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’s going to be a lot of files in your CAD tools. There are system files, database files, and different attribute and property files. Then there are the files created for manufacturing, including drills, pick and place, netlists, drawing PDFs, and of course, 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 is important to develop a naming system that is easy to understand and use, especially with the image files, more commonly known as Gerber data to prevent any confusion. Here are some recommendations for Gerber file names that can help keep your manufacturing data clean and up-to-date.
Gerber Data 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 were housed in a photo head suspended over a flat bed, and instructions in the Gerber file selected the proper aperture to use. Manufacturing tooling film would be laid out on the bed, and the photo head would move vertically and horizontally across the bed for the light to flash or draw the images detailed in the Gerber file.
Over the years, PCB fabrication techniques have evolved. The old vector photo plotters were replaced with faster and more configurable laser plotters. Now many fabricators use direct imaging to create the circuitry on a board layer without using film as a tooling media. To accommodate these changes, the standard Gerber format has also grown and now includes enhancements like meta-information to consolidate the amount of data in the file. However, these files still need to be named, and we’ll look at some naming conventions next.
Gerber File Naming Conventions
Gerber files are created by PCB CAD or CAM tools, and the default file names will vary depending on the tools being used. 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. To work around this, users would get very creative in their naming conventions. Using the eight-character filename for project identification, users would use the following extensions to identify the layers:
- APR: Aperture file
- GTL: Board top layer
- GTB: Board bottom layer
- G1, G2, etc.: Inner layers
- GP1, GP2, etc.: Power and ground plane layers
With the filename character restrictions now removed on operating file systems, you will see naming conventions range from the simple to the complex:
The key to successfully naming your Gerbers and other manufacturing files is to settle on a naming convention that makes sense for your company. When deciding how to name your files, consider the following:
- Gerber file naming conventions do not restrict most CAD systems.
- You’re generally free to use whatever naming style you want.
- Some designers find it easier to leave the generic names and name the Gerber file directory instead.
- The use of part numbers in your file names will help make the identification of the Gerbers a lot easier.
- Also, consider using dates or version numbers in your file names to help with identification.
- You can create automated scripts that will change CAD generic Gerber names to fit your company’s requirements. Many CAD systems already have this capability built into them.
- When in doubt, don’t forget to include a readme file. This way, the manufacturer doesn’t have to hold production while calling you for clarification.
And speaking of your manufacturer, they are also an excellent source of information you can go to for file name ideas and other design tips and recommendations.
Where to Find More Information on Gerber File Names
Before you commit to a course of action on structuring your Gerber and other manufacturing file names, it’s always a good idea to meet with your manufacturer. Typically a PCB contract manufacturer will work with any file structure and format that 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.
At VSE, we have been working with a wide range of customers for over 30 years to build various types of printed circuit boards. We understand the design process you are going through, and we can help with things like Gerber file naming conventions to simplify your workflow.