High-speed PCB signal routing rules TOP9 and 12 PCB wiring skills

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High-speed PCB signal routing rules TOP9 and 12 PCB wiring skills [Copy link]

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With the decrease of signal rise time and the increase of signal frequency, the EMI problem of electronic products has attracted more and more attention from electronic engineers.

The success of high-speed PCB design has attracted more and more attention for its contribution to EMI. Almost 60% of EMI problems can be controlled and solved by high-speed PCB.

Rule 1 High-speed signal routing shielding rule

In high-speed PCB design, the routing of key high-speed signal lines such as clocks needs to be shielded. If there is no shielding or only part of it is shielded, it will cause EMI leakage. It is recommended to punch holes for grounding every 1000mil for shielded lines.

[color=rgb(25, 25, Rule 2: Closed-loop rule for high-speed signal routing As the density of PCB boards increases, many PCB LAYOUT engineers are prone to making mistakes during routing, that is, high-speed signal networks such as clock signals generate a closed loop when routing on multi-layer PCBs. Such a closed loop will produce a loop antenna, increasing the radiation intensity of EMI.

Rule 3 Open-loop rules for high-speed signal routing

Rule 2 mentions that the closed loop of high-speed signals will cause EMI radiation, but the open loop will also cause EMI radiation. When the high-speed signal network such as the clock signal is routed on a multi-layer PCB, once an open loop is generated, a linear antenna will be generated, increasing the radiation intensity of EMI.

Rule 4 Characteristic impedance continuity rule of high-speed signals

For high-speed signals, the continuity of characteristic impedance must be ensured when switching between layers, otherwise EMI radiation will increase. In other words, the width of the wiring on the same layer must be continuous, and the impedance of the wiring on different layers must be continuous.

Rule 5: Routing direction rules for high-speed PCB design

The routing between two adjacent layers must follow the principle of vertical routing, otherwise it will cause crosstalk between lines and increase EMI radiation. In short, the adjacent wiring layers follow the horizontal and vertical wiring directions, and vertical wiring can suppress crosstalk between lines.

Rule 6 Topological structure rules in high-speed PCB design

In high-speed PCB design, the control of the characteristic impedance of the circuit board and the design of the topology under multiple load conditions directly determine the success or failure of the product. The figure shows a daisy chain topology, which is generally used in the case of a few MHz. It is recommended to use a star-shaped symmetrical structure at the back end in high-speed PCB design.

Rule 7 Resonance rule of trace length

[color=rgb(25, 25,Check whether the length of the signal line and the frequency of the signal constitute resonance, that is, when the wiring length is an integer multiple of 1/4 of the signal wavelength, the wiring will resonate, and the resonance will radiate electromagnetic waves and cause interference.

Rule eight return path rule

All high-speed signals must have a good return path. Try to minimize the return path of high-speed signals such as clocks. Otherwise, the radiation will be greatly increased, and the size of the radiation is proportional to the area surrounded by the signal path and the return path.

Rule 9 Rules for placing decoupling capacitors for devices

[color=rgb(25, 25, The placement of the decoupling capacitor is very important. An unreasonable placement will not achieve the decoupling effect. The placement principle of the decoupling capacitor is: close to the power pin, and the area surrounded by the power line and ground line of the capacitor is the smallest. Detailed Explanation of the Wiring Rules for Multi-layer High-speed PCBs PCB boards are divided into many layers, and the wiring of more than four layers is more complicated than ordinary single-layer and double-layer wiring. This requires us to master some skills. What are the specific skills? I will introduce them to you below, hoping to be of some help to engineers. 1. When connecting more than one point, try to let the line pass through each point in turn to facilitate testing, and keep the line as short as possible. 2. Try not to put wires between them, especially between and around the pins of integrated circuits. 3. Try not to parallel the lines on the same layer to avoid forming actual capacitance. 4. Try to use straight lines or 45-degree fold lines to avoid electromagnetic radiation. 25)]5. The wires and power lines should be at least 10-15 mils (for logic circuits);

6. Connect the multiple ground lines together to increase the grounding area. Try to keep the lines as neat as possible;7. Make sure the components are evenly arranged for installation, plug-in and welding operations. The text should be placed in the current character layer, with a reasonable position and direction to avoid being blocked for easy production;8. Consider the structure when arranging components. The positive and negative poles of SMD components should be marked on the package and at the end to avoid space conflicts;9. The front printed circuit board can be wired with 4-5mil, but usually with 6mil line width, 8mil line spacing and 12/20mil pad. The wiring should consider the influence of injection current, etc.; 10. Place components together as much as possible, and avoid placing components near LCD such as zebra strips too close; 11. Apply green oil (set to negative one); 12. Do not place pads or gaps under the base, and make sure the size of PAD and VIL is reasonable; The above 12 tips are applicable to most PCB wiring. Of course, sometimes special problems still need special analysis. After all, there is an old saying that "it is better to have no books than to believe in them completely".25)]All high-speed signals must have a good return path. Try to minimize the return path of high-speed signals such as clocks. Otherwise, the radiation will be greatly increased, and the size of the radiation is proportional to the area surrounded by the signal path and the return path.

Rule Nine Device Decoupling Capacitor Placement Rules

The placement of the decoupling capacitor is very important. An unreasonable placement will not achieve the decoupling effect at all. The placement principle of the decoupling capacitor is: close to the power pin, and the area surrounded by the power trace and ground wire of the capacitor is the smallest.

Detailed explanation of the wiring rules of multi-layer high-speed circuit boards

[color=rgb(25, 25, PCB board is divided into many layers, and the wiring of more than four layers is more complicated than that of ordinary single-layer and double-layer. This requires us to master some skills. What are the specific skills? The following is an introduction to you, hoping to be helpful to engineers.

1. When connecting more than one point, try to let the line pass through each point in turn to facilitate testing, and keep the line as short as possible;

2. Try not to put wires between them, especially between and around the pins of integrated circuits;

3. Try not to parallel the lines between the same layers to avoid forming actual capacitance;

4. Try to make the line a straight line or a 45-degree fold line to avoid electromagnetic radiation;

5. The wire and power line should be at least 10-15mil (for logic circuit);

6. Try to connect the multiple ground lines together to increase the ground area. Try to keep the lines as neat as possible;7. Make sure the components are evenly arranged for installation, plug-in and welding operations. The text should be placed in the current character layer, with a reasonable position and direction to avoid being blocked for easy production;8. Consider the structure when arranging components. The positive and negative poles of SMD components should be marked on the package and at the end to avoid space conflicts;9. The front printed circuit board can be wired with 4-5mil, but usually with 6mil line width, 8mil line spacing and 12/20mil pad. The wiring should consider the influence of injection current, etc.; 10. Place components together as much as possible, and avoid placing components near LCD such as zebra strips too close; 11. Apply green oil (set to negative one); 12. Do not place pads or gaps under the base, and make sure the size of PAD and VIL is reasonable; The above 12 tips are applicable to most PCB wiring. Of course, sometimes special problems still need special analysis. After all, there is an old saying that "it is better to have no books than to believe in them completely".25)]All high-speed signals must have a good return path. Try to minimize the return path of high-speed signals such as clocks. Otherwise, the radiation will be greatly increased, and the size of the radiation is proportional to the area surrounded by the signal path and the return path.