2 Ground Planes for 2-layer PCB?

[Guatiti]

2 Ground Planes for 2-layer PCB?

Hi everyone! This is my first time here.

I’m currently working on a pcb for a CNC motor driver and for this I’m following a design I got on the internet (also as a practice since this is one of my first projects in Kicad), I’m following the Gerbers files because I can’t see well the design in the pcb layout since it was made in an old version and it’s not 100% compatible with the one I’m using.

However, looking in detail at these Gerbers, it seems to me that they used 2 ground planes, even though the PCB is only 2 layers, i.e. one on the top layer and one on the bottom layer, so I would like to know if that makes sense and is normal? Or what could be the reason or benefit for doing that? Or if I’m misinterpreting the original designer’s implementation?

For example, when zooming to the pads of some components and then see the connection of this in the gerbers you can see that the GND pads go to what seems to be ground planes both in the top and bottom layer (I repeat, I can not check it in the pcb layout as it was made in an old version and is not 100% compatible with the one I’m using, so I’m guided by the gerbers):

I am attentive if you need more information or anything else.
Regards.

[DeepSOIC]

I wouldn’t call it a plane, as it’s sliced up by the tracks. Having 2 zone fills on both sides helps tie all the islands and semi-islands into an almost full ground plane - just throw in plenty of vias to stitch them together well. I do it all the time.

I would recommend disconnecting through-hole pads from the zone on the component side though - makes it much easier to desolder the component if you ever have to.

[Piotr]

@Guatiti

it seems to me that they used 2 ground planes, even though the PCB is only 2 layers, i.e. one on the top layer and one on the bottom layer

There are technology advantages of having comparable copper filling on both PCB sides. I think it is both in etching and in reflow soldering.

[paulvdh]

@Guatiti

and for this I’m following a design I got on the internet

When you find some random project on the 'net you should not immediately assume it is a well designed project. There is a whole lot of garbage out there. I see a bunch of stubs and “extra segments” in your screenshot. And although those are innocent in themselves, to me they are also an indication this was either a rush job, or the designer did not care much.

The red layer appears to be a continuous GND plane, and that is good. Having more GND is generally better ,but if the green / mint layer was intended as a gnd plane, then at least more clearance should have been used in between the tracks, so the plane can connect in between those tracks.

For a motor driver, it’s possible that on another part of the PCB the dual GND planes are used to lower the resistance of high current paths, and this corner is just given less attention. It’s also possible this PCB was designed by a beginner just experimenting a bit with how the software works.

Also, are you aware that you can create a PCB in KiCad by converting a set of Gerber files? I have written a tutorial for that in the link below.

Reverse engineering KiCad project from Gerber files

The goal of this reverse-engineering tutorial is to re-create a complete KiCad project from partial information assuming the only information available is a schematic in some readable, (but not EDA form, such as a .pdf or a .png picture), and a set of gerber files. The Gerber files will create a PCB with much PCB information missing, however, using this method is easier than re-designing a PCB from scratch, and can also be extended to any other program that creates Gerber files. What is “resc…

[Guatiti]

Thanks for your recommendations and I will check out that tutorial

[Guatiti]

Great! I hadn’t thought of it that way, thank you very much.

[Guatiti]

Thank you all for your answers.

I take this opportunity to ask something extra, since zooming into the original design I see that between certain tracks are drawn some small polygons as seen in the images below. I can’t select them to know what they are, but they are in the Top layer, although I suppose they are also grounded. Also, I see that they are there when there are tracks very close together, but I have no idea what they are for. What do you think?

[paulvdh]

I guess it’s some left overs from a zone creation algorithm. These screenshots do not look like they are made from KiCad and I do not know anything about that other program.

[thebigg]

Did you try Tools → Cleanup Tracks & Vias… to see if anything changes?

[Sagar_Saini]

@Reverse engineering KiCad project from Gerber files

of this reverse-engineering tutorial is to re-create a complete KiCad project from partial information assuming the only information available is a schematic in some readable, (but not EDA form, such as a .pdf or a .png picture), and a set of gerber files. The

It’s normal, a 2layer PCB may have two ground filling planes at top and bottom layer. Because in 2layer PCB signal return paths, EMI and EMC problems are often cause noise. The ground plane help to keep them minimum. Moreover these types are designs are not made for PCB CNC milling because of having complexicities in tracks. Try to go with simple one and then switch according to the milling capabilities. You can get some standard data from the capabilities section of a profession manufacturer like JLCPCB.