In general, PCB stack-up design mainly follows two rules: 1. Each trace layer must have an adjacent reference layer (power or ground layer); 2. Maintain a minimum distance between the adjacent main power layer and the ground layer to provide a large coupling capacitance; The following is an example to explain the stack-up from two-layer board to eight-layer board: I. Stack-up of single-sided PCB boards and double-sided PCB boards For two-layer boards, the problem of lamination is no longer due to the small number of layers. Controlling EMI radiation is mainly considered from wiring and layout. The electromagnetic compatibility problem of single-layer board and double-layer board is more and more prominent. The main reason for this phenomenon is that the area of the signal loop is too large, which not only generates strong electromagnetic radiation, but also makes the circuit sensitive to external interference. The easiest way to improve the electromagnetic compatibility