PCB boards support circuit components and devices in electronic products by providing electrical connections between them. As electrical technology continues to rapidly advance, the density of PCBs is increasing. The quality of the PCB board design is crucial for its ability to resist interference. Therefore, when designing a PCB board, it is essential to follow general principles and meet anti-interference design requirements.
The general principle of PCB board design focuses on achieving optimal electronic circuit performance. This includes careful consideration of component layout and wire placement. By adhering to these principles, a high-quality PCB board can be designed efficiently and cost-effectively.
1. Layout First, consider the size of the PCB board. When the size of the PCB board is too large, the printed lines will be long, the impedance will increase, the anti-noise ability will decrease, and the cost will increase; if the size is too small, the heat dissipation will be poor, and the adjacent lines will have easily interfered. After determining the size of the PCB board, locate special components based on the functional unit of the circuit, and layout all the components of the circuit. Follow these guidelines when locating special components:
1) Minimize the connection between high-frequency components to reduce distribution parameters and mutual electromagnetic interference. Components sensitive to interference should not be placed close to each other, and input and output components should be kept separate.
2) Increase the distance between components or wires with high potential differences to avoid accidental short circuits. High voltage components should be placed in less accessible areas during debugging.
3) Components weighing more than 15g should be fixed with brackets before welding. Heavy components generating heat should be mounted on the chassis bottom plate for better heat dissipation. Keep thermal elements away from heating elements.
4) For adjustable components like potentiometers and switches, consider the structural requirements of the whole machine. Place them conveniently for adjustment. Position them inside the machine for internal adjustments or outside for external adjustments.
5) Reserve space for the positioning hole of printed pulleys and fixing brackets. When laying out all components, follow these principles:
– Arrange functional circuits based on circuit flow for efficient signal circulation.
– Center the layout around each functional circuit element. Keep components neat, evenly spaced, and compact to minimize lead lengths.
– Consider distribution parameters for high-frequency circuits. Align components in parallel whenever possible for a clean and easily manufacturable layout.
– Components at the board edge should be at least 2mm away. For rectangular boards, maintain an aspect ratio of 3:2 to 4:3, especially for boards larger than 200x150mm to ensure mechanical strength.
2. Wiring:
1) Avoid adjacent or parallel wires at input and output terminals. Use ground wire between wires to prevent feedback coupling.
2) Wire width is determined by adhesion strength with the base plate and current value. A wire width of 1.5mm can support up to 2A. Use wider lines for power and ground for better performance. Ensure proper spacing for insulation resistance and breakdown voltage, especially for digital circuits.
3) Use arc-shaped corners for printed conductors to avoid electrical performance issues in high-frequency circuits. Minimize large copper foil areas to prevent expansion and detachment during heating. For larger copper foil areas, use a grid structure for better stability.
3. The pad center hole should be slightly larger than the lead diameter to prevent virtual soldering. The pad outer diameter should be at least (d+1.2) mm for lead holes. For high-density digital circuits, consider a diameter of (d+1.0) mm for pads. Anti-interference measures are closely related to specific circuits.
3.1 Power line design:
– Increase power line width based on current to reduce loop resistance.
– Align power and ground lines with data transmission direction for improved anti-noise capabilities.
3.2 Ground line design:
– Separate digital and analog grounds. Ground low-frequency circuits at a single point if possible. Use a series-parallel connection for grounding if necessary.
– Employ thick ground wires to maintain stability and prevent ground potential changes.
– Form closed loops for improved anti-noise performance in high-frequency circuits.
3.3 Decoupling capacitor configuration:
– Install appropriate decoupling capacitors in key areas of the board.
– Connect an electrolytic capacitor across the power input and place ceramic capacitors near integrated circuit chips.
– Directly connect decoupling capacitors to devices with weak anti-noise capabilities and power fluctuations.
– Keep lead wires short, especially for high-frequency bypass capacitors, and avoid long lead wires for optimal performance.
The general principle of PCB board design focuses on achieving optimal electronic circuit performance. This includes careful consideration of component layout and wire placement. By adhering to these principles, a high-quality PCB board can be designed efficiently and cost-effectively.
1. Layout First, consider the size of the PCB board. When the size of the PCB board is too large, the printed lines will be long, the impedance will increase, the anti-noise ability will decrease, and the cost will increase; if the size is too small, the heat dissipation will be poor, and the adjacent lines will have easily interfered. After determining the size of the PCB board, locate special components based on the functional unit of the circuit, and layout all the components of the circuit. Follow these guidelines when locating special components:
1) Minimize the connection between high-frequency components to reduce distribution parameters and mutual electromagnetic interference. Components sensitive to interference should not be placed close to each other, and input and output components should be kept separate.
2) Increase the distance between components or wires with high potential differences to avoid accidental short circuits. High voltage components should be placed in less accessible areas during debugging.
3) Components weighing more than 15g should be fixed with brackets before welding. Heavy components generating heat should be mounted on the chassis bottom plate for better heat dissipation. Keep thermal elements away from heating elements.
4) For adjustable components like potentiometers and switches, consider the structural requirements of the whole machine. Place them conveniently for adjustment. Position them inside the machine for internal adjustments or outside for external adjustments.
5) Reserve space for the positioning hole of printed pulleys and fixing brackets. When laying out all components, follow these principles:
– Arrange functional circuits based on circuit flow for efficient signal circulation.
– Center the layout around each functional circuit element. Keep components neat, evenly spaced, and compact to minimize lead lengths.
– Consider distribution parameters for high-frequency circuits. Align components in parallel whenever possible for a clean and easily manufacturable layout.
– Components at the board edge should be at least 2mm away. For rectangular boards, maintain an aspect ratio of 3:2 to 4:3, especially for boards larger than 200x150mm to ensure mechanical strength.
2. Wiring:
1) Avoid adjacent or parallel wires at input and output terminals. Use ground wire between wires to prevent feedback coupling.
2) Wire width is determined by adhesion strength with the base plate and current value. A wire width of 1.5mm can support up to 2A. Use wider lines for power and ground for better performance. Ensure proper spacing for insulation resistance and breakdown voltage, especially for digital circuits.
3) Use arc-shaped corners for printed conductors to avoid electrical performance issues in high-frequency circuits. Minimize large copper foil areas to prevent expansion and detachment during heating. For larger copper foil areas, use a grid structure for better stability.
3. The pad center hole should be slightly larger than the lead diameter to prevent virtual soldering. The pad outer diameter should be at least (d+1.2) mm for lead holes. For high-density digital circuits, consider a diameter of (d+1.0) mm for pads. Anti-interference measures are closely related to specific circuits.
3.1 Power line design:
– Increase power line width based on current to reduce loop resistance.
– Align power and ground lines with data transmission direction for improved anti-noise capabilities.
3.2 Ground line design:
– Separate digital and analog grounds. Ground low-frequency circuits at a single point if possible. Use a series-parallel connection for grounding if necessary.
– Employ thick ground wires to maintain stability and prevent ground potential changes.
– Form closed loops for improved anti-noise performance in high-frequency circuits.
3.3 Decoupling capacitor configuration:
– Install appropriate decoupling capacitors in key areas of the board.
– Connect an electrolytic capacitor across the power input and place ceramic capacitors near integrated circuit chips.
– Directly connect decoupling capacitors to devices with weak anti-noise capabilities and power fluctuations.
– Keep lead wires short, especially for high-frequency bypass capacitors, and avoid long lead wires for optimal performance.
