Electronic Design - Summary of pcb design experience

The overall idea of PCB design layout is to consider the overall beauty on the basis of meeting the requirements of the electrical and mechanical structure of the product. On a PCB board, the layout of the components must be balanced, dense and orderly.
1. The size of the printed board must be consistent with the size of the processing drawings, and meet the requirements of the PCB design and manufacturing process, and place the MARK point.
2. Are there any conflicts between the components in the two-dimensional and three-dimensional space in PCB design?
3. Can the PCB design components layout be dense and orderly and arranged uniformly? Can it all be finished?
4. Can the components that need to be changed frequently in PCB design be changed easily? Can the plug-in board be easily inserted into the device?
5. Is there a proper interval between the thermal element and the heating element?
6. Is it easy to adjust the adjustable components?
7. Is there a radiator in the center where heat dissipation is required? Is the air flow unobstructed?
8. Can the signal flow be smooth and the interconnection shortest?
9. Can plugs, sockets, etc. contradict the mechanical design?
10. The buzzer is far away from the cylindrical inductor to prevent the interference sound from being distorted.
11. Faster devices such as SRAM should be as close as possible to the CPU.
12. In the PCB design, the devices powered by the same power supply should be placed together as much as possible.

PCB design wiring:
1. PCB circuit board design and routing should have a reasonable direction: such as input/output, AC/DC, strong/weak signal, high frequency/low frequency, high voltage/low voltage, etc..., their direction should be linear (or separate ), must not merge with each other. The purpose is to avoid mutual interference. The best direction is to follow a straight line, but it is usually not easy to complete, to prevent circular routing. Regarding direct current, small signal, low voltage request can be lower. The edges of the input end and the output end should be prevented from being parallel adjacent to each other to avoid reflection interference. Ground wire isolation should be added when necessary, and the wiring of two adjacent layers should be perpendicular to each other. Parasitic coupling is likely to occur in parallel.
2. Choose a good grounding point: common ground is required under normal conditions, and the digital ground and the analog ground are connected at the power input capacitor.
3. Arrange power filter/decoupling capacitors reasonably: Arrange these capacitors as close as possible to these components, and they will be useless if they are too far away. The decoupling capacitor of the chip device is best placed on the belly of the device on the other side of the board. The power and ground must pass the capacitor first, and then enter the chip.
4. The lines are elegant: wide lines should never be thin if possible; high-voltage and high-frequency lines should be round and slippery, without sharp chamfers, and corners should not be at right angles. Generally, an angle of 135 degrees is used. The ground wire should be as wide as possible, and it is best to use a large area of copper, which can greatly improve the problem of grounding points. In the PCB design, the line holes should be reduced as much as possible, and the parallel line density should be reduced.
5. Widen the width of the power and ground wires as much as possible, preferably the ground wire is wider than the power wire, their relationship is: ground wire>power wire>signal wire.
6. With the co-location of analog circuits, many PCB designs are no longer a single functional circuit (digital or analog circuit), but are composed of a mixture of digital circuits and analog circuits. Therefore, when wiring, it is necessary to think about the mutual interference between them, especially the noise interference on the ground wire.
The frequency of the digital circuit is high, and the sensitivity of the analog circuit is strong. For the signal line, the high-frequency signal line should be as far away as possible from the sensitive analog circuit device. For the ground line, the whole PCB board only needs one node to the outside world. Therefore, it is necessary to stop dealing with the problem of digital and analog common ground inside the PCB, and the digital ground and the analog ground inside the board are actually separated, and they are not connected to each other, but at the interface where the PCB circuit board connects with the outside world (such as plugs). No). There is a short connection between the digital ground and the imitation ground.