PCB layout rules and layout skills
As PCB size requirements become smaller and smaller, device density requirements become higher and higher, and PCB design becomes more difficult. How to achieve a high PCB layout rate and shorten the design time, here we talk about the design skills of PCB planning, layout and wiring.
In the layout design of PCB, the layout design of components is very important. It determines the neatness and beauty of the board and the length and quantity of printed wires. It also has a certain impact on the reliability of the whole machine.
Several principles that should be followed in the layout of PCB components are:
1. Under normal circumstances, all components should be arranged on the same surface of the circuit board. Only when the top components are too dense, can some devices with limited height and low heat generation, such as chip resistors, chip capacitors, Chip ICs are placed on the lower layer.
2. Under the premise of ensuring the electrical performance, the components should be placed on the grid and arranged in parallel or perpendicular to each other in order to be neat and beautiful. Under normal circumstances, the components are not allowed to overlap; the arrangement of the components should be compact, and the components should be arranged on the entire layout. The distribution is uniform and dense.
3. The minimum distance between adjacent pad patterns of different components on the circuit board should be above 1mm.
4. The distance from the edge of the circuit board is generally not less than 2mm. The best shape of the circuit board is rectangular, and the aspect ratio is 3:2 or 4:3. When the size of the circuit board is larger than 200MM by 150MM, consider what the circuit board can withstand Mechanical strength.
PCB layout skills
In the layout design of the PCB, the units of the circuit board should be analyzed, and the layout design should be based on the starting function. When laying out all the components of the circuit, the following principles should be met:
1. Arrange the position of each functional circuit unit according to the circuit flow, so that the layout is convenient for signal circulation, and the signal is kept in the same direction as possible.
2. Take the core components of each functional unit as the center and lay out around him. The components should be uniformly, integrally, and compactly arranged on the PCB to minimize and shorten the leads and connections between the components.
3. For circuits operating at high frequencies, the distribution parameters between components should be considered. In general circuits, components should be arranged in parallel as much as possible, which is not only beautiful, but also easy to install and easy to mass produce.
PCB layout inspection
1. Whether the size of the circuit board meets the processing size required by the drawing.
2. Whether the layout of the components is balanced, neatly arranged, and whether they have all been laid out.
3. Whether there are conflicts at all levels. Whether the components, the frame, and the level of private printing are reasonable.
4. Whether the commonly used components are convenient to use. Such as switches, plug-in board insertion equipment, components that must be replaced frequently, etc.
5. Whether the distance between thermal components and heating components is reasonable.
6. Whether the heat dissipation is good.
7. Whether the line interference problem needs to be considered.