PCB Assembly File Guide for Production Ready Outputs

A complete PCB assembly file package tells the manufacturer what to build, which parts to fit, and where each component belongs. Export Gerber fabrication and paste data, a centroid file, a clean BOM, and assembly drawings from the same approved design revision. Then cross-check references, footprints, rotations, and board orientation before upload.

Key Takeaways

• Create every output from one released schematic and PCB revision; mixing revisions is the fastest way to create placement conflicts.

• Use Gerber data for board and stencil geometry, a centroid file for machine placement, a BOM or bill of material for sourcing, and assembly drawings for human-readable instructions.

• Treat export as the first half of the job. The second half is checking that reference designators, footprints, quantities, side, rotation, and polarity agree across all files.

• Package the final PCB assembly file set in one clearly named ZIP archive and include notes for DNP parts, substitutions, panelization, or special assembly handling.

Introduction

A board can pass electrical rule checks and still stall at assembly because its production data is incomplete or contradictory. The assembler cannot safely infer whether C17 is omitted, which way D3 faces, or whether a coordinate was exported from the top or bottom view.

The practical goal is simple: generate PCB assembly file outputs that describe one design revision without ambiguity. The workflow below shows what to include, how to export each file, and how to verify the package before ordering.

What Files Are Needed for PCB Assembly

A production-ready PCB assembly file package normally contains four coordinated outputs. Each answers a different manufacturing question, so one file cannot reliably replace the others.

If the project needs programming, functional testing, conformal coating, press-fit operations, or customer-supplied parts, add the relevant work instructions and test files. Keep those documents separate from the core package, but use the same revision identifier.

How to Generate PCB Assembly Files

Generate PCB assembly file outputs only after the schematic, layout, footprints, and variant settings are frozen. Use the CAD project as the source of truth and export all deliverables in one session so later edits do not split the package across revisions.

1. Gerber Files

Gerber files describe the physical board layers, while NC drill data defines plated and non-plated holes. For assembly, the top and bottom paste layers are especially important because they drive stencil creation; copper, mask, silkscreen, and board outline let the manufacturer verify the assembly against the fabricated PCB.

• Set the export format. Use RS-274X or Gerber X2 with embedded apertures. Select metric or inch units deliberately and use enough coordinate precision to preserve fine features.

• Select the layers. Export every copper layer, top and bottom solder mask, top and bottom silkscreen, board outline or mechanical profile, and top and bottom paste where components are assembled.

• Export drill data. Create separate plated and non-plated drill files when the CAD tool supports it. Include a drill map only as a visual reference, not as a substitute for NC drill data.

• Verify the result. Open the complete Gerber set in an independent viewer. Confirm that the outline closes, holes align with pads, text is readable, and paste openings match populated SMT pads. Check that no old layers remain in the output folder.

2 Centroid File

The centroid file, also called a pick-and-place or XY file, gives placement equipment the location and orientation of each fitted component. It should come from the same board origin and variant used for the other PCB assembly file outputs.

• Choose the assembly variant. Exclude DNP components or mark them clearly. Do not silently remove a part if the BOM still lists it as fitted.

• Export required fields. Include reference designator, center X, center Y, rotation, board side, footprint, and preferably a component comment or value. State the units in the header or file name.

• Check the origin and view. Use a defined board datum, normally a stable corner or CAD origin. Confirm whether bottom coordinates are mirrored and how the CAD tool reports bottom-side rotation; the assembler must not have to guess.

• Spot-check real parts. Compare at least one IC, polarized diode, connector, and bottom-side component against the assembly drawing. Verify both position and pin-1 orientation.

3 Bill of Material

The BOM identifies every part that must be purchased or supplied for the build. A usable bill of material is not a parts description alone; it must identify an orderable component and connect it to the exact reference designators on the PCB.

• Complete the source data. In the schematic library, fill in manufacturer, manufacturer part number, value, tolerance or rating where relevant, and the assigned PCB footprint. Use one exact MPN per approved choice and place alternates in separate columns.

• Export and group carefully. Generate the BOM from the released schematic or approved output job. Group parts only when the MPN and assembly status are identical; do not merge two values merely because they share a footprint.

• Keep essential columns. Include line item, quantity per board, reference designators, manufacturer, MPN, description or value, footprint/package, and DNP status. Add supplier and supplier part number only when they are controlled requirements.

• Reconcile quantities. Count the reference designators in every row and confirm that the count equals the stated quantity. Then compare the fitted references with the centroid file; each placed component should appear once in both.

• Resolve sourcing risk. Flag customer-supplied parts, approved substitutions, lifecycle concerns, and special packaging needs. Never let a generic description such as "10 k resistor" replace the MPN when size, tolerance, power, or voltage rating matters.

4. Assembly Drawings

Assembly drawings give engineers and operators a readable view of placement, polarity, and exceptions that machine files do not explain well. Export separate top and bottom PDFs, and label the viewing direction so the bottom view cannot be mistaken for a mirrored top view.

• Prepare clean views. Show the board outline, component outlines, reference designators, pin-1 or polarity marks, and key mechanical features. Hide copper detail if it makes the drawing harder to read.

• Add controlled notes. Identify DNP references, hand-soldered or press-fit parts, adhesive requirements, hardware, component height limits, and any polarity convention that is not obvious from the footprint.

• Make dense areas readable. Use enlarged detail views when references overlap. Keep the master drawing at a useful scale and place the revision, units, and page identification in the title block.

• Compare against data. Check that every visible fitted reference appears in the BOM and centroid file. Confirm that polarity marks agree with the footprint, silkscreen, and component datasheet.

Submit Your Files to PCBgogo and Move into Production

The last step is to package one verified revision and submit it to PCBgogo for fabrication and assembly review. Clear inputs allow engineering questions to be resolved before material purchasing, stencil preparation, or placement begins.

• Name files consistently, for example ProjectName_RevB_BOM.xlsx and ProjectName_RevB_TopAssembly.pdf.

• Remove obsolete exports, temporary backups, and unrelated CAD files from the delivery folder.

• Include a short readme with board quantity, assembly sides, variant, revision, units, special processes, and the contact for technical questions.

• Open the final ZIP after creation and confirm that the Gerber set, drill data, centroid file, BOM, bill of material notes, and assembly drawings are present and readable.

• Respond to DFM, BOM, and component questions by updating the controlled source files, then re-export the affected outputs under a new revision. Avoid correcting only a spreadsheet or PDF while leaving the CAD source unchanged.

Once the PCB assembly file package passes this check, submit it through PCBgogo's order workflow. The result is a cleaner handoff from design to manufacturing, fewer avoidable clarification cycles, and a stronger basis for building high-quality PCB assemblies that keep the project moving.

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