The design needs to set different points at different stages. In the layout stage, large grid points can be used for device layout.
For large devices such as ICs and non-positioning connectors, a grid point accuracy of 50~100mil can be used for layout, and for passive small devices such as resistors, capacitors and inductors, a 25mil grid point can be used for layout. The accuracy of the large grid points facilitates device alignment and layout aesthetics.
PCB layout rules:
1. Under normal circumstances, all components should be arranged on the same side 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 IC, etc. are placed on the lower layer.
2. On the premise of ensuring electrical performance, components should be placed on the grid and arranged in parallel or perpendicular to each other to be neat and beautiful. In general, components are not allowed to overlap. The arrangement of components should be compact, and components should be placed on the entire layout. The distribution is uniform and the density is consistent.
3. The minimum spacing between adjacent pad patterns of different components on the circuit board should be more than 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 a rectangle, and the aspect ratio is 3:2 or 4:3. When the surface size of the circuit board is greater than 200MM by 150MM, it should be considered that the circuit board can withstand Mechanical strength.
In the layout design of the PCB, the unit of the circuit board should be analyzed, and the layout design should be carried out according to the function. When laying out all the components of the circuit, the following principles should be followed:
1. Arrange the position of each functional circuit unit according to the circuit process, so that the layout is convenient for signal circulation, and the signal keeps the same direction as possible.
2. Centering on the core components of each functional unit, make layout around him. Components should be evenly, integrally and compactly arranged on the PCB to minimize and shorten the leads and connections between components.
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