Properties of the printed circuit board

The resistance of copper foil tracks, determined by its width, thickness and length, must be small enough for the current the conductor will carry. It is recommended that the power and force paths be larger than the signal paths.

In a multi-layer board, an internal layer may be mostly solid copper to act as a ground plane for shielding and power return.

For microwave printed circuits, transmission lines can be laid out in a planar form, such as stripline or microstrip, with dimensions carefully controlled to ensure consistent impedance.

In RF and fast switching circuits, the inductance and capacitance of the printed circuit board conductors become significant, usually unwanted, circuit elements; rather, they can be used as part of the circuit design, as in distributed element filters, antennas, and fuses, avoiding the need for additional separate components.

High Density Interconnect (HDI) PCBs have traces and/or insulation less than 125 micrometers in width or diameter.