PCB File Types Explained: Gerber, ODB++, IPC-2581 & BOM

Introduction

PCB file types provide the design, fabrication, and assembly data a manufacturer needs to build your board. An incomplete data package can delay quoting, engineering review, or production. This guide explains the main file formats and documents used for PCB fabrication and assembly. You will learn what each file carries and why it matters.

What PCB Files Do You Need for Manufacturing?

You need two distinct groups of files. One group handles bare board fabrication. The second group handles PCB assembly. Most delays start when a customer sends only half of the required PCB assembly data package.

Files Needed for Bare PCB Fabrication

Bare board fabrication needs PCB fabrication data that defines every physical layer and every hole. Our CAM engineers review these files before we cut a single panel.

• Gerber files: Export one file per copper, mask, and silkscreen layer, and name each one clearly so we match layer 3 to layer 3 without guessing.
• Excellon drill files: Send plated and non-plated holes in separate files. That split tells us which barrels need copper.
• Fabrication drawing: One sheet carrying finished dimensions, material, and surface finish. If the fabrication drawing conflicts with the Gerber data, the manufacturer should flag the discrepancy before production.
• Stack-up information: List every core, prepreg, and copper layer in order. We check it against our material inventory before quoting.
• Netlist (when required): Add an IPC-D-356A file when you order electrical test.

Files Needed for PCB Assembly

PCBA manufacturing files tell our SMT lines which components go where. You add these on top of your fabrication package when you order assembly.

• BOM: Every part you want populated, with full manufacturer part numbers.
• Pick-and-Place / Centroid: X, Y, rotation, and board side for each placement. Our programmers load it directly into the SMT line.
• Assembly drawings: Top and bottom views with polarity clearly marked.
• Solder paste data: Your paste layers define every stencil aperture. We adjust openings for fine pitch parts before laser cutting.
• STEP / 3D model (when required): Send a solid model when connectors sit near an enclosure wall or a heatsink.

PCB Fabrication File Types

Fabrication file types describe your board as a set of two-dimensional images plus a hole map. Gerber and Excellon dominate this category. Both formats carry decades of proven use across every major CAM system.

What Gerber Files Are

Gerber files are vector-based fabrication files that represent individual PCB layers or manufacturing features such as copper, solder mask, silkscreen, and paste. The format transfers layer data between your CAD tool and our CAM software without vendor lock-in. Gerber remains the most widely accepted of all PCB file formats.

What Information They Contain

Each set of Gerber layer files carries one distinct physical feature of your board.

• Copper layers: Traces, pads, planes, and pours, with one file per layer. We image this artwork onto photoresist.
• Solder mask: The openings that expose your solderable pads. Solder mask files define the openings around exposed pads. The required expansion depends on pad geometry, board density, solder mask registration capability, and the manufacturer’s process rules.
• Silkscreen: Reference designators, logos, and legend text. Keep silkscreen text and line widths within your manufacturer’s minimum feature requirements to avoid filling or loss of detail during printing.
• Board outline: One closed contour on a dedicated layer tells our router exactly where to cut your profile.
• RS-274X: The extended format embeds aperture definitions inside each file. The older RS-274D needed a separate aperture list, which caused constant mismatches.
• Gerber X2 format: X2 adds standardized attributes such as layer function, polarity, and pad function. These attributes help CAM systems interpret design intent more reliably than image data alone.

Excellon Drill Files

NC drill files use the Excellon drill format to map every hole in your board. We load them straight into our mechanical drilling and laser machines.

• Hole locations: X and Y coordinates expressed in your board origin system. Keep that origin identical to your Gerber origin.
• Hole sizes: A tool table assigns every diameter a number. State whether your sizes are finished or pre-plating.
• Plated / non-plated holes: Plated barrels carry current between layers. Bare holes for screws and standoffs belong in their own file.
• Slots: Routed slots list start and end coordinates with a tool diameter. Flag anything narrower than 1.0 mm.
• Drill tools: The drill chart PCB summary lists each tool, its size, its plating status, and its hole count for cross-checking.

Fabrication Drawing

The fabrication drawing PCB format is usually a PDF or a DXF PCB outline sheet, and it supplements the Gerber and drill data with manufacturing requirements that may not be fully defined by the artwork files alone.

• Board thickness: State the finished thickness including copper and mask. We hold roughly ±10 percent as standard on a 1.6 mm build.
• Material: Name the laminate grade, such as standard FR-4, high Tg FR-4, or a Rogers substrate. Tg rating drives lead-free assembly survival.
• Copper weight: Give the finished weight per layer, not the base foil. Outer layers gain close to 1 oz during electroplating.
• Surface finish: ENIG provides a flat surface for fine-pitch components, while HASL is a cost-effective option for many standard boards. OSP can also be suitable when its thermal and handling requirements match the assembly process.
• Tolerance: Call out the required tolerances for board outline, hole diameter, thickness, and other critical dimensions. Final tolerances depend on the board construction and manufacturing process.
• Impedance requirements: Name the target value, tolerance, and reference plane for each net class. We then select dielectric thicknesses that hit it.
• Special instructions: Note edge plating, via fill, castellations, gold fingers, or countersinks. Each one changes our process route and your price.

IPC-D-356A Netlist

The IPC-D-356 bare board test file lists every net and its connection points. We use it to program flying probe and fixture testing. It lets us verify continuity and isolation against your intended connectivity rather than against our own extraction. Send it whenever you order an electrical test.

Intelligent PCB Manufacturing Data Formats

Intelligent formats pack the entire board description into one structured dataset. They replace dozens of loose files with a single package. ODB++ and IPC-2581 lead this category, and both cut errors during the CAD-to-CAM PCB file handoff.

ODB++ Explained

An ODB++ PCB file is a single hierarchical database that holds layers, drills, stack-up, netlist, component data, and test data together. Valor created the format and Siemens maintains it today. You export one archive instead of juggling separate outputs. Our CAM team reads it directly, which removes most manual interpretation.

IPC-2581 Explained

The IPC-2581 standard is an open, vendor-neutral, XML-based format that carries complete fabrication and assembly data. IPC governs the specification, so no single software vendor controls it. The format handles HDI, rigid-flex, and embedded components.

ODB++ vs. Gerber

ODB++ carries intelligence that Gerber cannot. Gerber primarily represents graphical fabrication data, while additional Gerber attributes and companion files can provide manufacturing context. ODB++ goes further by organizing a broader set of design and manufacturing information within a structured data model.

IPC-2581 vs. Gerber

IPC-2581 can consolidate fabrication and assembly information that would otherwise be distributed across Gerber, drill, BOM, placement, and other files. Gerber needs several separate exports, and each export creates another chance for a mismatch. IPC-2581 keeps stack-up, netlist, and placement data aligned automatically. Adoption keeps growing, though it remains narrower than Gerber.

PCB Assembly File Types

Assembly file types define which components you want, where they sit, and how they orient. SMT programmers convert them into machine instructions. Mistakes here stop a production line faster than any fabrication issue.

Bill of Materials (BOM)

Your PCB BOM file lists every component we buy and solder. Send it as XLS, XLSX, or CSV so our sourcing team can parse it directly.

• Part number: The exact manufacturer part number, complete with package and tolerance suffixes. A truncated code stalls sourcing on day one.
• Manufacturer: Write the full company name rather than an abbreviation.
• Quantity: Specify the quantity required per board. The manufacturer can then calculate the total procurement quantity based on the production volume and applicable component allowances.
• Reference designator: Every designator that uses the part, comma-separated. The designator count must match your quantity exactly.
• Description: Value, tolerance, voltage rating, and dielectric for passives. This column catches mismatches between your part number and your intent.
• Package: The footprint you routed, such as 0402, SOT-23, or QFN-48. It confirms the part fits your land pattern.
• Approved alternatives: Substitutes you accept on each critical line. Approved alternatives can reduce sourcing delays when the primary part is unavailable, subject to engineering approval.

Pick-and-Place / Centroid File

The XY data file PCBA teams call a centroid tells our machines where each part lands. Supply it as CSV or Excel.

• Reference designators: Each entry must match your BOM and your assembly drawing. One orphan designator stops the line for clarification.
• X/Y coordinates: Measure from the component centroid, never from a corner or pin 1. Use the same origin as your Gerber files.
• Rotation: State degrees from 0 to 360, counterclockwise. Confirm your tool follows the IPC zero-degree convention, since library origins vary.
• Layer: Mark top or bottom for every part. Double-sided placement needs two reflow passes, which changes our process planning.
• Component side: Flag through-hole parts separately from surface mount. Many tools omit them because pick-and-place machines never touch them.

Assembly Drawings

Assembly drawings show the human-readable intent behind your placement data. Our operators check them during first article inspection.

• Component orientation: Show pin 1 and the body outline for every IC, connector, and module.
• Polarity: Mark cathode bands, plus signs, and pin 1 dots. Printed silkscreen often disappears under the part body after placement.
• Special assembly instructions: Note hand-soldered parts, masked areas, conformal coating zones, and DNP items on the drawing rather than in an email.
• Mechanical constraints: Show keep-out zones, connector heights, and mounting hole clearances. These limits tell us where fixtures and test probes can land.

Solder Paste and Stencil Data

Solder paste layers come from your Gerber set, and they define every stencil aperture. The solder paste layers define the starting aperture geometry for stencil fabrication. Aperture reductions or other modifications may be applied during stencil engineering based on component pitch, package type, and the manufacturer’s process rules. Confirm your paste layer matches your final pad geometry before you release the package.

STEP / 3D Model Files

A STEP file 3D PCB model gives us a solid representation of your assembled board. We use it to verify component heights, connector positions, and enclosure clearance. Send it whenever mechanical space runs tight.

Native CAD Files vs. Manufacturing Files

Native CAD files hold your complete project inside one vendor’s environment. Manufacturing files extract only what our machines need. Both have a place, yet only one drives production directly.

What Are Native CAD Files?

Native CAD files are proprietary project databases that bundle PCB schematic files, layout, libraries, and rules together. Each tool uses its own PCB layout file extensions.

• Altium: .PcbDoc holds the layout, and SchDoc holds the schematic, both wrapped in a .PrjPcb project file.
• KiCad: .kicad_pcb carries the board, and .kicad_sch carries the schematic, with footprints stored in .pretty libraries.
• Eagle: .brd stores the board, and .sch stores the schematic. Recent versions save both as XML inside the same extensions.
• OrCAD: .dsn holds the schematic database, and .brd holds the layout, with part libraries in .olb files.
• Allegro: .brd covers the board, and .dra covers footprint drawings, with padstack definitions in separate .pad files.

Why Manufacturers Usually Prefer Production Files

Manufacturers usually prefer standard PCB manufacturing files because they remove interpretation. Native files depend on the original CAD environment and export settings. Production files give the manufacturer a defined, reviewable manufacturing dataset. Any silkscreen shift or layer swap then becomes our decision instead of yours. You keep full control when you export the production files yourself.

PCB Manufacturing Files vs. PCB Assembly Files

Fabrication files build an empty board. Assembly files populate it. This table shows the split we apply when we review your PCB production files.

Common PCB File Errors That Cause Manufacturing Delays

Missing Drill Files

Missing drill files are a common problem in PCB manufacturing data packages. Many CAD tools export Gerbers and drills in two separate steps, so engineers forget the second one. Manufacturers cannot start drilling without hole data. Always zip your Gerber and Excellon output together into one archive.

Incorrect Board Outline

An unclear board outline stops us before routing. You need one closed contour on a dedicated layer with no gaps and no duplicates. Overlapping outlines across several layers force us to guess your true dimensions. Draw the profile once, then reference it from your fabrication drawing.

Gerber and Fabrication Drawing Conflicts

Conflicts appear when your drawing calls out one value, and your Gerbers show another. A common case notes 1.6 mm thickness while the stack-up adds up to 2.0 mm. Cross-check both documents against each other before you release them.

Incorrect BOM Part Numbers

Wrong part numbers halt procurement immediately. Obsolete, truncated, or distributor-specific codes fail to resolve to a real component. List the full manufacturer part number and name your approved alternatives up front.

Pick-and-Place Coordinate or Rotation Errors

Rotation errors place polarized parts backward. Many CAD tools export rotation relative to a library origin that differs from the IPC zero-degree convention. Coordinates that reference a board corner instead of the part center create similar offsets.

Missing Stack-Up or Impedance Requirements

Without stack-up data, the manufacturer selects dielectric thicknesses. That choice shifts trace impedance on your high-speed nets. Your board can pass continuity tests and still fail signal integrity in your product. State target impedance, tolerance, and reference layers explicitly.

FAQs

Is Gerber Better Than ODB++?

Neither format is better in every case. Gerber offers universal support, and every tool exports it. ODB++ carries more data in one package, so it cuts down on back-and-forth questions. Send ODB++ when your tool supports it, and send Gerber when you want the safest compatibility.

Do I Need to Send Native CAD Files to a PCB Manufacturer?

No. Standard production files cover everything we need to build your board. Native files occasionally help us answer a specific question during DFM review, but they never replace your exported data. Keep your project files and send us the outputs.

Does a PCB Manufacturer Need a BOM?

Only for assembly. Bare board fabrication needs no component data at all. Once you order assembly, the BOM drives sourcing, cost, and lead time. Send it early so we can flag stock problems before they delay your build.

Final Thoughts

Every layout tool saves your project in a proprietary format, using extensions such as .pcb, .sch, and .lib. Keep those files for your own work and send us the exported production data instead.

If you need a full DFM check and an accurate quotation for your project, submit your Gerber, BOM, and placement files to us. We support full-turnkey PCB fabrication, PCB assembly, and compliance validation for prototype and mass-production orders.