1. Incorrect File Format

One of the most common mistakes designers make is saving their Gerber files in the wrong format. PCB fabrication houses typically require Gerber files to be in the RS-274X format, also known as Extended Gerber or X2 format. This format includes aperture definitions and other essential information that ensures accurate interpretation of the design data.

To avoid this mistake, always double-check that your CAD software is set to export Gerber files in the RS-274X format. Most modern CAD tools have this option readily available in their export settings.

2. Missing or Incorrect Aperture Definitions

Aperture definitions are critical components of Gerber files, as they specify the shapes and sizes of the copper features on the PCB. Without proper aperture definitions, the fabrication house may misinterpret the design data, leading to manufacturing errors.

To prevent this issue, ensure that your Gerber files include a complete and accurate aperture list. Double-check that the aperture sizes and shapes match your design intent, and consider using a Gerber viewer to visually inspect the files before submitting them for fabrication.

3. Overlapping or Conflicting Copper Features

Overlapping or conflicting copper features can cause short circuits, unintended connections, and other manufacturing defects. This mistake often occurs when designers inadvertently create overlapping traces, pads, or polygons in their PCB layout.

To avoid this problem, use your CAD software’s design rule check (DRC) feature to identify and resolve any overlapping or conflicting copper features. Set appropriate clearance and width rules based on your PCB’s manufacturing capabilities and thoroughly review the DRC report before generating Gerber files.

4. Incorrect Layer Alignment

Proper layer alignment is essential for ensuring that the various layers of the PCB stack up correctly during the fabrication process. Misaligned layers can lead to manufacturing defects, such as drill holes that don’t line up with pads or vias.

To prevent layer alignment issues, use your CAD software’s layer stackup manager to define the correct layer order and thicknesses. When generating Gerber files, double-check that each layer is correctly labeled and positioned relative to the others. Consider using a Gerber viewer with a layer compare feature to verify proper alignment.

5. Insufficient or Incorrect Solder Mask Openings

Solder mask openings expose the copper pads and other features that require soldering during the assembly process. Insufficient or incorrect solder mask openings can lead to poor solderability, unintended connections, or even component placement issues.

To avoid this mistake, ensure that your solder mask openings are slightly larger than the copper pads they expose. Most PCB fabrication houses recommend a solder mask expansion of 0.05 to 0.1 mm beyond the pad edges. Use your CAD software’s solder mask generation tools to automatically create openings based on your design rules, and visually inspect the Gerber files to confirm proper solder mask placement.

6. Incomplete or Ambiguous Fabrication Notes

Fabrication notes provide essential information to the PCB manufacturer, such as material specifications, finish requirements, and special instructions. Incomplete or ambiguous fabrication notes can lead to misunderstandings, delays, and even incorrect manufacturing outcomes.

To prevent this issue, include clear and concise fabrication notes in your Gerber file package. Specify the PCB material, thickness, copper weight, surface finish, and any other relevant requirements. If your design has unique features or special considerations, communicate these clearly in the fabrication notes to avoid confusion.

7. Failing to Perform a Final Check

Perhaps the most critical mistake designers can make is failing to perform a final check of their Gerber files before submitting them for fabrication. Even minor oversights can lead to costly manufacturing errors and project delays.

To avoid this mistake, develop a comprehensive pre-submission checklist that includes the following items:

• Verify that all required Gerber files are present and named correctly
• Check that the files are in the correct format (RS-274X)
• Review the aperture list for completeness and accuracy
• Inspect the files for overlapping or conflicting copper features
• Confirm proper layer alignment and stackup
• Verify solder mask openings and expansions
• Ensure that fabrication notes are clear, complete, and accurate

By following this checklist and carefully reviewing your Gerber files, you can catch and correct any mistakes before they lead to manufacturing issues.

FAQ

1. What is the most common Gerber file mistake?

The most common Gerber file mistake is saving the files in the wrong format. PCB fabrication houses typically require Gerber files to be in the RS-274X format, which includes aperture definitions and other essential information.

2. How can I ensure proper layer alignment in my Gerber files?

To ensure proper layer alignment, use your CAD software’s layer stackup manager to define the correct layer order and thicknesses. When generating Gerber files, double-check that each layer is correctly labeled and positioned relative to the others. Consider using a Gerber viewer with a layer compare feature to verify proper alignment.

3. What is the recommended solder mask expansion for pad openings?

Most PCB fabrication houses recommend a solder mask expansion of 0.05 to 0.1 mm beyond the copper pad edges. This ensures adequate exposure of the pads for soldering during the assembly process.

4. How can I avoid overlapping or conflicting copper features in my Gerber files?

To avoid overlapping or conflicting copper features, use your CAD software’s design rule check (DRC) feature to identify and resolve any issues. Set appropriate clearance and width rules based on your PCB’s manufacturing capabilities and thoroughly review the DRC report before generating Gerber files.

5. What should I include in my fabrication notes to avoid misunderstandings with the PCB manufacturer?

In your fabrication notes, specify the PCB material, thickness, copper weight, surface finish, and any other relevant requirements. If your design has unique features or special considerations, communicate these clearly to avoid confusion. Be sure to include clear and concise instructions to minimize the risk of misunderstandings and manufacturing errors.

In conclusion, avoiding these top 7 Gerber file mistakes is crucial for ensuring a smooth and successful PCB manufacturing process. By following best practices, such as using the correct file format, providing accurate aperture definitions, and performing thorough pre-submission checks, designers can minimize the risk of costly errors and delays. At RAYPCB, we understand the importance of accurate and well-prepared Gerber files, and our experienced team is ready to assist you in bringing your PCB designs to life. Trust RAYPCB for your PCB fabrication needs and experience the peace of mind that comes with knowing your project is in capable hands.