Introduction to PCB-conversion

Printed Circuit Board (PCB) design is a crucial aspect of electronic product development. Once a PCB design is complete, it needs to be converted into a format that can be understood by PCB manufacturers. One of the most popular formats for PCB manufacturing is Gerber. CadSoft EAGLE is a widely used PCB design software that allows designers to create .brd files. In order to manufacture the PCB, these .brd files need to be converted into Gerber format. In this article, we will discuss the guidelines for converting Cadsoft Eagle .brd files to Gerber format.

Understanding Cadsoft Eagle .brd Files

Cadsoft Eagle is a powerful PCB design software that allows designers to create complex PCB layouts. The software uses its own proprietary file format, known as .brd, to store the PCB design data. The .brd file contains all the necessary information about the PCB, including the component placement, routing, and layer stackup.

Structure of a .brd File

A .brd file is a binary file that contains the following information:

• Header: The header contains information about the version of Eagle used to create the file, the number of layers, and the unit of measurement.
• Board Outline: The board outline defines the physical dimensions of the PCB.
• Components: The components section contains information about all the components used in the PCB, including their placement and orientation.
• Tracks: The tracks section contains information about all the copper traces on the PCB.
• Vias: The vias section contains information about all the vias used to connect different layers of the PCB.
• Texts: The texts section contains information about all the text elements on the PCB, such as component labels and silkscreen markings.
• Polygons: The polygons section contains information about any copper fill areas on the PCB.

Gerber Format

Gerber format is a standard file format used by PCB manufacturers to exchange PCB design data. It is a vector image format that describes the copper layers, solder mask, silkscreen, and drill holes of a PCB. Gerber files are ASCII text files that use a specific set of commands to describe the PCB geometry.

Gerber File Structure

A Gerber file consists of the following sections:

• Header: The header contains information about the file format, the unit of measurement, and the coordinate format.
• Aperture Definitions: The aperture definitions section defines the shapes and sizes of the apertures used to draw the PCB features.
• Copper Layer Data: The copper layer data section contains the actual geometry data for each copper layer of the PCB.
• Solder Mask Data: The solder mask data section contains the geometry data for the solder mask layer of the PCB.
• Silkscreen Data: The silkscreen data section contains the geometry data for the silkscreen layer of the PCB.
• Drill Data: The drill data section contains the location and size of all the drill holes on the PCB.

Converting Cadsoft Eagle .brd to Gerber

To convert a Cadsoft Eagle .brd file to Gerber format, you need to use a Gerber File Generation tool. There are several options available, including the built-in Gerber generation tool in Eagle and third-party tools like CAM350 and GerbView.

Using Eagle’s Built-in Gerber Generation Tool

Eagle includes a built-in Gerber generation tool that allows you to easily generate Gerber files from your .brd file. To use this tool, follow these steps:

1. Open your .brd file in Eagle.
2. Click on the “File” menu and select “CAM Processor”.
3. In the CAM Processor window, select “gerb274x” from the “Output Device” dropdown menu.
4. Click on the “File” menu and select “Open” to load the default Gerber job.
5. Click on the “Process Job” button to generate the Gerber files.

The generated Gerber files will be saved in the same directory as your .brd file.

Using Third-Party Gerber Generation Tools

If you prefer to use a third-party Gerber generation tool, you can export your .brd file from Eagle and import it into the tool. Most third-party tools support the import of Eagle .brd files.

Once you have imported your .brd file into the third-party tool, you can generate the Gerber files using the tool’s built-in Gerber generation feature. The specific steps will vary depending on the tool you are using, so refer to the tool’s documentation for detailed instructions.

Gerber File Naming Conventions

When generating Gerber files, it is important to follow a consistent naming convention to ensure that the PCB manufacturer can easily identify each file. The most common naming convention for Gerber files is the Extended Gerber format, which uses a specific set of file extensions to identify each layer of the PCB.

Layer	File Extension
Top Copper	.GTL
Bottom Copper	.GBL
Top Solder Mask	.GTS
Bottom Solder Mask	.GBS
Top Silkscreen	.GTO
Bottom Silkscreen	.GBO
Drill File	.TXT

Verifying Gerber Files

Before sending your Gerber files to a PCB manufacturer, it is important to verify that they are correct and complete. There are several tools available for verifying Gerber files, including online Gerber viewers and standalone Gerber viewing software.

Using an Online Gerber Viewer

Online Gerber viewers are web-based tools that allow you to upload your Gerber files and view them in your web browser. These tools are convenient because they don’t require any software installation and can be accessed from anywhere with an internet connection.

One popular online Gerber viewer is the Gerber Viewer by PCBWay. To use this tool, simply go to the PCBWay website and click on the “Gerber Viewer” link. Then, upload your Gerber files and click on the “View” button to see a visual representation of your PCB.

Using Standalone Gerber Viewing Software

Standalone Gerber viewing software is a more powerful option for verifying Gerber files. These tools typically offer more advanced features than online viewers, such as the ability to measure distances and check for design rule violations.

One popular standalone Gerber viewing software is GerbView, which is part of the KiCad EDA suite. To use GerbView, open the software and click on the “File” menu, then select “Open Gerber File”. Navigate to the directory where your Gerber files are saved and select the files you want to view. GerbView will display a visual representation of your PCB, which you can use to verify that everything looks correct.

Best Practices for Cadsoft Eagle to Gerber Conversion

To ensure that your Cadsoft Eagle .brd file is successfully converted to Gerber format, follow these best practices:

1. Use a consistent unit of measurement throughout your design. Most PCB manufacturers prefer to work in metric units, so it is a good idea to set your design units to millimeters in Eagle.
2. Make sure that your component footprints are correct and up-to-date. Incorrect footprints can lead to manufacturing errors and delays.
3. Use a consistent naming convention for your layers and files. This will make it easier for the PCB manufacturer to identify each file and layer.
4. Verify your Gerber files before sending them to the manufacturer. Use an online Gerber viewer or standalone Gerber viewing software to check for any errors or inconsistencies.
5. Communicate clearly with your PCB manufacturer. Provide them with all the necessary files and information, and be available to answer any questions they may have.

Troubleshooting Common Issues

If you encounter issues during the Cadsoft Eagle to Gerber conversion process, here are some common problems and solutions:

Incorrect File Extension

If you generate Gerber files with the wrong file extension, the PCB manufacturer may not be able to read them. Make sure that you are using the correct file extensions for each layer, as shown in the table above.

Missing Drill File

If you forget to include the drill file with your Gerber files, the PCB manufacturer will not be able to drill the holes in your board. Make sure that you generate the drill file and include it with your Gerber files.

Incorrect Aperture Definitions

If your Gerber files use incorrect aperture definitions, the PCB features may not be drawn correctly. Make sure that your aperture definitions match the actual sizes and shapes of the features on your PCB.

Overlapping or Missing Features

If your Gerber files contain overlapping or missing features, the PCB manufacturer may not be able to manufacture your board correctly. Use a Gerber viewing tool to check for any overlapping or missing features, and correct them in your design software before generating new Gerber files.

FAQ

1. What is the difference between a .brd file and a Gerber file?

2. A .brd file is the proprietary file format used by Cadsoft Eagle to store PCB design data. A Gerber file is a standard file format used by PCB manufacturers to exchange PCB design data. Gerber files are generated from .brd files using a Gerber generation tool.

3. Can I use any Gerber generation tool to convert my .brd file to Gerber format?

4. Yes, you can use any Gerber generation tool that supports the import of Eagle .brd files. Eagle includes a built-in Gerber generation tool, but you can also use third-party tools like CAM350 or GerbView.

5. What should I do if my PCB manufacturer reports errors in my Gerber files?

6. If your PCB manufacturer reports errors in your Gerber files, the first step is to verify the files using a Gerber viewing tool. If you find any errors or inconsistencies, correct them in your design software and generate new Gerber files. If you are unsure how to fix the errors, contact your PCB manufacturer for guidance.

7. Can I generate Gerber files from other PCB design software besides Eagle?

8. Yes, most PCB design software packages include a Gerber generation tool that allows you to export your design as Gerber files. The specific steps for generating Gerber files will vary depending on the software you are using, so refer to the software’s documentation for detailed instructions.

9. What should I include in my Gerber file package when sending it to a PCB manufacturer?

10. When sending your Gerber files to a PCB manufacturer, you should include all the necessary files for each layer of your PCB, including the copper layers, solder mask layers, silkscreen layers, and drill file. You should also include a README file that provides any additional information or instructions that the manufacturer may need.

Conclusion

Converting a Cadsoft Eagle .brd file to Gerber format is a critical step in the PCB manufacturing process. By following the guidelines and best practices outlined in this article, you can ensure that your Gerber files are accurate, complete, and ready for manufacturing. Remember to use a consistent naming convention, verify your files before sending them to the manufacturer, and communicate clearly with your PCB manufacturer throughout the process. With these steps, you can streamline your PCB design and manufacturing workflow and bring your electronic products to market faster.