PCB Assembly File Requirements
Make every part, position and process instruction traceable to one build.
One consistent file set, with a clear revision.
Include any questions for your project contact.
Connect the board, the parts and the placement
Manufacturing geometry does not, by itself, establish purchasing intent or the complete assembly process.
A BOM identifies the parts to be assembled. A component placement list identifies where included component references are placed, their rotation and their board side. Both must correspond to the same product configuration.
| File / information | What it should establish | Consistency check |
|---|---|---|
| Released PCB definition | Fabrication dataset or approved bare-board revision | Make the supplied bare boards and assembly documents refer to the same PCB revision. |
| Purchasing BOM | Manufacturer, exact primary MPN, designators, per-board quantity and populate state | Add approved alternatives and sourcing responsibility in separate fields. |
| Placement data | One position per component included in the placement scope | Declare origin, units, side, coordinate center and rotation conventions. |
| Assembly drawings | Top and bottom placement views, reference designators, pin 1 and polarity | Label the viewing direction; show nonstandard orientations and hand-fit details. |
| Paste / stencil inputs | Released paste apertures and special stencil instructions where relevant | Do not substitute solder-mask openings for the paste layer. |
| Variant and exceptions | DNP list, hand-fit parts, through-hole parts and mechanical assembly items | Explain any intentional BOM-to-placement mismatch. |
| Programming and testing | Applicable firmware, programming instructions and test procedure | Define versions, interfaces, fixtures, pass/fail limits and expected reports. |
| Consigned materials | Packing list, MPNs, quantities, packaging and agreed extra material | Separate board demand from setup/attrition allowance and pack quantities. |
Review the package as one configuration
Reference designators are the connection between files—not an instruction to ignore process exceptions.
- 01
Lock the PCB revision and assembly variant
Put the configuration on the manifest, BOM, placement file and drawings. Where one PCB supports several variants, identify the selected population rather than merging incompatible builds.
- 02
Reconcile references
Check that every fitted component is accounted for in the appropriate assembly operation. Find duplicate references, missing parts and intentional DNP positions. Do not delete a mismatch until its cause is understood.
- 03
Check polarity and orientation
Review pin 1, diode direction, polarized capacitors, LEDs, connectors and modules against the released drawings and component data. An angle in a CSV is not sufficient evidence by itself.
- 04
Close the exceptions
Record hand assembly, press-fit, hardware, fiducials, test points and excluded positions. The placement list and purchasing BOM need not contain identical classes of objects.
- 05
Approve the release
Resolve open questions, permitted substitutions, process exceptions and test coverage. A valid file import is not the same as an approved build.
Document the steps that coordinates cannot describe
Hand assembly and mechanical work
Identify component stand-off, connector orientation, hardware, torque or fixture needs where they apply. Reference a controlled instruction rather than a note buried inside a filename.
Programming
Where programming is required, include the approved image, version, checksum, target configuration, interface and success criteria. Handle secrets and device credentials through an approved process, not public templates.
Test and inspection
Define the requested inspection and test scope, fixtures, procedures, limits and evidence. Do not assume that assembly inspection includes a project-specific functional test.
Coating and special processes
Identify areas that must be coated or masked, material requirements and acceptance criteria where relevant. Confirm process compatibility instead of using an ambiguous instruction such as “coat all.”
Separate sourcing decisions from placement data
A clear owner per BOM line prevents duplicate buying and missing material.
Turnkey
Identify the exact primary part and any approved alternatives. Record who can authorize a substitution. A distributor stock code can help sourcing but should not obscure the approved manufacturer part.
Consigned
Supply a packing list that matches the BOM and identify delivered quantities, packaging and handling needs. Agree any additional material for setup or loss rather than applying a fixed universal percentage.
Mixed supply
Assign a sourcing owner to each line. Resolve which components are customer-supplied, factory-sourced or intentionally not fitted before the order is released.
Download the preparation files
Download the checklists and templates below without signing in or submitting a form.
PCB & PCBA workbook
Eight sheets: instructions, BOM and placement inputs/examples, RFQ review and batch arithmetic.
XLSX · 19.5 KBBlank BOM template
Header-only UTF-8 CSV. Add released purchasing data; no demonstration parts included.
CSV · 0.1 KBBlank placement template
Numeric millimeter / degree fields. Complete the accompanying coordinate convention notes.
CSV · 0.1 KBRelease & coordinate manifest
Identify the file revision, stackup and coordinate conventions, and list any details you need help confirming.
TXT · 2.8 KBFrequently asked questions
Can assembly start from Gerbers only?
Do not assume so. The team also needs the purchasing and population intent and appropriate assembly instructions. Integrated CAD-to-manufacturing data can contain useful assembly information, but verify its actual completeness and the receiver’s agreed workflow.
Must every BOM item appear in the SMT placement file?
No. Through-hole, hand-fit and mechanical items may be handled separately. Fiducials or test features may be present in positional data without being purchased parts. Document these exceptions rather than forcing a false one-to-one match.
Is the same BOM valid for all product variants?
Only when the selected population and substitutions are unambiguous. Prefer a released variant-specific BOM or a formally controlled variant structure accepted by the assembly team.
What is the difference between an assembly drawing and a placement file?
The drawing communicates visual and process intent. A placement export provides positional records; Altium’s output can include location, rotation and side in CSV or text. Use the two together.
Is a firmware file enough for programming?
No. State the target, version, programming method, configuration, success criteria and any controlled credentials. Mark programming not applicable when it is outside the requested scope.
Technical references & scope
- [6] Altium Designer — Preparing assembly data
- [10] KiCad — PCB Editor: Manufacturing Outputs and Design Rules
- [13] JLCPCB — BOM/CPL preparation and consistency checks
Use the checklists and templates on this page to prepare your manufacturing files. Confirm the required formats and approved design revision with your project contact before ordering; export steps may vary by CAD software.
File preparation resources for PCB & PCBA projects.