PCB and PCBA Files: Gerber, BOM and CPL for China

What files do I need for bare PCB versus PCBA?

A bare PCB is an unpopulated board. PCBA adds component assembly; state whether the factory will purchase components, receive your components or use a mixture.

Use the table as a recommended handover checklist for a Gerber-based order, then confirm the manufacturer's accepted formats and required information. Ask for assumptions in an incomplete quotation to be identified before comparing offers.

Gerber and drill files: send manufacturing data, not screenshots

Ask whether the manufacturer accepts your Gerber export, including extended Gerber, commonly called RS-274X. For a Gerber-based order, supply the manufacturing data rather than only screenshots or PDF previews.

Export copper, solder mask and legend layers as applicable, together with a clearly identified board outline. Supply drill and routing data in the manufacturer's accepted format, with units and hole plating requirements explicit. Include paste layers for assembly when requested.

Open the exported package in a separate viewer. Check layer alignment, outline closure, holes, slots and top/bottom identification. Keep drawing dimensions and explanatory text separate from production artwork.

Provide a design-derived netlist for a connectivity cross-check where the manufacturer's workflow supports it. Ask whether a schematic is also needed for connectivity or testing questions; provide it alongside the agreed fabrication package.

Stackup and fabrication notes: define the board requirements

State the board material requirements, layer sequence, finished board thickness and tolerance, copper requirements, surface finish and solder mask requirements. Identify critical mechanical dimensions and specify whether hole dimensions refer to finished holes.

For controlled impedance, identify the relevant traces, target impedance and tolerance. Ask the factory to return its proposed material and stackup for approval.

Say whether you are supplying a single-board design or an approved panel. Agree who designs the panel, including separation method, tooling features and assembly access. Request drawings for approval before accepting changes affecting enclosure fit or component placement.

BOM format: make every component purchasable

Use an editable spreadsheet or CSV in the manufacturer's agreed template. Include reference designators, quantity per board, description or value, package, manufacturer and full manufacturer part number. Put distributor stock codes in a separate column if supplied.

Identify do-not-populate positions in the release documentation and follow the assembler's instructions for excluding them from placement. Reconcile the BOM, CPL and assembly drawing. Distinguish quantity per board from total purchase quantity; agree purchasing allowances and handling of unused components.

List approved alternatives by exact manufacturer and part number. If none are approved, specify that substitutions require written approval. Assess proposed replacements against the circuit's requirements rather than approving them solely because their footprint or nominal value matches.

Ask the supplier to flag unavailable parts, uncertain lead times and proposed substitutions before ordering components. Keep the approved BOM attached to the production release.

CPL and assembly drawings: prevent placement and polarity errors

CPL means component placement list; placement data is also supplied as a pick-and-place or centroid file. Request the manufacturer's template. Include relevant reference designators, X/Y coordinates, rotation and board side; document units, origin and coordinate conventions.

Confirm rotation and bottom-side coordinate conventions with the assembler. Ask it to reconcile the placement file against the footprints and return a placement preview for approval.

Provide a readable assembly drawing showing component references, polarity, pin orientation, connector direction and unpopulated positions. Add instructions for through-hole parts, cables, heatsinks, adhesives and other work outside the placement file.

If the design uses spring contacts, use the separate PCB spring-contact sourcing guide for contact-specific purchasing requirements.

Testing notes: define what a passing board must do

Separate bare-board electrical testing, assembly inspection and functional testing in the order. A bare-board connectivity check does not establish that an assembled circuit performs its intended functions.

For functional testing, supply connection instructions, power conditions, test sequence, expected results and acceptance limits. Identify who supplies fixtures, software and required equipment. If programming is included, identify the approved firmware and programming procedure.

Agree which boards will be tested, which functions will be checked, what results will be recorded, how failures will be handled and what evidence accompanies shipment. Avoid an instruction that only says 'fully tested'.

Where relevant, name the agreed IPC standards: IPC-A-600, Acceptability of Printed Boards; IPC-A-610, Acceptability of Electronic Assemblies; and IPC J-STD-001, Requirements for Soldered Electrical and Electronic Assemblies. Agree the applicable revision and acceptance requirements in the order, and specify functional testing separately.

Agree the manufacturer's file review and DFM questions

Request a design-for-manufacture review, usually called DFM, before production release. Confirm its scope with the supplier, including whether fabrication, assembly and component-availability checks are included.

Ask the fabricator to review layer order, materials, copper clearances, holes, solder mask openings, slots, panelisation and conflicts between artwork and drawings. Ask the assembler to check BOM/CPL consistency, orientation, component availability, substitutions and access for assembly or testing.

Request a written query list with marked images or drawings. Ask that each proposed change identifies the affected feature, reason and expected effect. Refer unresolved design questions to the person responsible for the design.

Approve the final fabrication data, stackup, BOM and placement interpretation before production. Keep circuit verification, product-compliance evidence and test results separate from the DFM approval.

Common file mistakes to catch before release

Use a release manifest listing the board identifier, revision and included files. Keep superseded packages out of the production handover, and require written confirmation of the release the factory will build.

If you sell in the US or EU

US entry — checked 2026-10-18: CBP guidance states that the importer of record remains responsible for correct entry documentation and applicable duties, taxes and fees even when using a broker. Prepare an accurate description of the goods being imported alongside the engineering files.

US Section 301 — checked 2026-10-18: USTR provides an HTS-subheading search for the China Section 301 actions. Confirm classification and applicable measures for the actual shipment with your customs adviser. Do not assume bare PCBs and assembled boards receive identical treatment or treat this search as a complete landed-cost calculation.

EU CE marking — checked 2026-10-18: Your Europe explains that CE marking is required only where applicable EU rules mandate it. A business having a product made and selling it under its own name or brand is treated as its manufacturer, responsible for the whole product's compliance, including supplied components. Establish intended use and applicable rules before agreeing compliance evidence; manufacturing files alone do not establish conformity.

UK purchasing example: engineering files and customs valuation

For an order of assembled boards imported into Great Britain, retain the approved manufacturing release alongside purchase and shipping records. Prepare a goods description reflecting what is shipped rather than using design filenames as the description.

HMRC guidance, checked 2026-10-18, includes relevant delivery costs up to the UK place of introduction in customs value. Import VAT valuation starts with customs value and includes applicable import duties and charges, excluding import VAT itself, plus relevant incidental expenses to the first UK destination and a further UK destination known at importation. Account for costs already included in customs value. The factory's board price alone is therefore not necessarily the import VAT value.

Prepare a package for Cambridge China Bridge

Prepare the available files, intended use, required quantities, destination and delivery needs, and identify gaps before requesting a firm manufacturing quote. For enquiries about manufacturing scope, see PCB manufacturing in China.

For enquiries about prototypes or limited quantities, see the small-order service. Agree responsibility for file preparation, engineering decisions, component purchasing, testing and production approval before placing the order.

Sources

Ucamco supports Gerber terminology and fabrication-data handover; IPC supplies standard names and DFM topics. Manufacturer documentation illustrates BOM, placement and test-file requirements for those suppliers. CBP, USTR, Your Europe and HMRC support the destination-specific statements. The checklists are recommendations: confirm the chosen manufacturer's formats and contracted scope.