20H principle in PCB design

The principle of 20H is to refer to the distance between the power supply layer relative to the formation of 20h, of course, is also to suppress the edge radiation effect. Electromagnetic interference is radiated outward on the edge of the board. The power layer is contracted so that the electric field is only conducted within the range of the ground layer. Effectively increases EMC. If the inner zone is 20h, 70% of the electric field can be limited to the ground edge; the contraced 100h can be limited to 98% electric field. Be The use of the 20h rules refers to ensuring that the edge of the power plane is 20 times equivalent to the two flat alumina distances than the edge edge of the power supply plane. This rule is often required to be used as a side shot emission technology (inhibiting edge radiation effect) from the side shot of the 0V / power supply planar structure. However, 20h rules provide significant results only under certain specific conditions. These specific conditions include: 1. The rise / fall time of current fluctuations in the power bus is less than 1 ns. 2. The power supply plane is on the internal level of the PCB and is a 0V plane with the upper and lower levels adjacent to it. These two 0V plane extending outwardly to at least 20 times they are each and the power supply plane. 3. On any frequency care, the power bus structure does not generate resonance. 4. The total or more of the PCB is at least 8 or more. Read more

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