pcb design - Why does a 4 layer PCB board significantly reduce the trace Width needed for a 50 ohm transmission line when compared to a 2 layer PCB board? - Electrical Engineering Stack Exchange
6-Layer HD PCB Stackup - PCB Specification - AISLER Creative Community
4-Layer HD PCB Stackup - PCB Specification - AISLER Creative Community
4 or 6 layer PCB stackup for EMI hardening overkill - General Electronics - The Contextual Electronics Forums