QDrives , 10-21-2024, 08:17 PM
There are many opinions that state that (A) is better than (B), but (C) is the best.Here are my opinions...If you have the ability to have 2 plane layers, it is best to do so.If power and are closely coupled (<= 0.2mm) you benefit from the plane capacitance. However, in a 4 layer board, either the outer layers have a close coupling, or the two inner ones. Never, both (except for thin <= 0.8mm boards)Do you need a power plane? If not, it is easier to have 2 Gnd planes.Crossing the signals from L1 to L4 requires a return via. For a power plane, you cannot couple with a via so you need a capacitor.A 'plane' layer can either be done using an actual plane layer, or by a signal layer and a big (Gnd) polygon pour on it.In you first stack-up (Sig-Gnd-Sig-Sig) you need a polygon pour on L3 to balance the copper that is on L2. Otherwise you board will bend.