Multilayer PCB

A multilayer PCB board is used in situations where the density of connections needed is too high to be handled by two layers or where there are other reasons such as accurate control of line impedances or for earth screening. A multilayer PCB contains two reference planes and a signal via. The signal via allows a signal to flow through all the planes. A stitching via is connected to one of the planes next to the signal via and serves to reduce the area through which the signal passes through. This is very important as it may assist in reducing noise and cross talk.