The basic rules of component layout
1. Layout according to circuit modules. Related circuits that realize the same function are called a module. The components in the circuit module should adopt the principle of nearby concentration, and the digital circuit and the analog circuit should be separated. 2. Avoid placing vias under the horizontally mounted resistors, inductors (plug-ins), electrolytic capacitors and other components to avoid short circuit between the vias and the component shell after wave soldering;
3. The distance between the outside of the components and the board edge is 5mm;
4. The power socket should be arranged around the printed board as much 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;
5. Metal shell components and metal parts (shielding boxes, etc.) should not touch other components, and should not be close to printed lines and pads. , The spacing should be greater than 2mm. Positioning holes, fastener installation holes, elliptical holes and other square holes in the board are larger than 3mm from the edge of the board;
6. Heating elements cannot be adjacent to wires and heat-sensitive elements; high-heating components must be evenly distributed;
7. Other components Arrangement: 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;
8. Board wiring The density should be proper. When the density difference is too large, it should be filled with meshed copper foil, the grid is greater than 8mil (or 0.2mm);
9. The distance between the outside of the mounting component pad and the outside of the adjacent interposing component is greater than 2mm ;
10. The patch is aligned on one side, the character direction is the same, and the packaging direction is the same;
11. There should be no through holes on the patch pad, so as to avoid the loss of solder paste and cause false soldering of the component. Important signal lines are not allowed to pass between the socket pins;
12. Polarized components should be kept consistent as far as possible on the same board as possible.
13. No components or devices shall be mounted within 1.27mm of non-mounting holes such as positioning holes, standard holes, and 3.5mm (for M2.5) and 4mm (for M3) of 3.5mm (for M2.5) and 4mm (for M3) shall not be allowed to mount components;
Component wiring rules
1. Draw the wiring area within 1mm from the edge of the PCB board, and within 1mm around the mounting hole, wiring is prohibited;
2. The power line should be as wide as possible, not 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 vias of the power backbone should not be less than 30mil; 4. Note that the power line and the ground line should be as radial as possible, and The signal line cannot have looped traces. 5. Double in-line: 60mil pad, 40mil aperture; 1/4W resistance: 51*55mil (0805 surface mount); 62mil pad and 42mil aperture when in-line; Infinite capacitance: 51* 55mil (0805 surface mount); when in-line, the pad is 50mil and the aperture is 28mil;