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Why use ground fill on PCB?

colporteur

I'm looking for some insight into Ground Fill, extending the copper pour when manufacturing a PCB  to create a ground plane. I've just completed a PCB layout in Fritzing that uses an Arduino Mega. There is plenty of empty PCB real estate. I thought why not fill it.

I seem to recall doing some reading on Ground Fill. I have never used the technique before but have seen it used on PCB's. I found a number of benefits in my search but no downside. Methinks the PCB manufactures would want extra coins for this! I'm curious is there a use case where you would not use Ground Fill?

If Ground fill is used should it cover both sides of the PCB or limit it to one side?

I've used the Fritzing function and it appears to work. Looking for some experience to chime in.

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    The occasions where it might not be wanted could be where you need electrical clearances for (say) mains connections, and there are some circuits that may not like a ground plane too close or may want it with certain control over it, e.g. where the slight increase in capacitance between other signals and ground could cause an issue, and RF transmission lines. Some circuits fall into the category where no ground plane is needed, but there is no harm to add it.


    If you decide to have a ground plane, then if it's just on one side of a 2-layer board, then the board comes from the PCB factory slightly warped which can be annoying or might not matter.


    If it were me, then generally my approach when adding a ground plane for surface-mount component boards, is to put the ground plane on the underside, and have most traces on top (component) side (and maybe some short traces on underside if needed), and then fill the top component side empty areas with ground plane but with some clearance from components, no need for it to get super-close to components or traces, and then a few via holes for stitching top and bottom. The top layer copper pour then is mainly to help with preventing the warping.


    If I was doing a through-hole-only board and it had a ground plane, then I'd put the ground plane on the component side so that it's easy to access the other traces on the solder side. 


    If the warping doesn't matter then generally there is no need to have a plane on both sides for 2-layer boards, a single side of ground plane would then be OK. The top plane could be a different voltage if desired, e.g. use it as a 5V power plane, it's up to you.

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    The occasions where it might not be wanted could be where you need electrical clearances for (say) mains connections, and there are some circuits that may not like a ground plane too close or may want it with certain control over it, e.g. where the slight increase in capacitance between other signals and ground could cause an issue, and RF transmission lines. Some circuits fall into the category where no ground plane is needed, but there is no harm to add it.


    If you decide to have a ground plane, then if it's just on one side of a 2-layer board, then the board comes from the PCB factory slightly warped which can be annoying or might not matter.


    If it were me, then generally my approach when adding a ground plane for surface-mount component boards, is to put the ground plane on the underside, and have most traces on top (component) side (and maybe some short traces on underside if needed), and then fill the top component side empty areas with ground plane but with some clearance from components, no need for it to get super-close to components or traces, and then a few via holes for stitching top and bottom. The top layer copper pour then is mainly to help with preventing the warping.


    If I was doing a through-hole-only board and it had a ground plane, then I'd put the ground plane on the component side so that it's easy to access the other traces on the solder side. 


    If the warping doesn't matter then generally there is no need to have a plane on both sides for 2-layer boards, a single side of ground plane would then be OK. The top plane could be a different voltage if desired, e.g. use it as a 5V power plane, it's up to you.

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