PCB Countersink & Counterbore DFM Checklist
Pre-production design verification for mechanical mounting holes
v2.0 | March 2024 | IATF 16949 Certified
⚠️ Critical: These features require secondary CNC machining. Standard Gerber files are insufficient—mechanical drawings (DXF/DWG) are mandatory. Missing specifications cause production delays.
01
Basic Parameters (Must Confirm)
02
Dimensional Safety Check
| PCB Thickness | Max Countersink Depth | Max Counterbore Depth | Status |
|---|---|---|---|
| 0.8mm | Not Recommended | 0.3mm (Risk) | High Risk |
| 1.0mm | 0.5mm max | 0.5mm max | Caution |
| 1.6mm | 1.1mm max | 1.1mm max | Safe |
| 2.0mm+ | 1.5mm max | 1.5mm max | Optimal |
03
Mechanical & Environmental
04
Manufacturing Documentation
Countersink Template (Copy to Drawing)
90° COUNTERSINK ON [COMPONENT/SOLDER] SIDE, Ø6.5mm (+0.2/-0.0) x 1.2mm DEEP, FOR M3 FLAT HEAD SCREW (DIN 7991). MIN REMAINING THICKNESS 0.5mm. NPTH.
Counterbore Template (Copy to Drawing)
COUNTERBORE: Ø6.0mm (+0.1/-0.0) x 2.0mm (±0.1mm) DEEP ON [SIDE], BOTTOM RADIUS ≤0.2mm, FOR M4 SOCKET HEAD CAP SCREW (ISO 4762). NPTH.
05
Red Flags - Verify Against
06
Standard Dimensions Reference
| Screw | Countersink (90°) | Counterbore | Pilot Hole |
|---|---|---|---|
| M2 | Ø4.0mm x 0.8mm | Ø4.0mm x 1.0mm | Ø2.2mm |
| M2.5 | Ø4.5mm x 1.0mm | Ø4.5mm x 1.2mm | Ø2.7mm |
| M3 | Ø6.5mm x 1.2mm | Ø6.0mm x 2.0mm | Ø3.2mm |
| M4 | Ø8.0mm x 1.5mm | Ø8.0mm x 2.5mm | Ø4.3mm |
Need DFM Review Before Fabrication?
Upload your Gerber files and mechanical drawings for complimentary engineering review. We verify mounting hole specifications against IPC-2221A standards and your board stack-up.