How to Prepare Gerber Files for PCB Manufacturing:
A Practical Checklist

Most PCB order delays have nothing to do with the factory. They happen before the boards are even quoted, inside the zip file the designer uploads. After checking thousands of uploaded designs with our automated DFM pipeline, the same handful of file problems keep coming back. This checklist walks through them in the order we see them.

Export RS-274X, not RS-274D

Every modern EDA tool (KiCad, Altium, Eagle, EasyEDA, OrCAD) exports RS-274X extended Gerbers. The older RS-274D format separates aperture definitions from the image data, which means your fab has to guess. If your tool offers ODB++ as an alternative, that is also fine: it bundles the whole design, stackup included, in one structured archive.

Quick sanity check: open any exported layer in a text editor. An RS-274X file declares its apertures near the top with lines like %ADD10C,0.152400*%.

Include every layer you expect on the board

A surprising number of uploads are missing a layer the designer assumed was there. For a standard 2 layer board we expect at least:

• Top and bottom copper
• Top and bottom solder mask
• Top (and optionally bottom) silkscreen
• Board outline (mechanical or Edge.Cuts layer)
• Drill file (Excellon)

Multilayer designs add one copper file per inner layer. If your design uses them, also export paste layers, plated slot definitions and any v-score or panelisation notes.

The drill file is part of the design

Excellon drill files carry their own units and coordinate format, and they are the single most common source of scale errors. Export drills in the same units and format as your Gerbers, and if the tool asks, choose decimal coordinates with leading zeros suppressed rather than an ambiguous integer format.

Plated (PTH) and non-plated (NPTH) holes should be separate files or clearly marked in one file. A mounting hole that ends up plated can short a chassis to your ground plane.

Draw one clean board outline

The outline defines what gets routed. The rules are simple:

• One closed contour on its own layer, no gaps, no overlapping segments
• No dimension arrows, notes or construction geometry on the outline layer
• Internal cutouts drawn on the same layer as closed contours

If the outline layer contains three rectangles and a title block, the router does not know which one is the board.

Respect solder mask and silkscreen limits

Solder mask openings are expanded slightly around pads (typically 50 to 75 microns per side). If you have manually shrunk mask openings to zero, adjacent fine-pitch pads can end up with no mask dam between them, which invites solder bridges.

For silkscreen, keep line widths at or above 0.15 mm and text height at or above 1 mm, and keep silk off exposed pads. Anything smaller prints as smudge.

Say what the stackup should be

For 4 or more layers, include a stackup note: layer order, copper weights, target thickness and any controlled impedance requirements with the reference layers. A fab can build a 4 layer board a dozen ways; impedance controlled designs only work when both sides agree on the geometry.

Zip it flat and name things honestly

Put the Gerber and drill files in a single zip, at the top level or in one folder. Avoid uploading the entire project directory: intermediate files with stale copies of old revisions cause more confusion than missing files. File names like board-top-copper.gtl beat untitled(3).gbr.

The 60 second pre-upload check

1. Open the files in a separate Gerber viewer (not your EDA tool) and look at every layer
2. Confirm the drill hits land on pads
3. Confirm the outline is a single closed shape
4. Check one measured dimension against your CAD
5. Zip only what the fab needs

Our upload flow at cucircuits.com/pcb-manufacturing runs automated checks on layer completeness, outline closure and drill alignment the moment you upload, and prices the board instantly. The checklist above is still worth 60 seconds of your time: files that pass first try ship first try.