Perfect BOM Blog BannerThe perfect BOM is important for correct price calculation and seamless component sourcing

The Bill of Material (BOM) is the list that contains all electronic parts required to assemble a PCB. Based on the BOM list, the components are purchased and picked for the assembly of the PCB. To ensure that the transfer from design to production runs smoothly and without errors it is important that the BOM data file contains the necessary information, below are our recommendations for what the minimum and perfect BOM data file should contain.

The BOM data file format

A BOM file format is ideally an Excel or csv file. Other text-readable formats are also acceptable (e.g. .txt files).

  • The Excel or csv files must only contain one sheet and no additional formatting.
  • A text-readable file should be formatted correctly so the separate columns can be distinguished (e.g. by a single tab or a semicolon). It should not contain any additional formatting or general text describing what the file contains etc.

The format mostly used by our customers is the Excel file, because the columns are clearly separated. The first row of the data should contain the column headings clearly identifying what data is contained in the column as in the image below:

BOM with First Row Column Titles

  • Generating Gerber X3 or ODB++ from a CAD system will also include a BOM file based on the information created and stored in the CAD system.
  • In many cases the data stored in the CAD system is insufficient to enable sourcing of the required parts or even for performing DFM checks. Therefore, we will ignore this information and require a separate BOM file as described below.

What should the BOM data file contain?

Minimum BOM data

The minimum information a BOM data file must contain is:

  • Manufacturer part number (MPN) or generic part number (GPN)
  • The reference designators as a comma (,) separated list (e.g. R1,R3, R7….)

If this information is correct for each individual part then they can be sourced. However, this is not what we would define as a Perfect BOM.

The Minimum BOM

Example of BOM file with minimum required information

The Perfect BOM data

The Perfect BOM data file should contain the following information for each individual part:

  • Manufacturer part number (MPN) or generic part number (GPN)
  • The reference designator
  • Manufacturer
  • Quantity
  • Placed (YES/NO)

Including the additional parameters listed above can ensure the correct part is identified and the component is sourced correctly.

Optional parameters

Below are optional parameters that can help to identify individual parts:

  • Supplier name
  • Supplier part number

Below are some examples of BOM data files.


Example of a BOM File in Excel Format


Example of a BOM File in Tab Delimited Format


Example of a BOM File in Comma Delimited Format

What about Generic Components

Generic components are defined by their electrical parameters and it makes sense to define standard passive and electromechanical parts in the BOM by their electrical parameters and/or their GPN designation rather than by the manufacturer part number (MPN).

For example, many resistors, capacitors and pin headers can be produced by many different manufacturers with the same electrical/mechanical characteristics. Eurocircuits offers a wide range of generic parts, many of which are offered for free. Using generic parts provides our purchasing department maximum flexibility when sourcing these parts , they also reduce set-up time for assembly and storage costs.

See also:

In order for generic parts to be identified automatically, the correct notation is required. For more information please consult our guide on Understanding generic part numbers.

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