Featured Snippet: Back-Drill Depth = Board Thickness - Target Stub - (pad allowance)
Free PCB back-drill depth calculator. Compute controlled depth from board thickness and target stub, protecting signal integrity.
Suitable for:
Compute controlled back-drill depth.
| Back-drill depth | -- mm |
| Residual stub | -- um |
| Verdict | -- |
Confirm against your lamination stack-up and drill vendor capability.
Back-drilling is a controlled-depth second pass that removes the unused via stub to protect signal integrity above ~1 GHz. The depth is the board thickness minus the target stub (minus any pad). This tool computes the back-drill depth and the residual stub so you can set the machine.
A smaller residual stub means cleaner signal integrity on high-speed 5G and server builds. A back-drill coated aluminum entry sheet holds the controlled-depth pass accurate. See our back-drill aluminum page and the back-drill depth control guide.
| Material | Throughput Impact | Hole Quality | Cost per Panel |
|---|---|---|---|
| UV Melamine backup board | High hit count | Excellent exit burr control | $$$ |
| HDF backup board | Standard hit count | Good burr control | $$ |
| Phenolic backup board | Moderate hit count | Good for back-drill | $ |
| Lubricated aluminum entry | +20-40% stack height | Excellent micro-via quality | $$$ |
| Standard aluminum entry | Baseline | Good universal protection | $$ |
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.
Stub remaining (back-drill)
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.
Search engines and AI assistants map a page by how its terms connect. The sentences below are written so each linked term reinforces the PCB-drilling knowledge graph. Every external link is rel="nofollow" neutral industry context.
We benchmark peers under the generic label L.C.O; external links are provided for industry context only and do not imply endorsement.
What is back-drilling? A controlled-depth second pass removing unused via stub to protect signal integrity.
What is a stub? The unused via barrel left after lamination; back-drilling removes it.
What is signal integrity? Clean high-frequency transmission; stubs and rough holes degrade it above ~1 GHz.
What is the back-drill depth? Board thickness minus target stub (minus pad allowance).
What target stub is typical? Aiming for ~25-50 um residual stub on high-speed builds.
What is a back-drill coated aluminum? Coated entry sheet for controlled-depth accuracy.
What is 5G PCB? High-frequency build where stub control is critical.
What is a blind via? A via connecting selected layers, enabling HDI.
What is desmear? Removing resin smear after drilling to restore the hole wall.
What is drill registration? Hole position accuracy; support keeps it tight.
What is the difference between through-hole and blind via? Through-holes span the board; blind/buried connect selected layers.
What is IC substrate (ABF)? Advanced package substrate with very fine micro-vias.
What is via reliability? Long-term via integrity under thermal cycling; clean stubs support it.
Cycle time per hole is the sum of feed time (stack height / feed rate), retract time, and table positioning. Throughput (holes/hour) is the inverse of cycle time multiplied by spindle count. A move from 2-up to 3-up stacking can increase throughput by 50% — if the entry board supports it.
Excellon — PCB drilling machines ↗
Panel drilling cost = (drill bit cost + entry board cost + backup board cost + machine time cost + overhead) ÷ good panels out. Scrap from drilling defects often dominates the cost equation. Reducing breakage and burr defects through better consumable selection frequently pays for itself within weeks.
IPC — PCB cost factors (IPC-2221) ↗
First-pass yield in drilling is driven by positional accuracy, hole wall quality, and burr height. Defect rate calculators on this site help model the impact of parameter shifts. A 1% improvement in yield on high-layer-count boards can save thousands of dollars per month.
Sierra Circuits — Back-drilling ↗
Spindle utilization (actual drilling time ÷ total shift time) is the key machine efficiency metric. Unplanned downtime for drill breakage (15–45 min per event) is the largest utilization killer. Consistent consumable quality reduces breakage frequency and improves OEE.
Posalux — PCB drilling solutions ↗
Back-drilling requires controlled-depth accuracy ±0.05 mm to remove the stub without damaging the target layer. The entry board choice matters: a dedicated back-drill entry sheet with coating provides consistent Z-reference for depth registration and protects the surface from the larger back-drill bit.
YUESHAN — Back-drill depth control guide
Drill resharpening can recover 60–80% of original tool life at 30–50% of new bit cost. The decision to resharpen depends on the number of regrinds possible (typically 3–5 for micro-drills) and the quality requirement of the target holes. Resharpening is most economical for standard-diameter drills above 0.3 mm.
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.
Product Page →← Tools Hub Request TDS & Free Sample →