Anatomy of a PCB Design > Parts > Footprints (Land Patterns)

Footprint Part Values refer to the labels that represent the specific electrical or mechanical characteristics of a component on a PCB, such as resistance, capacitance, or other properties. These values are usually displayed alongside the Footprint Part Reference (e.g., R1 or C3) to provide additional information about the component.

Key Purposes of Footprint Part Values

Component Specification

The part value gives the precise specification of a component. For example:

•R1 with a value of 10kΩ indicates a 10 kilo-ohm resistor.

•C3 with a value of 0.1µF indicates a 0.1 microfarad capacitor.

•L2 with a value of 100µH indicates a 100 microhenry inductor.

Assembly and Placement

During assembly, the value helps identify the exact type of component to be placed at each reference location on the PCB. This helps in differentiating between components with similar footprints but different electrical properties.

Troubleshooting and Testing

The part value allows engineers and technicians to verify that the correct components were used in the design. It’s especially helpful during troubleshooting, testing, and validation of the PCB to ensure that all values match the intended design.

Documentation and BOM Integration

Part values are used in conjunction with reference designators in the Bill of Materials (BOM) to define each component's exact characteristics. This helps in procurement and ensures that the correct parts are ordered.

Examples of Footprint Part Values:

•Resistors: The value might be 1kΩ, 4.7Ω, or 220kΩ.

•Capacitors: The value might be 10nF, 0.1µF, or 47pF.

•Inductors: The value might be 100µH, 2mH, or 10nH.

•Diodes and Transistors: The value might represent the part number or type, such as 1N4148 or 2N2222.

Footprint part values are often included on the silkscreen layer of the PCB for easy identification and verification during the design, assembly, and testing phases.