**Wiring**
**Features:**
1. The placement orientation of components determines the direction of PCB wiring.
2. The wiring directions of adjacent layers differ. The surface layer of the two-panel board and the wiring of the soldering layer are oriented at 90° to each other.
3. The wiring direction of a rectangular PCB is vertical, and horizontal routing can easily lead to congestion or even make routing impossible.
4. Always try to ensure sufficient wiring space. If this is not feasible, use specialized components for routing and avoid placing vias beneath components. This is because, in the event of a circuit failure, it becomes difficult to visually inspect the condition of the via beneath a component, such as whether it has shorted with other traces or component pins.
**Analog and Digital Circuit Separation**
Both the analog and digital sections of the circuit should be kept at least 5mm apart, including their respective wiring, to prevent signal interference. When using a symbol to represent the ground line in the schematic, the PCB designer should analyze the circuit and allocate a designated area. The power and ground lines should be designed first. For two-layer and four-layer PCBs, the wiring structure differs significantly. In the case of multi-layer boards, power and ground planes are typically placed in the inner layers, with primary focus on fine-tuning the layout of the signal traces. For beginners, it is recommended to learn from the design of four-layer boards. Proper routing of power and ground lines has a significant impact on electrical performance and noise immunity, so it should be handled with care.
**Example: Two-layer PCB**
1. **The power line and the ground line are designed on the same layer; this configuration results in the worst performance.**
2. **The ground line is placed on the surface layer, while the power line is on the soldering layer, which is a common design choice.**
3. **In this design, the ground line is on the surface layer, and the power line is on the soldering layer, routed using copper foil. This provides better noise immunity. However, due to the inherent limitations of CAD design tools, PCB design can be more time-consuming than simple routing. Special attention should be given to ensuring the minimum trace width to prevent disconnections or blockages.**
4. **To put it simply: the power and ground lines are analogous to the aorta and veins in the human body, or more simply, like water pipes. A wider trace width allows more current to flow and facilitates faster heat dissipation. Conversely, narrower traces increase resistance under the same voltage, limiting current flow and slowing heat dissipation.**
5. **For the power and ground lines, a large copper foil routing method is typically employed.**
6. **Considerations for routing the power and ground lines on a two-layer PCB:**
Normally, the power line is routed on the soldering layer, and the ground line is routed on the surface layer. Wide-area copper foil is used for routing, and capacitors are often placed between the power and ground lines to mitigate interference. In general, this approach works well. However, if electromagnetic interference (EMI) is a concern, problems can arise. For instance, at frequencies above 8 MHz, issues may occur, and at frequencies above 25 MHz, instability becomes more pronounced. In such cases, it’s necessary to surround critical components with ground copper foil and add additional ground copper on the soldering layer.
7. **Key considerations for PCB design:**
**Routing of the crystal oscillator:**
To minimize interference, it’s best to surround components with ground copper foil as much as possible. Additionally, ground copper foil can be laid beneath the soldering layer around the crystal oscillator, with vias connecting the surface and soldering layers to enhance the anti-interference capability.
8. **Use of thermal pads:**
When using large copper areas for power and ground traces, it is advisable to incorporate heat-resistant pads. If a component pad is directly connected to a large copper area, heat dissipation during soldering can be rapid, which may prevent the solder from reaching the necessary temperature, leading to poor or incomplete solder joints.
9. **Thermal resistance pads:**
These pads help manage heat dissipation when connecting large copper areas to component pads.
10. **Introduction to PCB layout and design, power supply for analog circuits:**
The output section should be placed close to the power supply, while the high-sensitivity input section should be located some distance away from the output to avoid interference.
11. **Schematic of the analog circuit and separation of the digital and analog power supplies:**
**DC power supply:** When the power is sourced externally, it should first pass through an electrolytic capacitor before being supplied to the internal circuit. A typical wiring configuration is as follows:
In a two-layer PCB, the power is routed via point B rather than point A to reach the internal circuit. In a multi-layer PCB, the power is brought to an inner layer after passing through point B.
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**Features:**
1. The placement orientation of components determines the direction of PCB wiring.
2. The wiring directions of adjacent layers differ. The surface layer of the two-panel board and the wiring of the soldering layer are oriented at 90° to each other.
3. The wiring direction of a rectangular PCB is vertical, and horizontal routing can easily lead to congestion or even make routing impossible.
4. Always try to ensure sufficient wiring space. If this is not feasible, use specialized components for routing and avoid placing vias beneath components. This is because, in the event of a circuit failure, it becomes difficult to visually inspect the condition of the via beneath a component, such as whether it has shorted with other traces or component pins.
**Analog and Digital Circuit Separation**
Both the analog and digital sections of the circuit should be kept at least 5mm apart, including their respective wiring, to prevent signal interference. When using a symbol to represent the ground line in the schematic, the PCB designer should analyze the circuit and allocate a designated area. The power and ground lines should be designed first. For two-layer and four-layer PCBs, the wiring structure differs significantly. In the case of multi-layer boards, power and ground planes are typically placed in the inner layers, with primary focus on fine-tuning the layout of the signal traces. For beginners, it is recommended to learn from the design of four-layer boards. Proper routing of power and ground lines has a significant impact on electrical performance and noise immunity, so it should be handled with care.
**Example: Two-layer PCB**
1. **The power line and the ground line are designed on the same layer; this configuration results in the worst performance.**
2. **The ground line is placed on the surface layer, while the power line is on the soldering layer, which is a common design choice.**
3. **In this design, the ground line is on the surface layer, and the power line is on the soldering layer, routed using copper foil. This provides better noise immunity. However, due to the inherent limitations of CAD design tools, PCB design can be more time-consuming than simple routing. Special attention should be given to ensuring the minimum trace width to prevent disconnections or blockages.**
4. **To put it simply: the power and ground lines are analogous to the aorta and veins in the human body, or more simply, like water pipes. A wider trace width allows more current to flow and facilitates faster heat dissipation. Conversely, narrower traces increase resistance under the same voltage, limiting current flow and slowing heat dissipation.**
5. **For the power and ground lines, a large copper foil routing method is typically employed.**
6. **Considerations for routing the power and ground lines on a two-layer PCB:**
Normally, the power line is routed on the soldering layer, and the ground line is routed on the surface layer. Wide-area copper foil is used for routing, and capacitors are often placed between the power and ground lines to mitigate interference. In general, this approach works well. However, if electromagnetic interference (EMI) is a concern, problems can arise. For instance, at frequencies above 8 MHz, issues may occur, and at frequencies above 25 MHz, instability becomes more pronounced. In such cases, it’s necessary to surround critical components with ground copper foil and add additional ground copper on the soldering layer.
7. **Key considerations for PCB design:**
**Routing of the crystal oscillator:**
To minimize interference, it’s best to surround components with ground copper foil as much as possible. Additionally, ground copper foil can be laid beneath the soldering layer around the crystal oscillator, with vias connecting the surface and soldering layers to enhance the anti-interference capability.
8. **Use of thermal pads:**
When using large copper areas for power and ground traces, it is advisable to incorporate heat-resistant pads. If a component pad is directly connected to a large copper area, heat dissipation during soldering can be rapid, which may prevent the solder from reaching the necessary temperature, leading to poor or incomplete solder joints.
9. **Thermal resistance pads:**
These pads help manage heat dissipation when connecting large copper areas to component pads.
10. **Introduction to PCB layout and design, power supply for analog circuits:**
The output section should be placed close to the power supply, while the high-sensitivity input section should be located some distance away from the output to avoid interference.
11. **Schematic of the analog circuit and separation of the digital and analog power supplies:**
**DC power supply:** When the power is sourced externally, it should first pass through an electrolytic capacitor before being supplied to the internal circuit. A typical wiring configuration is as follows:
In a two-layer PCB, the power is routed via point B rather than point A to reach the internal circuit. In a multi-layer PCB, the power is brought to an inner layer after passing through point B.
If you have any PCB manufacturing needs, please do not hesitate to contact me.Contact me
