The PCB circuit board is a support component of components and devices in electronic products.Even schematic diagram is correct, but uncorrected PCB layout design will also effect the reliability of electronic products. In the design of printed circuit boards, attention should be paid to the correct method, to comply with the general principles of PCB design, and should meet the requirements of anti-interference design.
PCB circuit board layout design should follow the principles:
Consider the dimension of the PCB. When the dimension of the PCB is too large, the printed line is long, the impedance is increased, the noise resistance capacity is reduced, and the cost is increased; when PCB dimension is too small, heat dissipation is not good, and the adjacent lines are easily interfered. After determining the dimension of printed circuit board, the location of the special component is determined. Finally, according to the functional unit of the circuit, arrange all the components of the circuit board.
The following principles shall be observed when determining the location of a particular component:
- Shorten the connection between high frequency components as much as possible, and try to reduce their distribution parameters and electromagnetic interference. Vulnerable components should not be too close to each other, and input and output components should be kept as far away as possible.
- Some components or wires may have higher potential difference, should increase the distance between them, avoid discharge lead to unexpected short circuit. The components with high voltage shall be arranged as far as possible where the hand will not touched when debugging.
- Components weighing more than 15g shall be fixed with brackets and welded. Those large, heavy, and more heat components should not be installed on the printed board, but should be installed in the chassis of the whole machine chassis, and should consider the problem of heat dissipation. The heat sensitive element shall be away from the heating element.
- For potentiometers, adjustable inductors, coils, variable capacitors, micro switches and other adjustable components, should be consider the overall structure of the machine. If the machine is inside adjustment, the components places should be easy to adjust. If the machine is outside adjustment,its position should be adaptable to the knob in the box panel.
- Should keep the position for PCB tooling hole and fixed bracket.
The circuit components of the PCB layout, to meet the requirements of anti-interference design:
- Arrange the location of each functional circuit unit according to the circuit flow, so that the layout facilitates the flow of signals and keeps the signal in the same direction as possible.
- The core components of each functional circuit as the center, around it to layout. Components should be arranged evenly, neatly and compactly on the PCB. Minimize and shorten the lead and connection between components.
- In high frequency operation of the circuit, we should consider the distribution parameters between components. The general circuit should make the components arranged in parallel as much as possible. In this way, not only beautiful, but also easy to install welding, easy to mass production.
- located on the edge of the circuit board components, the distance is not less than 2mm from the edge to the circuit board. The best shape of the circuit board is rectangle. Long, wide, double, 3:2 or 4:3. The mechanical strength of the circuit board shall be considered when the circuit board dimension is larger than 200 * 150mm.
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