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PCB layout skills
1. Layout the components in the board in advance
Layout of components in advance tests the PCB designer’s understanding and design ability of schematic diagrams. The shape and size of the board must be determined before layout, which is related to the cost of production and actual use in reality. After drawing the board shape, the main control chip is generally placed in the center of the board. Of course, this is not a mandatory requirement and needs to be determined according to the actual use. The external thimble should be placed on the edge of the board. The power supply is generally placed in an open area of the board to facilitate heat dissipation. The real-time memory chip is placed around the main chip for storage.
2. Choose a good grounding point
Many engineers and technicians have discussed the small grounding point, which shows its importance. Under normal circumstances, a common ground is required, such as: multiple ground wires of the forward amplifier should be combined and then connected to the main ground, etc.... In reality, it is difficult to achieve this completely due to various restrictions, but we should try our best to follow. This question is quite flexible in practice. Everyone has their own set of solutions. It is easy to understand if it can be explained for a specific circuit board.
3. PCB design settings
PCB design needs to set up different points in different stages, and large grid points can be used for device layout in the layout stage.
For large devices such as ICs and non-positioning connectors, a grid point accuracy of 50-100 mils can be used for layout, while for passive small components such as resistors, capacitors and inductors, a grid point of 25 mils can be used for layout. The accuracy of the large grid points is conducive to the alignment of the device and the beautiful layout.
In the PCB layout design, it is necessary to analyze the units of the circuit board, and carry out the layout design according to the function. When the circuit components are laid out, the following principles must 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 must 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.
4. PCB design wiring design
⑴The trace length should be as short as possible to minimize the lead inductance. In low-frequency circuits, because the ground currents of all circuits flow through a common ground impedance or ground plane, avoid multi-point grounding.
⑵The public ground wire should be arranged as far as possible on the edge of the printed circuit board. Keep as much copper foil as the ground wire on the circuit board to enhance the shielding ability.
⑶The double-layer board can use the ground plane, the purpose of the ground plane is to provide a low impedance ground wire.
⑷The grounding layer can be set in the multilayer printed circuit board, and the grounding layer is designed into a mesh. The spacing of the ground wire grid should not be too large, because one of the main functions of the ground wire is to provide a signal return path. If the grid spacing is too large, a larger signal loop area will be formed. Large loop areas can cause radiation and sensitivity issues. In addition, the signal return actually takes a path with a small loop area, and other ground wires do not work.
⑸ The ground plane can minimize the radiation loop.
POE circuit board designers with 20 years of experience will minimize the cost of customers in the PCB circuit layout process. Please trust our ability.