Gerber File Requirements for PCB Manufacturing & Assembly
A complete checklist of every file your manufacturer needs — and the most common mistakes that delay orders.
What Is a Gerber File?
A Gerber file is the industry-standard format for communicating PCB design data to a manufacturer. Each Gerber file describes one layer of the board — copper traces, solder mask, silkscreen, board outline, and drill holes. The current standard is RS-274X(also called Extended Gerber), which embeds aperture definitions within the file itself, making it self-contained and unambiguous.
The older RS-274D format requires a separate aperture file and is no longer accepted by most manufacturers. Gerber X2 (an extension of RS-274X) adds metadata attributes and is supported by Kingdta's CAM system.
Required Files for PCB Fabrication
A complete fabrication package must include one Gerber file per layer, plus drill data. The table below lists the required files and their conventional extensions:
| Layer / File | Common Extension | Required? |
|---|---|---|
| Top Copper | .GTL | Yes |
| Bottom Copper | .GBL | Yes (if 2+ layers) |
| Inner Copper 1 | .G1 / .GL1 | Yes (if 4+ layers) |
| Inner Copper 2 | .G2 / .GL2 | Yes (if 4+ layers) |
| Top Solder Mask | .GTS | Yes |
| Bottom Solder Mask | .GBS | Yes |
| Top Silkscreen | .GTO | Recommended |
| Bottom Silkscreen | .GBO | Optional |
| Board Outline (Mechanical) | .GKO / .GM1 | Yes |
| Drill File (PTH) | .DRL / .XLN | Yes |
| Drill File (NPTH) | .DRL (separate) | If applicable |
| Paste Mask (Top) | .GTP | Required for SMT assembly |
| Paste Mask (Bottom) | .GBP | If bottom SMT |
Required Files for PCB Assembly
In addition to the fabrication Gerbers, assembly requires three additional files:
1. Bill of Materials (BOM)
The BOM must be in Excel (.xlsx) or CSV format and include the following columns for every component:
- Reference Designator(s) — e.g. R1, R2, C5
- Quantity
- Manufacturer Part Number (MPN)
- Manufacturer Name
- Description / Value — e.g. "10kΩ 1% 0402 0.1W"
- Package / Footprint — e.g. 0402, SOT-23, QFP-64
- Approved Alternates (optional but strongly recommended)
- DNP flag — mark any "Do Not Place" components explicitly
2. Pick-and-Place (Centroid) File
The centroid file tells the SMT machine where to place each component. It must be in CSV or TXT format and include:
- Reference Designator
- X coordinate (mm or inches)
- Y coordinate (mm or inches)
- Rotation angle (degrees)
- Side (Top / Bottom)
Most EDA tools (KiCad, Altium, Eagle, EasyEDA) can export this file directly. Ensure the coordinate origin matches the board outline origin in your Gerbers.
3. Assembly Drawing or Notes
An assembly drawing (PDF) is optional but highly recommended for boards with:
- Polarised components (electrolytic capacitors, diodes, ICs) — mark pin 1 clearly
- Connectors with specific mating direction
- Press-fit or hand-soldered components
- Special handling requirements (ESD-sensitive, moisture-sensitive level)
Common Gerber File Mistakes
Missing solder paste layer
Without the paste mask Gerber, the stencil cannot be manufactured and SMT assembly cannot proceed. Always include .GTP and .GBP.
Board outline in wrong layer
Embedding the outline in the copper layer causes the manufacturer's CAM software to interpret it as copper, leading to short circuits or incorrect routing.
Mismatched drill and copper layers
Via pads in the copper layer must align exactly with holes in the drill file. A common error is exporting drill files in a different unit (mm vs. inches) than the Gerbers.
Outdated RS-274D format
RS-274D requires a separate aperture file. If you export RS-274D without the aperture file, the manufacturer cannot process your order.
BOM with generic part numbers
Using generic descriptions like '10k resistor' without an MPN forces the manufacturer to make assumptions. Always include the full MPN.
How to Package and Submit Your Files
Compress all Gerber files, drill files, BOM, and centroid file into a single ZIP archive. Name the ZIP with your project name and revision (e.g. MyProject_Rev2.zip). Do not nest ZIP files inside ZIP files.
Submit via the Kingdta quote form or email to info@kingdta.com. Our CAM engineers perform a free DFM review on every order and will contact you within 24 hours if any issues are found.
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