1. Principle of 20H

If the printed circuit board has the ideal voltage and frequency, it will transmit electromagnetic into space; In order to reduce the probability of this situation, it is necessary to make the physical size of the signal line printed board of one floor and the physical size of the surrounding connection floor no larger than 20H. In multilayer printed circuit boards, 20H is usually equal to 3mm.
2. 2W principle

If there is no large distance between the printed wires, there will be electromagnetic interference, which will cause the circuit to lose its function. To prevent this from happening, you need to make all the lines larger than the width of the printed line, which is 2W.

Where W represents the width of printed circuit. The width is mainly determined by the line impedance. If it is wider, it will reduce the density of the wiring and increase the cost. If it is too narrow, it will interfere with the strength of the incoming signal.