What Files Are Needed for PCB Assembly? Gerber, BOM & Pick-and-Place Guide

Preparing a PCB design is only part of getting an electronic product manufactured. Before fabrication and assembly can begin, the manufacturer needs accurate production data that explains how the board should be made, which components should be installed, and where every component should be placed.

So, what files are needed for PCB assembly?

For most PCB assembly projects, the core package includes Gerber files, NC drill data, a Bill of Materials (BOM), and a pick-and-place or centroid file. Depending on the complexity of the PCB, you may also need an assembly drawing, fabrication notes, stack-up information, schematics, test information, or special assembly instructions.

Understanding these files is especially important when moving from PCB design into actual manufacturing. If you are still working through schematic capture, component selection or board layout, professional electronics design services can help prepare the design for a smoother transition into production.

This guide explains each of the important PCB assembly files, what information they contain, and what you should check before sending your PCB for production.

Quick Answer: What Files Are Required for PCB Assembly?

Here is a simple overview of the main files used during PCB fabrication and assembly.

For a standard PCBA project, the most important starting documents are generally the Gerber files + Drill files + BOM + Pick and Place data.

Depending on the board technology, assembly process and manufacturer the exact package can change.

1. Gerber Files: The Main PCB Manufacturing Data

Gerber files are one of the most important files for the manufacturing of PCBs. They define the particular physical layers of the printed circuit board.

The production outputs will define the board geometry and will be used by manufacturing teams, instead of the original PCB CAD project.

What Do Gerber Files Contain?

Depending on the board design, a Gerber package may include:

• Top copper
• Bottom copper
• Internal copper layers
• Top solder mask
• Bottom solder mask
• Top silkscreen
• Bottom silkscreen
• Top solder paste
• Bottom solder paste
• Board outline or profile

The exact number of files depends heavily on whether the PCB is single-layer, double-layer or multilayer.

If you are still preparing the board itself, our guide to key PCB layout design factors covers stack-up documentation, Gerber outputs, BOM preparation, assembly drawings and other considerations that should be addressed before manufacturing.

What Gerber Format Should Be Used?

RS-274X is one of the commonly accepted Gerber formats in PCB manufacturing.

But be sure to check the current submission requirements of the manufacturer prior to exporting your files. Manufacturing may accept other data formats than those offered by CAD software and manufacturers.

What Should You Check Before Sending Gerber Files?

Before uploading your Gerber package:

• Check that all required layers are included.
• Verify the board outline.
• Confirm that copper layers are aligned.
• Check solder-mask openings.
• Review silkscreen placement.
• Verify solder-paste layers where required.
• Confirm coordinate units and origin.
• Review the files using a Gerber viewer.
• Make sure every file belongs to the latest PCB revision.

A design may look completely correct inside the PCB design software while still producing an incorrect manufacturing export. Reviewing exported production data separately is therefore an important final check.

2. NC Drill File: Where Should the PCB Be Drilled?

Another important PCB manufacturing file is the NC drill file.

Although drill files are commonly delivered together with Gerber data, the drill file itself is separate manufacturing information.

It defines features such as:

• Hole positions
• Hole diameters
• Through-holes
• Vias
• Blind vias where applicable
• Buried vias where applicable
• Mounting holes

Is an NC Drill File a Gerber File?

Technically, no.

Gerber files represent the imaging information used for PCB layers, while NC drill data identifies where holes need to be created and their required dimensions.

However, designers generally package Gerber and drill files together when sending production data to the manufacturer.

3. BOM: What Components Go on the PCB?

The Bill of Materials, or BOM, identifies the electronic components required to build the assembled PCB.

A simple way to understand it is:

Gerber files describe the board. The BOM describes the parts that go onto that board.

What Should a PCB BOM Include?

A useful PCB BOM can contain:

Why Are Manufacturer Part Numbers Important?

But a description like “10 kΩ resistor” might not be enough to reliably source the part.

An exact Manufacturer Part Number (MPN) can help to indentify:

• Size of package
• Tolerance
• Rating of the voltage
• Specifications related to temperature
• Seller
• Electrical properties

Knowing the exact part information removes uncertainty in the PCB purchase and assembly.

What Does DNP Mean in a PCB BOM?

DNP is typically Do Not Populate or Do Not Place.

For example, the PCB layout may have footprint R17 but a particular product version may not require a component to be installed there.

This should be marked clearly so the assembler doesn’t accidentally fill the component.

4. Pick-and-Place File: Where Does Every Component Go?

A pick-and-place file provides component positioning information for automated PCB assembly.

It may also be referred to as:

• Centroid file
• XY file
• XYRS file
• Component placement file
• Pick-and-place data

The purpose is to communicate where a component belongs on the PCB and how it should be oriented.

What Information Is Included in a Pick-and-Place File?

Typical information includes:

For example:

U4 | X = 42.50 mm | Y = 28.20 mm | Rotation = 90° | Top

Modern automated PCB assembly relies heavily on this data.

Elemental Electronics’ own PCB manufacturing and assembly capabilities include automated pick-and-place equipment for assembling electronic components accurately during production.

Why Is Component Rotation Important?

The X/Y location tells the equipment where to position a component.

Rotation tells it which direction the component should face.

Correct rotation is particularly important for:

• Integrated circuits
• Diodes
• LEDs
• Electrolytic capacitors
• Connectors
• Other polarised components

What About Custom or Asymmetrical Components?

Special attention should be given to custom footprints and unusual components.

Check:

• Footprint origin
• Component centroid
• Pin 1 orientation
• Rotation
• Package dimensions
• Manufacturer datasheet
• Top/bottom placement

Do not assume that an automatically exported centroid file is correct without reviewing critical components.

5. Assembly Drawing: The Human-Readable Reference

A pick-and-place file primarily communicates coordinate information. An assembly drawing gives engineers and technicians a visual reference.

It may show:

• Component locations
• Reference designators
• Connector orientation
• Polarity
• Mechanical hardware
• Heat sinks
• Labels
• Special mounting requirements
• Critical assembly notes

Assembly drawings become particularly useful when a PCB contains unusual connectors, mechanical parts, hardware or placement requirements that cannot be communicated clearly through the BOM and centroid file alone.

For a broader view of how bare boards become functioning electronic assemblies, see our guide explaining PCBA and how it transforms a PCB design into a functional product.

6. Are Gerber, BOM and Pick-and-Place Files Enough?

For many standard projects, Gerber files, BOM and pick-and-place data form the core PCB assembly documentation.

However, they may not represent the complete manufacturing package.

Depending on your PCB, additional information may include:

• NC drill files
• Fabrication drawings
• Assembly drawings
• PCB stack-up
• Controlled impedance requirements
• Schematics
• Panelisation information
• Testing requirements
• Programming instructions
• Mechanical assembly instructions
• Component substitution rules
• Special soldering requirements

The better question is therefore not simply:

Can I manufacture the PCB with only three files?

Instead, ask:

Does the manufacturer have enough accurate information to fabricate, source, place, assemble and test the PCB without having to guess?

That is a much better standard for assessing manufacturing readiness.

7. Bare PCB Fabrication vs PCB Assembly Files

PCB fabrication and PCB assembly are closely connected, but they are different manufacturing stages.

PCB fabrication creates the bare printed circuit board.

PCB assembly or PCBA installs the electronic components onto that board.

Because the processes are different, their data requirements are also different.

For a complete fabrication-and-assembly project, these files form a coordinated production package.

If you are deciding whether a board is still in validation or ready for larger-scale production, the guide on prototype PCB vs production PCB explains how manufacturing requirements, documentation, testing and production processes change as a board moves towards commercial manufacture.

8. Common PCB Assembly File Mistakes

Even an electrically correct PCB design can create production problems if the manufacturing data is incomplete, incorrect or inconsistent.

BOM and PCB Revisions Do Not Match

When you rework a PCB with an old BOM you may end up with missing or wrong parts. Make sure to have version control on all manufacturing files.

Missing Manufacturer Part Numbers

Generic descriptions may cause uncertainty during component sourcing.

Use exact manufacturer part numbers wherever practical.

Incorrect Component Rotation

Rotation errors can be particularly serious for orientation-sensitive components.

Incorrect XY Coordinates or Origin

Coordinate data needs to match the board reference system expected during assembly.

Missing Reference Designators

Reference designators should match between the PCB design, BOM, placement file and assembly drawing.

Missing Drill Data

Gerber layers alone do not completely describe the drilled features required in a PCB.

Missing Board Outline

The manufacturer should have one clear and unambiguous board profile.

DNP Components Are Not Clearly Identified

Components that should not be fitted need to be clearly marked in the BOM and associated documentation.

Old Files Are Included in the Final Package

Avoid placing several outdated file revisions in the production ZIP.

Use one clearly identified manufacturing release.

Incorrect documentation can contribute to placement, soldering and assembly problems. You can also review the common causes covered in our guide to PCB assembly defects and how to prevent them.

9. PCB Assembly File Submission Checklist

Before submitting your PCB assembly files, complete this final check.

Gerber and Fabrication Data

• Confirm the final PCB revision.
• Include all copper layers.
• Include solder-mask layers.
• Include silkscreen layers.
• Include solder-paste layers where required.
• Include the board outline.
• Include NC drill files.
• Check coordinate units and origin.
• Review layer alignment.
• Inspect exported Gerber files in a viewer.

BOM

• Verify reference designators.
• Check component quantities.
• Confirm component values.
• Verify package sizes.
• Add manufacturer part numbers.
• Include supplier part numbers where useful.
• Recognize DNP components.
• Add any approved substitutions that apply.
• Check BOM is updated with latest PCB revision.

Pick-and-Place Data

• Verify X/Y coordinates.
• Verify component rotation.
• Check top/bottom placement.
• Confirm reference designators.
• Review custom components.
• Check polarity-sensitive devices.

Supporting Documentation

• Include an assembly drawing where required.
• Add fabrication notes.
• Add stack-up requirements.
• Include special assembly instructions.
• Provide mechanical requirements.
• Add programming or testing information if required.

10. How PCB Assembly Files Work Together

Each file does a different job but together they are the instructions needed to manufacture the electronic assembly.

A simple workflow goes like this:

PCB Design → Gerber & Drill Data → PCB Manufacture → BOM & Component Sourcing → Pick-and-Place Programming → PCB Assembly → Inspection → Testing

In practice :

Gerber files tell the manufacturer what board to produce.

NC drill data tells the manufacturer where holes go.

The BOM tells the manufacturer which components are required.

The pick-and-place file tells the assembly equipment where SMT components should go and how they should be oriented.

The assembly drawing provides additional visual and mechanical guidance.

When these documents all represent the same design revision, the manufacturer receives a much clearer and more reliable production package.

FAQs About PCB Assembly Files

What files are required for PCB assembly?

Most PCB assembly projects require Gerber files, NC drill files, a Bill of Materials and pick-and-place data. Depending on the complexity of the board, assembly drawings, schematics, stack-up details, fabrication notes and special instructions may also be required.

Is a pick-and-place file the same as a centroid file?

The terms are commonly used for similar component-placement information. A centroid or pick-and-place file usually contains the component reference designator, X/Y coordinates, rotation and board side.

Is an NC drill file part of a Gerber file?

No. NC drill data is technically separate from Gerber layer data. However, Gerber and drill files are normally packaged together when PCB manufacturing files are submitted.

What should be included in a PCB BOM?

A PCB BOM normally includes reference designators, component quantities, values, descriptions, footprints and manufacturer part numbers. Supplier part numbers, alternative components and DNP information may also be included.

Do I need a BOM for bare PCB fabrication?

Normally, a BOM is primarily needed when components are being sourced and assembled. Bare PCB fabrication relies mainly on Gerber data, drill files and the board’s fabrication specifications.

Why does PCB assembly need a pick-and-place file?

The automatic SMT placement equipment needs to know the exact position and direction of the components. The pick-and-place file supplies this information so components can be placed at the correct position and rotation.

What Gerber format is commonly used?

RS-274X is a common Gerber format used for PCB manufacturing. Always check the export format required by your selected PCB manufacturer before you send your production files.

Are assembly drawings mandatory?

Not for every PCB. They become especially useful when the board includes special connectors, mechanical hardware, unusual components, polarity requirements or assembly instructions that require additional visual clarification.

Final Thoughts

Accurate PCB assembly files are essential for converting a finished electronic design into a reliable physical product.

Gerber files define the PCB layers. The holes are defined by NC drill data. The components are identified in the BOM . Pick and place data provides component position and orientation. Assembly drawings and supporting documentation communicate additional production requirements.

Just as importantly, every file should belong to the same approved PCB revision.

Before production, review the Gerbers, BOM, placement data and supporting documentation together rather than treating each file independently.

For companies preparing prototypes or production-ready electronic boards, Elemental Electronics provides PCB manufacturing and PCB assembly services in Australia covering component sourcing, automated pick-and-place assembly, soldering, inspection, testing and low-volume manufacturing.