PCB is also known as a printed circuit board. It enables the connection of electronic components and the realization of functions, and is an important component in power circuit design. Today, this article will introduce the basic rules for PCB layout and wiring.

Basic rules for component layout：

1.The layout is carried out according to circuit modules. The circuits with the same function are called a module. The components in the circuit module should follow the principle of centralized placement as close as possible. Moreover, digital circuits and analog circuits should be separated.
2.Within 1.27mm around the positioning holes and standard holes (non-installation holes), no components, components or screws can be mounted. Within 3.5mm (for M2.5) and 4mm (for M3) around the installation holes, no components can be mounted.
3.Avoid placing vias under components such as resistors, inductors (pads), and electrolytic capacitors to prevent short circuits between the vias and the component shells after wave soldering.
4.The distance from the outer side of the components to the edge of the board should be 5mm.
5.The outer side of the solder pads for mounted components should be at least 2mm away from the outer side of adjacent surface-mounted components.
6.Metal-shell components and metal parts (such as shielding boxes) should not come into contact with other components and should not be close to the printed lines or solder pads. The distance between them should be greater than 2mm. The dimensions of the outer side of positioning holes, fastening holes, elliptical holes, and other square holes in the board should be greater than 3mm.
7.Heat-generating components should not be adjacent to wires and thermally sensitive components. High-heat devices should be evenly distributed.
8.The power sockets should be arranged around the printed circuit board, and the connection terminals of the power sockets and the corresponding busbars should be placed on the same side. Special attention should be paid to not placing the power sockets and other welding connectors between the connectors, to facilitate the welding of these sockets, connectors, and the design and wiring of the power cables. The spacing of the power sockets and welding connectors should be considered for the ease of plugging and unplugging of the power plugs;
9.Layout of other components: All IC components should be aligned on one side, and the polarity of components should have clear polarity markings. On the same printed circuit board, the polarity markings should not exceed two directions, and when there are two directions, they should be perpendicular to each other;
10.The wiring on the board surface should be appropriately dense and sparse. When the difference between density is too large, it should be filled with a mesh copper foil, with a grid larger than 8mil (or 0.2mm);
11.There should be no through holes on the surface mount pads to avoid solder paste leakage and cause component short circuits. Important signal lines should not pass through the socket pins;
12.Surface mount components should be aligned on one side, with consistent character directions and packaging directions;
13.Components with polarity should try to maintain the same polarity marking direction on the same board.

Basic wiring rules for components：

1. In the area within 1mm from the edge of the PCB board and within 1mm around the mounting holes, no wiring is allowed.

2. The power lines should be as wide as possible, no less than 18 mil; the width of the signal lines should be no less than 12 mil; the CPU input/output lines should be no less than 10 mil (or 8 mil); the line spacing should be no less than 10 mil.

3. The normal through-holes should be no less than 30 mil.

4. For dual-row surface-mounting: the pad is 60 mil, the hole diameter is 40 mil; for 1/4W resistors: 51*55 mil (0805 surface mount); for surface-mounting, the pad is 62 mil, the hole diameter is 42 mil; for non-polar capacitors: 51*55 mil (0805 surface mount); for surface-mounting, the pad is 50 mil, the hole diameter is 28 mil.

5. Pay attention that the power lines and ground lines should be as radiating as possible, and the signal lines should not have looped routing.