Copper is one of the most important elements in printed circuit boards (PCBs). Copper Weight or Copper Thickness in a Printed Circuit Board represents the thickness of 1 ounce of copper rolled out over an area of 1 square foot. For example, a PCB that has a copper weight of 1 oz will have a layer of copper that is 1.4 mils in thickness. Copper Weight is measured in ounces per square foot (oz/ft²).

Copper Weight  in oz vs Copper Thickness in Mils

Why is Copper Weight Important for Printed Circuit Boards?

The current carrying capacity of a PCB depends on the thickness of the copper trace. So PCB's with a higher Copper weight will be able to carry more current.