Electronic Design - Principles to be followed in pcb design

The PCB circuit board is the support of the circuit components and devices in the electronic product. Even if the circuit schematic design is correct and the printed circuit board is not properly designed, it will adversely affect the reliability of electronic products. When designing a printed circuit board on a PCB, you should pay attention to adopting the correct method, abide by the common guidelines, and meet the requirements of anti-interference design.
1. Principles to be followed in PCB design:
First, consider the size of the PCB. When the PCB size is too large, the printed lines will be long and the impedance will increase, and the noise resistance will be reduced, and the cost will increase. If the PCB size is too small, the heat dissipation will not be good, and the adjacent lines will be easily disturbed. After confirming the size of the printed circuit board, confirm the location of the special components. Finally, according to the functional unit of the circuit, all the components of the circuit are planned.
When affirming the location of special components, the following guidelines must be adhered to:
1. Shorten the wiring between high-frequency components as much as possible, try to reduce their dispersion parameters and mutual electromagnetic interference. Components that are susceptible to interference should not be too close to each other, and input and output components should be kept as far away as possible.
2. There may be a relatively high potential difference between some components or wires, and the interval between them should be increased to avoid accidental short circuits caused by discharge. The components with high voltage should be placed as far as possible in the center that is not easy to touch during debugging.
3. Components weighing more than 15g should be fixed with brackets and then welded. Those components that are large, heavy, and generate a lot of heat should not be mounted on the printed circuit board, but should be mounted on the chassis bottom plate of the whole machine, and the heat dissipation problem should be considered. Thermal components should be far away from heating components.
4. Regarding the planning of adjustable components such as potentiometers, adjustable inductance coils, variable capacitors, micro switches, etc., the construction requirements of the whole machine should be considered. If it is in-machine conditioning, it should be placed in the center of the bento conditioning on the printed circuit board; if it is out-of-machine conditioning, its position should be consistent with the position of the conditioning knob on the chassis panel.
5. The position occupied by the positioning hole of the printed board and the fixed bracket should be reserved.

2. When designing PCB for circuit components, it is necessary to meet the requirements of anti-interference design:
1. Arrange the position of each functional circuit unit in accordance with the circuit flow, so that the planning is convenient for signal circulation, and the signal is as consistent as possible in different directions.
2. Take the central component of each functional circuit as the center, coil it to stop planning. Components should be evenly, uniformly, and compactly arranged on the PCB. Minimize and shorten the leads and connections between components.
3. For circuits operating at high frequencies, consider the dispersion parameters between components. Ordinary circuits should be arranged in parallel as far as possible. In this way, it is not only beautiful, but also easy to assemble and weld, and it is easy to produce in batches.
4. The components located on the edge of the circuit board are generally not less than 2mm away from the edge of the circuit board. The best shape of the circuit board is rectangular. The length and width pairs are 3:2 or 4:3. When the PCB circuit board surface size is larger than 200*150mm, the mechanical strength of the circuit board should be considered.
The PCB design layout is done according to the specification to reduce errors.