Experience in drawing high-frequency PCB

This article is reproduced on the Internet and is only for personal learning. The copyright belongs to the original work.

 

1. when you start to draw a PCB, please do not arrange your high-frequency cabling according to the common signal line. It is the right way to obtain the reference design from the chip manufacturer. the general chip data manual or related manual will have a high frequency part of the line reference.

2. High-frequency lines are very concerned about impedance matching and cabling. If possible, they can be exactly the same as the manufacturer's reference design. After all, the manufacturer's design has been fully calculated.

3. Do not place a crystal oscillator next to a high frequency cable. High Frequency affects high frequency. This is common sense. Try to stay a little farther away. Of course, other signal lines should not be too close to high frequency lines. High Frequency also has an impact on low frequency.

4. the high-frequency line is placed next to the hole, which effectively improves the signal quality. the high frequency itself should require a Screen Shield or screen layer, but the Board cannot provide Screen Shield when going offline. At this time, the PCB itself can only be used to create a screen layer, through the hole can be understood as the screen layer, the ground below is another layer. the above may not be blocked, because it should be exposed for debugging.

5. the whole high-frequency part can be tapped through multiple holes to increase the connectivity of the ground. copper overlay has a great influence on high-frequency cabling. If the cables are not properly laid, 100k-300k interference signals may occur on the power supply or other signal lines.

6. Do not separate the ground. at least ensure that the ground on one side is a complete ground. Ensure that all the ground on one side can be copper-coated, and do not separate the ground with a signal line.

7. the rationality of the layout directly affects the product's life, stability, EMC (Electromagnetic compatibility), etc, the overall layout of the circuit board, the accessibility of the wiring, and the manufacturing properties, mechanical structure, heat dissipation, EMI (electromagnetic interference), reliability, and signal integrity of the PCB Board must be comprehensively considered.

8. Automatic Layout is available in almost every piece of software, but as a PCB engineer, you should discard it and make the layout more effectively and reasonably.

9. Generally, components at a fixed position related to the mechanical size are placed first, special and large components are placed, and small components are finally placed. At the same time, it is necessary to take into account the requirements of wiring, the placement of high-frequency components should be as compact as possible, the wiring of the signal line can be as short as possible, so as to reduce the cross interference of the signal line.

10. Both schematic drawing and PCB Board copying design should be considered from the high-frequency working environment in which the PCB Board copying is ideal.

11. The original is generally not too close to the edge, it is best to leave a 3-5mm. The interface between power outlet, switch, PCB Board copying, indicator light, etc. are positioning plug-ins related to the mechanical size. Usually, the interface between the power supply and the PCB is placed at the PCB edge, and there must be 3mm ~ 5mm pitch; LEDs should be accurately placed as needed; switches and some fine-tuning components, such as adjustable inductance and adjustable resistance, should be placed near the PCB edge, to facilitate adjustment and connection; components that require frequent replacement must be placed in a relatively small position for easy replacement.