job, Rainbow TAC retains performance throughout extended high speed drilling cycles.

Performance Validated Through Joint Evaluations with Customers

Collaborative evaluations on 16 layer FR4 boards at 120,000 RPM confirmed Rainbow-TAC’s ability to suppress burr formation under demanding production conditions:

These joint trials demonstrated that Rainbow-TAC drills consistently produced clean, flat entry surfaces, safeguarding plating adhesion and lamination integrity.

The Value for PCB Fabricators

By suppressing burr formation, Rainbow-TAC delivers measurable advantages:

• Cleaner hole entries that reduce plating irregularities
• Reliable Class 3 compliance across extended runs
• Lower rework and scrap rates, cutting cost per hole
• Greater process stability in high density production environments

Conclusion

Burr formation may seem like a small defect, but its impact cascades through every stage of PCB manufacturing. Rainbow-TAC, validated through joint evaluations with customers, provides a proven pathway to cleaner entries, fewer defects, and consistently higher yields. For manufacturers competing in the most advanced markets, controlling burrs is no longer optional, it is essential, and Rainbow-TAC delivers the precision needed to achieve it.