Introduction to Gerber Files

Gerber files are the standard format used in the printed circuit board (PCB) industry for the design and manufacture of PCBs. They contain all the necessary information for the fabrication of a PCB, including the copper layers, solder mask, silkscreen, and drill holes. Outputting Gerber files correctly is crucial for ensuring that the PCB is manufactured according to the designer’s specifications. In this article, we will discuss the 9 key questions to consider when outputting Gerber files to ensure a smooth and accurate PCB fabrication process.

What are the Essential Layers in a Gerber File?

A complete set of Gerber files should include the following layers:

1. Top and bottom copper layers
2. Solder mask layers
3. Silkscreen layers
4. Solder paste layers (for surface mount components)
5. Drill files (for through-hole components and vias)

Ensure that all necessary layers are included in the Gerber file output to avoid any confusion or delays in the manufacturing process.

What is the Appropriate Naming Convention for Gerber Files?

Using a clear and consistent naming convention for Gerber files is essential for easy identification and processing. The recommended naming convention is as follows:

• <board_name>_<layer_name>.<extension>

For example:
– my_pcb_top_copper.gbr
– my_pcb_bottom_solder_mask.gbs

Stick to a standardized naming convention to ensure that the manufacturer can easily identify and process the files.

What are the Common Gerber File Extensions?

Different Gerber file extensions are used to identify the type of layer. The most common extensions are:

Ensure that the correct file extensions are used for each layer type to avoid confusion and potential manufacturing issues.

What are the Recommended Gerber File Format Settings?

When outputting Gerber files, it is essential to use the correct format settings to ensure compatibility with the manufacturer’s equipment. The recommended settings are:

• Format: RS-274X (Extended Gerber)
• Coordinate format: 2.4 (leading zero omitted, absolute coordinates)
• Aperture table: Embedded in the Gerber file
• Drill files: ASCII format (with embedded drill sizes and tool definitions)

Using these settings will ensure that the Gerber files are compatible with most PCB manufacturing equipment and minimize the risk of errors during fabrication.

How to Handle Apertures and Aperture Lists?

Apertures define the shapes and sizes of the features in a Gerber file, such as pads, traces, and vias. An aperture list is a table that defines the D-codes (aperture codes) used in the Gerber file. To handle apertures and aperture lists effectively:

1. Embed the aperture list in the Gerber file to ensure that the manufacturer has all the necessary information.
2. Use standard aperture shapes (e.g., circles, rectangles, and ovals) whenever possible to ensure compatibility with manufacturing equipment.
3. Avoid using custom aperture shapes unless absolutely necessary, as they may require special processing and increase the risk of errors.

By following these guidelines, you can ensure that the apertures and aperture lists are correctly defined and processed during PCB fabrication.

What are the Best Practices for Panelization?

Panelization is the process of arranging multiple PCBs on a single panel for efficient manufacturing. When panelizing PCBs, consider the following best practices:

1. Include fiducial markers on the panel to help align the PCBs during assembly.
2. Use mouse bites or V-scoring to separate the individual PCBs from the panel.
3. Ensure adequate spacing between the PCBs to allow for clean breakouts and to minimize the risk of damage during depaneling.
4. Discuss panelization requirements with the manufacturer to ensure that the panel design is compatible with their equipment and processes.

By following these best practices, you can optimize the panelization process and ensure that the PCBs are manufactured efficiently and with minimal risk of damage.

How to Handle Solder Mask and Silkscreen Layers?

Solder mask and silkscreen layers are critical for protecting the PCB and providing useful information for assembly. When handling these layers, consider the following:

1. Ensure that the solder mask openings are slightly larger than the pads to allow for proper solder joint formation.
2. Avoid placing silkscreen text or graphics too close to pads or other features, as this can interfere with soldering or cause readability issues.
3. Use a contrasting color for the silkscreen to ensure clear visibility against the solder mask background.
4. Discuss any special requirements, such as selective solder masking or custom silkscreen colors, with the manufacturer to ensure feasibility and correct implementation.

By carefully considering the design and placement of solder mask and silkscreen layers, you can enhance the functionality and appearance of the PCB.

What are the Considerations for Drill Files?

Drill files contain information about the location, size, and type of drill holes required for the PCB. When generating drill files, consider the following:

1. Use the correct drill file format (ASCII or binary) as specified by the manufacturer.
2. Ensure that the drill file includes all necessary holes, including those for through-hole components and vias.
3. Specify the drill sizes and tolerances according to the manufacturer’s requirements and the PCB design’s demands.
4. Include plated and non-plated holes in separate drill files or clearly distinguish them within the same file to avoid confusion during manufacturing.

By providing accurate and complete drill file information, you can ensure that the PCB is drilled correctly and that components can be properly installed.

How to Perform a Final Check Before Submitting Gerber Files?

Before submitting Gerber files to the manufacturer, it is essential to perform a final check to catch any errors or inconsistencies. Follow these steps:

1. Verify that all necessary layers are included in the Gerber file set.
2. Check that the Gerber files use the correct format, extensions, and settings.
3. Review the aperture list to ensure that all required apertures are defined and used correctly.
4. Inspect the solder mask and silkscreen layers for any design issues or potential manufacturing challenges.
5. Confirm that the drill files include all necessary holes and are formatted correctly.
6. Compare the Gerber files to the original PCB design to ensure that no information has been lost or altered during the output process.

By performing a thorough final check, you can minimize the risk of errors and delays in the PCB manufacturing process.

FAQ

1. What is the difference between ASCII and binary drill file formats?

2. ASCII drill files are human-readable and contain drill hole information in a text format, while binary drill files are machine-readable and contain drill hole information in a compact binary format. ASCII drill files are more common and easier to debug, while binary drill files are more space-efficient.

3. Can I use custom aperture shapes in my Gerber files?

4. While it is possible to use custom aperture shapes, it is generally recommended to stick to standard shapes (circles, rectangles, and ovals) to ensure compatibility with manufacturing equipment. If custom shapes are necessary, discuss the requirements with the manufacturer to ensure feasibility and proper implementation.

5. What is the purpose of fiducial markers in panelization?

6. Fiducial markers are used to help align the PCBs during the assembly process. They serve as reference points for pick-and-place machines and other assembly equipment, ensuring that components are placed accurately on the PCBs.

7. How do I ensure that my solder mask openings are the correct size?

8. Solder mask openings should be slightly larger than the pads to allow for proper solder joint formation. The exact size of the openings depends on the pad size and the manufacturer’s requirements. Consult with the manufacturer to determine the appropriate solder mask expansion for your PCB design.

9. What should I do if I’m unsure about any aspect of my Gerber files?

10. If you have any doubts or questions about your Gerber files, it is best to consult with the PCB manufacturer. They can provide guidance on their specific requirements, help you resolve any issues, and ensure that your Gerber files are optimized for their manufacturing process.

Conclusion

Outputting Gerber files correctly is essential for ensuring a smooth and accurate PCB manufacturing process. By considering the 9 key questions discussed in this article, you can minimize the risk of errors, delays, and manufacturing issues. Remember to include all necessary layers, use the correct file formats and extensions, handle apertures and drill files appropriately, and perform a final check before submitting your Gerber files. By following these best practices and maintaining clear communication with your PCB manufacturer, you can achieve successful PCB fabrication and bring your electronic designs to life.