Featured Snippet: Exit Burr (um) = base(material) x feedFactor x wearFactor / supportFactor
Free PCB exit burr calculator. Estimate exit burr height (um) from feed rate, backup board, drill wear and material, then read a burr class and fix.
Suitable for:
Estimate exit burr height.
| Est. exit burr | -- um |
| Burr class | -- |
| Fix | -- |
Relative estimate - confirm with cross-section measurement on your panel.
Burr at the hole exit is the most common drilling defect - raised material that needs a cleaning step and hurts via reliability. Exit burr is driven by feed rate, backup board quality, drill wear and material. This tool estimates a relative exit burr height (um) and a class so you can act before production.
The strongest lever is the backup board: UV melamine 880/950 give the cleanest exit, HDF is a cost-balanced mid, phenolic leaves more burr. Feed above the stable band and a worn bit both raise burr. As a rule, aim for sub-10 um on HDI and sub-20 um on standard FR4; see the 2026 backup board comparison.
| Material | Density (kg/m³) | Surface Hardness (HD) | Best For |
|---|---|---|---|
| UV Melamine 950 | 980 ± 30 | 80 ± 5 | IC Substrate, HDI micro-via |
| UV Melamine 880 | 950 ± 30 | 80 ± 5 | HDI, high-layer-count FR4 |
| HDF 880 | 880 ± 30 | 70 ± 2 | Standard FR4 multilayer |
| Phenolic (standard) | 750 ± 40 | 55 ± 5 | Back-drilling, rigid-flex |
| Aluminum entry sheet | N/A (metal foil) | N/A | Universal entry protection |
| Lubricated aluminum (LE) | N/A (coated foil) | N/A | Micro-via, HDI, high-Tg |
Stable feed rate and clean exits are what let you push hit count without micro-drill breakage. Pair the right board with the parameters from this tool — see our backup board range and aluminum entry boards.
| Material | RPM | Chip load | Feed (m/min) | Entry | Backup |
|---|---|---|---|---|---|
| FR4 (standard multilayer) | 90,000 | 0.012 | 2.16 | Aluminum entry sheet | HDF backup board |
| HDI / micro-via | 110,000 | 0.008 | 1.76 | Lubricant aluminum | UV melamine 880 backup board |
| Rogers (high-frequency) | 80,000 | 0.010 | 1.60 | Aluminum entry sheet | Phenolic backup board |
| PTFE / Teflon | 60,000 | 0.008 | 0.96 | Aluminum entry sheet | Phenolic backup board |
| IC substrate (ABF) | 120,000 | 0.006 | 1.44 | Lubricant aluminum | UV melamine 950 backup board |
| Ceramic PCB | 50,000 | 0.008 | 0.80 | Aluminum entry sheet | Phenolic backup board |
| Aluminum PCB (IMS) | 40,000 | 0.010 | 0.80 | Aluminum entry sheet | Phenolic backup board |
| Copper-core PCB | 30,000 | 0.010 | 0.60 | Aluminum entry sheet | Phenolic backup board |
Figures are qualified starting points cross-checked with published fabrication guidance and supplier benchmarks — validate on your own panels.
Exit burr (0.20 mm, FR4)
Representative field benchmarks for a 0.20 mm drill on standard FR4; actual results vary with stackup, machine and consumables — validate on your own panels.
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What is exit burr? Raised material at the hole exit; the most common drilling defect.
What causes burr? High feed, poor backup support, worn bit or wrong material settings.
What is a good burr height? Sub-10 um on HDI, sub-20 um on standard FR4 is a common target.
How does backup board affect burr? UV melamine 880/950 give the cleanest exit; phenolic leaves more.
What is nail heading? A mushroomed burr from poor backup support or wrong feed.
What is drill wear? Edge dulling that raises burr and rough hole wall.
How do I reduce burr? Trim feed, use a melamine backup, resharpen the bit, keep RPM matched.
What is via reliability? Long-term via integrity; clean exits support it.
What is desmear? Removing resin smear after drilling to restore the hole wall.
What is hole wall roughness? Inside-hole roughness; burr and wear both worsen it.
What backup grade for HDI? UV melamine 880 - highest burr control for fine stacks.
What is the relationship between feed and burr? Above ~15 mm/min burr risk climbs; stay in the 6-12 mm/min band.
Standard aluminum 1100 H18 entry foil (0.15–0.20 mm) is the universal choice for FR4 and back-drilling. Lubricated aluminum entry sheets (LE/CAE) add a thermoset coating that phase-change cools the drill tip by 15–22%, reducing resin smear and drill breakage on HDI and micro-via work. Water-soluble coated entry boards offer an alternative for rigid-flex where residue cleanliness is critical.
UV melamine 950 (980 kg/m³, 80±5 HD) is the premium choice for IC substrate and HDI where exit burr must be near zero. UV melamine 880 (950 kg/m³) suits high-layer-count FR4. HDF 880 (880 kg/m³, 70±2 HD) balances cost and performance for standard multilayer. Phenolic boards are preferred for back-drilling and rigid-flex due to their machinability.
1100 H18 (99% Al) is the industry standard for entry foil. 3003 and 5052 alloys offer higher strength for thicker entry boards but may increase drill wear. The choice of alloy affects chip load stability and burr formation on the entry side.
Kyocera Precision Tools — PCB drilling ↗
Thermoset-coated (LE/CAE) entry boards provide lubrication through phase-change cooling at 120–180°C. Water-soluble coated boards dissolve in cleaning. Uncoated aluminum relies purely on mechanical centering. The coating choice directly affects drill temperature, chip evacuation, and hit count.
YUESHAN — LE Sheet drill temperature data
Drill tip temperature can exceed 300°C on standard FR4 without proper consumables. The entry board absorbs 20–30% of frictional heat; the backup board dissipates exit heat. Lubricated entry systems reduce peak temperatures by up to 30%, directly reducing resin smear and hole wall roughness.
Rogers Corp — RO4000 laminates ↗
Micro-drill breakage is most often caused by chip clogging in the flute, not by mechanical overload. Lubricated entry boards eliminate the chip adhesion failure mode. A worn entry board (excessive hits per sheet) increases drill wander risk — replace entry sheets at the same interval as drill change.
Process and CAM engineers use these numbers across demanding builds:
The right entry and backup board is what actually lets you hold a stable feed rate without breakage. Explore the product lines:
HDF, UV melamine and phenolic backup boards for stable exits and burr control.
Product Page →Plain and coated aluminum entry boards, including lubricated grades for micro-holes.
Product Page →Self-lubricating entry sheets that cool and center the bit on HDI / micro-via drilling.
Product Page →Coated back-drill entry sheets built for controlled-depth second-pass accuracy.
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