How to Prepare PCB Gerber Files for Manufacturing

1. First Things First: What Even Are Gerber Files?

Let's start with the basics. Gerber files are like the "blueprints" for your PCB. They're not a single file, but a collection of files—each representing a specific layer of your board (copper, solder mask, silkscreen, etc.). Manufacturers use these files to set up their machines: where to etch copper, where to apply solder mask, which components go where during pcb smt assembly . Think of it this way: if your PCB design is a cake recipe, Gerber files are the step-by-step photos that show the baker exactly how to mix, layer, and decorate.

Why not just send your design file (like .PCB or .SCH) directly? Because every design software (Altium, KiCad, Eagle) saves files in its own format. Gerber is the universal language—manufacturers worldwide understand it, no matter what tool you used to design. That's why mastering Gerber preparation is non-negotiable.

2. Gather Your Tools (And Clean Up Your Design)

Before generating Gerber files, you need to make sure your design is "clean." I'm talking about fixing errors that might not show up in your design software but will cause headaches in manufacturing. Start by running a Design Rule Check (DRC). Most tools have this built-in—Altium calls it "Design Rule Checker," KiCad has "DRC" under the Tools menu. This will flag issues like short circuits, trace widths that are too thin, or components placed too close together.

Next, organize your component libraries. If you're using component management software (like PartQuest or Octopart), now's the time to double-check footprints. I once worked with a designer who used a resistor footprint for a capacitor—Gerber files looked fine, but during assembly, the components didn't fit. Component management tools help avoid that by linking footprints to real-world parts, ensuring what you design is what gets soldered.

Finally, simplify where you can. Remove any unused layers (do you really need that "Notes" layer for manufacturing?). ｄｅｌｅｔｅ stray tracks or empty components. The cleaner your design, the cleaner your Gerber files will be.

3. Generate Each Layer (Yes, All of Them)

Here's where the rubber meets the road: exporting individual layers. Gerber files are layer-specific, so you'll need to generate a separate file for each part of your PCB. Let's break down the essential layers—don't skip any of these!

Copper Layers

These are the conductive layers where your traces live. For a 2-layer board, you'll have Top Copper and Bottom Copper. For multi-layer boards, add Inner Layers (GND, VCC, etc.). When exporting, make sure "Mirror" is disabled (unless you're exporting the bottom layer—some tools mirror it by default, which is correct). Set the units to inches or millimeters (mm is more common) and resolution to 0.001 inches (25.4 microns) or higher—this ensures sharp, accurate traces.

Solder Mask Layers

Solder mask is the green (or black, or red) coating that protects copper traces and prevents short circuits during soldering. You'll need Top Solder Mask and Bottom Solder Mask layers. The key here is "solder mask expansion"—the gap between the copper pad and the solder mask opening. Most manufacturers recommend 0.002–0.004 inches (50–100 microns). Too small, and the mask might cover the pad; too large, and the pad could oxidize.

Silkscreen Layers

Silkscreen is the white text and symbols that label components (like "R1," "C3") and add logos. Export Top Silkscreen and Bottom Silkscreen (if you have components on the bottom). Keep text size at least 0.08 inches tall with 0.02 inches line width—anything smaller might smudge during printing. Avoid placing silkscreen directly on pads—manufacturers will either print over them (ruining solderability) or skip them (making your labels incomplete).

Drill Files

Drill files tell the machine where to drill holes for vias and through-hole components. You'll need two files here: a drill drawing (which shows hole positions) and a drill table (which lists hole sizes and counts). Use the Excellon format (most common) and include both plated and non-plated holes. Pro tip: Label holes clearly—if a via is 0.3mm and a through-hole is 0.8mm, the drill file needs to reflect that difference.

3. Double-Check for Common Mistakes (You'll Thank Me Later)

You've generated all your layers—great! Now it's time to play detective. Even small mistakes in Gerber files can lead to big problems. Let's walk through the most common ones and how to spot them.

Missing Layers: This is the #1 issue I see. Imagine sending everything except the bottom copper layer—your board would have no traces on the bottom! Open each Gerber file in a viewer (I use GerberView or KiCad's built-in viewer) and cross-verify against your design. Check that the outline layer matches your board shape—no one wants a PCB that's 10mm too small.

Incorrect Scaling: If your traces look tiny or gigantic in the viewer, you probably messed up the units. Most manufacturers use millimeters, but if you exported in inches, the scale will be off. A 0.2mm trace shouldn't look like a hairline—zoom in and check the dimensions.

Silkscreen Over Pads: Remember earlier advice about silkscreen on pads? Use the viewer to overlay silkscreen and copper layers. If text or symbols overlap with pads, go back to your design and move them. This is especially critical for pcb smt assembly —smt machines rely on clear pad visibility to place components accurately.

Unconnected Traces: A DRC should catch this, but it's worth double-checking. In the Gerber viewer, trace continuity might not show up, so export a copper pour layer and ensure all pours are connected to their nets. A floating pour is a wasted pour—and could cause EMI issues later.

4. Package Everything Up (And Hit Send!)

You've triple-checked, fixed errors, and verified all layers—now it's time to package your files. Manufacturers prefer zipped folders with clear naming. Name each file logically: "TopCopper.GBR," "BottomSilkscreen.GBR," "DrillFile.XLN," etc. Avoid special characters or spaces—stick to letters, numbers, and underscores.

Include a README.txt file with notes for the manufacturer: board thickness (1.6mm is standard, but maybe you need 0.8mm), solder mask color (green is default, but red/black/blue are options), and any special requests (like "no silkscreen on bottom layer"). If your design requires conformal coating (a protective layer for harsh environments), mention that here too—manufacturers might need extra steps to mask certain areas before coating.

Finally, send the zip file to your manufacturer. Most have an upload portal on their website, or you can email it. If they have questions (and they might—manufacturers are human!), respond quickly. The faster they clarify, the faster your PCB goes into production.

5. Beyond Gerber Files: What Comes Next?

Once your Gerber files are approved, the manufacturer will start production. But your job isn't done yet! After manufacturing, your PCB will go through pcba testing process —functional tests, continuity checks, maybe even X-ray for BGA components. If you included test points in your design (smart move!), this process will be faster and more accurate.

And remember that conformal coating I mentioned? If your PCB will be exposed to moisture, dust, or chemicals (like in industrial or outdoor devices), conformal coating is a must. It's applied after assembly and testing, forming a thin, protective film over the board. Your manufacturer can handle this—just make sure to specify the type (acrylic, silicone, urethane) based on your environment.

Wrapping Up: You've Got This!

Preparing Gerber files might seem tedious, but it's the bridge between your hard work in design and a functional PCB. By following these steps—understanding the basics, generating clean layers, checking for mistakes, and communicating clearly with your manufacturer—you'll avoid delays and get a board that matches your vision.

Remember, even seasoned designers make mistakes. The key is to be methodical and use tools like component management software and Gerber viewers to catch issues early. And when in doubt, ask your manufacturer—they're partners in this process, not just vendors.

Now go hit that "export" button. Your PCB is waiting to be built!