Best practices for using ground pours on 4-layer PCBs with internal planes

[timothy.phillips]

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Should empty spaces on a 4-layer PCB be filled with ground?

For a 4-layer PCB with the following stack-up: Layer 1: High-speed signal Layer 2: Dedicated ground plane Layer 3: Power plane (5V, 3.3V, 1.8V) Layer 4: Normal-speed signal On single/double-layer boards, the usual practice is to fill all unused space with ground. Since a dedicated ground plane already exists on Layer 2, is it still beneficial to fill the empty spaces on Layer 1 and Layer 4 with a ground pour? Would this improve signal integrity, or could it introduce potential issues?