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I designed a test board for connectors and it doesn't have any ground net. I am new at designing pcbs and I always used ground polygon pour. I don't know what to do without gnd polygon. What should I do? Should I leave the polygon without any net or is there any way to pour ground in design without gnd connection?

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3 Answers 3

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A polygon pour can be "associated" with any net you choose. It doesn't have to be linked to "ground" and, on all the packages I've used, it doesn't need to be linked to an actual specific net. How do you think people apply a power-plane in their design? Answer: they link the polygon pour to a net that is called "+5V" (or similar).

If you have a polygon pour that isn't connected to a net you might be asking for trouble in terms of it acting like an antenna so, I would recommend that it is connected to a net of some type.

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  • \$\begingroup\$ Thank you for your reply. I will connect it to a net. \$\endgroup\$ Jul 9, 2020 at 16:34
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Despite me not being a professional, I try to give my 2 cents:

  1. As you wrote, the default people use to pour a polygon is for GND. The reason is that GND is needed almost everywhere on a PCB board, and it reduces noise.

  2. As AndyAka wrote, +5V (or any VCC that is used) can also be used. After GND it is used also at many places probably on your PCB, and a non-changing voltage will also reduce noise (correct me if I'm wrong).

  3. If there is no GND and no VCC (which seems very unlikely), it might even be useful to use a polygon with a fixed voltage for the sake of reducing noise.

Conclusion: if reducing the number of traces is not applicable (as no GND/VCC is used), a fixed voltage polygon is still useful for reducing noise.

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It's not clear why you are adding the polygon pour, however assuming it's for shielding purposed, keep in mind that DC supply voltages are at AC ground.

You can also add a small capacitor between the polygon net and a DC supply voltage, which might help prevent damage if the polygon gets shorted to some other net.

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