A ground plane is a solid copper layer or region tied to ground, giving every return current a low-impedance path directly beneath its signal trace. It keeps loop areas and EMI small, sets the reference for controlled impedance and acts as a shield and heat spreader. Splits, slots and crowded via antipads break the return path and cause signal integrity and emissions problems, so experienced designers guard plane integrity jealously.
Don't route that clock across the gap in the ground plane, the return current has to go all the way around it.
Also heard as
- GND plane
- ground layer
- plane
Related terms
Copper pour
Area of copper flooded in by the CAD tool around traces and pads, usually tied to ground or a power net.
Swiss cheese
Designer slang for a plane so riddled with via clearance holes that its copper is barely continuous.
Impedance control
Designing and building traces to a target impedance, such as 50 or 100 ohms, within a set tolerance.
Thermal relief
Spoked connection between a pad and a copper plane that limits heat flow so the joint can be soldered.