Generating accurate Gerber files from Altium Designer (AD) is a crucial step in the PCB manufacturing process. This comprehensive guide will walk you through the process, best practices, and common pitfalls to avoid when generating Gerber files from your Altium Designer projects.
Understanding Gerber Files
Gerber File Types
File Extension | Layer Type | Description |
.GTL | Top Layer | Top copper layer |
.GBL | Bottom Layer | Bottom copper layer |
.GTO | Top Overlay | Top silkscreen |
.GBO | Bottom Overlay | Bottom silkscreen |
.GTS | Top Solder Mask | Top solder mask |
.GBS | Bottom Solder Mask | Bottom solder mask |
.GTP | Top Paste | Top solder paste |
.GBP | Bottom Paste | Bottom solder paste |
.GKO | Keep-Out | Board outline |
.GML/.GM1 | Mechanical 1 | Dimensions, assembly |
Gerber Format Standards
Format | Description | Usage |
RS-274X | Extended Gerber | Modern standard |
RS-274D | Standard Gerber | Legacy format |
X2 | Latest format | Advanced features |
Pre-Generation Checklist

Design Verification
Check Item | Description | Critical Level |
DRC | Design Rule Check | Critical |
ERC | Electrical Rule Check | High |
Copper Balance | Layer copper distribution | Medium |
Component Clearance | Spacing verification | High |
Board Outline | Edge clearances | Critical |
Layer Stack Management
Standard Layer Stack
Layer Name | Type | Include in Gerber |
Top Overlay | Silk Screen | Yes |
Top Paste | Paste Mask | Yes |
Top Solder | Solder Mask | Yes |
Top Layer | Copper | Yes |
Inner Layer 1 | Copper | Yes |
Inner Layer 2 | Copper | Yes |
Bottom Layer | Copper | Yes |
Bottom Solder | Solder Mask | Yes |
Bottom Paste | Paste Mask | Yes |
Bottom Overlay | Silk Screen | Yes |
Mechanical 1 | Mechanical | Yes |
Drill Drawing | Drill | Yes |
Gerber Generation Process
Output Configuration
General Settings
Setting | Recommended Value | Purpose |
Units | mm | Standard metric |
Format | 4:04 | Precision level |
Zero Suppression | Leading | Industry standard |
Reference Point | Relative | Position accuracy |
Layer Setup
Export Options
Option | Setting | Reason |
Polygon Fill Mode | Solid | Better manufacturing |
Drill Pairs | Layer Pairs | Clear drill definition |
Drill Drawing | Separate File | Manufacturing requirement |
Mirror | As Required | Layer-specific |
NC Drill Configuration

Drill File Settings
Parameter | Value | Description |
Format | Excellon 2 | Industry standard |
Units | Metric | Standard measurement |
Zeros | Keep zeros | Accuracy maintenance |
Tool Assignment | Optimize | Efficient drilling |
Drill Table Configuration
Field | Include | Format |
Tool Number | Yes | Integer |
Hole Size | Yes | Metric |
Plated Status | Yes | Boolean |
Hole Count | Yes | Integer |
Tool Description | Optional | Text |
Output Generation
File Naming Convention
File Type | Naming Format | Example |
Top Layer | ProjectName_GTL | PCB_GTL |
Bottom Layer | ProjectName_GBL | PCB_GBL |
Drill File | ProjectName_DRL | PCB_DRL |
Assembly | ProjectName_Assembly | PCB_Assembly |
Output Job Configuration
Job File Structure
Section | Content | Purpose |
Documentation | Assembly drawings | Assembly guide |
Fabrication | Gerber files | Manufacturing |
NC Drill | Drill files | Hole creation |
Report | Quality records | Documentation |
Verification Steps
Post-Generation Checks
Check Type | Tool | Purpose |
Gerber View | CAM Editor | Visual verification |
Layer Stack | Layer Stack Manager | Stack-up verification |
Drill Data | NC Drill Editor | Hole verification |
DFM | DFM Checker | Manufacturability check |
Common Issues Table
Issue | Cause | Solution |
Missing Layers | Incorrect setup | Review layer setup |
Misaligned Data | Reference point error | Check origin setting |
Incomplete Outline | Layer assignment | Verify board layer |
Drill Mismatch | Format error | Check drill settings |
Manufacturing Package
Required Files
File Category | Contents | Format |
Gerber Set | All layers | .gbr |
Drill Files | Through-holes | .drl |
Assembly Drawing | Component placement | |
BOM | Component list | .xlsx |
README | Special instructions | .txt |
Zip File Structure
Folder | Contents | Purpose |
Gerber | Layer files | Manufacturing |
Drill | Drill data | Hole creation |
Assembly | Drawings, BOM | Assembly guide |
Documentation | Instructions | Reference |
Frequently Asked Questions
Q1: What are the essential Gerber files needed for PCB manufacturing?
A: The essential Gerber files include:
- Top and bottom copper layers (.GTL, .GBL)
- Solder mask layers (.GTS, .GBS)
- Silkscreen layers (.GTO, .GBO)
- Board outline (.GKO)
- NC drill file (.DRL)
- Solder paste layers if required (.GTP, .GBP) Always verify manufacturer-specific requirements as they may vary.
Q2: How do I verify my Gerber files are correct?
A: Follow these verification steps:
- Use Altium’s Built-in Gerber viewer
- Check all layers are present
- Verify drill file alignment
- Confirm board dimensions
- Review layer polarity
- Check component clearances Consider using third-party Gerber viewers for additional verification.
Q3: What are common Gerber generation mistakes to avoid?
A: Common mistakes include:
- Wrong unit selection (mil vs. mm)
- Incorrect layer assignment
- Missing drill files
- Improper board outline definition
- Wrong polarity on negative layers
- Forgetting to include all required layers Regular verification prevents most common errors.
Q4: How should I organize Gerber files for manufacturers?
A: Organize files as follows:
- Use clear, consistent naming conventions
- Group files by type in separate folders
- Include a README file with special instructions
- Compress all files into a single ZIP
- Maintain proper file hierarchy
- Include all necessary documentation Good organization reduces manufacturing delays.
Q5: What Gerber format should I use in Altium Designer?
A: Use these recommended settings:
- Format: RS-274X (Extended Gerber)
- Units: Millimeters
- Resolution: 4:4
- Zero Suppression: Leading
- Coordinate Format: Absolute These settings ensure maximum compatibility with manufacturers.
Conclusion
Generating Gerber files from Altium Designer requires attention to detail and a systematic approach. Success depends on proper setup, careful verification, and following industry standards. By following the guidelines in this document and maintaining good documentation practices, you can ensure your Gerber files are accurate and ready for manufacturing.