What is a Gerber File?

Gerber files, also known as Gerber image or Gerber format files, contain the essential information needed to manufacture a printed circuit board (PCB). They are generated from PCB design software like Altium Designer and sent to PCB fabricators. A complete Gerber file package includes:

• Copper layers (e.g., Top Layer, Bottom Layer)
• Solder mask layers
• Silkscreen layers
• Drill files
• Fabrication drawings

Gerber is a vector image file format that uses X,Y coordinates and simple code to describe a 2D binary image. It was originally developed by Gerber Systems Corp. in the 1960s for vector photoplotters, but has since been adapted as the de facto standard for PCB fabrication data.

Why Use Gerber Format?

There are several reasons why Gerber is the preferred format for PCB manufacturing:

1. Universality: Almost all PCB manufacturers accept Gerber files. It is the most widely used data transfer format in the industry.

2. Simplicity: Gerber is a simple, human-readable ASCII format that describes 2D images. It doesn’t contain complex information like connectivity or net lists.

3. Reliability: Gerber files have been used for decades and are well-understood by fabricators. They produce reliable, high-quality results when used correctly.

4. Compatibility: Gerber files can be generated from virtually any PCB design software, making it a flexible format for designers.

While some newer PCB data formats like ODB++ and IPC-2581 have emerged, Gerber remains the most common and widely supported. Unless your fabricator specifies otherwise, Gerber is usually the best choice.

How to Export AD Files to Gerber

Now let’s dive into the process of generating Gerber files from your Altium Designer PCB project. We’ll assume you have a completed PCB design ready for manufacturing.

Step 1: Open the PCB Project

Launch Altium Designer and open the PCB project you want to export to Gerber. Ensure all design rule checks (DRC) are passed and the layout is finalized.

Step 2: Open the Fabrication Outputs Window

From the top menu, select File > Fabrication Outputs > Gerber Files. This will open the Gerber Setup window where you can configure your export settings.

Step 3: Select Layers to Export

In the Gerber Setup window, choose which layers to include in your Gerber output. Typically, you’ll want to export:

• All copper layers (e.g., Top Layer, Bottom Layer, inner layers)
• Top and Bottom Solder Masks
• Top and Bottom Silkscreens (Overlays)
• Solder Paste Masks (if applicable)

Make sure to select the mechanical layers that define the board outline and any cutouts or holes.

Layer Type	Include in Gerber?
Copper Layers	Yes – All
Solder Masks	Yes – Top & Bottom
Silkscreens	Yes – Top & Bottom
Solder Paste	Optional
Board Outline	Yes
Drill Files	Yes

Step 4: Configure Gerber Settings

Next, configure the Gerber export settings to match your fabricator’s requirements:

• Format: Choose between RS-274X (Extended Gerber) or RS-274D. Extended Gerber is most common.
• Units: Specify either Inches or Millimeters.
• Coordinate Format: Select the number format for coordinates (e.g., 4.5, 4.6).
• Aperture Table: Choose an aperture file or embed apertures in the Gerber file.
• Output File: Set the directory and naming convention for the exported files.

Consult with your PCB manufacturer if you’re unsure about any settings. They can provide guidance on their preferred Gerber configuration.

Step 5: Run Gerber Export

Once you’ve selected the layers and configured the export settings, click “OK” to generate the Gerber files. Altium will create a separate Gerber file for each layer in the output directory you specified.

Step 6: Review Gerber Files

After exporting, it’s a good idea to review your Gerber files in a Gerber viewer program. This allows you to visually inspect the layers, check for any obvious errors, and ensure the export was successful. Popular Gerber viewers include:

• GC-Prevue
• ViewMate
• Ucamco’s GerberLogix

If everything looks correct in the Gerber viewer, your files are ready to send to the manufacturer.

Step 7: Generate Drill Files

In addition to the Gerber files, you’ll also need to export NC drill files that specify the location and size of holes in the PCB.

To export drill files from Altium:

1. Go to File > Fabrication Outputs > NC Drill Files.
2. In the NC Drill Setup window, select the drill pairs to export (e.g., Plated Holes, Non-Plated Holes).
3. Configure the drill file settings like units, format, and output file name.
4. Click “OK” to generate the drill files.

Step 8: Create Assembly Drawings

While not strictly part of the Gerber file package, it’s often helpful to include assembly drawings that show the component placement on the PCB. These drawings help the manufacturer during assembly and can be used for visual reference.

To create assembly drawings in Altium:

1. Go to File > Fabrication Outputs > Assembly Drawings.
2. In the Assembly Drawing Setup window, choose the layers to include (e.g., Top Overlay, Top Paste).
3. Set the drawing format, scaling, and output file name.
4. Click “OK” to generate the assembly drawings.

Step 9: Package and Send Files

Finally, package your Gerber files, drill files, and assembly drawings into a single ZIP file or folder. Name the package clearly with your project name and revision number.

Send the packaged files to your PCB manufacturer, along with any special instructions or requirements. They will use these files to fabricate and assemble your PCB.

FAQ

What if my manufacturer requires a different file format?

While Gerber is the most common PCB data format, some manufacturers may prefer or require other formats like ODB++ or IPC-2581. Consult with your manufacturer and follow their data submission guidelines. Altium can export to various formats beyond just Gerber.

How do I check if my Gerber files are correct?

Reviewing your Gerber files in a Gerber viewer is the best way to visually inspect the layers for errors. Look for any missing features, incorrect pad sizes, or misaligned drill holes. You can also use automated tools like the GerberLogix Analyzer to check for common Gerber file issues.

What if I need to make changes after generating Gerber files?

If you discover an error or need to modify your design after generating Gerber files, go back to your Altium PCB project and make the necessary changes. Then, re-export the affected layers to Gerber format. Be sure to clearly communicate any changes to your manufacturer.

How do I handle PCBs with multiple copies or panels?

If your design includes multiple copies of the same PCB or is arranged in a panel for production, you’ll need to generate panel-level Gerber files. Altium has tools for creating PCB arrays and panels. Consult the Altium documentation or work with your manufacturer to ensure your panel Gerber files are set up correctly.

What other information should I provide to my manufacturer?

In addition to the Gerber files, it’s helpful to provide your manufacturer with:

• Bill of Materials (BOM)
• Pick and place files for automated assembly
• Fabrication drawings or notes
• Any special instructions or requirements

The more information you can provide upfront, the smoother the manufacturing process will be.

Conclusion

Generating Gerber files is a critical step in the PCB design process, as it transfers your digital design into the format needed for physical manufacturing. By following the steps outlined in this guide and working closely with your PCB manufacturer, you can ensure your AD designs are accurately converted to Gerber format and ready for production.

Remember to:

• Select all necessary layers for export
• Configure Gerber settings per your manufacturer’s guidelines
• Review Gerber files in a viewer for errors
• Generate drill files and assembly drawings
• Package and send files clearly to your manufacturer

With a solid understanding of Gerber file generation, you’ll be well-equipped to take your PCB designs from concept to reality.