Introduction to KiCad and Gerber Files

KiCad is a popular open-source software suite for electronic design automation (EDA). It facilitates the design of electronic schematics and printed circuit boards (PCBs). One of the crucial steps in the PCB fabrication process is generating Gerber files from the KiCad PCB design. Gerber files are industry-standard file formats used to describe the layout of a PCB, including the copper layers, solder mask, silkscreen, and drill holes.

In this comprehensive guide, we will walk you through the step-by-step process of exporting your KiCad PCB design to Gerber files, ensuring that your design is ready for manufacturing.

Table of Contents

1. Understanding Gerber Files
2. Preparing Your KiCad PCB Design
3. Generating Gerber Files in KiCad
4. Reviewing and Verifying Gerber Files
5. Sending Gerber Files to PCB Manufacturers
6. Frequently Asked Questions (FAQ)
7. Conclusion

Understanding Gerber Files

Gerber files are named after the Gerber Systems Corp., the company that originally developed the file format. These files contain the necessary information for PCB manufacturers to fabricate your designed circuit board accurately. Each Gerber file represents a specific layer or aspect of the PCB, such as:

• Copper layers (e.g., top and bottom layers)
• Solder mask layers
• Silkscreen layers
• Drill files (for holes and vias)

The Gerber file format has evolved over time, with the current standard being the Extended Gerber or RS-274X format. This format includes aperture definitions, which describe the shapes and sizes of the features on the PCB.

Gerber File Extensions

Gerber files use specific file extensions to identify the different layers and aspects of the PCB. Some common file extensions include:

Extension	Description
.GTL	Top copper layer
.GBL	Bottom copper layer
.GTS	Top solder mask
.GBS	Bottom solder mask
.GTO	Top silkscreen (overlay)
.GBO	Bottom silkscreen (overlay)
.TXT	Drill file (Excellon format)

Understanding these file extensions will help you identify and manage the Gerber files generated from your KiCad PCB design.

Preparing Your KiCad PCB Design

Before generating Gerber files, it is essential to ensure that your KiCad PCB design is complete and error-free. Follow these steps to prepare your design:

1. Double-check the schematic: Verify that all components are correctly placed, and the connections are accurate.
2. Run design rule checks (DRC): Use KiCad’s DRC tool to identify any design rule violations, such as insufficient clearances or trace widths.
3. Confirm the board outline: Ensure that the board outline is correctly defined and matches your desired PCB shape.
4. Review the layer stackup: Verify that the layer stackup is correct and includes all the necessary layers (e.g., copper, solder mask, silkscreen).
5. Add necessary text and markings: Include any required text, logos, or markings on the silkscreen layer.

By thoroughly preparing your KiCad PCB design, you minimize the chances of errors and inconsistencies in the generated Gerber files.

Generating Gerber Files in KiCad

Once your KiCad PCB design is ready, follow these steps to generate the Gerber files:

1. Open the PCB layout editor in KiCad.
2. Click on “File” in the top menu and select “Plot” from the dropdown menu. This will open the “Plot” dialog box.
3. In the “Plot” dialog box, select the “Gerber” tab.
4. Choose the desired output directory for the Gerber files by clicking on the “Output directory” button and navigating to the target folder.
5. Set the appropriate plotting options:
6. Select the desired layers to plot (e.g., copper, solder mask, silkscreen) by checking the corresponding checkboxes.
7. Choose the appropriate plot format (usually “4.6 (unit mm)”) and check the “Use Protel filename extensions” option.
8. Adjust other settings, such as the plot border and exclude edge layer, as needed.
9. Click on the “Plot” button to generate the Gerber files.
10. KiCad will generate the Gerber files and save them in the specified output directory.

Generating Drill Files

In addition to the Gerber files, you also need to generate the drill files, which contain information about the holes and vias on the PCB. To generate drill files:

1. In the “Plot” dialog box, select the “Drill Files” tab.
2. Choose the desired output directory for the drill files.
3. Set the appropriate drill file options:
4. Select the drill units (usually “Inches”) and the drill file format (typically “Excellon”).
5. Choose the desired drill map file format (e.g., PostScript or Gerber).
6. Click on the “Generate Drill File” button to create the drill files.

KiCad will generate the drill files and save them in the specified output directory.

Reviewing and Verifying Gerber Files

After generating the Gerber files, it is crucial to review and verify them to ensure that they accurately represent your PCB design. There are several tools available for viewing and analyzing Gerber files:

1. GerbView: KiCad includes a built-in Gerber viewer called GerbView. To open GerbView, click on “Tools” in the top menu and select “GerbView” from the dropdown menu. Load your generated Gerber files into GerbView and visually inspect them for any errors or discrepancies.

2. Online Gerber viewers: Several online Gerber viewers, such as PCBWay Gerber Viewer and CircuitPeople Gerber Viewer, allow you to upload and view your Gerber files directly in a web browser. These tools provide a convenient way to quickly review your Gerber files without installing additional software.

3. CAM software: Computer-aided manufacturing (CAM) software, such as CAM350 or ViewMate, offer advanced features for analyzing and verifying Gerber files. These tools can help identify potential manufacturing issues and ensure that your Gerber files are suitable for production.

When reviewing your Gerber files, pay attention to the following aspects:

• Layer alignment: Ensure that all layers are correctly aligned and there are no obvious mismatches or offsets.
• Feature completeness: Verify that all the necessary features (e.g., pads, traces, vias) are present and correctly shaped.
• Aperture definitions: Check that the aperture definitions are correct and match the intended feature sizes.
• Drill holes: Confirm that the drill holes are correctly positioned and sized.

By thoroughly reviewing and verifying your Gerber files, you can catch any errors or issues before sending them to the PCB manufacturer, saving time and potential rework costs.

Sending Gerber Files to PCB Manufacturers

Once you have reviewed and verified your Gerber files, you are ready to send them to a PCB manufacturer for fabrication. When choosing a PCB manufacturer, consider factors such as:

• Manufacturing capabilities: Ensure that the manufacturer can accommodate your PCB specifications, such as the number of layers, minimum feature sizes, and material requirements.
• Lead time: Check the manufacturer’s lead time to ensure that it meets your project timeline.
• Cost: Compare pricing from different manufacturers to find the best value for your budget.
• Quality and reliability: Look for manufacturers with a proven track record of producing high-quality PCBs and positive customer reviews.

When sending your Gerber files to the PCB manufacturer, follow these guidelines:

1. Package the Gerber files: Compress all the generated Gerber files (including drill files) into a single ZIP or RAR archive. This makes it easier to transfer the files and ensures that no files are missed.

2. Provide clear instructions: Include a readme file or email with clear instructions for the PCB manufacturer. Specify any special requirements, such as the desired PCB thickness, copper weight, surface finish, or solder mask color.

3. Request a design for manufacturability (DFM) check: Many PCB manufacturers offer a free DFM check service, where they analyze your Gerber files for potential manufacturing issues. Take advantage of this service to catch any problems before production begins.

4. Communicate with the manufacturer: Maintain open communication with the PCB manufacturer throughout the fabrication process. Promptly respond to any questions or clarifications they may have to avoid delays.

By following these guidelines and working closely with your chosen PCB manufacturer, you can ensure a smooth transition from your KiCad PCB design to the final manufactured product.

Frequently Asked Questions (FAQ)

1. What are the most common issues encountered when exporting KiCad PCB designs to Gerber files?
   Some common issues include incorrect layer settings, missing or incorrect aperture definitions, and incomplete or misaligned drill files. Double-checking your design and carefully reviewing the generated Gerber files can help prevent these issues.

2. Can I use the same Gerber files for different PCB manufacturers?
   Yes, Gerber files are an industry-standard format, and most PCB manufacturers should be able to work with the same set of files. However, it’s always a good idea to check with the specific manufacturer for any unique requirements or preferences they may have.

3. What should I do if the PCB manufacturer reports issues with my Gerber files?
   If the PCB manufacturer reports issues with your Gerber files, first try to understand the nature of the problem. Check if there are any specific design rules or guidelines you may have overlooked. If necessary, go back to your KiCad PCB design, make the required changes, and regenerate the Gerber files. Communicate with the manufacturer to ensure that the revised files meet their requirements.

4. How can I ensure that my KiCad PCB design is manufacturable?
   To ensure that your KiCad PCB design is manufacturable, follow best practices such as adhering to the manufacturer’s design rules, using appropriate trace widths and clearances, and avoiding complex or unrealistic features. Running design rule checks (DRC) in KiCad and requesting a DFM check from the manufacturer can also help identify potential manufacturability issues.

5. What should I include in the readme file when sending Gerber files to a PCB manufacturer?
   In the readme file, include essential information such as the PCB specifications (e.g., dimensions, thickness, copper weight), the desired surface finish, solder mask color, and any special instructions or requirements. Also, provide your contact information in case the manufacturer needs to reach out for clarifications or updates.

Conclusion

Exporting your KiCad PCB design to Gerber files is a critical step in the PCB fabrication process. By following the steps outlined in this guide, you can generate accurate and complete Gerber files that are ready for manufacturing. Remember to thoroughly prepare your KiCad PCB design, carefully review and verify the generated Gerber files, and communicate clearly with your chosen PCB manufacturer.

By understanding the Gerber file format, its various layers, and the best practices for generating and handling these files, you can streamline your PCB design workflow and ensure a successful transition from design to manufacturing. With the right tools, attention to detail, and effective communication, you can bring your KiCad PCB designs to life and create high-quality, functional electronic products.