A bill of materials, or product structure – often referred to simply as BOM or associated list – is essentially a meticulous blueprint that enumerates all the raw materials, sub-assemblies, intermediate assemblies, sub-components, parts, and the exact quantities of each required to bring an end product to life.

For example, consider the manufacturing of a sophisticated bicycle. The raw materials could include high-quality aluminum for the frame, durable rubber for the tires, and tough steel for the gears. Sub-assemblies might consist of prefabricated brake systems or assembled seat posts. Intermediate assemblies could involve partially constructed chain mechanisms or half-built handlebar assemblies. Sub-components could encompass precision-engineered bearings or advanced suspension elements, while the parts could comprise minute screws, nuts, and washers.

In the dynamic world of electronics, the BOM acts as a precise inventory of the components gracing the printed wiring board or printed circuit board. It's more than just a list; it's a strategic roadmap detailing everything from minuscule resistors and capacitors to complex microprocessors and cutting-edge integrated circuits. Once the circuit design reaches its completion, this BOM list transforms into the guiding star for the PCB layout engineer and component engineer, directing them precisely in procuring the necessary components for the design to become a reality.

In electronics, the BOM represents the list of components used on the printed wiring board or printed circuit board. Once the design of the circuit is completed, the BOM list is passed on to the PCB layout engineer as well as component engineer who will procure the components required for the design.

For PCB assembly, you can find a BOM template to download on right side. The following BOM is a simple one for us to use.

1. Item: To calculate how many kind of material using for this product.  This list must be filled.

2. Ref.: Indicating components’ corresponding location on PCB.  This list must be filled.

3. MPN: Components’ Manufacturing Part Number like ID.  This list must be filled.

4. Digikey PN/Mouser PN/Links: Components’ special ID on Digikey/Mouser or other websites.

5. Quantity: The quantity of each kind of component for this boards. This list must be filled.

6. Others: you could add the component's value, package, alternative MPN, remarks etc.