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For a single or double layered PCB board, usually I will cover all the empty spaces in the layout with Ground.

This is the 1st time I am designing a 4 layer PCB layout.
Layer 1: top signal (high speed)
Layer 2: Ground plane
Layer 3: Power plane (5v, 3.3v, 1.8v)
Layer 4: bottom signal (normal speed)

Since now I already got a dedicated Ground plane (Layer 2), my question is:
After finished all the routing, for Layer 1 & 4, should I still cover all the emptied space with Ground as well?

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  • \$\begingroup\$ It is not really needed, but doesn't hurt if done correctly, and might help. The thing to watch out for is if you flood ground on the top layer and it connects to a pad, you still need a via right there to make sure it is directly connected to the continuous plane below. \$\endgroup\$ – Evan May 8 '17 at 3:57
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It is a good practice to provide Ground Planes into the Top layer, and Bottom Layer. If you can't accommodate in the Top/Bottom layers, Make sure that you make a Top-Bottom Via which connects in the internal plane. This reduces the current return paths. Generally Via's are placed on the corner and wherever free space is available.

TI has great design guidelines. https://www.ti.com/lit/an/szza009/szza009.pdf

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Answer is yes, if you can. It won't harm anyway.

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You have a few obvious options with pour- any of the supply rails, including ground, or nothing. Since you have a bunch of supply rails a power pour would get complex.

I would say the ground pour is okay, but increase the clearance gap beyond what you normally use, to improve manufacturability, since the benefit is limited.

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