PCB BOM File

A PCB BOM file, or Bill of Materials, is a document that details all the components needed for the construction of a printed circuit board. It includes information such as part numbers, descriptions, quantities, and component specifications like resistance or capacitance. It also indicates the manufacturer, supplier, and the physical location of each component on the PCB through reference designators.

PCB BOM serves as the reference for board assembly and ensures that the correct components are sourced, facilitating the procurement and assembly processes in PCB manufacturing. Typically, it’s provided in formats like CSV or Excel for easy use.

Why is the PCB BOM file important?

The BOM contains detailed information about each component, serving as the primary means for the customer to convey all necessary component details to the assembly unit. Additionally, the bill of materials assists designers in estimating the cost of producing the required number of circuit boards.

How to prepare a bill of materials

A BOM is essentially an Excel sheet containing all the necessary information. While you can manually create it by inputting the required details, using software that can automatically generate the BOM saves time and effort. Popular tools for this purpose include KiCad, Altium Designer, and Cadence Allegro.

Each manufacturer recommends a specific format, so when preparing the list, the designer should ensure they are following the template provided by the manufacturing company.

Tips to keep in mind while preparing your BOM file

  • Including everything: It is essential to understand that all components needed for different versions of a circuit board are purchased based on the BOM. Therefore, it is crucial to include every item required for assembling all the boards in this list.
  • Verified information: Ensure that the information in the list is accurate and error-free to avoid any negative impact on the product’s quality.
  • Send the most updated version: Ensure that all the information provided in the BOM is current and accurate.

What goes into a BOM file?

Item # Quantity per board Manufacturer Part # Do Not Install Reference designators Vendor (optional) Vendor Part Number (optional) Value (optional) Size/ Footprint (optional) Part description/ specs (optional, but recommended) Manufacturer (optional)
1 2 T520L337M2R5ATE025 C12,C15 Digi-Key 399-5134-1-ND 330uF C6032 CAP TANT 330UF 2.5V 20% SMD Kemet
2 2 T520L337M2R5ATE025 DNI C16,C17 Digi-Key 399-5134-1-ND 330uF C6032 CAP TANT 330UF 2.5V 20% SMD Kemet
3 2 RMCF0805FT2K40 R19,R24 Digi-Key 541-2.40KCCT-ND RES SMD 2.4K OHM 1% 1/8W 0805 Vishay Dale
4 5 C3225X7R1E106M DNI C65,C66,C67,C68,C119 Mouser 810-C3225X7R1E106M 10uF C1210 (3225 metric) CAP CER 10UF 25V X7R 20% SMD 1210 TDK

An example of a BOM

Although BOM templates may vary between manufacturers, the fundamental information they contain remains consistent across the board.

The Excel sheet consist of the following information:

  • Quantity per board
  • Manufacturer part number (MPN)
  • Reference Designators
  • DNI/DNP
  • Vendor (optional)
  • Vendor part number (optional)
  • Value (optional)
  • Size/footprint
  • Part description/specs
  • Manufacturer (optional)