In PCB (printed circuit board) design, layout planning and routing design are key steps to ensure normal circuit function, stable performance and manufacturing feasibility. A well-designed PCB can not only guarantee electrical performance, but also reduce manufacturing costs, improve signal integrity and anti-interference ability. Here are some common layout planning and design tips:

1. Reasonable component layout
  Proximity of important components: The layout of power supplies and ground cables should be as close as possible to important components (such as processors and power components) in the power/ground area to reduce the impact of power noise.
      Power decoupling capacitor layout: The power decoupling capacitor should be as close as possible to the high-frequency circuit, such as near the chip power pin. This can effectively filter out high-frequency noise and ensure stable power supply.
      Short signal line: high-speed signal lines should be as short and direct as possible to avoid long paths and unnecessary bending to reduce signal reflection and interference.
      High power and sensitive circuit separation: large power components (such as power modules, power amplifiers, etc.) and high-precision analog circuits or high-speed digital circuits should be separated to avoid interference.
      Arrange a reasonable ground plane: the ground wire should be designed as a continuous surface to avoid the formation of multiple ground wire regions and reduce the interference of grounding noise and current.
  
2. Signal cable wiring skills
  Direction of the signal line: try to keep the straight line of the signal line and avoid sharp turns. Bending between lines can affect signal quality, especially for high frequency signal lines. Bending at a 45 degree Angle is better than bending at a 90 degree right Angle.
      Signal line spacing: Maintain proper spacing between signal lines, especially for high-speed signals, to avoid signal crosstalk. For high frequency or differential signal pairs, the signal line spacing needs to be optimized based on the frequency and characteristics of the signal.
      Impedance matching: For high-speed signal lines, impedance control is required. The impedance can be controlled by adjusting the width of the signal line and the thickness of the dielectric layer of the PCB. Common impedance values are 50Ω (single-ended signal) and 100Ω (differential signal).
      Differential signal line design: For differential signal lines, ensure that the length of the two lines is consistent, try to maintain its parallel layout, avoid too many corners, and maintain good coupling.

3. Design of power supply and ground wire
  Power cabling: Power cables need to be thick enough to minimize voltage drop. Avoid passing through small power cables for high current paths. For multiple supply voltages, separate power layers are used.
      Ground wiring: The design of ground ground is very important, and a large area of ground ground should be used to reduce noise and current reflux impedance. The ground layer and the power layer usually work together for good power and ground management.
      Multi-layer PCB design: For more complex circuits, multi-layer PCB is usually used, and the power layer and the ground layer are used as the inner layer to reduce power noise and ground potential difference.
  
4. Through holes and interlayer connections

  Reduce the number of holes: Minimize the use of holes, especially for high-speed signal lines. Overhole can cause signal delay, reflection and loss, reducing signal integrity.
      Hole optimization: In the case of the use of holes, ensure that the size of the hole is appropriate, and try to avoid laying holes on the high-frequency signal path when wiring. For high frequency circuits, blind and buried holes can be used to optimize the layout.
  
5. Anti-interference design
  Shielding and isolation: Use ground or power cables to shield signal lines, especially for high-frequency or noise-sensitive signals.
      Reasonable layout of the ground: the ground wiring should avoid the formation of a loop as far as possible to reduce the reflux noise of the ground current. Use a single ground plane to avoid the formation of multiple ground areas.
      Filter design: Use filter components (such as inductors, capacitors, etc.) in appropriate places to suppress noise signals.
  
6. Thermal design and heat dissipation

  Heat source component layout: High-power components (such as power ics, power amplifiers, etc.) should be avoided near heat-sensitive components (such as high-frequency transistors, sensors, etc.). At the same time, sufficient heat dissipation space should be reserved to avoid overheating affecting the performance and life of components.
      Heat dissipation design: The temperature of the PCB can be effectively reduced by increasing the copper foil area, using heat sinks or heat pipes and other heat dissipation solutions to improve thermal management capabilities.
  
7. Electrical performance optimization
  Timing requirements: When designing the PCB, it is necessary to consider the timing requirements of each signal to ensure the consistency of signal transmission delay and timing. The correctness of the signal is ensured by the length of the wiring and the propagation speed of the signal.
  Electromagnetic compatibility (EMC) design: In order to avoid electromagnetic interference, avoid the cross wiring of high-frequency signals and sensitive circuits, the appropriate use of electromagnetic shielding technology, optimize the layout of the ground wire, and reduce electromagnetic radiation.
  
8. Manufacturing and testing
  Manufacturability design: When designing PCB, it is necessary to consider the limitations in the actual manufacturing process, such as line width, through hole size, etc., to avoid designing circuits that are too complex or not suitable for production.
  Test point layout: Reasonable test points should be considered in the design, especially in the debugging stage, and interfaces should be reserved for later testing and fault diagnosis.
  
9. Multi-layer PCB design
  Reasonable planning level: In a multi-layer PCB, ensure that the signal layer, power layer and ground layer are reasonably located, usually the power and ground layer are arranged in the inner layer, and the signal layer is between the outer or inner layer.
     Interlayer signal transmission: by choosing reasonable interlayer wiring, the transmission delay and loss of the signal are made.

10. Use of EDA tools
  Layout optimization: Using modern EDA (Electronic Design Automation) tools such as Altium Designer, KiCad, OrCAD, etc., you can speed up the design process through automatic routing, layout optimization tools, and avoid human design errors.
  Design Rule Check (DRC) : The DRC function automatically checks electrical rules, size limits, and wiring specifications in the design, reducing errors in the manufacturing process.