Electronics manufacturing what a BOM should include before requesting a quotation

A bill of materials may list every component on a board and still leave questions that prevent a manufacturing quotation from being prepared. A manufacturer part number is missing, two positions have conflicting descriptions, or it is unclear which components must be fitted. Each ambiguity holds up a purchasing decision or requires clarification.

The BOM, short for bill of materials, is a central part of the documentation needed to manufacture a printed circuit board assembly. Its purpose is to identify what the product requires and in what quantity. Before requesting a quotation, review it as a shared document for design, procurement and manufacturing teams.

Identify the product and its revision

The list should state which board or assembly it covers and which revision is current. Include a date and a contact who can answer technical questions. A filename such as “final” does not reliably distinguish two versions sent at different times.

Check that the revision matches the schematic, drawings and manufacturing files. A product change must be reflected in all relevant documentation. The supplier should not have to infer which file takes priority from an email date or a folder containing several copies.

Define each component beyond its generic description

A description such as “resistor” or “connector” provides context but does not identify a part adequately. Include the manufacturer and manufacturer part number when the selection is fixed. If an item is defined by a specification, provide the parameters needed to evaluate a proposal and identify who must approve it.

Manufacturer and distributor references

Do not confuse a manufacturer part number with a distributor's ordering code. Both may be useful, but they serve different purposes. A commercial link can change or become unavailable, so component identification should not depend on that page alone. If you include a purchasing reference, retain the technical information that identifies the part.

Value, package, tolerance and other relevant characteristics must agree with the design. Components with the same nominal value are not necessarily interchangeable. Differences in geometry, performance or behaviour can affect assembly and equipment operation.

Check quantities and reference designators

Reference designators link the list to positions on the circuit. Check for duplicates, omissions and discrepancies with the assembly drawing. The quantity per board must be separate from the total number of boards requested and from other materials required for the complete assembly.

Components that must not be fitted

If the design includes positions that remain unpopulated, identify them unambiguously. Leaving them out and expecting the assembler to interpret the omission is insufficient. Product variants need clear identification so that everyone knows which configuration is being quoted and which will be authorised for production.

Also identify customer-supplied items and materials that the manufacturer must procure. This distinction helps establish availability, responsibilities and quotation conditions without mixing assumptions about the scope of supply.

Document alternatives and change approval

An alternative can help address supply difficulties, but it must be evaluated and authorised. State whether approved alternatives exist and under what conditions they may be used. Matching a package or nominal value does not establish automatic equivalence.

If the supplier proposes a change, agree who reviews it and how approval will be recorded. The procedure must connect the alternative to the product revision. Where a characteristic is critical, explain its function and the limits that must be maintained, preventing substitutions based solely on price or availability.

Supply the BOM alongside the remaining documentation

The bill of materials does not replace manufacturing files, the assembly drawing or placement information required by the process. These should form a coherent release package. Include testing, programming, identification and packaging requirements where they are part of the order.

Reference designs from manufacturers such as Texas Instruments show a BOM, schematic and assembly drawing as separate documents. They illustrate a useful documentation structure without defining a universal format for every manufacturer or project.

Commercial information that supports the quotation

State whether you require prototypes, a pilot batch or series production, and provide quantities and expected repeat orders. Explain delivery constraints and which documents are released. If further changes are expected, flag them so that an initial estimate can be distinguished from a quotation based on a released configuration.

The file format should allow fields to be reviewed without reconstructing them from an image. Before sending it, check that filters, hidden columns and formulas do not conceal necessary information. A readable export and an identified revision make communication between teams easier.

For example, a spreadsheet may show an acceptable printed view while a filter hides components required for another variant. Review the actual file as the recipient will receive it, including the variant identification and any explanatory notes. This is a document control check, rather than a substitute for the engineering review of the design.

Frequently asked questions

Should components that are not fitted appear in the BOM?

Yes. Mark them DNP, or use the agreed convention, and link them to the relevant variant to prevent ambiguity.

Is the same nominal value enough to approve an alternative?

No. Check package, performance and circuit function. Any substitution must follow the agreed approval procedure.

Does the BOM quantity refer to one board or the batch?

State this explicitly. Separate quantity per board from the requested number of boards to avoid procurement errors.

Review the package with Electrolomas

Electrolomas provides technical office, procurement and industrialisation services associated with electronics manufacturing. Submit your project documentation and explain the scope you need, from a prototype to preparation for series production.

A preliminary BOM review helps resolve questions before materials are purchased or assembly begins. Request an assessment of the documentation package and agree how outstanding clarifications will be addressed. A quotation is more useful when everyone involved can identify the same product, revision and manufacturing conditions.