Introduction to PCB-Conversion

Printed Circuit Board (PCB) design is a crucial aspect of electronic product development. Eagle, a popular PCB design software, allows designers to create board layouts using its proprietary .brd file format. However, to manufacture the designed PCB, the .brd file needs to be converted to Gerber format, which is the industry standard for PCB Fabrication. This article provides a comprehensive guide on converting Eagle .brd files to Gerber format, ensuring a smooth transition from design to manufacturing.

Understanding the Eagle .brd File Format

The Eagle .brd file is a binary format that contains all the necessary information for a PCB layout, including:

• Board outline and dimensions
• Component placement
• Copper traces and vias
• Drill holes and sizes
• Silkscreen and solder mask layers

While the .brd file is essential for designing the PCB within the Eagle software, it cannot be directly used for manufacturing. PCB fabrication houses require Gerber Files, which are industry-standard file formats that contain the necessary information for each layer of the PCB.

What are Gerber Files?

Gerber files, also known as RS-274X format, are ASCII-based file formats used to describe the printed circuit board images. Each Gerber file represents a single layer of the PCB, such as the top copper layer, bottom copper layer, silkscreen, solder mask, and drill files. These files contain the necessary information for the PCB fabricator to manufacture the board accurately.

Common Gerber file extensions include:

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

Preparing the Eagle .brd File for Conversion

Before converting the Eagle .brd file to Gerber format, it is essential to ensure that the board layout is complete and error-free. Follow these steps to prepare the .brd file:

1. Design Rule Check (DRC): Run the DRC tool within Eagle to identify any design rule violations, such as trace width, clearance, or hole size issues. Resolve all the errors flagged by the DRC.

2. Electrical Rule Check (ERC): Perform an ERC to detect any electrical issues, such as unconnected pins, shorted nets, or missing components. Address any problems identified by the ERC.

3. Board Outline: Ensure that the board outline is correctly defined and matches the desired dimensions of the PCB.

4. Layers: Verify that all the necessary layers are present and correctly assigned, including copper layers, silkscreen, solder mask, and drill layers.

5. Text and Labels: Check that all text and labels on the PCB are correctly placed and sized. Ensure that they do not overlap with any other components or traces.

Converting Eagle .brd to Gerber using Eagle CAM Processor

Eagle provides a built-in tool called the CAM Processor, which allows users to generate Gerber files directly from the .brd file. Follow these steps to convert the .brd file to Gerber format using the CAM Processor:

1. Open the .brd file in Eagle and click on the “CAM” button in the top toolbar to open the CAM Processor.

2. In the CAM Processor window, select “File” > “Open” and choose the “gerb274x.cam” job file. This job file contains the necessary settings for generating Gerber files.

3. Click on the “Process Job” button to start the Gerber File Generation process.

4. Eagle will prompt you to select an output directory. Choose a suitable location to save the generated Gerber files.

5. Once the process is complete, Eagle will create a set of Gerber files in the selected output directory, representing the various layers of the PCB.

Verifying the Generated Gerber Files

After generating the Gerber files, it is crucial to verify their accuracy and completeness before submitting them to the PCB fabricator. There are several methods to check the Gerber files:

1. Visual Inspection: Open the Gerber files using a Gerber viewer software, such as GC-Prevue or ViewMate. Visually inspect each layer to ensure that the copper traces, pads, and drill holes are correctly positioned and sized.

2. Gerber Compare: If you have access to a PCB design software that can import Gerber files, such as Altium Designer or KiCad, you can import the generated Gerber files and compare them with the original Eagle .brd file. This process helps identify any discrepancies or missing features.

3. Fabricator Check: Many PCB Fabricators offer a free Gerber file check service. Submit your Gerber files to the fabricator, and they will review the files for any issues or incompatibilities with their manufacturing process. They may provide feedback or request changes if necessary.

Common Issues and Troubleshooting

During the Eagle .brd to Gerber conversion process, you may encounter some common issues. Here are a few problems and their possible solutions:

1. Missing Layers: If some layers are missing in the generated Gerber files, ensure that the layers are correctly assigned in the Eagle .brd file and that the CAM Processor job file includes all the necessary layers.

2. Incorrect Board Outline: If the board outline in the Gerber files does not match the desired dimensions, check that the board outline layer in the Eagle .brd file is correctly defined and assigned.

3. Incorrect Drill Sizes: If the drill sizes in the Gerber files are incorrect, verify that the drill sizes are correctly specified in the Eagle .brd file and that the drill layer is properly assigned in the CAM Processor job file.

4. Overlapping Text or Components: If text or components overlap in the Gerber files, adjust their placement in the Eagle .brd file to ensure proper clearance and readability.

Best Practices for Eagle to Gerber Conversion

To ensure a smooth and error-free conversion from Eagle .brd to Gerber format, follow these best practices:

1. Use a Standard Naming Convention: Adopt a consistent naming convention for your Eagle .brd files and the generated Gerber files. This practice helps in organizing and identifying the files easily.

2. Keep Track of Revisions: If you make changes to the Eagle .brd file after generating the Gerber files, make sure to regenerate the Gerber files and keep track of the revisions. Use version numbers or dates to differentiate between different iterations of the files.

3. Communicate with the PCB Fabricator: Establish clear communication with your PCB fabricator regarding their specific requirements for Gerber files. Some fabricators may have additional guidelines or preferences for file formats, layer assignments, or drill file specifications.

4. Archive the Files: Create a complete archive of the Eagle .brd file, generated Gerber files, and any other relevant documentation (e.g., BOM, assembly instructions) for each PCB project. This archive serves as a reference for future manufacturing runs or design modifications.

Frequently Asked Questions (FAQ)

1. Can I use Eagle’s CAM Processor to generate Gerber files for a PCB designed in another software?
   No, the CAM Processor in Eagle is specifically designed to work with Eagle .brd files. If you have a PCB design created in another software, you’ll need to use that software’s built-in Gerber generation tools or use a third-party Gerber file generator.

2. How do I know if my PCB fabricator accepts Eagle .brd files directly?
   Most PCB fabricators prefer to work with Gerber files, as they are the industry standard. However, some fabricators may accept Eagle .brd files directly. It’s best to check with your specific fabricator and inquire about their file format requirements.

3. What should I do if my PCB fabricator reports issues with the generated Gerber files?
   If your PCB fabricator reports issues with the Gerber files, first verify the files using a Gerber viewer or compare them with the original Eagle .brd file. If the issues persist, consult with the fabricator to understand their specific requirements and make the necessary adjustments in the Eagle design or CAM Processor settings.

4. Can I include multiple PCB designs in a single set of Gerber files?
   No, each set of Gerber files should represent a single PCB design. If you have multiple PCB designs, generate separate sets of Gerber files for each design to avoid confusion and manufacturing errors.

5. How can I ensure the accuracy of my PCB design before generating Gerber files?
   To ensure the accuracy of your PCB design, thoroughly review the design in Eagle, running both Design Rule Check (DRC) and Electrical Rule Check (ERC) to identify and resolve any errors or violations. Additionally, carefully inspect the board layout, component placement, and routing to ensure they meet your design requirements and manufacturing constraints.

Conclusion

Converting an Eagle .brd file to Gerber format is a critical step in the PCB manufacturing process. By following the guidelines outlined in this article, you can ensure a smooth and accurate conversion, minimizing the risk of manufacturing issues and delays. Remember to prepare your Eagle .brd file carefully, use Eagle’s CAM Processor to generate the Gerber files, and verify the generated files before submitting them to your PCB fabricator. By adhering to best practices and maintaining clear communication with your fabricator, you can successfully bring your PCB design to life.

Task	Description
Design Rule Check (DRC)	Run DRC to identify design rule violations and resolve them.
Electrical Rule Check (ERC)	Perform ERC to detect electrical issues and address them.
Board Outline	Ensure the board outline is correctly defined and matches the desired dimensions.
Layers	Verify that all necessary layers are present and correctly assigned.
Text and Labels	Check text and labels for proper placement and sizing.
CAM Processor	Use Eagle’s CAM Processor with the “gerb274x.cam” job file to generate Gerber files.
Gerber File Verification	Visually inspect the generated Gerber files, compare them with the .brd file, or submit them for fabricator check.
Troubleshooting	Address common issues such as missing layers, incorrect board outline, drill sizes, or overlapping elements.
Best Practices	Follow best practices for file naming, revision tracking, fabricator communication, and project archiving.

By following this comprehensive guide, you can streamline your PCB-Conversion process, ensuring accurate and manufacturable Gerber files for your Eagle PCB designs.