Note that, just because you put power on an internal layer, that doesn’t necessarily mean you are able to’t put power somewhere else. It is possible to nonetheless route power with your other signal layers as rails working with copper pour, or as thick traces. In mmWave and microwave equipment, https://double-sided-immersion-go84837.thenerdsblog.com/37051116/examine-this-report-on-8-layer-first-order-pcb