According to incomplete statistics, 70-80% of the production defects of electronic products are caused by design reasons. If people say that the board is scrapped, it may be a pot of research and development.

 

 

1. Novice Xiaobai's "burning board"

The short circuit was found as soon as the power was turned on, and the components were removed one by one to eliminate it. Finally, it was found that the PCB was short-circuited. Finally, I checked the PCB and found that the power vias accidentally hit the ground plane. (Here is a reminder, be sure to do an open and short circuit test before powering on, it should not be too exciting)

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2. How to deal with isolated islands (also called dead copper)

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What is the harm of dead copper?

Those who have studied antennas or communications should know that under high frequency conditions, the distributed capacitance of the wiring on the printed circuit board will play a role. When the length is greater than 1/20 of the corresponding wavelength of the noise frequency, an antenna effect will occur and the noise will pass The wiring emits outwards. If there is a poorly grounded copper pour in the PCB, the copper pour becomes a noise propagation tool.

 

So we can delete some small islands. However, copper coating can also increase the mechanical properties of the board, and it is not easy to bend and warp. It is more helpful to handle the islands well. For example, the islands can be well connected to GND through ground holes to form a shield and increase the flow capacity.

 

3. Improper control of spacing introduces noise or crosstalk

 

In the hardware design of complex high-speed systems, due to the sensitivity of the high-speed bus, when checking the PCB, in addition to checking the established impedance, the spacing must also be checked. Some boards have high density and are often easy to spacing. Something went wrong.

 

For example, at the feedback end of the power chip, because it is a high-frequency signal, this is a dirty signal. We don't want it to pollute high-speed signals, such as USB3.0 signals and HDMI signals. We want the high-speed signal line to reach the power feedback end. For example, the via distance can be greater than n mil. Assuming that this distance is not considered in the actual design, the packet loss problem and the screen blur problem may occur.

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The above design problems, experienced engineers will often avoid these risks, but they are often not considered for newcomers. Therefore, each company often has its own design specifications and check items to control PCB manufacturing problems.

 

 

However, different people may have different understandings of such norms, so there may still be mistakes. Therefore, the appropriate automation tools can help us quickly get these things done.

 

Luffy recommends a domestic free software that can be used to check these PCB problems. Luffy tested it and can directly import PCB files and analyze various errors. The red ones are problematic. Click to view. The problem can be located, which is equivalent to a "PCB antivirus software".

 

 

It’s only 90% of those who travel a hundred miles, and the schematic design is only 30% of the product research and development. Careful inspections must be done before boarding to ensure that the first version is successful, in order to occupy the market earlier and gain an advantage.