Q1:How to arrange the layers to reduce EMI in PCB design?
First of all, we should consider from the system, PCB can not solve the problem. For EMI, I think it is mainly to provide the shortest reflux path, reduce the coupling area and suppress the differential mode interference. In addition, the tight coupling between the formation and the power supply layer is beneficial to the suppression of common-mode interference.
Q2:why to add copper in PCB design?
1.EMC will shield a large area of ground or power supply with copper, some special, such as PGND.
2. PCB process requirements. Generally in order to ensure electroplating effect, or lamination does not deform, for less wiring PCB layer copper.
3.Signal integrity requires that high-frequency digital signals be given a complete return path and that DC network routing be reduced. Of course, there are heat dissipation, special device installation requirements for copper and other reasons.