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Plane clearance rule

Tom Yunghans , 12-13-2021, 09:35 AM
Hi Robert,

I have been listening to some Eric Bogatin material lately (including your videos with him, thank you for that!). Eric has an entire recorded 2 day seminar on-line right now for free to AD users (for 90 days). In one of those sessions he was talking about signal distortion due to vias, and mentioned that the clearance around the vias on the plane layers can have an effect on the signal distortion. I went and looked at your iMX6 design and saw that you only have a 0.1mm (4mil) plane clearance around your vias on the plane layers. It looks to me that this is almost impossible to achieve from a manufacturing perspective. Looking at some low-cost board manufacturers they recommend that the copper clearance around the via hole on inner layers be on the order of 10mils. Even the higher end shops want this to be no less than 7-8 mils. If this is true, I would imagine that the fabrication house would just have modified your design and made the clearances bigger. Do you think that is what they did? Why did you use such a small number (0.1mm) for this clearance in your design rules?
qdrives , 12-13-2021, 06:04 PM
You can have 0.1mm clearance, but it is:
1) Going to cost you more.
2) Requires thin copper (ie. 12um or 18um).
Below screenshots taken from the online calculator of Eurocircuits ( https://www.eurocircuits.com/ ).

robertferanec , 12-17-2021, 07:46 AM
The via pads are removed from the layers where they are not used (connected), so in reality there is bigger clearance.
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