Definition

A ground plane is a continuous copper layer connected to system ground, serving as current return path, voltage reference, and electromagnetic shield. Ground planes are essential for controlled impedance (providing the reference for microstrip and stripline), signal return currents (which flow beneath their traces), and EMI containment. Plane splits and voids can cause signal integrity problems by disrupting return current flow. Good practice places ground planes adjacent to signal layers and avoids routing signals over plane gaps.