pcb layout

PCB layout and wiring rules:

1. PCB layout and wiring is a very important step in power circuit design, which will directly affect the performance and reliability of the circuit. The following are the basic rules for PCB layout and wiring:

1. Layout rules:

(1) According to the circuit function and signal transmission characteristics, the circuit is divided into several modules and laid out in a suitable position to make the layout compact, beautiful, and convenient for maintenance and repair.

(2) Components related to the power supply should be as close to the power interface as possible to avoid voltage reduction and noise interference caused by long-distance transmission lines.

(3) Pay attention to the spacing between components to avoid mutual interference or short circuit.

2. Wiring rules:

(1) Use single-sided wiring as much as possible to avoid the cost and signal interference problems caused by double-sided wiring.

(2) When wiring, the line length should be minimized to avoid signal distortion and noise interference.

(3) Avoid cross wiring to avoid signal interference and crosstalk.

(4) For high-frequency signals, ground plane shielding and impedance matching should be used to avoid signal distortion and interference.

3. Ground wire rules:

(1) Separate wiring: Route the ground wire separately to avoid mixing with signal wires to avoid signal distortion and interference.

(2) Ground plane shielding: For high-frequency signals, ground plane shielding should be used to avoid signal interference and crosstalk.

(3) Reference plane: For analog circuits, reference planes should be used to reduce the impedance and noise interference of the ground wire.

PCB board layout and wiring need to follow some basic rules, such as compact layout, short signal transmission path, and avoidance of signal interference, to ensure circuit performance and reliability. At the same time, reasonable design needs to be carried out according to factors such as circuit characteristics and application environment.


2.Anti-interference ability

Anti-interference ability is a very important point in the design of electronic products with processors, especially in the case of complex electromagnetic environment and severe signal noise interference. The strength of anti-interference ability is directly related to the performance and stability of the product. The following are some methods to improve anti-interference ability:

(1). Layout optimization: For key components such as processors, clocks, memory, power supplies, etc. in the circuit, distribute them as far away from the noise source as possible, and shorten the distance between them as much as possible to reduce the impact of noise.
(2). Ground wire processing: Use double-layer or multi-layer PCB boards to separate the ground wire and power wire, and try to use ground planes to reduce the impact of ground impedance and mutual inductance on signal interference.
(3). Shielding processing: For high-frequency signals, shielding covers or metal shielding covers can be used to reduce the impact of external interference on the circuit.
(4). Device selection: Select devices with good anti-interference performance, such as processors, filters, amplifiers, etc. with anti-interference capabilities.
(5). Filtering processing: For input signals, filters and other methods can be used to reduce the impact of high-frequency noise.
(6). Grounding processing: The grounding of the processor should be processed separately and separated from the grounding of other devices to reduce interference from the ground loop.
(7). Test verification: After the design is completed, strict test verification is carried out, especially in a noisy environment, to ensure that the product’s anti-interference ability meets the requirements.
In summary, improving the anti-interference ability of electronic products with processors requires multiple aspects, including layout optimization, ground wire processing, shielding processing, device selection, filtering processing, grounding processing and test verification.


3. Electromagnetic interference is an important issue that needs to be considered

In the design of electronic systems, especially in the modern environment with dense electronic equipment. Some measures need to be taken to improve the system’s anti-electromagnetic interference ability.

The following are some common measures:

1. Shielding: Use shielding covers, shielding plates or metal shells to wrap the circuits and components inside the system in a metal shell to reduce the impact of external electromagnetic waves on the system and the interference of internal electromagnetic waves on the outside.
2. Filtering: Use appropriate filters to filter out high-frequency noise and electromagnetic wave signals in the circuit to reduce interference to the system. It is generally used on signal lines and power lines.
3. Ground wire processing: The ground wire in the circuit is the main transmission channel for interference signals, so attention needs to be paid to the processing of the ground wire. For example, when processing high-speed digital signals, single-point grounding is required to avoid ground loops; when processing analog signals, reference ground is required to reduce the impact on the signal.
4. Device selection: Selecting devices with good anti-interference performance in system design, especially key devices such as processors, clocks, and memories, can improve the system’s anti-interference ability.
5. Layout optimization: In system design, the circuit should be divided into several modules according to the circuit function and signal transmission characteristics, and laid out in a suitable position to make the layout compact, beautiful, and convenient for maintenance and repair.
6. System testing: After the design is completed, strict system testing is carried out, especially in a noisy environment, to ensure that the system’s anti-interference ability meets the requirements.
In summary, by taking measures such as shielding, filtering, ground wire processing, device selection, layout optimization and system testing, the system’s anti-electromagnetic interference ability can be improved and the system’s stability and reliability can be ensured.

What is pcb layout design

PCB layout design

Layout design is to place devices in the PCB board frame according to design requirements. Generate a network table in the schematic tool (Design→Create?Netlist), and then import the network table in the PCB software (Design→Import?Netlist). After the network table is successfully imported, it will exist in the software background.

Through the Placement operation, all devices can be called out, and there will be flying wire prompts between each pin. At this time, the device layout design can be performed. PCB layout design is the first important process in the entire PCB design process. The more complex the PCB board, the more directly the layout will affect the difficulty of later wiring.

Layout design relies on the circuit foundation and design experience of the circuit board designer, and it is a higher level requirement for the circuit board designer. Junior circuit board designers have little experience and are suitable for small module layout design or PCB layout design tasks with lower difficulty for the whole board.

PCB wiring design is the most labor-intensive process in the entire PCB design, which directly affects the performance of the PCB board. In the design process of PCB, there are generally three levels of wiring: first, wiring is smooth, which is the most basic entry requirement for PCB design; second, electrical performance is satisfied, which is the standard for measuring whether a PCB board is qualified. After the line is smooth, the wiring is carefully adjusted to achieve the best electrical performance; third, neat and beautiful.

Disorganized wiring, even if the electrical performance is passed, will bring great inconvenience to the later board optimization, testing and maintenance. The wiring requirements are uniform and cannot be crisscrossed without any rules.

Wiring optimization and silk screen placement “PCB design has no best, only better”, “PCB design is an art of defects”, this is mainly because PCB design needs to realize the design requirements of all aspects of hardware, and individual requirements may conflict with each other, and you can’t have your cake and eat it too.

For example: a PCB design project needs to be designed as a 6-layer board after evaluation by the circuit board designer, but the product hardware requires that it must be designed as a 4-layer board for cost considerations, so the signal shielding ground layer can only be sacrificed, which will increase the signal crosstalk between adjacent wiring layers and reduce the signal quality. The general design experience is: the time for optimizing wiring is twice the time for initial wiring. After the PCB wiring optimization is completed, post-processing is required. The first thing to deal with is the silk screen logo on the PCB board. When designing, the silk screen characters on the bottom layer need to be mirrored to avoid confusion with the top layer silk screen.

Network DRC inspection and structural inspection

Quality control is an important part of the PCB design process. General quality control methods include: design self-inspection, design mutual inspection, expert review meeting, special inspection, etc.

The schematic diagram and structural element diagram are the most basic design requirements. The network DRC inspection and structural inspection are to confirm that the PCB design meets the two input conditions of the schematic netlist and structural element diagram respectively.

Generally, circuit board designers will have their own accumulated design quality inspection checklist, some of which are derived from the company or department’s specifications, and the other part is derived from their own experience summary. Special inspections include the design Valor inspection and DFM inspection. These two parts focus on the back-end processing photolithography files of the PCB design output.

Conclusion.PCB board making? Before the PCB is officially processed and made, the circuit board designer needs to communicate with the PE of the PCB A board factory and answer the manufacturer’s confirmation questions about PCB board processing.

These include but are not limited to: selection of PCB board model, adjustment of line width and line spacing of circuit layers, adjustment of impedance control, adjustment of PCB stacking thickness, surface treatment processing technology, aperture tolerance control and delivery standards, etc.

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