PCB News - PCB design and wiring principles and affect the performance of the PCB board

Wiring is the most important process in the entire PCB design. This will directly affect the performance of the PCB board. In the process of PCB design, there are generally three levels of wiring for wiring: First, the layout is the most basic requirement for PCB design. If the lines are not connected and there are flying lines everywhere, it will be a substandard board, and it can be said that you have not yet started. The second is the satisfaction of electrical performance. This is a measure of whether a printed circuit board is qualified. This is after the deployment, carefully adjust the wiring, so that it can achieve the best electrical performance. Then comes aesthetics. If your wiring is properly routed, there is nothing to affect the performance of the electrical appliance, but at first glance, it is messy, plus colorful and colorful, then no matter how good your electrical performance is, it is still a piece of rubbish in the eyes of others. This brings great inconvenience to testing and maintenance. The wiring should be neat and uniform, not crisscross and out of order. All of these must be achieved while ensuring the performance of electrical appliances and meeting other individual requirements, otherwise it will be the end of the day. The wiring is mainly carried out according to the following principles:

1. Wire the lines with strict requirements (such as high-frequency lines) in advance, and the edge lines of the input end and the output end should be avoided adjacent to parallel to avoid reflection interference. If necessary, ground wire should be added for isolation, and the wiring of two adjacent layers should be perpendicular to each other. Parasitic coupling is easy to occur in parallel.

2. The key line should be as short and thick as possible, and protective ground should be added on both sides.

3. Under normal circumstances, the power line and ground line should be wired first to ensure the electrical performance of the circuit board. Within the range allowed by conditions, try to widen the width of the power and ground lines, preferably the ground line is wider than the power line, their relationship is: ground line>power line>signal line, usually signal line width: 0.2 ~ 0.3mm, The smallest width can reach 0.05～0.07mm, and the power cord is generally 1.2～2.5mm. For the PCB of the digital circuit, a wide ground wire can be used to form a loop, that is, to form a ground net to use (the ground of the analog circuit cannot be used in this way)

4. Use 45-degree polyline wiring as much as possible, and 90o polyline should not be used to reduce the radiation of high-frequency signals; (highly demanding lines should also use double-curved lines)

5. Do not form a loop on any signal line. If it is unavoidable, the loop should be as small as possible; signal lines should have as few vias as possible;

6. The housing of the oscillator is grounded, and the clock line should be as short as possible, and it should not be drawn everywhere. Under the clock oscillation circuit, the area of the special high-speed logic circuit should be enlarged, and other signal lines should not be used to make the surrounding electric field approach zero;

7. When transmitting sensitive signals and noisy field band signals through flat cables, they should be led out in the way of "ground wire-signal-ground wire".

8. Key signals should be reserved for testing points to facilitate production and maintenance testing

9. After the schematic wiring is completed, the wiring should be optimized; at the same time, after the preliminary network inspection and DRC check are correct, the unwiring area is filled with ground wire, and a large area of copper layer is used as the ground wire. All places used are connected to the ground as a ground wire. Or it can be made into a multilayer board, and the power supply and ground wires occupy one layer each.

The above is the introduction of PCB design and wiring principles. Ipcb also provides PCB manufacturers and PCB manufacturing technology.