The bill of materials connects procurement to the intended population of the board. It must identify what to buy and where each fitted item belongs. Treat the BOM as controlled design data, especially when a spreadsheet is edited outside the CAD system.
Include the decision-making fields
Use manufacturer, full orderable part number, reference designators, quantity per assembly, description or value, and package information. Keep distributor stock numbers in separate fields. An internal part number is useful only if the receiving team can resolve it to an approved purchasable item.
Make variants explicit
Identify do-not-populate references and variant-specific alternatives. Check fitted quantity against the actual reference list. Avoid using blank part-number cells or cell colors as the only way to communicate a population decision, because those conventions can be lost during export.
Control approved alternates
Record which alternatives are approved and the conditions of use. An alternate may require a firmware, footprint or process change. Purchasing should not infer equivalence from a similar description, value or package label.
Reconcile before release
Compare the BOM with the assembly drawing and placement data at the same revision. Check duplicate references, missing identifiers and unexpected changes from the prior build. Preserve the original release and record later corrections through a new coordinated revision.
Release checklist
- Use exact manufacturer part numbers.
- Reconcile references, quantities and variants.
- Separate purchasing identifiers from design identifiers.
- Approve and record alternates before ordering.