If your PCB project is running behind schedule, it’s tempting to look at the obvious suspects — a backordered component, a busy fab queue, a complex stack-up. But more often than not, the delay didn’t start on the manufacturing floor. It started in the data package you sent.
Misnamed, incomplete, or ambiguous files are one of the leading causes of fabrication errors and delays. A fabricator can’t quote what it can’t read, and it can’t build what it has to guess at. The encouraging part is that, unlike component lead times, your data package is something you fully control.
This guide breaks down the three things that make or break a release: avoiding the common Gerber mistakes, assembling a complete file package, and writing an explicit fabrication specification.
Common Gerber mistakes to avoid
A small set of recurring problems accounts for a disproportionate share of fab delays. Watch for these before you export:
- Missing board outline layer. Fab shops cannot quote or produce a board without it — this is the most common dead stop.
- Solder mask clearance set to zero. This causes all pads to be covered by mask.
- Drill file units mismatch. Metric versus imperial errors slip through easily. Verify your EDA export settings.
- Aperture macros not included. Some older Gerber viewers and importers require explicit aperture definitions.
- Silkscreen artwork crossing into pads. This causes inspection issues and can create shorts.
- Multiple board outlines in separate files. Consolidate all outlines into a single layer.
The Gerber file package
Provide a complete, clearly labeled Gerber package. A consistent naming convention removes ambiguity with your fab partner and keeps your files from being misinterpreted.
| Layer / File | Standard naming convention |
|---|---|
| Top Copper | *.GTL or *_Top_Copper.gbr |
| Bottom Copper | *.GBL or *_Bot_Copper.gbr |
| Inner Layers (L2, L3…) | *_L2.gbr, *_L3.gbr (etc.) |
| Top Solder Mask | *.GTS or *_Top_Mask.gbr |
| Bottom Solder Mask | *.GBS or *_Bot_Mask.gbr |
| Top Silkscreen | *.GTO or *_Top_Silk.gbr |
| Bottom Silkscreen | *.GBO or *_Bot_Silk.gbr |
| Board Outline | *.GKO or *_Outline.gbr |
| Drill File (PTH) | *.DRL or *_Drill_PTH.xln |
| Drill File (NPTH) | *_Drill_NPTH.xln (if applicable) |
| NC Drill / Excellon | include tool size table in header |
| IPC-2581 or ODB++ | acceptable as a comprehensive single-file alternative |
Best practice: Always include a README.txt or layer-mapping document in the Gerber ZIP that identifies each file and its purpose. This eliminates ambiguity with fab partners — and it takes about five minutes.
PCB fabrication specification
Provide explicit fab notes either in the Gerber package or as a separate fab drawing. Do not rely on fab-shop defaults — if you don’t state a parameter, someone else will choose it for you.
| Specification item | Guidance / example |
|---|---|
| Layer Count | Specify total layer count (e.g., 4-layer) |
| Material | FR-4 standard, FR-4 high-Tg (>170°C), Rogers, Polyimide, etc. |
| Board Thickness | Specify in mm or inches (e.g., 1.6mm / 0.063″) |
| Finished Copper Weight | Outer layers (e.g., 1oz); inner layers (e.g., 0.5oz) |
| Surface Finish | HASL (lead-free), ENIG, OSP, Immersion Silver, ENEPIG |
| Solder Mask Color | Green standard; specify if blue, black, red, etc. |
| Silkscreen Color | White standard; specify if yellow or black |
| Min Trace / Space | e.g., 4/4 mil (0.1/0.1mm) |
| Min Drill (PTH) | e.g., 0.2mm finished hole |
| Via Fill / Cap | Specify if vias need tenting, plugging, or cap plating |
| Controlled Impedance | State layer, trace width, target ohms, tolerance (e.g., ±10%) |
| IPC Class | IPC-6012 Class 2 or Class 3 |
| UL Marking | Required or not — specify |
| RoHS Compliance | Specify if required for your program |
The takeaway
You can’t always control your component lead times or how busy a fab line is. You can control whether your data package answers every question before it’s asked. Clear file names, a README, and an explicit fabrication spec are the cheapest, fastest schedule insurance available to a hardware team.
A clean package is also what makes instant quoting possible. With RapidRFQ, you can upload your BOM, Gerbers, and CPL and get a PCB assembly quote in minutes — but that speed only works when the underlying data is unambiguous.
Ready to put it to the test? Get an instant quote with RapidRFQ, or explore the full PCB Gerber & Fabrication Spec Best Practices guide in the Amtech Resource Center.
Amtech is an electronics manufacturing services partner based in Troy, Michigan. 701 Minnesota Drive, Troy, MI 48083 · (248) 583-1801
