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In my project, I have a label in the schematic as Vcc. When I created my backside copper pour in PCBnew, I gave it the Vcc net.

Thus, when joining a Vcc pad on the frontside layer, via a via to the backside, the unrouted count decreases by one.

The thing is, how does this backside copper has the same voltage as Vcc? When I inspected the backside, I saw no evidence of an existing Vcc frontside pad be connected to the backside with a via, in order to give the whole backside copper pour the same potential as Vcc.

Do I have to explicitly connect a Vcc pad to the backside with a via, in order to give the backside Vcc potential, then connect all the rest of the Vcc pads to the backside?

How do I know that when I connect a frontside Vcc pad to the backside, and see the unrouted count decrease, that this connection is valid, if the backside copper does not have a Vcc potential in the first place?

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2 Answers 2

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Placing the copper pour with an assigned net increased the unrouted count, since you gave KiCad another element that needs to be connected to Vcc: the copper plane.

So whatever supplies Vcc needs to be connected to either the backside or something that is already connected to the backside, but since the point of the exercise is to have a low-resistance current path, you want to connect the supply pad to the plane, which should also decrease your unrouted count.

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  • \$\begingroup\$ So i do have to connect the copper zone to a pad that had Vcc supply, in order to give the copper that potential, in order to connect the rest of the pads to it. \$\endgroup\$ Aug 23, 2023 at 14:11
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    \$\begingroup\$ KiCad doesn't care where the power comes from, it just checks that everything that should be connected is connected. One of the "unrouted" elements is the Vcc pad on the connector where the power comes in, and connecting it to the zone solves that. \$\endgroup\$ Aug 24, 2023 at 5:17
  • \$\begingroup\$ I didn't notice that behaviour. I mean that when I created the copper pour, the unconnected count did not increase. But still, I connected the pour to a VCC source. \$\endgroup\$ Aug 25, 2023 at 19:52
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The copper zone will be connected to the net defined in the property window. Regardless of wether it is connected or not to something of the same Net.

enter image description here

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  • \$\begingroup\$ So i do have to connect the copper zone to a pad that had Vcc supply, in order to give the copper that potential, in order to connect the rest of the pads to it. \$\endgroup\$ Aug 23, 2023 at 14:10
  • \$\begingroup\$ Yes you have to assign the VCC net to the copper zone. All VCC as to be interconnected, thus the copper zone will also connect to the VCC. I advise on connecting the zon through more than one point. One popular thing is to stitch copper zone (usually GND) with plenty of vias. A copper zone that is floating is basically a big antenna/capacitor. \$\endgroup\$
    – benguru
    Aug 24, 2023 at 7:09

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