To achieve the best performance of electronic circuits, electronic component circuit boards are the support for circuit components and devices in electronic products. Even if the circuit schematic is designed correctly, the printed circuit board is not properly designed, which will have an adverse effect on the reliability of electronic products. When designing a printed circuit board, it is important to pay attention to the correct method, follow the general principles of PCB design, and meet the requirements of anti-interference design. The layout of components and the layout of wires are very important. In order to design a PCB board with good quality and low cost, the following general principles should be followed:
First of all, the size of the PCB multilayer circuit board should be considered. When the size of the pcb multilayer circuit board is too large, the printed lines will be long, the impedance will increase, the anti-noise ability will decrease, and the cost will increase too small, then the heat dissipation will not be good, and the adjacent lines will be easily disturbed. After determining the size of the pcb multilayer circuit board, determine the position of the special components. Finally, according to the functional unit of the circuit, all the components of the circuit are laid out.
The following principles should be followed when determining the location of special electronic components:
1. The position occupied by the positioning hole of the printed board and the fixing bracket should be reserved.
2. Shorten the connection between high-frequency components as much as possible, and try to reduce their distribution parameters and mutual electromagnetic interference. Components that are susceptible to interference cannot be too close to each other, and input and output components should be kept as far away as possible.
3. There may be a high potential difference between some components or wires, and the distance between them should be increased to avoid accidental short circuit caused by discharge. Components with high voltage should be placed as far as possible in places that are not easily accessible by hand during debugging.
4. 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 installed on the printed board, but should be installed on the chassis bottom plate of the whole machine, and the heat dissipation problem should be considered. Thermal components should be kept away from heating components.
5. For the layout of adjustable components such as potentiometers, adjustable inductance coils, variable capacitors, and micro switches, the structural requirements of the whole machine should be considered. If it is adjusted inside the machine, it should be placed on the printed board where it is convenient to adjust; if it is adjusted outside the machine, its position should be adapted to the position of the adjustment knob on the chassis panel.
When laying out the PCB multilayer circuit board for the electronic components of the circuit, it must meet the requirements of the anti-interference design:
1. Arrange the position of each functional circuit unit according to the flow of the circuit, so that the layout is convenient for signal circulation, and the direction of the signal is kept as consistent as possible.
2. For circuits operating at high frequencies, the distribution parameters between components must be considered. Generally, the circuit should arrange the components in parallel as much as possible. In this way, it is not only beautiful, but also easy to assemble and weld, and easy to mass produce.
3. Take the core components of each functional circuit as the center and make layout around it. Components should be evenly, neatly and compactly arranged on the PCB multilayer circuit board. Minimize and shorten the leads and connections between components.
4. The electronic 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 for a circuit board is a rectangle. The aspect ratio is 3:2 or 4:3. When the size of the circuit board is larger than 200×150mm, the mechanical strength of the circuit board should be considered.
