Converting .brd files to Gerber files is a critical step in the PCB manufacturing process that every electronics engineer and PCB designer must master. This comprehensive guide will walk you through everything you need to know about converting board files to industry-standard Gerber format, ensuring your designs are ready for professional fabrication.
Understanding .brd Files and Gerber Files
What is a .brd File?
A .brd file is a board layout file format primarily used by Autodesk Eagle PCB design software. These files contain complete information about your printed circuit board design, including component placement, routing, layers, drill holes, and design rules. The .brd format stores all design data in a proprietary binary format that includes:
- Component footprints and placement information
- Copper trace routing on all layers
- Via definitions and drill hole specifications
- Silkscreen graphics and text
- Solder mask and paste mask definitions
- Board outline and mechanical dimensions
- Design rule constraints and electrical connectivity
What are Gerber Files?
Gerber files represent the industry standard for PCB manufacturing data exchange. Named after the Gerber Scientific Instrument Company, these files use the RS-274X extended Gerber format to describe individual PCB layers in a vector-based format. Each layer of your PCB design is exported as a separate Gerber file, creating a complete manufacturing dataset.
The Gerber format uses ASCII text commands to define geometric shapes, apertures, and drawing operations. Modern Gerber files (RS-274X) are self-contained and include all necessary aperture definitions within the file itself, eliminating the need for separate aperture files.
Why Convert .brd Files to Gerber Format?
Manufacturing Compatibility
The primary reason for converting .brd files to Gerber format is manufacturing compatibility. While .brd files are specific to Eagle software, Gerber files are universally accepted by PCB manufacturers worldwide. This standardization ensures that your design can be fabricated by any professional PCB manufacturer regardless of their internal CAD systems.
Design Protection
Gerber files provide an additional layer of intellectual property protection. Unlike .brd files that contain complete design information including component values and connectivity, Gerber files only contain the physical manufacturing data. This allows you to share manufacturing files with fabricators without exposing sensitive design information.
Quality Control
Converting to Gerber format enables comprehensive design verification through specialized Gerber viewing software. These tools allow you to inspect individual layers, measure features, and verify design integrity before committing to manufacturing.
Essential Tools for .brd to Gerber Conversion
Autodesk Eagle PCB Design Software
Eagle remains the primary tool for working with .brd files and generating Gerber outputs. The software includes built-in CAM (Computer-Aided Manufacturing) processors specifically designed for Gerber file generation. Eagle's CAM processor supports various output formats and provides extensive customization options for different manufacturer requirements.
Alternative CAD Software Options
Several other PCB design software packages can import .brd files and generate Gerber outputs:
| Software | .brd Import Support | Gerber Export Quality | Cost | Best For |
|---|---|---|---|---|
| KiCad | Limited (via conversion) | Excellent | Free | Open-source projects |
| Altium Designer | Via import filters | Excellent | High | Professional design |
| DipTrace | Direct import | Good | Moderate | Small to medium designs |
| EasyEDA | Web-based import | Good | Free/Low | Hobbyist projects |
| DesignSpark PCB | Limited import | Good | Free | Educational use |
Gerber Viewing and Verification Tools
After generating Gerber files, specialized viewing software helps verify output quality:
- GerbView (KiCad): Free, comprehensive Gerber viewer with measurement tools
- ViewMate: Professional Gerber viewer with advanced analysis features
- CAM350: Industrial-grade PCB verification and analysis platform
- Gerbv: Open-source Gerber viewer for Linux and Windows systems
Step-by-Step Conversion Process in Eagle
Preparing Your .brd File
Before beginning the conversion process, ensure your .brd file is properly prepared:
- Design Rule Check (DRC): Run a complete DRC to identify and resolve any design violations
- Electrical Rule Check (ERC): Verify all electrical connections are properly defined
- Layer Stack-up Verification: Confirm all required layers are properly defined and assigned
- Component Placement Review: Ensure all components are properly placed and oriented
- Routing Completion: Verify all nets are fully routed with no airwires remaining
Accessing the CAM Processor
In Eagle, access the CAM processor through the File menu:
- Open your .brd file in Eagle's Board Editor
- Navigate to File → CAM Processor
- The CAM Processor dialog will open, displaying available job configurations
- Load an appropriate CAM job file or create a custom configuration
Configuring Layer Outputs
The CAM processor requires specific configuration for each layer output:
Copper Layers Configuration
For copper layers, configure the following settings:
- Device: Set to "GERBER_RS274X" for modern Gerber format
- File Extension: Use standard extensions (.gtl for top, .gbl for bottom)
- Layers: Select appropriate copper layers (Top, Bottom, Inner1, Inner2, etc.)
- Mirror: Enable for bottom layers only
- Drills: Exclude drill information from copper layers
- Rotate: Typically set to 0 degrees unless specific rotation required
Solder Mask Configuration
Solder mask layers require specific settings:
- Device: GERBER_RS274X format
- File Extension: .gts (top solder mask), .gbs (bottom solder mask)
- Layers: tStop for top mask, bStop for bottom mask
- Polarity: Typically positive (clear areas represent exposed copper)
- Mirror: Enable for bottom mask layer
Silkscreen Layer Setup
Silkscreen configuration includes:
- Device: GERBER_RS274X format
- File Extension: .gto (top silkscreen), .gbo (bottom silkscreen)
- Layers: tPlace, tNames, tValues for top; bPlace, bNames, bValues for bottom
- Text Handling: Ensure vector text mode for compatibility
- Line Width: Set minimum line width per manufacturer specifications
Standard Gerber File Naming Conventions
Consistent file naming is crucial for manufacturing success:
| Layer Type | Standard Extension | Alternative Extensions | Description |
|---|---|---|---|
| Top Copper | .gtl | .cmp, .top | Top layer copper traces |
| Bottom Copper | .gbl | .sol, .bot | Bottom layer copper traces |
| Inner Layer 1 | .g2l | .ly2, .in1 | First inner copper layer |
| Inner Layer 2 | .g3l | .ly3, .in2 | Second inner copper layer |
| Top Solder Mask | .gts | .stc, .tsm | Top solder mask openings |
| Bottom Solder Mask | .gbs | .sts, .bsm | Bottom solder mask openings |
| Top Silkscreen | .gto | .plc, .tsk | Top component markings |
| Bottom Silkscreen | .gbo | .pls, .bsk | Bottom component markings |
| Top Paste Mask | .gtp | .crc, .tsp | Top solder paste stencil |
| Bottom Paste Mask | .gbp | .crs, .bsp | Bottom solder paste stencil |
Generating Drill Files
Drill file generation requires separate configuration:
- Create a new CAM job section for drill data
- Set device to "EXCELLON" format
- Configure drill file parameters:
- Units: Match PCB design units (inches or millimeters)
- Format: Set coordinate format (typically 2:4 for inch, 3:3 for metric)
- Zero Suppression: Configure leading or trailing zero handling
- Tool List: Include tool list for manufacturer reference
Advanced CAM Job Configuration
Professional PCB designs often require advanced CAM job configurations:
Multi-layer Board Considerations
For complex multi-layer boards, consider these factors:
- Layer Registration: Ensure proper layer alignment through registration marks
- Via Types: Configure different via types (through-hole, blind, buried) appropriately
- Controlled Impedance: Include impedance control layers if required
- HDI Features: Handle high-density interconnect features like microvias
Panelization Support
When panelizing designs, configure:
- Panel Outline: Define panel boundaries and separation methods
- Fiducial Markers: Add panel-level fiducial marks for assembly
- Tooling Holes: Include manufacturing tooling hole definitions
- V-Score Lines: Define V-groove separation if required
Drill File Generation and Configuration
Understanding Drill File Formats
Drill files use the Excellon format to define hole locations and sizes. This format includes:
- Header Information: Tool definitions and format specifications
- Tool Changes: Commands to select appropriate drill tools
- Coordinate Data: X/Y coordinates for each hole location
- Programming Commands: Drilling operation instructions
Drill File Best Practices
Optimize drill file generation with these practices:
- Tool Optimization: Minimize the number of different drill sizes
- Hole Tolerances: Specify appropriate hole tolerances for your design
- Plating Requirements: Clearly indicate plated vs. non-plated holes
- Slot Definition: Properly define routed slots and complex hole shapes
Creating Comprehensive Drill Reports
Generate detailed drill reports including:
- Tool List: Complete list of all drill tools required
- Hole Count: Total number of holes for each tool size
- Plating Status: Indication of plated vs. non-plated holes
- Hole Types: Classification of holes by function (via, component, mounting)
Quality Control and Verification
Visual Inspection Techniques
After generating Gerber files, perform thorough visual inspection:
- Layer Alignment: Verify proper layer registration and alignment
- Aperture Integrity: Check that all apertures are properly defined
- Text Readability: Ensure all text elements are clearly readable
- Minimum Feature Compliance: Verify compliance with manufacturer minimums
Automated Verification Tools
Utilize automated tools for comprehensive verification:
Design Rule Verification
Automated DRC tools can verify:
- Minimum Trace Width: Compliance with manufacturing capabilities
- Minimum Spacing: Adequate spacing between conductors
- Via Specifications: Proper via sizes and drill-to-copper ratios
- Annular Ring: Adequate annular rings on all drilled features
Electrical Connectivity Verification
Verify electrical integrity through:
- Net List Comparison: Compare Gerber connectivity to original design
- Short Circuit Detection: Identify potential short circuits
- Open Circuit Detection: Find incomplete connections
- Layer Stack-up Verification: Confirm proper layer assignments
Common Conversion Issues and Solutions
| Issue | Symptom | Solution |
|---|---|---|
| Missing Apertures | Circular or rectangular features appear as outlines only | Regenerate with proper aperture definitions |
| Incorrect Mirroring | Bottom layer components appear mirrored incorrectly | Adjust mirror settings in CAM processor |
| Text Problems | Text appears as outlines or is unreadable | Switch to vector text mode |
| Drill Registration | Drill holes don't align with pads | Verify coordinate system consistency |
| Layer Misalignment | Layers don't properly align when overlaid | Check origin settings and coordinate systems |
Manufacturer-Specific Requirements
Understanding Fabricator Capabilities
Different manufacturers have varying capabilities and requirements:
Standard PCB Manufacturers
Typical specifications for standard PCB fabrication:
- Minimum Trace Width: 0.1mm (4 mils) to 0.15mm (6 mils)
- Minimum Spacing: 0.1mm (4 mils) to 0.15mm (6 mils)
- Minimum Via Size: 0.2mm (8 mils) finished hole
- Layer Count: Up to 16-20 layers standard
- Board Thickness: 0.4mm to 6.4mm typical range
High-End/HDI Manufacturers
Advanced manufacturers offer enhanced capabilities:
- Minimum Trace Width: Down to 0.05mm (2 mils)
- Minimum Spacing: Down to 0.05mm (2 mils)
- Microvias: 0.1mm (4 mils) laser-drilled vias
- Layer Count: 30+ layers possible
- Embedded Components: Component embedding capabilities
Customizing CAM Jobs for Specific Manufacturers
Many manufacturers provide specific CAM job files optimized for their processes:
- Download Manufacturer CAM Jobs: Obtain pre-configured CAM files
- Customize for Your Design: Modify job files to match your layer stack
- Validate Output: Verify generated files meet manufacturer requirements
- Submit for Review: Send files for manufacturer design review before production
Advanced Gerber Features and Applications
Embedded Gerber Attributes
Modern Gerber files support embedded attributes for enhanced manufacturing information:
Net Attributes
Include electrical net information directly in Gerber files:
- Net Names: Embed net names for traceability
- Electrical Properties: Include impedance and timing requirements
- Test Point Information: Identify test points and probe locations
Component Attributes
Embed component information for assembly:
- Component References: Link pads to component designators
- Component Values: Include component values and part numbers
- Assembly Information: Provide pick-and-place data
Gerber X2 Format Advantages
The enhanced Gerber X2 format provides additional benefits:
- Self-Documenting Files: Embedded metadata reduces confusion
- Automated Processing: Enables automated CAM processing
- Error Reduction: Reduces manual interpretation errors
- Future Compatibility: Supports evolving manufacturing technologies
Industry Standards and Compliance
IPC Standards Compliance
Ensure your Gerber files comply with relevant IPC standards:
IPC-2581 (Generic Requirements for Printed Board Assembly Products Manufacturing Description Data and Transfer Methodology)
This standard defines requirements for manufacturing data transfer:
- Data Completeness: Ensure all required manufacturing data is included
- Format Standardization: Use standardized data formats and structures
- Traceability: Maintain design-to-manufacturing data traceability
IPC-D-356 (Generic Requirements for Bare Board Electrical Test Data)
For electrical test data requirements:
- Test Point Definition: Clearly define electrical test access points
- Net List Accuracy: Ensure net list matches physical implementation
- Test Coverage: Provide adequate test coverage for quality assurance
Quality Management Integration
Integrate Gerber generation into your quality management system:
- Version Control: Implement proper version control for Gerber files
- Change Management: Track changes between design revisions
- Documentation: Maintain comprehensive documentation packages
- Approval Processes: Establish approval workflows for manufacturing releases
Troubleshooting Common Conversion Problems
File Format Issues
Address common file format problems:
Character Encoding Problems
Resolve character encoding issues:
- ASCII Compliance: Ensure all text uses ASCII-compatible characters
- Special Characters: Remove or replace special characters that may cause issues
- File Headers: Verify proper file header formatting
Coordinate System Mismatches
Fix coordinate system problems:
- Units Consistency: Ensure consistent units throughout all files
- Origin Definition: Verify proper origin point definition
- Scaling Issues: Check for inadvertent scaling during conversion
Layer Definition Problems
Resolve layer-related issues:
Missing Layer Information
Address incomplete layer definitions:
- Layer Names: Use consistent, meaningful layer names
- Layer Functions: Clearly define the function of each layer
- Stack-up Documentation: Provide complete layer stack-up information
Incorrect Layer Assignments
Fix layer assignment errors:
- Review Layer Mapping: Verify proper mapping of design layers to Gerber files
- Check Mirror Settings: Ensure appropriate mirroring for bottom layers
- Validate Drill Layers: Confirm drill data matches copper layer requirements
Best Practices for Professional PCB Manufacturing
Design for Manufacturability (DFM)
Optimize your designs for reliable manufacturing:
Copper Pour Considerations
Implement effective copper pour strategies:
- Thermal Relief: Use thermal reliefs for ground connections to large pours
- Minimum Copper: Maintain minimum copper features for etching reliability
- Copper Balance: Balance copper distribution across layers for warpage control
Via Design Optimization
Optimize via designs for manufacturing:
- Aspect Ratios: Maintain appropriate drill-to-thickness aspect ratios
- Via-in-Pad: Consider manufacturing implications of via-in-pad designs
- Tenting Options: Specify via tenting requirements clearly
Documentation Package Assembly
Create comprehensive manufacturing documentation packages:
Essential Documentation Components
Include these critical documents:
| Document Type | Content | Purpose |
|---|---|---|
| Gerber Files | All manufacturing layers | Physical layer definitions |
| Drill Files | Hole locations and sizes | Drilling instructions |
| Pick and Place | Component placement data | Assembly automation |
| Bill of Materials | Component specifications | Procurement and assembly |
| Assembly Drawings | Visual assembly guide | Manual assembly reference |
| Fabrication Notes | Special requirements | Manufacturing instructions |
Manufacturing Notes Template
Develop standardized manufacturing notes covering:
- Board Specifications: Thickness, material, and finish requirements
- Special Processes: Any non-standard manufacturing processes required
- Quality Requirements: Specific quality standards and testing requirements
- Delivery Instructions: Packaging and shipping requirements
Future Trends in PCB Data Exchange
Emerging Standards and Technologies
Stay current with evolving industry standards:
ODB++ Format Evolution
The ODB++ format continues to evolve with enhanced capabilities:
- Integrated Design Data: Single file containing all design information
- Advanced Verification: Built-in design rule checking capabilities
- Industry Adoption: Increasing adoption by major manufacturers
IPC-2581 Advancement
The IPC-2581 standard continues to develop:
- XML-Based Structure: Modern XML-based data structure
- Comprehensive Data Model: Complete product manufacturing description
- Tool Support: Growing CAD tool and manufacturer support
Automation and AI Integration
Future developments in automated PCB manufacturing:
Intelligent Design Analysis
AI-powered tools for design optimization:
- Automated DFM Analysis: AI-driven design for manufacturability checking
- Predictive Quality: Machine learning for quality prediction
- Process Optimization: Automated manufacturing process optimization
Frequently Asked Questions (FAQ)
What is the difference between .brd files and Gerber files?
.brd files are proprietary board layout files specific to Autodesk Eagle that contain complete design information including components, connectivity, and design rules. Gerber files are industry-standard manufacturing files that describe individual PCB layers in a vector format accepted by all PCB manufacturers. While .brd files contain the complete design context, Gerber files focus specifically on the physical manufacturing requirements for each layer.
Can I convert .brd files to Gerber format without Eagle software?
While Eagle is the most straightforward tool for converting .brd files since it's the native format, some alternative approaches exist. KiCad can import .brd files with varying degrees of success, though complex designs may require manual correction. Some online conversion services also exist, but these may not preserve all design details accurately. For professional results, using Eagle or a high-end CAD package with proper .brd import filters is recommended.
How many Gerber files do I need for a typical PCB design?
A typical 2-layer PCB requires approximately 8-10 Gerber files: top copper, bottom copper, top solder mask, bottom solder mask, top silkscreen, bottom silkscreen, and potentially top/bottom paste masks if SMD components are used. Additionally, you'll need an Excellon drill file and potentially a board outline file. Multi-layer designs require additional files for each inner layer. The exact number depends on your design complexity and manufacturing requirements.
What should I do if my manufacturer rejects my Gerber files?
If your Gerber files are rejected, first request specific feedback about the issues identified. Common problems include missing aperture definitions, incorrect file formats, layer misalignment, or non-compliance with the manufacturer's design rules. Review your CAM job configuration, regenerate the files addressing the identified issues, and use Gerber viewing software to verify the corrections. Many manufacturers offer design rule check services that can identify potential issues before production.
Are there any free tools for viewing and verifying Gerber files?
Yes, several excellent free tools are available for Gerber file viewing and verification. GerbView (part of KiCad suite) provides comprehensive viewing with measurement tools and layer management. Gerbv is an open-source viewer that works on multiple platforms. Online viewers like EasyEDA's Gerber viewer allow quick file inspection without software installation. While these free tools are excellent for basic verification, professional applications may benefit from commercial tools with advanced analysis features.
Conclusion
Converting .brd files to Gerber format is a fundamental skill for PCB designers and engineers working in the electronics industry. This process bridges the gap between design and manufacturing, ensuring your carefully crafted circuits can be reliably fabricated by professional PCB manufacturers worldwide.
The conversion process requires attention to detail, understanding of manufacturing requirements, and proper tool configuration. By following the comprehensive guidelines outlined in this article, you can ensure your Gerber files meet industry standards and manufacturer requirements, leading to successful PCB fabrication with minimal revisions.
Remember that Gerber file generation is not just a technical process but a critical quality control step. Take time to verify your outputs, understand your manufacturer's requirements, and maintain comprehensive documentation. As PCB technology continues to evolve toward higher density and more complex designs, mastering these fundamental skills becomes even more valuable.
Whether you're a hobbyist working on your first PCB design or a professional engineer managing complex multi-layer boards, the principles and practices outlined in this guide will serve you well throughout your PCB design career. The investment in understanding proper Gerber file generation pays dividends in reduced manufacturing iterations, improved product quality, and stronger relationships with your PCB fabrication partners.
