How To Design To Strengthen Anti-interference In PCB Design

Publish Time: January 05,2019

Even if the circuit schematic design is correct and the printed circuit board is not designed properly, it will adversely affect the reliability of electronic products. When designing a printed circuit board, you should pay attention to the correct method and observe the general principles of PCB design. Among them, the layout of the parts that meet the requirements of anti-interference design and the layout of the wires are very important. In order to design a PCB of good quality and low cost, the following general principles should be followed:

Layout:

First, we must consider the PCB size. When the PCB size is too large, the printed lines are long, the impedance increases, the anti-noise ability decreases, and the cost also increases; if the PCB size is too small, the heat dissipation is not good, and the adjacent lines are easily interfered. After determining the PCB size, then determine the location of the special components. Finally, according to the functional unit of the circuit, layout all components of the circuit.

Observe the following principles when determining the location of special components:

1. Shorten the connection between high-frequency components as much as possible, try to reduce their distribution 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 as far away as possible.

2. There may be a higher 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 in places that are not easily accessible by hand during commissioning.

3. Components weighing more than 15g should be fixed with brackets and then welded. 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 of the whole machine, and heat dissipation should be considered. The thermal element should be far away from the heating element.

4. 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 for convenient adjustment; if it is adjusted outside the machine, its position should be adjusted to the position of the adjustment knob on the chassis panel.

5. The position occupied by the positioning holes of the printed board and the fixing bracket should be reserved.

When layout the components of the circuit, it is necessary to meet the requirements of anti-interference design:

1. Arrange the position of each functional circuit unit according to the flow of the circuit, make the layout convenient for signal circulation, and keep the signal as consistent as possible.

2. Centering on the core component of each functional circuit, layout around it. The components should be evenly, neatly and compactly arranged on the PCB. Minimize and shorten the leads and connections between components.

3. For circuits operating at high frequencies, the distribution parameters between components should be considered. The general circuit should arrange the components in parallel as much as possible. In this way, it is not only beautiful, but also easy to install and weld, and easy to mass produce.

4. 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, and long and wide are 3: 2 or 4: 3. When the size of the circuit board is greater than 200×150mm, the mechanical strength of the circuit board should be considered.