Basic Rules of PCB Layout And Wiring

Basic Rules of Component Layout:
1. Layout according to the circuit module, the related circuits that realize the same function are called a module, the components in the circuit module should adopt the principle of nearest concentration, and the digital circuit and the analog circuit should be separated at the same time.

2. Components and devices shall not be mounted within 1.27mm around non-mounting holes such as positioning holes and standard holes, and components shall not be mounted within 3.5mm (for M2.5) and 4mm (for M3) around mounting holes such as screw.

3. Avoid placing vias below components such as horizontally mounted resistors, inductors (plug-ins), and electrolytic capacitors to avoid short circuits between the vias and the component shell after wave soldering.

4. The distance between the outside of the component and the edge of the board is 5mm.

5. The distance between the outside of the pad of the mounted component and the outside of the adjacent component is larger than 2mm.

6. Metal shell components and metal parts (shielding boxes, etc.) cannot touch other components, and cannot be close to printed lines and pads, and the spacing should be larger than 2mm. The size of the positioning holes, fastener installation holes, elliptical holes and other square holes in the plate is greater than 3mm from the edge of the plate.

7. The heating element cannot be close to the wire and the thermal element. The high-heating element should be evenly distributed.

8. The power socket should be arranged around the printed board as much as possible, and the bus bar terminals connected to the power socket should be arranged on the same side. Special care should be taken not to arrange power sockets and other soldered connectors between the connectors, in order to facilitate the soldering of these sockets and connectors and the design and tying of power cables. The arrangement spacing of power sockets and welding connectors should be considered to facilitate the insertion and removal of power plugs.

9. Arrangement of other components:

All IC components are unilaterally aligned, and the polarity of polar components is clearly marked. The polarity marking on the same PCB should not be more than two directions. When two directions appear, the two directions are perpendicular to each other.

10. The wiring on the board should be properly dense. When the difference in density is too large, it should be filled with mesh copper foil, and the mesh should be greater than 8mil (or 0.2mm).

11. There should be no through-holes on the patch pads, so as to avoid the loss of solder paste and cause the components to be soldered. Important signal lines are not allowed to pass between socket pins.

12. The patch is aligned on one side, the character direction is the same, and the packaging direction is the same.

13. For devices with polarity, the direction of polarity marking on the same board should be as consistent as possible.

Component Wiring Rules

1. In the area where the wiring area is ≤1mm from the edge of the PCB, and within 1mm around the mounting hole, wiring is prohibited.

2. The power line should be as wide as possible and should not be less than 18mil. The signal line width should not be less than 12mil. The CPU input and output lines should not be less than 10mil (or 8mil); the line spacing should not be less than 10mil.

3. The normal via hole is not less than 30mil.

4. Dual in-line: pad 60mil, aperture 40mil.

1/4W resistor: 51*55mil (0805 surface mount); when plugged directly, the pad is 62mil, and the aperture is 42mil.

Electrodeless capacitor: 51*55mil (0805 surface mount); when plugged directly, the pad is 50mil, and the aperture is 28mil.

5. Note that the power wire and the ground wire should be as radial as possible, and the signal wire should not be looped.