Background Theory > Design Units

In PCB (Printed Circuit Board) design, various units of measurement are used to specify dimensions, distances, and other physical parameters. The choice of units depends on the design requirements, the region or country where the design is being created, and the preferences of the designer or design team. The most common units of measurement used in PCB design are:

Inches (in)

Inches are a widely used unit of measurement in PCB design, especially in regions like the United States.

Millimeters (mm)

Millimeters are commonly used in PCB design, particularly in regions that follow the metric system, such as Europe and many parts of Asia.

Mils (thousandths of an inch)

Mils are commonly used for specifying very small distances, especially for trace widths and clearances in high-density PCB designs. One mil is equal to one-thousandth of an inch (0.001 inches).

Micrometers (µm)

Micrometers, also known as microns, are used for extremely fine measurements in PCB manufacturing, such as specifying the thickness of copper layers or the width of very narrow traces.

Designers and PCB manufacturers must be consistent in using units throughout the design process to avoid errors and ensure accurate fabrication of the PCB. Many Electronic Design Automation (EDA) software tools allow designers to set the preferred unit of measurement and automatically convert values when switching between units.

For example, a typical PCB design software might have options to choose units, such as inches or millimeters, as well as convert values between them seamlessly.

Designers should also follow industry standards and guidelines when specifying measurements to ensure that the PCB meets the required specifications and performs reliably in its intended application.