Understanding PCB Manufacturing File Formats
A practical guide to Gerber, ODB++, Excellon drill files, IPC-2581, pick-and-place data, BOM files and PCB production workflows.
Designing a printed circuit board is only one part of the electronics manufacturing process. Before a PCB can be fabricated or assembled, the design must be exported into manufacturing files that PCB manufacturers, assembly houses and production engineers can understand.
These files form the connection between PCB design software and the factory floor. They describe the copper layers, drill holes, solder mask, silkscreen, board outline, component placement and other information needed to manufacture the finished circuit board.
Why PCB Manufacturing Files Are Needed
PCB design applications such as Altium Designer, KiCad, Cadence Allegro and Autodesk EAGLE store projects in their own design formats. These formats are useful during design, but they are not always suitable for direct use in fabrication and assembly.
PCB manufacturers normally require standardized production data. This makes it possible to manufacture the board without needing access to the original CAD system.
PCB manufacturing files commonly describe:
- Copper layers
- Solder mask layers
- Silkscreen layers
- Drill holes and vias
- Board outline and mechanical data
- Component placement
- Assembly and bill of materials information
Gerber Files
Gerber is the most widely used PCB manufacturing file format. A Gerber file describes the graphical content of a PCB layer using vector-based instructions. Each PCB layer is normally stored as a separate Gerber file.
A complete PCB manufacturing package often includes several Gerber files, one for each copper, solder mask, silkscreen and mechanical layer.
Common Gerber File Extensions
| PCB Layer | Common Extension |
|---|---|
| Top copper | .GTL |
| Bottom copper | .GBL |
| Top solder mask | .GTS |
| Bottom solder mask | .GBS |
| Top silkscreen | .GTO |
| Bottom silkscreen | .GBO |
| Board outline / mechanical layer | .GKO, .GM1 or similar |
Modern Gerber files are usually based on RS-274X, which includes embedded aperture definitions and is much easier to exchange than older Gerber formats.
Learn more in our dedicated Gerber file format guide.
Excellon Drill Files
Gerber files describe PCB layer graphics, but they do not usually contain all drilling information.
Drill data is commonly stored in Excellon drill files.
Excellon files define:
- Drill hole coordinates
- Tool numbers
- Drill diameters
- Plated and non-plated holes
- Vias and component holes
Common drill file extensions include .DRL and .TXT.
A PCB manufacturing package without drill data is usually incomplete.
Learn more in our Excellon file format guide.
ODB++
ODB++ is a more structured PCB manufacturing data format. Instead of using many separate files for individual layers, ODB++ stores PCB manufacturing information inside a structured dataset.
ODB++ can include:
- Layer graphics
- Drill data
- Netlists
- Component placement
- Stack-up information
- Manufacturing attributes
This can reduce ambiguity and improve automation in manufacturing workflows. However, Gerber remains more widely supported across the PCB industry.
Learn more in our ODB++ file format guide.
IPC-2581
IPC-2581 is an open PCB manufacturing data standard designed to transfer fabrication and assembly information in a single intelligent data package.
IPC-2581 can contain layer graphics, drill data, stack-up information, netlists, assembly information and bill of materials references.
The format is intended to reduce the need for multiple separate files and make PCB production data easier to validate and automate.
Pick-and-Place Files
Pick-and-place files are used during PCB assembly. They tell automated assembly machines where components should be placed on the circuit board.
Pick-and-place data usually includes:
- Component reference designators
- X and Y coordinates
- Rotation angle
- Component side
- Package or footprint information
These files are often exported as CSV or text files from the PCB design system.
BOM Files
The bill of materials, often called the BOM, lists the components needed to assemble the PCB.
A BOM commonly includes:
- Reference designators
- Component quantities
- Manufacturer part numbers
- Supplier part numbers
- Descriptions and values
PCB assemblers use the BOM to source components and prepare the assembly process.
Gerber vs ODB++ vs IPC-2581
| Feature | Gerber | ODB++ | IPC-2581 |
|---|---|---|---|
| Industry adoption | Very high | Medium to high | Growing |
| Single dataset | No | Yes | Yes |
| Includes assembly data | Limited | Yes | Yes |
| Open standard | Yes | No | Yes |
| Common use | PCB fabrication | Fabrication and assembly | Fabrication and assembly |
Gerber remains the most common format because it is simple, well known and supported by nearly every PCB manufacturer. ODB++ and IPC-2581 are more intelligent formats that can contain a broader set of manufacturing data.
Common PCB Manufacturing File Problems
Missing Drill Files
A PCB package without Excellon drill files may not contain enough information to manufacture holes, vias and plated through-holes correctly.
Missing Board Outline
The board outline defines the physical shape and size of the PCB. If the outline is missing or unclear, the manufacturer may need clarification before production.
Incorrect Layer Naming
Poor file naming can cause confusion. Clear layer names make it easier to identify top copper, bottom copper, solder mask, silkscreen and mechanical layers.
Unit and Format Issues
Older manufacturing files may use coordinate formats or unit settings that need to be interpreted correctly by the viewer or manufacturing system.
Opening and Reviewing PCB Manufacturing Files
Many people involved in PCB production are not PCB designers. Purchasing departments, quality control teams, production engineers and customers may need to inspect PCB data without using a full PCB CAD system.
This is where a dedicated PCB viewer can be useful. A viewer allows users to inspect production files, verify layer alignment, check drill data, print documentation and convert files into more accessible formats such as PDF.
How GerbView Helps
GerbView can open and analyze Gerber, ODB++, Excellon and other PCB manufacturing files. It allows users to inspect PCB layers, review drill data, measure geometry, compare revisions and convert manufacturing data to formats such as PDF, DXF, SVG, TIFF and other image formats.
Why Convert PCB Manufacturing Files to PDF?
PCB manufacturing data is often technical and difficult for non-designers to review. Converting Gerber or ODB++ data to PDF makes it easier to share PCB documentation with customers, purchasing teams, quality control departments and project managers.
PDF output is useful for:
- Manufacturing documentation
- Customer approval
- Internal review
- Archiving
- Printing
- Communication with non-CAD users
See also: Gerber to PDF conversion.
Best Practices Before Sending Files to Manufacturing
- Include all required Gerber layers.
- Include Excellon drill files.
- Verify that the board outline is present.
- Use clear and consistent file names.
- Check layer alignment in a PCB viewer.
- Inspect drill holes and vias.
- Include assembly files when required.
- Generate PDF documentation for easier review.
Open and Review PCB Manufacturing Files with GerbView
GerbView is designed for viewing, printing, converting and comparing PCB manufacturing files.
It supports Gerber, ODB++, Excellon drill data and other formats used in PCB production workflows.
Frequently Asked Questions
What files are needed to manufacture a PCB?
A typical PCB manufacturing package includes Gerber files for the board layers, Excellon drill files for holes and vias, a board outline, and often assembly data such as pick-and-place files and a bill of materials.
What is a Gerber file?
A Gerber file is a standard PCB manufacturing file that describes the graphical data for one PCB layer, such as copper, solder mask, silkscreen or board outline.
What is an Excellon drill file?
An Excellon drill file contains drilling information for a PCB, including hole positions, drill sizes and tool definitions.
What is the difference between Gerber and ODB++?
Gerber usually stores PCB layer graphics as separate files, while ODB++ is a structured dataset that can include layer data, drill information, netlists, components and stack-up information.
Can GerbView open PCB manufacturing files?
Yes. GerbView can open and view Gerber, ODB++, Excellon and other PCB manufacturing files. It can also print, convert and compare PCB production data.
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