What is Gerber file format for PCB?
For PCB fabrication, we require PCB design file in Gerber RS-274X format (most preferred), *.PCB/DDB (Protel, inform your program version) format or *.BRD (Eagle) format.
PCB Files Format
For PCB Manufacturing or quotation , You need send us Gerber RS-274X files to check.
Below please find the instructions you’ll need for submitting your Gerber files to us for production of your printed circuit boards. If you need assistance, our customer service representatives can help you determine all of the file types you will need to submit for your PCB order.
Gerber File Format and ODB++ File Format
Gerber is an open ASCII vector format for printed circuit board design that shows parts of a board like copper layers, solder mask design, etc. Many applications can read this format because it simple, has detailed specifications, and has few bugs because of its wide use and subsequent debugging. The simple format of a Gerber means it is easy to identify and fix bugs as well.
There are three Gerber generations: Gerber X2 (current format), Extended Gerber, or RS-274X, and Standard Gerber, or RS-274-D, which is now obsolete. The Gerber X2 format contains layer stackup information, which was not in previous versions. Software that supports the X2 format will read and identify each item’s function in the file.
A RS-274X file contains the complete description of a PCB layer image without requiring any external files. It has all the imaging operators needed for a PCB image. Any aperture shape can be defined as well as positive and negative objects. Planes can be specified without the need to “paint” or “vector-fill” as in RS-274-D.
RS-274X is a complete, powerful and unambiguous standard to describe a PCB layer. It can be input and processed fully automatically. This makes it well suited for fast and secure data transfer and for reliable and automated workflows.
Remember to include the following when submitting Gerbers:
All copper layers (inner & outer)
Soldermask layers
Silkscreen/legend layers
Via plugging layers (if applicable)
Solder paste layers (for assembly)
Aperture list if apertures are not embedded in Gerber data
During the PCB layer assignment in our Auto File Verification, you will have to tell us which gerber file is which layer. This table will help you for some common packages.
Software: Eagle
| File Extension | Description |
|---|---|
| cmp | Top Copper |
| sol | Bottom Copper |
| stc | Top Soldermask |
| sts | Bottom Soldermask |
| plc | Top Silkscreen |
| pls | Bottom Silkscreen |
| drd | NC Drill |
Software: Orcad
| File Extension | Description |
|---|---|
| gtl | Top Copper |
| gbl | Bottom Copper |
| gts | Top Soldermask |
| gbs | Bottom Soldermask |
| gto | Top Silkscreen |
| gbo | Bottom Silkscreen |
| drl | NC Drill |
ODB++ File Format
There has been a lot of debate between whether Gerber format or ODB++ formats are better for PCB design. Some designers and shops prefer one format over the other. At Raypcb, we prefer ODB++ formats. Here’s a summary of both formats and their pros and cons.
ODB++ stands for Open Database and serves as a way to exchange data between computer-aided design (CAD) and computer-aided manufacturing (CAM) formats for circuit boards. This format was first introduced as ODB, and the “++” was added after a new version included components. ODB++ is an ASCII file that has all the information pertaining to the circuit board design.
Printed circuit boards are designed in CAD and transferred into CAM. CAD and CAM programs are usually made by different companies, so they need to agree on the type of data exchange. ODB++ is a manufacturing-oriented program. Many shops prefer this format for this reason because one file can consolidate all the information needed for the job, whereas some Gerbers need additional information from several files to make sense of the image layers. This eliminates the need to analyze each file to eliminate bugs.
| ODB++ | Gerber | ||
|---|---|---|---|
| Pros | Cons | Pros | Cons |
| One file includes stackup, layers, drilling, masking, net data | Different image format | Simple | Multiple files needed |
| Widely used | More complex format than Gerber | Widely used | Requires examination of all files at fabricator |
| Undergoes DFM / quality checks | Specification is precise | ||
| Easy to transfer to fabricator | Format supported by free viewers | ||
Introduction
Gerber files are the standard format used to transfer PCB design data from CAD software to PCB fabrication and assembly. Gerber files provide detailed information on copper layers, solder mask, drill data, etc. needed to manufacture a printed circuit board.
This article provides an in-depth overview of Gerber file format covering:
- History and development
- Gerber file types and purposes
- Gerber file extensions
- Gerber data format
- Advantages of Gerber
- Limitations of Gerber format
- Gerber file generation
- Manipulating and viewing Gerber data
- Gerber validation tools
- Best practices for Gerber file preparation
Understanding Gerber file format is critical for efficient data handoff and successful board fabrication.
History of Gerber File Format
Gerber file format was developed by Gerber Systems Corporation, pioneers in photoplotting and PCB imaging equipment.
- 1960s – Gerber introduced the first automated PCB plotter
- 1970s – Development of Gerber bar code standardized CAD data transfer
- 1980s – RS-274X Gerber file format released
- 1990s – Gerber Format becomes industry standard for PCB layout data
- 1998 – Revision RS-274X Rev D released
- Today – Gerber remains predominant despite newer formats like ODB++
Types of Gerber Files
A complete set of Gerber files provides all data needed to assemble a PCB. Typical Gerber file types include:
- Copper layers – Top, bottom, inner layers
- Solder mask layer – Solder resist opening shapes
- Silkscreen layer – Component legends and markings
- Solder paste layer – Paste print template
- Drill file – Hole sizes and locations
- Profile file – Board outline and cutouts
- Route file – Breakouts and scoring lines
- Netlist file – Component pinouts and nets
- Assembly drawings – Top/bottom assembly diagram
Gerber File Extensions
Standard Gerber file extensions help identify file types:
- .GTL – Top layer copper
- .GBL – Bottom layer copper
- .GTS/GTP – Top solder mask
- .GBS/GBP – Bottom solder mask
- .GTO – Top silkscreen legend
- .GBO – Bottom silkscreen legend
- .TXT – Drill file
- .GM1, .GM13 – Mechanical layer
- .APR/.GKO – Aperture file
Gerber Data Format
Gerber data represents PCB images using vector photoplotter commands. Key elements:
Apertures
- Geometric shapes – circle, rectangle, obround, etc.
- Defines flash tool size and shape for photoplotting
Primitives
- Graphics commands like line, arc, circle
- Specifies image shapes using apertures
Coordinates
- X and Y location
- Positioning commands and interpolation
Polarity
- Dark or clear polarity
- Determines exposed or unexposed areas
- Defines units, coordinate format, etc.
Advantages of Gerber Format
Reasons Gerber remains the predominant PCB layout format:
- Standard data exchange format independent of CAD tools
- Supports all data required for fabrication and assembly
- Vector rather than raster format reduces file size
- Established format with long history of use
- Highly accurate format suited for photoimagable processes
- Dedicated viewer tools available
- Well-understood by PCB manufacturers worldwide
Limitations of Gerber Format
Despite its advantages, Gerber format also has some drawbacks:
- Does not fully represent all PCB data model attributes
- Limited support for non-orthogonal geometry
- Ambiguity in interpretation of layers
- Plotter-based format less suited for direct DFM analysis
- Individual files provide fragmented data
- No ECAD-MCAD data integration
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Gerber File Generation
Gerber files are typically generated from PCB CAD tools:
CAD Software
- Design files prepared in CAD programs like Altium, Cadence, Mentor, Zuken
- Files saved to industry standard formats like ODB++
CAM Processing
- ODB++ imported to CAM software like Genesis or BluePrint
- CAM software optimizes data for manufacturing
- Panelization, netlist generation, etc.
Gerber Export
- CAM software outputs standard Gerber, drill and netlist files
- Validation performed before release to manufacturer
Viewing and Manipulating Gerbers
Several options exist for working with Gerber data:
Gerber Viewers
- Dedicated viewers like GC-Prevue and Gerbv
- Allow visual examination of layers
- Limited editing capability
CAM Tools
- Full editing ability to fix and optimize
- Changes output as revised Gerber files
Viewer/Editors
- Hybrid tools support viewing and editing
- Example Ucamco LayerVu
Online Gerber Viewers
- Cloud-based apps like Tracespace Viewer
- Quick viewing without installation
Gerber File Validation
Before sending Gerber files for PCB fabrication, they should be validated:
Design Rule Checking
- Run DRC check for errors like spacing violations
- Fix violations before generating Gerbers
Visual Examination
- Carefully examine each layer for completeness
- Look for missing design data or artifacts
Gerber Analysis
- Use pre-flight tools to validate files per RS-274X
- Confirm proper orientation, plotter modes
Test Imports
- Try sample Gerber import at manufacturer
- Request CAM engineer review of data
Best Practices for Gerber Preparation
Recommendations when working with Gerber files:
- Use standardized naming conventions for layers
- Include documentation on layer identifications
- Eliminate unused apertures, layers, blocks
- Use unique apertures for each net or designator
- Validate netlist matches PCB CAD schematic
- Check all layers present and order is correct
- Confirm no unintended design data in files
- Review artwork centered within panel border
- Obtain manufacturer feedback on files
Conclusion
Gerber format provides the backbone for transferring PCB design data to fabrication and assembly. Developed decades ago, this vector photoplotting format maintains dominance as a standard exchange medium between engineers and manufacturers. With careful validation and best practices, Gerber files enable smooth manufacturing handoff and successful board production.
Frequently Asked Questions
Here are some common questions about the Gerber file format for PCBs:
Q: What are the main benefits of the Gerber file format?
Gerber is a vector format that provides a complete dataset package for PCB fabrication and assembly in standardized files.
Q: What are some limitations of Gerber format?
Gerber has limited support for non-orthogonal geometries, does not fully represent PCB data models, and splits data across separate files.
Q: What file extensions are used for Gerber files?
Standard extensions like .GTL, .GBL, .TXT, and .GM1 identify layer types like copper, solder mask, drill and mechanical.
Q: How can Gerber files be viewed and validated?
Gerber viewers like GC-Prevue allow visual examination while analysis tools validate against RS-274X format.
Q: What are some best practices when generating Gerber files?
Perform DRC checking; validate layers are present and ordered correctly; eliminate unused data; use unique apertures; confirm netlist matches schematic.