Practical PCB design layout rules

The routing direction of adjacent planes is orthogonal to the structure
Avoid running different signal lines in the same direction on adjacent layers to reduce unnecessary crosstalk between layers; when it is difficult to avoid this situation due to board structure limitations (such as some backplanes), especially when the signal rate is high, It should be considered to isolate each wiring layer with a ground plane, and isolate each signal line with a ground signal line.

Small discrete components should be routed symmetrically
The leads of SMT pads with relatively dense spacing should be connected from the outside of the pads, and direct connection in the middle of the pads is not allowed.

cycle minimum rule
The ring area formed by the signal line and its loop should be as small as possible. The smaller the ring area, the less external radiation and the smaller the interference from the outside world.

STUB does not appear

The same network wiring width is consistent
The wiring width of the same network should be consistent, the change of the line width will cause the uneven characteristic impedance of the line, and reflection will occur when the transmission speed is high. Under certain conditions, such as connector lead-out wires and similar structures of BGA package lead-out wires, the change in line width may not be avoided due to too small spacing, and the effective length of the inconsistent part in the middle should be minimized.

Prevent signal lines from forming self-loops between different layers
Such problems are prone to occur in multi-layer board design, and self-loop will cause radiation interference.

Avoid sharp and right angles
Acute angles and right angles should be avoided in PCB design, resulting in unnecessary radiation, and the performance of PCB production process is not good.

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