Introduction
Exporting Gerber files is a crucial step in the PCB manufacturing process, serving as the universal language between designers and manufacturers. This comprehensive guide will walk you through the entire process of generating Gerber files from KiCad, ensuring your design is ready for production. Whether you're a beginner or an experienced PCB designer, this guide covers everything from basic concepts to advanced techniques.
Understanding Gerber Files
What Are Gerber Files?
Gerber files are the standard format used in the PCB industry to communicate design information to manufacturers. They contain vector-based instructions that describe the various layers and features of your PCB design.
Gerber File Types
| Layer Type | File Extension | Description | Required |
|---|---|---|---|
| Top Copper | .GTL | Contains top layer copper traces and pads | Yes |
| Bottom Copper | .GBL | Contains bottom layer copper traces and pads | Yes |
| Top Solder Mask | .GTS | Defines areas where solder mask should be removed | Yes |
| Bottom Solder Mask | .GBS | Defines areas where solder mask should be removed | Yes |
| Top Silkscreen | .GTO | Contains component markings and text | Optional |
| Bottom Silkscreen | .GBO | Contains component markings and text | Optional |
| Board Outline | .GM1 | Defines the board shape and dimensions | Yes |
| Drill Files | .DRL | Contains hole locations and sizes | Yes |
Gerber File Formats
| Format Type | Version | Features | Industry Support |
|---|---|---|---|
| RS-274X | Extended | Self-contained aperture definitions | High |
| RS-274D | Legacy | Requires separate aperture file | Low |
| X2 | Latest | Enhanced metadata support | Growing |
Prerequisites
Required Software
Before starting the Gerber export process, ensure you have:
- KiCad 6.0 or later installed
- Your PCB design completed and validated
- A Gerber viewer (recommended for verification)
Design Checklist
| Check Item | Description | Critical Level |
|---|---|---|
| DRC | Design Rule Check completion | Mandatory |
| Net Connectivity | All connections verified | Mandatory |
| Layer Stack | Correct layer configuration | Mandatory |
| Board Outline | Properly defined edge cuts | Mandatory |
| Drill Holes | All holes placed and sized | Mandatory |
Step-by-Step Export Process
1. Preparing Your Design
Before exporting Gerber files, ensure your design meets all manufacturing requirements:
- Complete all routing
- Place all components
- Add any necessary fiducials
- Include manufacturing marks if required
- Verify board dimensions
2. Accessing the Plot Dialog
- Open your PCB file in KiCad PCB Editor (Pcbnew)
- Select File > Plot from the main menu
- The Plot dialog window will appear
3. Basic Plot Settings
| Setting | Recommended Value | Purpose |
|---|---|---|
| Plot Format | Gerber | Industry standard format |
| Output Directory | gerber/ | Keeps files organized |
| Drill Units | Inches | Common manufacturer preference |
| Coordinate Format | 4.6, inch | Standard precision format |
| Zero Suppression | No | Maintains file compatibility |
4. Layer Selection
Select the appropriate layers for plotting:
- F.Cu (Top copper)
- B.Cu (Bottom copper)
- F.Mask (Top solder mask)
- B.Mask (Bottom solder mask)
- F.Silkscreen (Top silkscreen)
- B.Silkscreen (Bottom silkscreen)
- Edge.Cuts (Board outline)
Layer Configuration
Layer Stack Management
| Layer | Common Settings | Special Considerations |
|---|---|---|
| Copper | Use negative plot | Include thermal reliefs |
| Solder Mask | Use negative plot | Consider minimum solder dam |
| Silkscreen | Use positive plot | Check minimum text size |
| Edge Cuts | Single layer | Ensure closed outline |
Advanced Layer Options
Detailed settings for each layer type:
- Copper Layers
- Plot pad holes
- Plot vias
- Plot microwave features
- Solder Mask
- Minimum clearance
- Pad expansion
- Via masking
- Silkscreen
- Text scaling
- Line width
- Component markings
Advanced Settings
Plot Options
| Option | Description | Recommended Setting |
|---|---|---|
| Use Protel Extensions | File naming compatibility | Enabled |
| Exclude PCB Edge Layer | Edge cut handling | Disabled |
| Use Auxiliary Axis | Reference point | Project specific |
| Subtract Mask from Silk | Improve readability | Enabled |
Drill File Generation
- Open the drill file generator
- Configure drill file format
- Set drill map options
- Generate drill files
Extended Options
| Setting | Purpose | Impact |
|---|---|---|
| Mirror Plot | Reverse layer image | Manufacturing specific |
| Negative Plot | Invert layer polarity | Layer specific |
| Fine Scaling | Size adjustments | Manufacturing compensation |
| Line Width | Trace thickness | Manufacturing capability |
Common Issues and Solutions
Troubleshooting Guide
| Issue | Possible Cause | Solution |
|---|---|---|
| Missing Layers | Incorrect layer selection | Review plot settings |
| Incomplete Board Outline | Broken edge cuts | Check edge cut continuity |
| Drill File Errors | Wrong format settings | Verify drill file configuration |
| Silkscreen Overlap | Insufficient clearance | Adjust text placement |
| Copper Pour Issues | Pour settings | Review zone settings |
Quality Control Steps
- Layer Alignment
- Drill-to-Copper Registration
- Solder Mask Coverage
- Silkscreen Readability
- Board Outline Verification
Best Practices
File Organization
- Use consistent naming conventions
- Create separate folders for different versions
- Include readme files with specific instructions
- Maintain backup copies
Manufacturing Considerations
| Aspect | Recommendation | Reason |
|---|---|---|
| Trace Width | Follow manufacturer minimums | Ensure manufacturability |
| Drill Sizes | Use standard sizes | Reduce costs |
| Layer Registration | Include alignment marks | Improve accuracy |
| Documentation | Include assembly drawings | Clear communication |
Verification Process
Using Gerber Viewers
- Load all generated files
- Check layer alignment
- Verify dimensions
- Confirm hole positions
- Review copper clearances
Final Checklist
| Check Point | Verification Method | Critical Level |
|---|---|---|
| Layer Count | Visual inspection | High |
| Board Size | Measurement tool | High |
| Drill Counts | Compare with design | Medium |
| Copper Features | DFM check | High |
| Silkscreen Quality | Visual inspection | Medium |
Frequently Asked Questions
Q1: Why are my Gerber files showing different dimensions than my design?
A: This typically occurs due to unit mismatches. Ensure your plot settings use the same units (inches or millimeters) as your design. Check the plot dialog's unit settings and verify the coordinate format matches your manufacturer's requirements.
Q2: How do I know if my Gerber files are complete?
A: A complete Gerber file set should include:
- All copper layers
- Solder mask layers
- Silkscreen layers
- Board outline
- Drill files Use a Gerber viewer to verify all layers are present and properly aligned.
Q3: Why do manufacturers reject my Gerber files?
A: Common reasons for rejection include:
- Missing or incomplete layers
- Incorrect file format
- Design rule violations
- Poor layer registration Always verify your files with a Gerber viewer and follow manufacturer-specific guidelines.
Q4: How do I handle different layer stackups?
A: KiCad allows you to define custom layer stackups. Configure your layer stack in the Board Setup dialog before generating Gerber files. Ensure all necessary layers are included in your plot settings.
Q5: What should I do if my Gerber viewer shows errors?
A: Follow these steps:
- Check plot settings for correct format
- Verify layer selection
- Review design rule violations
- Compare against original design
- Consider regenerating files with different settings
Conclusion
Exporting Gerber files from KiCad is a critical process that requires attention to detail and understanding of manufacturing requirements. By following this comprehensive guide and implementing the recommended best practices, you can ensure your design is properly prepared for production. Remember to always verify your files before submission and maintain clear communication with your manufacturer regarding specific requirements.
