How to Prepare the Correct BOM in Electronics Manufacturing

A Bill of Materials (BOM) is an essential element of a product’s technical documentation.

It lists all components required to manufacture a single unit of a finished product. An inaccurate BOM can result in deviations from specifications and poor product quality, disrupt manufacturing, delay production, and increase unnecessary costs.

How can you create an accurate BOM that includes all necessary information and is error-free? Read this article for recommendations.

Accuracy and relevancy

For a BOM to be effective, it must be consistent, relevant, and up-to-date. However, before you start filling this document, choose an appropriately structured format.

An Excel spreadsheet, which will allow you to organise information clearly in separate cells, is a suitable option. This format is easily readable for both Original Equipment Manufacturers (OEMs) and Electronics Manufacturing Service (EMS) providers.

While the format is important, maintaining a consistent structure across all BOMs is also crucial. This consistency will facilitate reviewing, updating, and sharing BOMs with key stakeholders.

To prevent the distribution of outdated BOMs, consider implementing a version control system to track changes and revisions effectively.

Detailed component descriptions and specifications

Experts in contract electronics manufacturing, such as Polish-based Assel, emphasise that a more detailed BOM helps EMS providers accurately identify components. However, all the shared information should be both relevant and unambiguous. Each component in the BOM should be precisely specified, including storage conditions, maximum storage period, and the quantity required for each production unit, listed separately at each stage if needed.

To safeguard against supply issues, mention alternative parts with similar specifications. Include an Approved Vendor List (AVL) identifying approved suppliers for each item. The reference designator (RefDes) must clearly define where each component is mounted on the PCB. Additionally, the Manufacturer Part Number (MPN) should be fully specified for each component, with no potential for misinterpretation, alongside packaging and storage details, such as temperature and humidity requirements.

Additional documentation

A comprehensive BOM should also include supplementary documentation, particularly for box-build products or those containing electromechanical assemblies. In such a scenario, provide detailed, bulleted manufacturing steps, which can be created in CAD or shared in PDF format.

Furthermore, a separate appendix to the BOM should contain a complete set of manufacturing instructions, including all steps, materials, and components involved, with visualisations of the final product in a graphical model. If packaging is part of the contractor’s responsibilities, provide detailed packaging specifications, too. The full set of documents, including the BOM and all related instructions, forms the Assembly Documentation.

Final considerations

By following these guidelines and ensuring the information you share is comprehensive, relevant, and well-organised, you can create a document that is precise, sufficient, and tailored for efficient, streamlined manufacturing. For more information on electronics manufacturing services, visit asselems.com.