DFM Checklist: 10 Things to Check Before Sending Gerbers to Fab

Getting a PCB right the first time is about preparation. Most re-spins are not caused by complex signal-integrity issues — they are caused by simple oversights that a quick DFM pass would have caught. Here are the ten checks our fab engineers recommend before you upload your Gerbers.

1. Minimum trace width and spacing

Confirm every trace meets your fab's minimum width (typically 0.1 mm / 4 mil for standard processes). Pay special attention to power planes where clearances can accidentally shrink after copper pours are recalculated.

2. Drill-to-copper clearance

Leave at least 0.25 mm from the edge of any drill hole to the nearest copper feature. Tighter tolerances are possible but add cost — and violating them causes shorts after plating.

3. Silkscreen over pads

Silkscreen ink over exposed pads causes solderability issues. Run a DRC rule that flags any silkscreen geometry overlapping a pad — most layout tools have this built in but leave it off by default.

4. Solder mask expansion

Standard solder mask expansion is 0.05 mm per side. If you are using fine-pitch components (0.5 mm pitch or tighter) make sure the solder mask dams between pads are at least 0.1 mm wide — narrower dams are often rejected by fab.

5. Board outline on a dedicated layer

The board outline must be a single, closed, unambiguous path on its own Gerber layer (typically Edge.Cuts in KiCad). Any gaps or duplicate lines cause automated routers to misinterpret the board shape.

6. Copper to board edge clearance

Keep copper at least 0.3 mm from the board edge. Routing equipment removes material during singulation and copper too close to the edge will be exposed, causing shorts and corrosion in the field.

7. Via-in-pad without fill

Unfilled vias placed inside SMD pads will wick solder during reflow, causing starved joints and tombstoning on passive components. Either move the via off the pad, tent it, or specify via-fill (which adds cost but is correct for high-density designs).

8. Missing or incorrect stackup callout

Always include a fabrication drawing or notes file that specifies layer count, finished board thickness, copper weight per layer, controlled impedance requirements and surface finish. Missing callouts lead to fab assumptions that may not match your design intent.

9. Thermal relief on through-hole pads in ground planes

Solid connections between through-hole pads and large copper pours cause uneven heating during soldering. Use spoke-style thermal reliefs (4 spokes, 0.25–0.5 mm wide) so the pad reaches soldering temperature before the plane conducts the heat away.

10. Net list versus schematic cross-check

Run an ERC on the schematic and a DRC on the layout, then perform a netlist comparison. It sounds obvious but many PCB respins come down to a net that was renamed in the schematic after the netlist was imported into the layout — leaving an unconnected pin that does not appear as an airwire.

Running through this checklist takes less than 30 minutes and can save days of re-spin lead time. If you would like our engineers to review your Gerbers before submission, contact us for a free DFM review with any PCB quote.