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Reduced Drilling Defects in PCB Drills with Rainbow-TAC

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Home > Case Studies > Reduced Drilling Defects for PCB Drills with Rainbow-TAC

Importance of Advanced Coating for PCB Drills

In today’s electronics manufacturing, PCB drill performance is a key driver of product quality, yield, and cost efficiency. Defects such as burrs, nail heading, or rough hole walls can compromise plating reliability, lower yields, and increase rework. As boards grow denser and production volumes rise, manufacturers need drills that last longer and perform consistently. Advanced coatings like Rainbow-TAC make this possible improving throughput, reducing defects, and safeguarding reliability in high-density PCB production.

pcb drilling defects

Common PCB Drilling Defects

Hole Entry Burr - Jagged and raised edges around the hole entry. Excessive wear at the cutting edge or flute tip fails to shear through copper cleanly, leading to burr formation on entry.​ 

Nail Heading - Copper pad compressed outward, forming a flat rim at the hole entrance. A blunt drill tip plastically deforms the copper instead of cutting, leading to smeared copper and poor plating quality. 

Hole Wall Roughness - Uneven wall texture with fiber protrusions or scoring. Worn or chipped flutes and poor coating scrape rather than slice, disrupting chip evacuation and degrading wall finish.

Our Solution: Rainbow-TAC

Developed with NTI Nanofilm’s proprietary Filtered taC Coating Technology, delivers exceptional hardness and an ultra-smooth surface finish. By minimizing friction and wear, it keeps cutting edges sharp and stable even at extreme spindle speeds. Rainbow-TAC actively prevents nail heading, suppresses burr formation, reduces resin adhesion, and improves hole wall smoothness ensuring consistently higher hole quality. 

As a result, manufacturers achieve significantly longer drill lifespan, fewer tool replacements, reduced production downtime, and lower cost per hole in high-density PCB manufacturing.

taC Coating Uncoated

*Based on internal test. Results subject to changes from different materials under different operating environment.

Key Benefits

Achieve cleaner holes, longer drill life, fewer defects, and lower cost per hole in high-density PCB manufacturing.

  • Reduce Resin Buildup

    Low friction coefficient (<0.1) prevents sticking and reduces the resin build up, cuts cleaning downtime.

  • Improve Drill Quality

    Low Roughness (Ra <0.1) enables clean cuts and reduces nail heading.​

  • Extend Tool Life

    High Hardness prevents abrasion and fatigue.

  • Reduced Drilling Defects Nail Heading test

    41% lower overall drilling cost through
    superior defect control

  • Extend Tool Life top flute test

    Maintain top flute integrity over
    3x longer than uncoated bits

Coating Performance Comparison

Rainbow-TAC achieves ultra-high hardness and ultra-low friction, outperforming standard TiN and DLC coatings in both durability and anti-adhesion properties

Coating Type Hardness (GPa)​Friction Coefficient​Max Service Temperature​
(Thermal Stability) (℃)		 Resin Adhesion
Tendency
Uncoated 15~18 0.7-1.0 600 Severe
TiN 20~25 0.4-0.6 800 Moderate
Standard DLC 20~30 0.1-0.2 ≤300 Minor​
Rainbow-TAC50<0.1≤500Minimal

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Frequently Asked Questions

  • What causes drilling defects in PCBs such as burrs and nail heading?

    Drilling defects like burrs, nail heading, and rough hole walls are typically caused by worn or blunt drill tips, excessive tool wear, or inadequate coating. These conditions deform material instead of cleanly cutting it, leading to defects that compromise plating reliability and yield.

  • How does Rainbow-TAC improve PCB drill performance?

    Rainbow-TAC, developed with NTI Nanofilm’s proprietary Filtered taC Coating Technology, reduces friction and wear while maintaining sharp cutting edges at high spindle speeds. It minimizes burr formation, nail heading, and resin buildup, ensuring higher hole quality and longer tool life.

  • Why is drill coating important in high-density PCB manufacturing?

    In high-density boards, where hole precision and smooth walls are critical, drill coating significantly reduces defects and tool replacements. Coatings like Rainbow-TAC help manufacturers increase throughput, cut downtime, and lower cost per hole.

  • How does Rainbow-TAC extend PCB drill lifespan?

    With exceptional hardness and ultra-low surface roughness, Rainbow-TAC resists abrasion, fatigue, and resin adhesion. This extends drill lifespan, reduces cleaning frequency, and lowers replacement costs.

  • What are the benefits of using Rainbow-TAC coated drills compared to uncoated drills?

    Rainbow-TAC coated drills provide cleaner cuts, smoother hole walls, and reduced defects. Manufacturers benefit from higher yields, consistent quality, fewer tool changes, and reduced production downtime.

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