Component Layout Rules on PCB board
There are 13 basic rules about component layout on the PCB board.
- 1. Layout according to circuit modules, and related circuits that achieve the same function are called a module. In the circuit module, the components should adopt the principle of nearby concentration, and the digital circuit and the analog circuit should be separated;
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2. Do not mount components, devices, screws, etc. around non-mounting holes such as positioning holes, standard holes, etc. within 1.27mm, and do not mount components within 3.5mm (for M2.5) and 4mm (for M3) around mounting holes;
- 3. Avoid placing via holes under the horizontally mounted resistors, inductors (plug-ins), electrolytic capacitors and other components to avoid short-circuiting 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 mounting component pad and the outside of the adjacent interposing component is greater than 2mm;
- 6. Metal shell components and metal parts (shielding boxes, etc.) should not be in contact with other components, and they should not be close to printed lines and pads. The distance between them should be greater than 2mm. The size of the positioning holes, fastener installation holes, oval holes and other square holes in the board from the outside of the board edge is greater than 3mm;
7. Heating elements should not be in close proximity to wires and heat-sensitive elements; high-heating elements should be evenly distributed;
8. The power socket should be arranged around the printed board as far as possible, and the power socket and the bus bar terminal connected to it should be arranged on the same side. Particular care should be taken not to arrange power sockets and other welding connectors between the connectors to facilitate the welding of these sockets and connectors, as well as the design and tie-up of power cables. The arrangement spacing of power sockets and welding connectors should be considered to facilitate the plugging and unplugging of power plugs;
9. Arrangement of other components: All IC components are aligned on one side, and the polarity of polar components is clearly marked. The polarity of the same printed board cannot be marked in more than two directions. When two directions appear, the two directions are perpendicular to each other. ；
10. The wiring on the board surface should be dense and dense. When the difference in density is too large, it should be filled with mesh copper foil, and the grid should be greater than 8mil (or 0.2mm);
11. There should be no through holes on the SMD pads to avoid the loss of solder paste and cause false soldering of the components. Important signal lines are not allowed to pass between the socket pins;
- 12. The patch is aligned on one side, the character direction is the same, and the packaging direction is the same;
- 13. As far as possible, the polarized devices should be consistent with the polarity marking direction on the same board.
Component wiring rules
There are 5 basic rules about the component wiring on the PCB board.
- 1. Draw the wiring area within 1mm from the edge of the PCB board and within 1mm around the mounting hole, wiring is forbidden;
- 2. The power cord 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 is not less than 10mil;
- 3. The normal via is not less than 30mil;
- 4. Dual in-line: pad 60mil, aperture 40mil; 1/4W resistance: 51*55mil (0805 surface mount); when in-line, pad 62mil, aperture 42mil; electrodeless capacitor: 51*55mil (0805 surface mount); When in-line, the pad is 50mil and the aperture is 28mil;
- 5. Note that the power line and the ground line should be as radial as possible, and the signal line must not be looped.
