PCB File Formats Explained: 30+ Formats Every Engineer Should Know

If you’ve ever sent a design package to a PCB manufacturer and waited nervously for that “files received” confirmation, you know the feeling. Missing drill files, wrong Gerber version, incompatible native formats—these small oversights can cost days of back-and-forth communication and delay your project timeline significantly.

After years of working with various EDA tools and fabrication houses, I’ve learned that understanding PCB file formats isn’t just about technical compliance—it’s about smooth communication between your design intent and the manufacturing floor. Whether you’re a seasoned hardware engineer or just getting started with your first board, knowing which file does what will save you countless headaches.

This guide covers over 30 PCB file formats you’ll encounter throughout the design, fabrication, and assembly process. I’ve organized them by their primary purpose, so you can quickly find what you need when preparing your next design package.

Whether you’re designing consumer electronics, industrial controls, medical devices, or aerospace systems, these formats form the common language between your design workstation and the factory floor. Let’s break down each category and understand when and why you’d use specific file types.

Why PCB File Formats Matter

Before diving into specific formats, let’s address the elephant in the room: why are there so many different file types in PCB design?

The answer lies in the complexity of modern electronics manufacturing. A single PCB project involves multiple stakeholders—schematic designers, layout engineers, mechanical teams, procurement specialists, and manufacturing technicians. Each group needs specific information presented in formats their tools can understand.

Your design software speaks one language. The photoplotter at the fab house speaks another. The pick-and-place machine on the assembly line has its own requirements. PCB file formats act as translators between these different worlds.

Getting your file formats right means:

• Faster turnaround times from your manufacturer
• Fewer misinterpretations of your design intent
• Reduced risk of costly board respins
• Smoother collaboration with mechanical engineering teams
• Better documentation for future revisions

Manufacturing Output Formats

These are the formats your fabrication house needs to actually build your board. Think of them as the “final deliverables” of your PCB design process.

Gerber Formats

Gerber files remain the backbone of PCB manufacturing communication. Named after the Gerber Scientific Instrument Company (now Ucamco), these files have been the industry standard since the 1980s.

Gerber RS-274X is the extended Gerber format that most engineers work with today. Unlike the older RS-274D format, it embeds aperture definitions directly within the file. This means you don’t need to send a separate aperture list—reducing the chance of mismatched configurations. When someone asks for “Gerber files,” they typically mean this format.

Gerber X2 adds metadata capabilities to the RS-274X foundation. The X2 format includes file attributes that help CAM software automatically identify layer types, copper weights, and other manufacturing parameters. If your manufacturer supports X2, I recommend using it—the automatic layer identification alone is worth the upgrade.

Gerber X3 takes things further by incorporating component information, net data, and full assembly details. It’s essentially trying to be a complete manufacturing package in one format family. Adoption is still growing, but forward-thinking manufacturers are starting to support it.

.gbr / .pho Files are the actual file extensions you’ll see when exporting Gerbers. Different EDA tools use different naming conventions (.GTL, .GBL, .GTS, .GBS, etc.), but they’re all variations of the same underlying format. The .pho extension comes from “photo plot”—a reference to how these files drive photoplotters in manufacturing.

Gerber Job File (.gbrjob) is a JSON-based companion file that describes your complete Gerber package. It lists all included files, defines the layer stackup, and provides manufacturing specifications. Think of it as a “readme” file that helps the manufacturer understand your complete design package.

Gerber Format	Key Feature	Best Use Case
RS-274X	Embedded apertures	Standard fabrication (most common)
Gerber X2	Layer metadata	Automated CAM processing
Gerber X3	Full component data	Complete manufacturing packages

Unified Data Formats

Modern electronics manufacturing increasingly favors unified formats that package all necessary data into a single, comprehensive file structure.

ODB++ was developed by Valor (now part of Siemens) to address the limitations of Gerber files. Instead of separate files for each layer, ODB++ creates a hierarchical database structure containing everything: copper layers, drill data, component placement, netlist information, and fabrication specifications. Many advanced manufacturers prefer ODB++ because it eliminates the “which file goes with which layer” guesswork.

The format stores data in multiple files organized into folders, but you’ll typically compress everything into a single archive for submission. Major EDA tools including Altium Designer, Cadence Allegro, and Mentor PADS can export ODB++ directly.

One significant advantage of ODB++ is its inclusion of intelligent data—netlist connectivity, component information, and design intent that Gerber files simply cannot convey. This allows manufacturers to perform more sophisticated Design for Manufacturing (DFM) analysis before production begins. When a manufacturer can trace connections and understand component relationships, they can catch potential issues that might slip through with layer-by-layer Gerber review.

The downside? Not every manufacturer supports ODB++ equally well. Smaller fab houses may have limited ODB++ capabilities or prefer the familiar Gerber workflow. Always verify your manufacturer’s ODB++ support before committing to this format exclusively.

Drill and Aperture Files

Your fabrication package isn’t complete without proper drill data. Missing or incorrect drill files is one of the most common submission errors I see.

Excellon / NC Drill files tell the CNC drilling machines exactly where to make holes and what size bits to use. The format is named after Excellon Automation Company, a major manufacturer of PCB drilling equipment. These files contain coordinates for every hole location, plus tool definitions specifying drill diameters.

A typical Excellon file has three sections: a header with unit and format settings, tool definitions listing available drill sizes, and coordinate data specifying each hole position. Always verify your drill file export settings—units (inches vs. millimeters), coordinate format (2:4 vs. 2:5), and zero suppression can all cause problems if misconfigured.

Aperture File (.apt) defines the shapes and sizes used in older RS-274D Gerber files. While RS-274X made separate aperture files largely obsolete by embedding definitions, some legacy workflows still require them. If your manufacturer specifically requests an aperture file, they’re likely using older CAM equipment.

Specialty Manufacturing Files

Beyond the core fabrication data, several file types address specific manufacturing needs.

Stencil Gerber files define the openings in solder paste stencils used during SMT assembly. These are typically derived from your paste layer Gerbers but may require modifications—adjusted aperture sizes for fine-pitch components, home plate shapes for thermal pads, or removed openings for components you’ll hand solder.

Panelization Files describe how multiple PCB copies should be arranged on a manufacturing panel. While many fab houses handle panelization themselves, providing your own panel design gives you control over board orientation, spacing, fiducials, and breakaway tab placement.

File Type	Purpose	When You Need It
Excellon/NC Drill	Hole locations and sizes	Every fabrication order
Aperture (.apt)	Shape definitions for RS-274D	Legacy workflows only
Stencil Gerber	Paste stencil openings	SMT assembly orders
Panelization	Multi-board panel layout	High-volume production

Design Software Native Formats

These proprietary formats store your actual design data within specific EDA tools. Understanding them matters when collaborating with other engineers or transitioning between software platforms.

Altium Designer Formats

Altium Designer has become one of the most popular professional PCB design tools, and its file formats reflect the software’s comprehensive feature set.

.PcbDoc files contain your PCB layout—copper routing, component placement, board outline, and all physical layer data. This is Altium’s native board file format. When you open a PCB in Altium Designer, you’re working with a .PcbDoc file.

.SchDoc files store schematic sheets. Unlike some tools that use a single file for the entire schematic, Altium creates separate .SchDoc files for each sheet in hierarchical designs. This approach works well for team collaboration but requires careful project organization.

.PrjPcb is the project file that ties everything together. It references your schematics, PCB layouts, and library files, maintaining the relationships between design documents. Always include the .PrjPcb file when sharing Altium projects—without it, recipients won’t have the full project context.

Eagle and Autodesk Formats

Eagle has long been a favorite among hobbyists and startups due to its accessible pricing and active community. Autodesk acquired Eagle in 2016 and has since integrated it with Fusion 360.

.BRD files are Eagle’s board layout format. The .brd extension is also used by Cadence Allegro, so context matters when you encounter this file type. Eagle .brd files are XML-based, making them relatively human-readable if you ever need to inspect them manually.

.sch is Eagle’s schematic format. Like the board files, Eagle schematics are stored as XML. This openness has enabled a robust ecosystem of third-party tools and scripts that can parse and modify Eagle designs.

KiCad Formats

KiCad has matured significantly in recent years, earning adoption by professional teams including those at CERN. As open-source software, KiCad’s file formats are well-documented and accessible.

.kicad_pcb files contain KiCad board layouts. The format uses S-expression syntax (similar to LISP), which is both human-readable and easy to parse programmatically. This transparency has enabled impressive community tools like the Interactive HTML BOM generator.

KiCad’s approach to file formats reflects the open-source philosophy—everything is text-based and documented. This means you can script manipulations, build custom tools, and even track changes in version control systems like Git. Try doing that with binary proprietary formats!

The KiCad ecosystem also includes .kicad_sch for schematics and .kicad_pro for project files. Recent versions have shifted from the older .sch format to the new S-expression based schematic files, offering better structure and forward compatibility.

For engineers transitioning from commercial tools, KiCad includes importers for Eagle and Altium projects. The conversion isn’t always perfect—complex designs may need manual cleanup—but it provides a reasonable starting point for migrating existing work.

Legacy and Specialized Formats

Several other native formats remain relevant in specific contexts.

.PCB files are associated with older Protel software (Altium’s predecessor) and are still encountered when working with legacy designs. Some Asian manufacturers also accept .PCB files directly, converting them to manufacturing outputs themselves.

.DRC files contain Design Rule Check settings—the constraints that govern trace widths, clearances, and other manufacturing limits. Sharing DRC files ensures consistent rule enforcement across team members.

.asc is a text-based format used by LTspice for circuit simulation. While not strictly a PCB format, it’s relevant when your design workflow includes SPICE simulation before layout.

Software	PCB File	Schematic File	Project File
Altium Designer	.PcbDoc	.SchDoc	.PrjPcb
Eagle	.BRD	.sch	.sch (combined)
KiCad	.kicad_pcb	.kicad_sch	.kicad_pro
Protel (Legacy)	.PCB	.SchDoc	.PrjPcb

Assembly and Documentation Files

Getting your bare boards fabricated is only half the battle. Assembly requires its own set of documentation that tells the manufacturing line what components go where.

Component Placement Data

Pick and Place / Centroid files are essential for automated SMT assembly. These files list every component with its reference designator, X/Y coordinates, rotation angle, and board side (top or bottom). The pick-and-place machine reads this data to position components before reflow soldering.

Centroid files are typically CSV or Excel format with columns for designator, X position, Y position, rotation, and layer. Different assembly houses may require slightly different column formats, so always check their template requirements.

Getting the rotation values correct is critical—and surprisingly tricky. Different EDA tools define zero-degree rotation differently, and component libraries may not be consistent in their pin 1 orientation. I’ve seen boards assembled with all the ICs rotated 180 degrees because the centroid file used one convention while the manufacturer’s system expected another.

The solution is to carefully review your manufacturer’s rotation requirements and generate sample centroid files for verification before committing to full production. Most assembly houses will do a quick review if you’re uncertain.

CPL (Component Placement List) serves a similar purpose to centroid files but may include additional information like footprint names or part values. The distinction between CPL and centroid files is often manufacturer-specific. Some use the terms interchangeably, while others have specific format requirements for each.

Bill of Materials and Connectivity

BOM List files enumerate every component needed for assembly along with quantities, values, manufacturer part numbers, and supplier information. A well-structured BOM accelerates procurement and reduces substitution errors.

Your BOM should include reference designators, component values, footprint names, manufacturer part numbers, and optionally, approved alternates. Some assembly houses also want package descriptions and component heights for planning purposes.

Creating a good BOM is almost an art form. The key is providing enough detail to eliminate ambiguity while keeping the document manageable. For passive components like resistors and capacitors, specify tolerance, voltage rating, and package size—not just the value. For semiconductors, include the complete manufacturer part number with any suffix codes that indicate packaging or temperature range.

One common mistake I see is incomplete part numbers. “LM7805” might seem sufficient, but manufacturers produce dozens of variations with different packages, temperature ranges, and suffixes. “LM7805CT” specifies the TO-220 package variant you actually designed for. This level of detail prevents costly substitution errors during assembly.

Consider including secondary supplier options in your BOM, especially for components with long lead times or single-source availability. The recent supply chain disruptions have made alternate sourcing more important than ever.

Netlist files describe electrical connectivity—which pins connect to which nets. While primarily used during design (for transferring schematic connections to layout), netlists also support manufacturing test development and debugging.

Assembly Documentation

Assembly Drawing provides a visual reference showing component placement, polarity markings, and assembly notes. These drawings help technicians during manual operations and serve as reference documentation.

Fabrication Drawing communicates manufacturing specifications that don’t fit in Gerber files: board dimensions, layer stackup, material requirements, surface finish, impedance targets, and special instructions. Never assume your manufacturer will guess these details—document everything explicitly.

Assembly File	Primary Purpose	Format
Pick and Place / Centroid	Automated component placement	CSV, Excel
CPL	Component positions and details	CSV, Excel
BOM	Parts list for procurement	Excel, CSV
Netlist	Electrical connectivity data	Various
Assembly Drawing	Visual placement reference	PDF, Gerber
Fabrication Drawing	Manufacturing specifications	PDF

CAD Exchange and 3D Formats

Modern PCB design doesn’t exist in isolation. Your board must fit within enclosures, interface with mechanical components, and satisfy thermal requirements. These formats bridge the gap between electrical and mechanical design.

Mechanical CAD Formats

STEP / .stp has become the standard for exchanging 3D models between different CAD systems. STEP (Standard for the Exchange of Product Data) files preserve accurate geometry including curves and curved surfaces. When your mechanical engineer asks for a 3D model of your PCB, STEP is typically the preferred format.

Most professional PCB tools can export STEP files of the populated board, including component 3D models. The quality of your export depends heavily on having accurate 3D models assigned to your footprints.

STEP files enable crucial mechanical integration workflows. Your mechanical team can import the board model into SolidWorks, Fusion 360, or other MCAD tools to verify enclosure fit, check connector alignment, and analyze thermal considerations. This collaboration catches clearance issues before prototypes are built—potentially saving thousands of dollars in revision costs.

The STEP format comes in two main flavors: AP203 and AP214. AP214 is more comprehensive and includes color information, making it preferable for most PCB exports. Check your export settings to ensure you’re using AP214 when color-coded visualization matters.

One practical tip: always verify your STEP exports in a third-party viewer before sending them to mechanical teams. Occasionally, complex component models or unusual footprints can cause export issues that aren’t obvious in your EDA tool’s preview.

IGES / .igs is an older exchange format that predates STEP. While IGES handles curved surfaces well, it sometimes loses data during complex transfers. STEP is generally preferred for newer workflows, but IGES remains relevant when working with legacy mechanical systems.

VRML / .wrl files provide 3D visualization with color and texture information. VRML (Virtual Reality Modeling Language) is commonly used for preview renderings and visual presentations, but lacks the geometric precision needed for mechanical fit analysis.

2D Exchange Formats

.dxf (Drawing Exchange Format) transfers 2D geometry between applications. DXF files are commonly used for board outlines, mechanical keepouts, and panel designs. If your mechanical team provides enclosure cutouts or mounting hole locations, they’ll likely send a DXF file.

HPGL (Hewlett-Packard Graphics Language) is a plotter file format occasionally used for PCB documentation. While largely superseded by PDF for documentation, some legacy systems still generate HPGL output.

PDF/A is an archival PDF variant designed for long-term document preservation. For manufacturing documentation that must remain readable years later, PDF/A ensures consistent rendering regardless of viewer software.

Format	Type	Best For
STEP / .stp	3D solid	Mechanical integration, enclosure design
IGES / .igs	3D solid	Legacy mechanical CAD systems
VRML / .wrl	3D visual	Presentations, visual checks
.dxf	2D vector	Board outlines, mechanical interfaces
PDF/A	Document	Long-term documentation archival

Routing and Autorouter Formats

These specialized formats support automated routing tools and design optimization workflows.

.dsn (Specctra) is the input format for Specctra autorouters. The .dsn file contains board geometry, component placement, netlist data, and routing constraints. Even if you don’t use Specctra directly, some third-party autorouters accept this format.

.ses (Specctra Session) files contain autorouter output—the actual routing results. After the autorouter completes, you import the .ses file back into your layout tool to apply the generated traces.

GenCAD is an ASCII format developed for transferring CAD data to test equipment. GenCAD files support automated test development by providing complete board geometry and connectivity information.

Quick Reference: Files by Manufacturing Stage

Different manufacturing phases require different file packages. Here’s what you typically need for each stage:

PCB Fabrication Package

Your bare board manufacturer needs:

• Gerber files (RS-274X or X2) for all layers
• Excellon drill files for holes
• Fabrication drawing with specifications
• Optional: ODB++ as a unified alternative

PCB Assembly Package

For populated board assembly, add:

• Pick and place / centroid file
• Bill of materials with manufacturer part numbers
• Assembly drawing
• Stencil Gerbers (if ordering stencils)

Mechanical Collaboration

For enclosure and mechanical integration:

• STEP file of populated board
• DXF of board outline and mounting holes
• 3D component models as needed

Useful Resources and Tools

Having the right tools makes file management significantly easier. Here are some resources worth bookmarking:

Gerber Viewers let you verify your manufacturing outputs before submission. Free options include Gerbv (open source), KiCad’s built-in GerbView, and online viewers from various manufacturers. I recommend always checking your Gerbers in a third-party viewer—your EDA tool’s preview may differ from what the manufacturer sees.

Some popular Gerber viewer options worth trying:

• Gerbv – Open source, lightweight, runs on Windows, Mac, and Linux
• ViewMate by Pentalogix – Free viewer with good layer alignment tools
• HQDFM by NextPCB – Online viewer with DFM analysis capabilities
• Reference Gerber Viewer by Ucamco – Made by the Gerber format maintainers

File Conversion Tools help when you need to translate between formats. FreeCAD handles STEP/IGES/VRML conversions well. For Gerber manipulation, tools like CAM350 (commercial) or gerbmerge (open source) can merge, panelize, or modify files.

Component Libraries with 3D models save time during design. SnapEDA, Ultra Librarian, and manufacturer websites provide pre-built symbols, footprints, and 3D models that you can import into your EDA tool.

Format Specifications are available for most common file types. The Gerber format specification is maintained by Ucamco and freely downloadable. Understanding the underlying spec helps when troubleshooting unusual file issues.

Online DFM Tools from various manufacturers can check your Gerber files for common issues before you submit orders. These automated checks catch problems like missing layers, drill/pad misalignment, acid traps, and silkscreen on pads that might otherwise delay your order.

Community Forums and resources like the EEVblog forums, Reddit’s r/PrintedCircuitBoard, and manufacturer-specific communities provide real-world troubleshooting help when you encounter unusual file format issues.

Frequently Asked Questions

What’s the difference between Gerber RS-274X and Gerber X2?

RS-274X embeds aperture definitions within each file, eliminating the need for separate aperture lists that older RS-274D required. Gerber X2 extends RS-274X by adding file attributes—metadata that identifies layer types, functions, and other properties. This metadata helps CAM software automatically recognize layers, reducing manual setup errors. Most manufacturers accept both, but X2 provides better automation and fewer interpretation errors.

Can I send native design files instead of Gerbers?

Some manufacturers accept native files (.PcbDoc, .brd, .kicad_pcb) and convert them internally. However, this approach has risks. The manufacturer’s software version may differ from yours, potentially causing conversion issues. You also lose control over exactly what gets fabricated. I recommend generating your own Gerbers and verifying them before submission—this way, you know exactly what the manufacturer will build.

What files do I need for PCB assembly?

At minimum, you need your fabrication files (Gerbers, drill files) plus assembly-specific files: a pick-and-place or centroid file with component positions, a bill of materials listing all parts, and typically an assembly drawing. Some manufacturers also want paste layer Gerbers for stencil fabrication. Check your assembler’s specific requirements, as formats and column orders vary between companies.

Why doesn’t my 3D STEP export include component models?

STEP export quality depends on having 3D models assigned to your footprints. If components appear as simple rectangles or are missing entirely, your footprints likely lack 3D model references. You’ll need to assign STEP models to each footprint in your library. Sources like GrabCAD, 3D ContentCentral, and manufacturer websites provide downloadable component models.

How do I know which Gerber file is which layer?

Naming conventions vary by EDA tool. Altium uses extensions like .GTL (top layer), .GBL (bottom layer), .GTS (top solder mask), and .GTO (top silkscreen). KiCad uses descriptive names like F.Cu.gbr (front copper) and B.Mask.gbr (bottom mask). Gerber X2 files include metadata attributes that identify layer function automatically. When in doubt, open files in a Gerber viewer and visually confirm each layer’s content.

Making the Right Choice

With so many format options available, how do you decide what to use? Here’s my practical advice:

For fabrication, stick with Gerber RS-274X unless your manufacturer specifically requests something different. It’s universally supported and well-understood. If you’re working with an advanced manufacturer who supports Gerber X2 or ODB++, those formats can reduce setup errors through better metadata.

For design collaboration, native files are fine within the same software ecosystem. When sharing with teams using different tools, consider whether they need editable designs or just reference information. STEP and PDF work well for cross-platform reference without requiring specific EDA software.

For assembly, follow your manufacturer’s templates exactly. Assembly houses optimize their processes around specific file formats and column orders. Fighting their preferred format wastes everyone’s time.

The best file format is the one your recipient can actually use. When in doubt, ask before sending—a quick email confirming format requirements saves days of back-and-forth corrections.

Understanding these formats transforms you from someone who exports files and hopes for the best into an engineer who communicates clearly with every link in the manufacturing chain. Your designs deserve that level of attention.

The PCB industry continues to evolve, and file formats evolve with it. Standards like IPC-2581 are gaining traction as unified alternatives to the Gerber ecosystem. New capabilities in design software enable richer data exchange. Staying current with these developments helps you take advantage of improved workflows as they become available.

Start by mastering the fundamentals—Gerber files, drill data, and assembly documentation. Once you’re comfortable with these core formats, explore advanced options like ODB++ and 3D exchange formats based on your specific project needs. The investment in understanding these file types pays dividends in smoother manufacturing relationships and fewer costly delays.