If there’s one thing you can count on in the circuit board design process, it’s that no matter what type of board it is, there will be a lot of files in your CAD tools. There are system files, database files, and attribute and property files. Then, the files created for manufacturing, including drills, pick and place, netlists, drawing PDFs, and Gerber files. With the number of files associated with a PCB design, it is easy to get confused and lose track of which files are current and what they contain. It’s necessary to develop a naming system that is easy to understand and use, especially with image files, more commonly known as Gerber data. Here are some recommendations for the Gerber file format that can help keep manufacturing data clean and up-to-date.
| Gerber File Format Extensions | |
|---|---|
| APR | Aperture file |
| GTL | Board top layer |
| GTB | Board bottom layer |
| G1, G2, …, Gn-1, Gn | Board inner signal layers (descending) |
| GP1, GP2, …, GPn-1, GPn | Board reference plane layers (descending) |
The Gerber File Format and PCB Manufacturing
Gerber files have a long history of use in printed circuit board design and manufacturing. The standard Gerber file format originated from the Gerber Systems Corporation as an enhanced version of numeric control (NC) data to drive the vector photo plotters they produced. Before long, Gerber had become the standard data format used in PCB fabrication and assembly. Gerber files convey ASCII PCB image information of each circuit board layer for manufacturing. The original vector photo plotters created the circuit images on film using a light focused through differently shaped apertures. The light and the apertures are in a photo head suspended over a flatbed, containing instructions in the selected Gerber file for the proper aperture. After laying out the manufacturing tooling film on the bed, the photo head moves vertically and horizontally across the bed so that the light can flash or draw the images detailed in the Gerber file.
Over the years, PCB fabrication techniques have evolved. Faster and more configurable laser plotters have replaced the old vector photo plotters. Many fabricators use direct imaging to create the circuitry on a board layer without using film as a tooling medium. The standard Gerber format has also grown and now includes enhancements like meta-information to consolidate the data in the file to accommodate these changes.
Gerber File Naming Conventions
Gerber files rely on PCB CAD or CAM tools; the default file names will vary depending on the tool. Gerber files also do not require a specific format of their name or file extension to be used since they are plain ASCII text files. They simply have to be loaded into the tool or viewer. Many tools or users prefer using a default file extension for their Gerber files to help distinguish them from other files. These extensions are usually GBR or GB, although any descriptive extension will work.
When Gerber files first came out in older DOS-based computer systems, there was an eight-character filename and three-character extension limitation due to the restrictions of the OS. Users would get creative in their naming conventions to work around this. With the filename character restrictions now removed on operating file systems, you will see naming conventions range from the simple to the complex:
- Simple:
-
- gerber_1
- gerber_2
- gerber_3
- Complex:
-
- 401-0183-01_controller_inner_layer_2.gbr
- 401-0183-01_controller_3_3v_12v_split_plane.gbr
- 401-0183-01_controller_top_silkscreen.gbr
The key to successfully naming your Gerbers and other manufacturing files is to settle on an organizational naming convention. When deciding how to name your files, consider the following:
- Gerber file naming conventions do not restrict most CAD systems.
- Some designers find it easier to leave the generic names and name the Gerber file directory instead.
- Using part numbers in file names will help make identifying the Gerbers much easier.
- Also, consider using dates or version numbers in file names to aid identification.
- Automated scripts can change CAD generic Gerber names to fit organizational requirements. Many CAD systems offer this as a standard feature.
- When in doubt, don’t forget to include a readme file; the manufacturer won’t have to hold production while requesting clarification.
Your Contract Manufacturer Can Manage Your Artwork Files
Before you commit to a course of action on structuring your Gerber file format and other manufacturing outputs, meeting with your manufacturer is always a good idea. Typically, a PCB contract manufacturer will work with any file structure and format you have, but checking first will guarantee smooth communication and fewer errors. They can also provide you with other design recommendations to enhance the performance of your circuit board and increase its production yields while decreasing expenses. We have worked with customers for over forty years at VSE to build various printed circuit boards, and we understand design processes like Gerber file naming conventions that simplify workflows.
