Question: Printed Circuit Boards Stack up: In a PC board technology with 6 mil line and space rules, find a stack up that will support six internal signal layers (three pairs of layers like the inner layers of Figure), each with 50-Q impedance. A spreadsheet is a very convenient way to do this; use the empirical formulas in [JohnGrah93], the plots in [RefDat93], or some other reference for calculating the impedance. What is the smallest practical via possible with your stack up?
