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Hope Everyone is doing well.

I got confused in the grounding of PCB. I checked many open hardware boards I noticed they don't flood GND plane in the top side to connect SMD components( all components on top ) which is appeared to me the best way to minimize the number of vias instead they use vias for each pad connected to GND PLANE IN THE bottom layer and they run only signal/power traces on the top.

Can anyone explain this to me please

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2 Answers 2

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A ground plane in the top layer via is ok but it’s likely to be fragmented, especially if the board density is high. If you have a ground plane on an internal layer then you’re only ever one via away from a low-impedance ground. In contrast, if your fill has lots of necks and fingers then it won’t work as effectively.

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    \$\begingroup\$ Further to @Frog ‘s comment, if you do use a fill, you need to ensure it is ‘nailed’ to the groundplane by lots of vias otherwise you end up with a lot of antennas. In the case of a vcc fill, that the track inductance is sufficiently low that you don’t have resonant circuits. \$\endgroup\$
    – Kartman
    Commented Jan 3, 2021 at 0:45
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Using a thin dielectric layer (<=32 mil) will provide better stray shielding and lower controlled impedance , when using this size board with a gnd plane below.

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