An 8 layer pcb stackup is to add 2 a lot of routing layers or to boost EMC performance by adding 2 a lot of planes. though we tend to see samples of each cases, i’d say that the bulk of eight layer board stack-ups area unit wont to improve EMC performance instead of add extra routing layers. the proportion increase in value of associate degree eight-layer board over a six-layer board is a smaller amount than the proportion increase in going from four to 6 layers, therefore creating it easier to justify the price increase for improved EMC performance. Therefore, most eight-layer boards (and all those that we’ll consider here) comprises four wiring layers and 4 planes.
An 8 layer pcb stackup provides United States of America, for the primary time, the chance to simply satisfy all of the 5 originally expressed objectives. though there area unit several stack-ups potential, we’ll solely discuss many of them that have established themselves by providing glorious EMC performance. As expressed higher than, eight layers is sometimes wont to improve the EMC performance of the board, to not increase the amount of routing layers.
The 8 layer pcb stackup provides ample routing house for multiple power islands. within the higher than typical pile up all communication layers have a minimum of one referencing power plane. the ability and ground layer within the center provides sensible inhume plane capacitance. If your system has several power islands and these power islands area unit next to the lowest layer, they are doing not have enough power to ground capacitance. conjointly the come path for the high speed signals in bottom layer (signal4) talk over with the ability plane that isn’t adjacent to a ground plane.