What File Type is Used for PCB: A Comprehensive Guide

Introduction to PCB File Formats

Printed Circuit Board (PCB) design and manufacturing involve a complex workflow that requires various file formats at different stages of the process. These file formats serve as the digital blueprints that communicate design intent between engineers, designers, and manufacturers. Understanding PCB file types is essential for anyone involved in electronics design, from hobbyists to professional engineers.

PCB file formats can be broadly categorized into:

• Design files (native CAD formats)
• Intermediate exchange formats
• Manufacturing output files
• Documentation files

Each file type serves a specific purpose in the PCB development lifecycle, ensuring accurate translation of electronic designs into physical circuit boards.

Native PCB Design File Formats

CAD-Specific Design Files

Every PCB design software uses its own proprietary file format to store complete design information:

1. Altium Designer (.PcbDoc, .SchDoc)

• The industry-standard Altium Designer uses .PcbDoc for board layouts and .SchDoc for schematic files
• Contains complete design information including components, traces, layers, and design rules
• Supports version control integration

1. Cadence Allegro (.brd)

• Allegro’s .brd files store complex PCB layouts
• Used extensively in high-speed and high-density designs
• Includes constraint management data

1. Mentor Graphics Xpedition (.pcb)

• Used in enterprise-level PCB design
• Supports advanced features like concurrent team design

1. KiCad (.kicad_pcb, .sch)

• Open-source alternative with growing popularity
• .kicad_pcb for board files, .sch for schematics
• Uses human-readable file format

1. Eagle (.brd, .sch)

• Popular among hobbyists and small businesses
• Now owned by Autodesk
• Uses XML-based file structure

These native formats contain the complete design database including schematic connections, component placements, routing information, layer stackup, and design rules. They are typically only readable by the originating software or compatible versions.

Intermediate Exchange Formats

To enable collaboration between different design tools and teams using various software, several industry-standard intermediate formats have been developed:

Gerber Files (RS-274X)

The most widely used format for PCB manufacturing:

• File extension: Typically .gbr or .ger
• Standard: RS-274X (extended Gerber)
• Purpose: Represents each PCB layer as a 2D vector image
• Characteristics:
• Each layer (copper, solder mask, silkscreen, etc.) gets separate files
• Contains aperture definitions and draw/flash commands
• Human-readable ASCII format
• Supported by all PCB manufacturers

ODB++

A more modern alternative to Gerber:

• Developed by: Valor (now part of Siemens)
• Structure: Directory containing multiple files in a standardized hierarchy
• Advantages:
• Single package contains all manufacturing data
• Includes layer stackup, materials, and netlist information
• Reduces interpretation errors
• Supports intelligent data exchange

IPC-2581

An emerging open standard:

• Developed by: IPC
• Features:
• XML-based format
• Contains complete product manufacturing information
• Supports bidirectional data flow
• Gaining industry adoption

DXF (Drawing Exchange Format)

• Used for: Mechanical outline and layer exchange
• Application:
• Transferring board outlines to mechanical CAD
• Importing/exporting simple layer information
• Not suitable for complete PCB data transfer

Netlist Formats

Critical for design verification:

1. IPC-D-356

• Standard netlist format for bare board testing
• Contains node lists with reference designators and pin numbers

1. SPICE Netlists

• Used for circuit simulation
• Text-based representation of components and connections

Manufacturing Output Files

Drill Files

Essential for PCB fabrication:

• Excellon Format (.drl, .txt)
• Standard for NC drill data
• Contains tool sizes and drill coordinates
• May include routing information
• Gerber X2 Drill Files
• Newer format combining drill data with layer information

Pick and Place Files

For assembly process:

• CSV or Text Formats
• Contains component reference designators, coordinates, and rotations
• Used by automated assembly machines
• Often includes package types for verification

Bill of Materials (BOM)

Critical for procurement and assembly:

• Formats: CSV, Excel (.xlsx), XML
• Contents:
• Component reference designators
• Manufacturer part numbers
• Quantities
• Descriptions
• Footprint information

Assembly Drawings

• PDF: Most common for documentation
• DWG/DXF: For mechanical integration
• STEP Files: 3D models for enclosure design

Specialized PCB File Formats

3D Model Files

For mechanical integration and visualization:

• STEP (.stp)
• Standard for 3D PCB representation
• Used in mechanical CAD software
• Contains accurate component heights and board outline
• VRML (.wrl)
• Alternative 3D format
• Lighter weight than STEP files

Simulation Files

For signal and power integrity analysis:

• IBIS Models
• I/O Buffer Information Specification
• Used for signal integrity simulation
• S-Parameter Files
• For high-frequency analysis
• Typically in Touchstone format (.sNp)

Library Files

Component management:

• Schematic Symbols
• Footprint Libraries
• 3D Model Libraries
• Part Data Files

Choosing the Right File Format

The appropriate file format depends on the specific stage of the PCB development process:

1. Design Phase

• Use native CAD formats for active design work
• Maintain version control of these files

1. Design Review

• Export to PDF for documentation
• Generate 3D STEP files for mechanical review

1. Manufacturing Preparation

• Gerber RS-274X for fabrication
• Excellon for drill files
• ODB++ as alternative to Gerber

1. Assembly

• Pick and place files in CSV format
• Comprehensive BOM with sourcing information

1. Testing

• IPC-D-356 netlist for bare board testing
• Test point reports

Best Practices for PCB File Management

1. File Naming Conventions

• Use clear, consistent naming (e.g., “TopLayer.gbr”)
• Include revision information
• Follow manufacturer recommendations

1. File Packages

• Always provide complete sets of files
• Include readme files with explanations
• Use ZIP compression for transfer

1. Version Control

• Maintain history of design changes
• Use descriptive commit messages
• Archive major revisions

1. Verification

• Use Gerber viewers before submission
• Check for layer alignment
• Verify drill files match design

Common Issues with PCB Files

1. Format Compatibility

• Problems opening files in different software versions
• Solution: Use intermediate formats or request specific versions

1. Missing Files

• Incomplete Gerber sets causing manufacturing delays
• Solution: Create checklists and verify before submission

1. Outdated Revisions

• Manufacturing wrong versions of designs
• Solution: Clear revision tracking and file naming

1. Interpretation Errors

• Different understanding of file contents
• Solution: Include detailed documentation and layer maps

Future Trends in PCB File Formats

1. Increased Use of ODB++

• More comprehensive than Gerber
• Reduced interpretation errors
• Growing industry adoption

1. IPC-2581 Adoption

• Open standard gaining traction
• Complete product definition in single file
• Potential replacement for Gerber long-term

1. Cloud-Based Collaboration

• Direct design sharing without file exchange
• Real-time collaboration features
• Version management in the cloud

1. AI-Assisted Design

• Intelligent file interpretation
• Automated error detection
• Design optimization suggestions

Conclusion

Understanding PCB file formats is crucial for successful design, manufacturing, and collaboration in electronics development. From native CAD formats that capture the complete design intent to manufacturing standards like Gerber and ODB++ that translate designs into physical boards, each file type serves a specific purpose in the PCB ecosystem.

As the industry evolves, we’re seeing a shift from traditional Gerber files toward more intelligent formats like ODB++ and IPC-2581 that reduce interpretation errors and improve efficiency. Regardless of the specific formats used, following best practices in file management, verification, and communication with manufacturers remains essential for producing high-quality printed circuit boards.

By mastering PCB file formats and their proper use, engineers and designers can ensure smooth transitions between design stages, minimize manufacturing errors, and ultimately bring their electronic products to market more efficiently. The careful selection and handling of these digital blueprints form the foundation of successful PCB development in today’s interconnected electronics industry.