What should I do if the EMC test for CE certification fails?

 Radiation is one of the test items of CE-EMC's, and to obtain a CE certificate, all items must meet the requirements.

Many enterprises in the application for CE certification, often stuck in the radiation here.

Sometimes do CE certification, do the EMC test is not passed, is not issued to the certificate, what should I do, Xiaobian summed up the content!

There are many reasons for excessive EMC radiation, such as poor interface filter, low structural screen efficiency, and defective cable design, which may lead to excessive radiation data.

But the root cause of radiation is actually in the design of PCB, from the EMC aspect to focus on PCB, mainly focusing on the following aspects:

1. From the perspective of reducing radiation interference, multi-layer boards should be used as much as possible, with the inner layers serving as power supply layers and ground layers respectively, to reduce the impedance of power supply lines, suppress public impedance noise, form a uniform ground for signal lines, increase the distributed capacitance of signal lines and ground, and inhibit their ability to radiate into space.

2. The power line, ground wire and printing board should maintain low impedance to the high frequency signals.

In the case of high frequency, the power cord, ground wire or printed board wiring will become a small antenna to receive and transmit harassment.

The method to reduce this harassment in addition to the filter capacitor, more attention is to reduce the high frequency impedance of the power cord, ground wire and other printed board wiring itself.

Therefore, the lines of the various inhibition plates should be short and thick, and the lines should be uniform.

3. The power line, ground line and printed circuit wire on the printed board should be properly arranged, as short and straight as possible to reduce the loop area formed between the signal line and the return line.

4. The layout of circuit elements and signaling pathways must minimize the mutual coupling of useless signals.

In different design stages of PCB:

For example, in the component layout stage, we should pay attention to:

1. Whether the filtering, protection and isolation of the interface signal are placed near the interface connector, first protection and then filtering; whether the power supply module, filter and power protection device are placed near the entrance of the power supply to ensure the shortest power input line, the input and output of the power supply are separated, and the lines do not cross each other;

2. Whether the crystal, crystal vibration, relay, switching power supply and other strong radiation devices or sensitive devices are far away from the single plate handle and connector;

3. Whether the filter capacitor is placed close to the power supply pin of the IC, and the position and quantity are appropriate;

4. Whether the clock circuit is close to the load, and the load is balanced;

5. Whether the input and output of the interface filter device do not cross the split area; except for optical coupling, magnetic beads, isolation transformer, A / D, D / A, etc.