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8 Rules about Common Wiring in PCB Design

1. In order to meet the requirements of the production process capability, the line width of the conventional PCB sheet is ≥4mil (0.1016mm) (3.5mil, that is, 0.0889mm, can be used in special cases).


2. PCB sheet traces should not be traced at any angle, which will greatly challenge the manufacturer's production capacity and production quality, and cause many problems when etching copper wires. Therefore, Hunan Speeda Technology recommends you to use 45° or 135° traces.


3. The same network is not suitable for 90° right-angle or acute-angle wiring. This is generally a situation that is required to be avoided as much as possible in the PCB sheet layout. It has almost become one of the standards for measuring the quality of wiring. Right-angle wiring will change the line width of the transmission line, causing discontinuity in impedance, signal reflection, and EMI at the tip that affects the line.


4. Adopt a reasonable wiring method. The pad connection adopts a fan-out method symmetric about the long axis, which can effectively reduce the bad rotation after the CHIP component is mounted. If the fan-out line of the pad is also symmetrical about the short axis, it can also reduce the drift of CHIP components after mounting.


5. Adjacent pads are in the same network and cannot be directly connected. You need to connect the pads before connecting. The straight chain is easy to cause continuous welding during manual welding.


6. The connector management cable needs to be pulled out from the center of the pad and then walked out. No other angles should appear to avoid tearing the cable when the connector is plugged in.


7. Differential wiring. Compared with ordinary single-ended signal routing, the most obvious advantage of differential signal is that it has strong anti-interference ability, which can effectively suppress EMI and accurate timing positioning. For PCB board design engineers, the most concern is how to ensure that these advantages of differential wiring can be fully utilized in actual wiring. Perhaps anyone who has been in touch with layout will understand the general requirement of differential wiring, which is "equal length and equal spacing". The equal length is to ensure that the two differential signals maintain opposite polarities at all times and reduce the common mode component; the equal spacing is mainly to ensure that the differential impedance of the two is consistent and reduce reflection. The most important rule in the design of PCB differential traces is to match the line length. Other rules can be based on it, and the design can be handled flexibly according to the actual application.


8. Serpentine line. Snake line is a type of wiring method, which is often used in Layout. Its main purpose is to match the timing. The designer must first have this understanding: the serpentine line will destroy the signal quality, change the transmission delay, and avoid using it when wiring. However, in actual design, in order to ensure that the signal has sufficient hold time, or to reduce the time offset between the same group of signals, it is often necessary to deliberately wire.


As a professional Chinese PCB manufacturer, Hunan Speeda Technology will provide you with the most professional PCB sheet layout design. Welcome to contact us!

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