PCB layout design should follow the following principles:

a) Reasonably arrange the position of the components and increase the density of the components as much as possible in order to reduce the length of the wire, control the crosstalk and reduce the size of the printed board;

b) Logic devices with signals entering and exiting the printed board should be placed as close to the connector as possible and arranged in the order of circuit connection relationship as much as possible;

c) Zoning layout. According to the logic level, signal conversion time, noise tolerance and logic interconnection of the components used, measures such as relative partitioning or strict separation of loops are adopted to control the crosstalk noise of the power supply, ground and signal;

d) Deploy evenly. The arrangement of the components on the entire board surface should be neat and orderly. The distribution of heating components and wiring density should be uniform;

e) Meet the heat dissipation requirements. For air cooling or adding heat sinks, an air duct or sufficient space for heat dissipation should be reserved; for liquid cooling, corresponding requirements should be met;

f) Thermal components should not be placed around high-power components, and a sufficient distance should be kept from other components;

g) When heavy components need to be installed, they should be arranged as close to the support point of the printed board as possible;

h) Should meet the requirements of component installation, maintenance and testing;

i) Many factors such as design and manufacturing costs should be considered comprehensively.

PCB wiring rules

1. Wiring area

The following factors should be considered when determining the wiring area:

a) The number of types of components to be installed and the wiring channels required to interconnect these components;

b) The distance between the conductive pattern (including the power layer and the ground layer) of the printed conductor wiring area that does not touch the printed wiring area during the outline processing should generally be no less than 1.25mm from the printed board frame;

c) The distance between the conductive pattern of the surface layer and the guide groove should not be less than 2.54mm. If the rail groove is used for grounding, the ground wire shall be used as the frame.

2. Wiring rules

The printed board wiring should generally follow the following rules:

a) The number of printed conductor wiring layers is determined according to needs. The wiring occupied channel ratio should generally be more than 50%;

b) According to process conditions and wiring density, reasonably select wire width and wire spacing, and strive for uniform wiring within the layer, and the wiring density of each layer is similar, if necessary, auxiliary non-functional connection pads or printed wires should be added to the lack of wiring areas;

c) Two adjacent layers of wires should be laid out perpendicular to each other and diagonally or bent to reduce parasitic capacitance;

d) The wiring of printed conductors should be as short as possible, especially for high-frequency signals and highly sensitive signal lines; for important signal lines such as clocks, delay wiring should be considered when necessary;

e) When multiple power sources (layers) or ground (layers) are arranged on the same layer, the separation distance should not be less than 1mm;

f) For large area conductive patterns larger than 5×5mm2, windows should be partially opened;

g) A thermal isolation design should be carried out between the large-area graphics of the power supply layer and the ground layer and their connection pads, as shown in Figure 10, so as not to affect the welding quality;

h) The special requirements of other circuits shall comply with relevant regulations.

3. Wiring sequence

In order to achieve the best wiring of the printed board, the wiring sequence should be determined according to the sensitivity of various signal lines to crosstalk and the requirements of wire transmission delay. The signal lines of priority wiring should be as short as possible to make their interconnecting lines as short as possible. Generally, the wiring should be in the following order:

a) Analog small signal line;

b) Signal lines and small signal lines that are particularly sensitive to crosstalk;

c) System clock signal line;

d) Signal lines with high requirements for wire transmission delay;

e) General signal line;

f) Static potential line or other auxiliary lines.