Top 5 Gerber File Mistakes That Cause PCB Production Delays — Fixed

Every PCB starts its manufacturing journey as a pile of Gerber files. Those fabrication outputs take your schematic intent and communicate the information necessary to mill copper, drill holes, and apply solder mask in a language a manufacturer can understand.

However, an astonishing number of boards are delayed not by complicated design errors but by silly mistakes that manufacturers see all the time: missing drill files, inverted scaling, misaligned layers, and more. PCB files that don’t process cleanly during CAM stop production before any panels have been cut.

No designer wants to waste time (or money) dealing with unnecessary PCB production delays, so let’s dive into the five issues your PCB vendor encounters most often, highlighting Gerber files mistakes, why they happen, and what you can do to prevent them.

Preventing PCB Production Delays Starts With Understanding Gerber Files Mistakes! 

CAM or computer-aided manufacturing engineers import Gerber files, verify them against customer requirements, and prepare tool files that control every aspect of PCB production. If there’s any question about what the engineer sees, they must query the customer before proceeding.

Hours may pass between these clarifications, so queries pile up while your board waits its turn. Then, once you’ve fixed the issue, your board must move to the back of the queue while they process caught-up queries.

Fixing errors after file submission costs time and money. Correcting and re-submitting new files may require another engineer review. Uncaught errors can lead to scrapped panels or worse — manufactured boards that fail visually or in PCB assembly because someone missed something crucial.

Share the blame for preventable errors with your fab; they’re just as busy as you are. Fortunately, you can stop silly mistakes before they’re sent for PCB fabrication by taking care in how you create and verify your Gerber files.

Missing Drill Files

What happens when your PCB fab opens Gerber files but can’t find the drill file? Production can’t begin. Every PCB needs drill data.

It’s surprisingly common for a designer to export their layers and forget about drills. Why? Drills don’t sit inside a typical Gerber file; they’re output separately (typically Excellon or NC drill format).

The fab can see every pad in every layer but has no way to know where holes need to be drilled or plated, CNC programmers cannot begin work, and your board remains on hold.

Reasons you may forget drill files:

• Your EDA tool may require drill files to be exported separately.
• You may be in a hurry and accidentally skip the drill step.
• Your export wizard may not list drill files by default.

Fixes and Prevention:

• Ensure your output directory contains at least one file with .DRL or .TXT extension.
• Open your drill file in a Gerber viewer to confirm that drill hits are present and in expected locations.
• Include a check for missing drill files on your design-to-manufacture checklist.
• For designs with blind or buried vias, verify your CAM process outputs a drill file for every drill span

Incorrect Scaling or Units

Incorrect scaling occurs when the designer exports files in inches but designed in millimetres, or vice versa. When their CAM software opens your files, the board appears dozens or hundreds of times the intended size. Not to mention that these are most common Gerber files mistakes that can cuase massive trouble to your PCB Manufacturing process! 

That may sound obvious, but real-world examples include:

• Pads and traces too small to register in CAM software. Design rule check fails immediately.
• A board designed with dimensions of 100 mm x 80 mm but defined as 100 inches x 80 inches.
• Failed silkscreen printing strikes because the fab can’t find text or graphics.

CAM engineers can spot incorrect scaling quickly, but what happens if your board is only half the intended size? Small errors may not be caught until boards are manufactured.

Fixes and Prevention:

• Open your Gerber files in a free Gerber viewer. Do not use your EDA tool’s built-in viewer.
• Measure an object you know the size of, like a mounting hole or board edge. Compare the measured value to your intent.
• Check that all layers use the same units. Look for “UNITS = INCH” or “UNITS = MM” in the header of each Gerber and drill file.

Misaligned Layers

Misalignment errors occur when layers don’t quite line up. One side’s pads register 100 microns off from where they should be, or the silkscreen is shifted by half the width of a font size.

Possible causes of misalignment:

• Save your design in different locations or with different names between schematic and board layout. This changes the PCB’s origin point.
• Move your board from one part of the workspace to another before exporting Gerber files.
  Combine files from older iterations of your PCB design with newer ones.
• CAM engineers may notice when copper and solder mask don’t line up, but misalignment between solder mask and silkscreen is easy to miss during CAM processing.
• A quick glance at your completed board reveals every error, but missing, offset, or overlapping features can cause headaches with assembly, AI navigation, and PCB testing.

Fixes and Prevention:

• Set your origin to the same location for every export. Lower-left corner of the board outline is standard.
• Export all layers at once instead of stepping through each layer in turn.
• Open every layer in your Gerber viewer. Tile them so you can see every layer at once and confirm alignment.

Missing Layers or Unclear File Naming

• Ever received a file called “Gerber1.zip” that contains “Layer1.gbr”, “Layer2.gbr”, and “Layer3.gbr”? How did the manufacturer know which file was Top Copper, Bottom Copper, internal signal layers, and so on?
• If they guessed wrong, your entire board could be built on the wrong layer stack-up. That won’t be apparent until panels are manufactured and someone notices the pads are on the inside of the board instead of out.
• Layers may be assigned correctly, but what happens if an inner layer is missing from your Gerber zip file? Depending on your board, it might not be noticed until PCB assembly.
• Damage could occur during shipping if a fab assumes your board is a 2-layer instead of 4-layer and places inner layers on opposite sides of your copper.

Fixes and Prevention:

Name each layer file correctly. For example:

• Top_Copper.gtl
• Inner1_GND.g2
• Inner2_PWR.g3
• Bottom_Copper.gbl

Include a fabrication drawing or README file documenting your desired layer stack-up, materials, and copper weights.
Clearly communicate how many layers your board should have within your order notes and saved in the files themselves.

Solder Mask and Silkscreen Errors

Solder mask and silkscreen defects can cause PCB production delays, but unlike Gerber files mistakes discussed above, they won’t prevent a board from being built. At best, poor solder mask clearance or silkscreen errors make assembly difficult or impair reliability. At worst, it makes you look like a sloppy designer.

Common solder mask and silkscreen mistakes:

• Tight solder mask clearance around pads causes solder mask to overlap into the solderable area.
• Printing reference designators across pads will clip them in manufacturing, making them unreadable.
• Leaving too little solder mask between fine-pitch pads increases the risk of solder bridging during reflow.

Fixes and Prevention:

• Confirm your solder mask clearance meets your manufacturer’s minimum. Most fabs require 50-75 microns of mask on each side of a pad.
• Run a design rule check (DRC) for all text overlapping pads. Use your fab’s minimum font size and stroke width to ensure all text will print.
• For fine-pitch devices down to 0.5mm pitch and smaller, verify your solder mask follows your manufacturer’s PCB design for manufacturing guidelines.

Validating Gerber Files Before Manufacturing Saves Time and Money

Checking your Gerber files takes minimal time and costs you nothing. Conversely, allowing errors to reach the fab adds countless unseen hours to your schedule.

Open files in a free Gerber viewer app. Every PCB fab has access to professional-grade viewers that cost thousands of dollars. Use theirs.
Follow your fab’s checklist for common issues. Do drill files use mm or inches? How many layers should my files include? What about solder mask layers?
Create your own checklist.

• Include files for every layer: all copper layers, solder mask top and bottom, silkscreen top and bottom.
• Confirm your drill file(s) is present and uses the same units as your Gerber files.
• Verify your board outline is on a layer by itself.
• Include a fabrication drawing or README file that specifies your stack-up, materials, copper weight, and other preferences.
• Confirm you’re submitting the correct design revision.
  

When in Doubt, Ask Your PCB Manufacturer!

If you have questions about whether your files are ready to send for PCB fabrication, contact your manufacturer. It only takes a few minutes to confirm your files are correct, well before they would be processed for manufacture.

A few moments of prevention at the front end of the PCB production process saves hours or days on the back end.

So, if you are planning a PCB design project and want it done right the first time, connect with our experienced team and let’s turn your idea into a high performance, production ready board!