MLB (Multi-Layer Boards) in order to increase the size of wiring, multilayer PCB used more single-or double-sided wiring boards. With a double, two single-sided as outer layer or two double-sided for inner, outer of two single-sided printed circuit boards through alternate positioning systems and insulation adhesive material and conductive pattern according to the design requirements for interconnected printed circuit boards became four-story, six-layer printed circuit board, also known as a multilayer printed circuit board. Layer does not mean the Board has several layers of independent wiring, in exceptional cases, adding an empty layer to control thickness, layers are usually even-numbered and contain two layers on the outside. Most of the motherboard is 4 to 8 layer structure, but technically theory can be done nearly 100 layer PCB Board. Large supercomputers mostly use quite a lot of motherboards, however, because the computer can already use many clusters instead of ordinary computer, Super multilayer PCB are not to be used. Because each layer of the PCB close bond, generally not so easy to see the actual number, but if you look at motherboard, can still be seen.