Introduction

Gerber files are essential in the manufacturing of printed circuit boards (PCBs). They contain all the necessary information for PCB Fabrication, including the layout, drill holes, and solder mask. AutoCAD, a popular computer-aided design (CAD) software, is widely used for creating PCB designs. In this article, we will discuss the step-by-step process of generating Gerber files from AutoCAD.

What are Gerber Files?

Gerber files, also known as Gerber format or RS-274X format, are standard file formats used in PCB manufacturing. They were developed by Gerber Systems Corporation (now Ucamco) in the 1960s and have since become the industry standard for PCB fabrication data exchange.

Gerber files contain all the necessary information for manufacturing PCBs, including:

• Copper layers
• Solder mask
• Silkscreen
• Drill data
• Board outline

Each layer of the PCB is represented by a separate Gerber file. For example, a typical double-sided PCB would have the following Gerber files:

Gerber File	Description
Top Copper	The top copper layer of the PCB
Bottom Copper	The bottom copper layer of the PCB
Top Solder Mask	The solder mask for the top layer
Bottom Solder Mask	The solder mask for the bottom layer
Top Silkscreen	The silkscreen for the top layer
Bottom Silkscreen	The silkscreen for the bottom layer
Drill Data	The drill hole information
Board Outline	The outline of the PCB

Prerequisites for Generating Gerber Files from AutoCAD

Before generating Gerber files from AutoCAD, ensure that you have the following:

1. AutoCAD software installed on your computer
2. A completed PCB design in AutoCAD
3. A Gerber file generation tool (either built-in or third-party)

AutoCAD Software

AutoCAD is a CAD software developed by Autodesk. It is used for creating 2D and 3D designs across various industries, including electronics and PCB design. To generate Gerber files from AutoCAD, you need to have AutoCAD installed on your computer.

Completed PCB Design

To generate Gerber files, you must have a completed PCB design in AutoCAD. The design should include all the necessary layers, such as copper, solder mask, silkscreen, and drill holes. Ensure that your design adheres to the PCB manufacturing guidelines provided by your chosen PCB fabricator.

Gerber File Generation Tool

AutoCAD does not have a built-in Gerber file generation tool. However, there are several third-party tools available that can generate Gerber files from AutoCAD designs. Some popular options include:

• CAM350 by DownStream Technologies
• GerbTool by WISE Software Solutions
• GerbMaster by Lavenir Technology

These tools typically integrate with AutoCAD and provide a user-friendly interface for generating Gerber files.

Step-by-Step Guide to Generating Gerber Files from AutoCAD

Follow these steps to generate Gerber files from your AutoCAD PCB design:

Step 1: Prepare Your PCB Design

1. Open your PCB design in AutoCAD.
2. Ensure that all layers are correctly assigned and named according to the PCB fabricator’s requirements.
3. Check that all components, traces, and drill holes are positioned accurately.
4. Verify that your design meets the PCB manufacturing guidelines provided by your chosen fabricator.

Step 2: Set Up the Gerber File Generation Tool

1. Open your chosen Gerber file generation tool.
2. Set up the tool to work with your AutoCAD design. This may involve specifying the AutoCAD version, file format, and other settings.
3. Configure the Gerber file output settings, such as the file format (RS-274X), units (metric or imperial), and aperture definitions.

Step 3: Select the Layers for Gerber File Generation

1. In the Gerber file generation tool, select the layers you want to generate Gerber files for. This typically includes copper layers, solder mask, silkscreen, and drill data.
2. Assign the appropriate file extensions to each layer, as specified by your PCB fabricator. Common file extensions include:
3. .GTL: Top copper layer
4. .GBL: Bottom copper layer
5. .GTS: Top solder mask
6. .GBS: Bottom solder mask
7. .GTO: Top silkscreen
8. .GBO: Bottom silkscreen
9. .TXT or .DRL: Drill data
10. .GKO or .GM1: Board outline

Step 4: Generate the Gerber Files

1. Once you have selected the layers and assigned the file extensions, initiate the Gerber file generation process in the tool.
2. The tool will create separate Gerber files for each layer you selected.
3. Save the generated Gerber files in a designated folder on your computer.

Step 5: Verify the Generated Gerber Files

1. Open the generated Gerber files in a Gerber viewer to ensure that they are correct and complete.
2. Check for any errors, such as missing apertures, incorrect layer assignments, or design discrepancies.
3. Make any necessary corrections in your AutoCAD design and regenerate the Gerber files if needed.

Step 6: Package and Send the Gerber Files to Your PCB Fabricator

1. Once you have verified the Gerber files, package them together in a compressed folder (e.g., ZIP or RAR).
2. Include any additional files or information required by your PCB fabricator, such as the Bill of Materials (BOM), assembly drawings, or special instructions.
3. Send the packaged Gerber files to your PCB fabricator for manufacturing.

Best Practices for Generating Gerber Files from AutoCAD

To ensure a smooth and error-free Gerber file generation process, follow these best practices:

1. Use a consistent naming convention: Adopt a consistent naming convention for your layers and files to avoid confusion and errors.
2. Adhere to PCB fabricator guidelines: Follow the PCB manufacturing guidelines provided by your chosen fabricator to ensure that your design is manufacturable and meets their requirements.
3. Verify your design before generating Gerber files: Double-check your PCB design for errors, such as overlapping traces, missing connections, or incorrect component placement, before generating Gerber files.
4. Use a reliable Gerber file generation tool: Choose a reputable and reliable Gerber file generation tool that is compatible with your version of AutoCAD and provides the necessary features and settings.
5. Review generated Gerber files: Always review the generated Gerber files in a Gerber viewer to catch any errors or discrepancies before sending them to your PCB fabricator.

Troubleshooting Common Issues

Issue 1: Missing or Incorrect Apertures

If your generated Gerber files have missing or incorrect apertures, it may be due to:

• Incorrect aperture definitions in the Gerber file generation tool settings
• Incompatible aperture lists between your design and the Gerber file generation tool

To resolve this issue:

1. Double-check the aperture definitions in your Gerber file generation tool settings and ensure they match your PCB fabricator’s requirements.
2. Verify that the aperture list used in your AutoCAD design is compatible with the Gerber file generation tool.
3. If necessary, manually edit the aperture list in the Gerber file generation tool to match your design.

Issue 2: Layer Misalignment

If the layers in your generated Gerber files are misaligned, it may be caused by:

• Incorrect layer positioning in your AutoCAD design
• Improper layer assignment during the Gerber file generation process

To resolve this issue:

1. Verify that all layers in your AutoCAD design are positioned correctly and aligned with each other.
2. Double-check the layer assignments in your Gerber file generation tool and ensure they match your design.
3. If necessary, manually adjust the layer positions in your AutoCAD design or the Gerber file generation tool.

Issue 3: Incorrect File Extensions

If your generated Gerber files have incorrect file extensions, it may lead to issues during PCB manufacturing. To resolve this:

1. Consult with your PCB fabricator and obtain their required file extensions for each layer.
2. Update the file extension assignments in your Gerber file generation tool to match your fabricator’s requirements.
3. Regenerate the Gerber files with the correct file extensions.

FAQ

1. What is the difference between Gerber files and CAD files?
   Gerber files are industry-standard file formats used for PCB manufacturing, containing information about the copper layers, solder mask, silkscreen, and drill data. CAD files, on the other hand, are design files created in AutoCAD or other CAD software, used for designing the PCB Layout and components.

2. Can I generate Gerber files directly from AutoCAD without using a third-party tool?
   AutoCAD does not have a built-in Gerber file generation feature. To generate Gerber files from your AutoCAD PCB design, you need to use a third-party Gerber file generation tool that integrates with AutoCAD.

3. What should I do if my PCB fabricator requires a specific file format other than Gerber?
   If your PCB fabricator requires a specific file format other than Gerber, such as ODB++ or IPC-2581, consult with them to determine the best course of action. Some Gerber file generation tools may support exporting to these file formats, or you may need to use a different tool altogether.

4. How do I ensure that my generated Gerber files are correct and complete?
   To ensure that your generated Gerber files are correct and complete, follow these steps:

5. Verify your PCB design in AutoCAD for errors and adherence to manufacturing guidelines.
6. Double-check the layer assignments and file extension settings in your Gerber file generation tool.
7. Review the generated Gerber files in a Gerber viewer for any discrepancies or errors.

8. Consult with your PCB fabricator and obtain their feedback on the generated Gerber files.

9. What should I include in the package when sending Gerber files to my PCB fabricator?
   When sending Gerber files to your PCB fabricator, include the following in the package:

10. All generated Gerber files (copper layers, solder mask, silkscreen, drill data, and board outline)
11. Bill of Materials (BOM)
12. Assembly drawings
13. Any special instructions or requirements
14. Compress all files into a single folder (ZIP or RAR) for easy transfer.

Conclusion

Generating Gerber files from AutoCAD is a crucial step in the PCB manufacturing process. By following the step-by-step guide and best practices outlined in this article, you can ensure that your generated Gerber files are accurate, complete, and ready for fabrication. Remember to use a reliable Gerber file generation tool, adhere to your PCB fabricator’s guidelines, and always verify your files before sending them for manufacturing. With these steps in mind, you can streamline your PCB design and manufacturing workflow, reducing errors and ensuring a successful end product.