Design is crucial throughout the entire process of circuit board production. High-quality PCB boards require careful selection, ground wire design, electromagnetic compatibility design, decoupling capacitor configuration, printed circuit board size, device layout, and reliability design such as thermal design, all of which will be discussed in detail by the following editor.
Currently, printed circuit boards remain the primary assembly method for various electronic equipment and systems. It has been proven that even if the circuit schematic design is correct, improper PCB design can significantly impact the reliability of electronic equipment. For instance, if two thin parallel lines on the printed board are placed close together, it can lead to signal waveform delays and the formation of reflection noise at the transmission line’s end. As a result, it is essential to adopt the correct design approach when creating a printed circuit board.
A. Ground Wire Design
In electronic equipment, grounding is a critical technique for interference control. Properly combining grounding and shielding can address most interference issues. The ground structure of electronic equipment typically includes system ground, chassis ground (shielding ground), digital ground (logical ground), and analog ground. The following considerations are crucial in ground wire design:
1. Correct Selection of Single-Point and Multi-Point Grounding
In low-frequency circuits (signal frequency below 1MHz), the inductance between the wiring and the device has minimal impact, while the circulating current in the grounding circuit significantly influences interference. Therefore, single-point grounding is recommended. For signals above 10MHz, where ground wire impedance increases substantially, multiple points should be used for grounding to reduce impedance. For frequencies between 1 and 10MHz, if single-point grounding is chosen, ensure the ground wire length does not exceed 1/20th of the wavelength; otherwise, opt for multi-point grounding.
2. Separate Digital and Analog Circuits
It is important to separate high-speed logic circuits from linear circuits on the PCB and avoid mixing their ground wires. Connect them instead to the power supply terminal ground wire. Increase the grounding area of the linear circuit as much as possible.
3. Use Thicker Ground Wires
Thin ground wires can cause ground potential fluctuations with variations in current, resulting in unstable timing signal levels and degraded anti-noise performance. Therefore, ground wires should be as thick as possible to carry the necessary current. Ideally, ground wire width should exceed 3mm.
4. Form a Closed Loop for Ground Wires
In a printed circuit board with only digital circuits, creating a closed loop for the ground wire system significantly enhances anti-noise capabilities. When numerous integrated circuit components, especially high-power-consuming ones, are present on the PCB, a large potential difference may occur at the ground junction due to the limited thickness of the ground wire, reducing anti-noise performance. Forming a loop in the grounding structure decreases potential differences and improves the equipment’s anti-noise capabilities.
Currently, printed circuit boards remain the primary assembly method for various electronic equipment and systems. It has been proven that even if the circuit schematic design is correct, improper PCB design can significantly impact the reliability of electronic equipment. For instance, if two thin parallel lines on the printed board are placed close together, it can lead to signal waveform delays and the formation of reflection noise at the transmission line’s end. As a result, it is essential to adopt the correct design approach when creating a printed circuit board.
A. Ground Wire Design
In electronic equipment, grounding is a critical technique for interference control. Properly combining grounding and shielding can address most interference issues. The ground structure of electronic equipment typically includes system ground, chassis ground (shielding ground), digital ground (logical ground), and analog ground. The following considerations are crucial in ground wire design:
1. Correct Selection of Single-Point and Multi-Point Grounding
In low-frequency circuits (signal frequency below 1MHz), the inductance between the wiring and the device has minimal impact, while the circulating current in the grounding circuit significantly influences interference. Therefore, single-point grounding is recommended. For signals above 10MHz, where ground wire impedance increases substantially, multiple points should be used for grounding to reduce impedance. For frequencies between 1 and 10MHz, if single-point grounding is chosen, ensure the ground wire length does not exceed 1/20th of the wavelength; otherwise, opt for multi-point grounding.
2. Separate Digital and Analog Circuits
It is important to separate high-speed logic circuits from linear circuits on the PCB and avoid mixing their ground wires. Connect them instead to the power supply terminal ground wire. Increase the grounding area of the linear circuit as much as possible.
3. Use Thicker Ground Wires
Thin ground wires can cause ground potential fluctuations with variations in current, resulting in unstable timing signal levels and degraded anti-noise performance. Therefore, ground wires should be as thick as possible to carry the necessary current. Ideally, ground wire width should exceed 3mm.
4. Form a Closed Loop for Ground Wires
In a printed circuit board with only digital circuits, creating a closed loop for the ground wire system significantly enhances anti-noise capabilities. When numerous integrated circuit components, especially high-power-consuming ones, are present on the PCB, a large potential difference may occur at the ground junction due to the limited thickness of the ground wire, reducing anti-noise performance. Forming a loop in the grounding structure decreases potential differences and improves the equipment’s anti-noise capabilities.
