Ground Plane Overlap

Explanation of the Ground Plane Overlap PRC, verifying consistent ground coverage beneath impedance controlled signals to ensure signal integrity and minimize EMI.

Description

Ground Plane Overlap determines if the ground plane below a specified net traces overlaps at all relevant points.

Relevant points are defined outside a small margin provided in order to account for cutouts around the attached pins and vias.

Passing Criteria: This check passes if there is complete overlap of both sides of the differential pair with the ground plane on the layer below it at all locations except the last 2*clearance length endpoints of the trace paths.

Reporting Units: BOOLEAN

Examples

Passing Message:

Complete Ground Plane Overlap is True

Failing Message:

Complete Ground Plane Overlap is False

Physics Justification

Sufficient ground plane coverage below all traces in a net addresses the following:

• Signal Return Path The ground plane provides a low-impedance return path for current, which reduces electromagnetic interference (EMI) and enhances signal integrity.

• Controlled Impedance The space between the trace and the ground plane determines the trace's impedance. This must remain consistent for high-speed signals to prevent reflections and distortion.

• Noise Shielding The ground plane acts as a shield, minimizing external noise and preventing crosstalk—the interference between signals.