polygon pour purpose question in PCB gnd

Thread Starter

yef smith

Joined Aug 2, 2020
696
Hello, in PCB there is polygon pour where whe have some shapes inside and gnd net defined it.
As i see it GND is a flat whole surface plane?
Why theu define GND wich is not a flat surface?
maybe i didnt understand properly the polygon pour purpose on GND?
Thanks.
1692446071391.png
 

dl324

Joined Mar 30, 2015
16,688
in PCB there is polygon pour where whe have some shapes inside and gnd net defined it.
As i see it GND is a flat whole surface plane?
Why theu define GND wich is not a flat surface?
maybe i didnt understand properly the polygon pour purpose on GND?
If by flat, you mean a plane with no openings, that wouldn't be practical.

The part of the fill region in the picture that has "traces" (called thermals) with openings around them are to make it easier to solder them. If you've ever tried to unsolder something soldered to a solid plane, you'll appreciate when they're used.

I make my own boards and I use copper fill to reduce the amount of copper removed; to etch faster and to make etchant last longer.
 

dl324

Joined Mar 30, 2015
16,688
Pour could be defined as an area that's filled with copper. There could be a number of reasons why you would use them.
  1. Ground planes from any supply for shielding and/or convenience of routing power.
  2. Reducing cross coupling between critical signals. For this, the fill works best if it's connected to an AC ground, but it still helps even if it's floating because it still reduces the coupling capacitance.
  3. Reduce etching time and etchant load since less copper needs to be removed.
 
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