Due to the increase in packing density in the integrated circuit, which brings a highly concentrated interconnection, which requires the use of a multilayer circuit board. In the design of printed circuit boards, sometimes you will have some unforeseen design problems, such as noise, parasitic capacitance, interference, etc.
So when designing the printed circuit board, you must commit to making the length of the board of printed circuit. Point out as short as possible and avoid parallel circuits, etc.
Obviously, it is difficult to obtain a satisfactory solution of the single-sided PCB or even double-sided PCBs because the number of crossed circuits is limited. In the demand for massive interconnection and interdigitation, if the printed circuit board wishes to achieve satisfactory performance, it must extend to more than two layers, so that the multilayer PCB has appeared.
Multilayer PCBs have at least three conductive layers, two layers on the side of the surface, and the rest of the layers are synthesized within the isolation part. The electrical connection between each layer is usually made through the hole. Unless there are special instructions, both multilayer PCBs and double-sided PCBs are placed on printed circuit boards.
There are many PCB manufacturing companies with more than 10 years PCB manufacturing experience, offer single sided PCB, Double sided PCB and multilayer PCB.