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Question related to 20H rule for a 4 layer PCB with the goal of passing CE Marking

oscargomezf , 03-11-2019, 03:11 AM
Hi everyone,

I am working on a low complexity design, but I have to pass EMC because I need to get the CE Marking. So far so good.

The design is very simple so with a 4 layer stackup is good enough. I would like to use the 20H rule, but due to the fact I am going to use a 4 layer stackup:

Between the VCC layer to GND layer I have 0.71mm so the 20H layer is 20x0.71 = 14.2 mm and this distance is too much.

Does anyone think it could be enough with only 1.5 mm?

Best regards.
robertferanec , 03-15-2019, 02:40 AM
You do not really have many options - I would just make it slightly smaller, same as you are suggesting. 4 layer PCB should not be so expensive to manufacture, in the worst case you would add more layers. I am quite sure, if your PCB would fail, it is not going to be because you did not follow 20H rules (there are many articles saying this rule even doesn't help, but I still keep doing it - I think it may help in some cases). If your PCB would fail EMC, it will be probably because there will be much bigger problem.

Lets stay positive Fingers crossed.
oscargomezf, 03-15-2019, 02:05 PM
Thank you for your help.
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