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I am trying to design a PCB where the device is sitting on an elevated pedestal (or island) on a PCB, like the image shown here. enter image description here I have spoken to a PCB company about how to achieve this, and they suggested adding 2 copper layers to form the pedestal, as shwon in the image below. enter image description here

(I understand that in KiCad, all copper layers are going to be sandwiched between mask and silk layers. So, in 3D view, the PCB will still appear as a think rectangular box)

So, I went back to my KiCad PCB file and added two copper layers on the bottom. Then I realized, there does not seem to be an obvious way to manually define the boundary of each copper layer. I think KiCad assumes that the dimensions of the copper layers are the same as 'Edge.cuts' layer.

The closest I could think of was doing what I wanted was 'Add filled zones', as shown in the images below enter image description hereenter image description here.

However, you can see that, since KiCad assumes the bottom 2 layers have the same dimensions as other copper layers, they also have all the vias and through holes outside the filled zones. The filled zones in my images represent the desired size for the bottom 2 copper layers.

Is there a way to adjust the size of each copper layer inside a PCB?

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  • \$\begingroup\$ How are they going to do that physically? The board house said they can somehow laminate a smaller copper sub board to that existing board? if so I probably wouldn't even do it as a single board file I would make two separate board files with two separate schematics and everything. \$\endgroup\$
    – MadHatter
    Commented Apr 11, 2020 at 2:42
  • \$\begingroup\$ Or just make note on drawings about whatever the board house is doing. No one uses the 3d model anyways, and for any mechanical cad use, just have the designer add the appropriate sized rectangle in their software. \$\endgroup\$
    – MadHatter
    Commented Apr 11, 2020 at 2:43
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    \$\begingroup\$ Is there a reason as to why you can't use headers? Sorry, it's hard to envision the final product. The bottom of your device just has pads, like a BGA array? \$\endgroup\$ Commented Apr 11, 2020 at 3:17
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    \$\begingroup\$ But why? This seems like the hardest, most expensive, roundabout way to do something for no discernible purpose. \$\endgroup\$
    – DKNguyen
    Commented Apr 11, 2020 at 3:36
  • \$\begingroup\$ @MadHatter Indeed the pedestal and the mainboard are going to be two separate pieces. Then, the company will connect them together. But for some reason, they do not want two separate sets of gerber files in KiCad. They want everything represented in a single set of gerber files. \$\endgroup\$ Commented Apr 11, 2020 at 14:36

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Put keepouts on the two layers that need to be smaller. You'll probably need to make two per layer, or possibly make one donut on each layer with ends that butt up against each other.

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