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Ground pour

A copper area filled around everything else and connected to GND. It gives every part a short return path, shields signals and saves routing.

What it is#

On the board, a pour (zone) is an outline that the app fills with copper, keeping clearance from tracks and pads of other nets. A GND pour on both layers of a 2-layer board connects all ground pads without tracks and makes a near-plane under the circuit.

Why it matters#

Current always returns to its source. With a solid ground under a signal track, the return current flows right below the track, the loop is small, and the board neither radiates nor picks up noise. Decoupling capacitors only work when their ground side reaches the chip’s ground through a short, wide path, which a pour provides.

Example circuit: Every GND flag here becomes a pad on the pour after Update PCB; the regulator's and capacitors' grounds join through it.
Every GND flag here becomes a pad on the pour after Update PCB; the regulator's and capacitors' grounds join through it. Open the ldo_3v3 example from this page in PCB Canvas: “Insert into my schematic”.

How in PCB Canvas#

  1. Update PCB, place the parts, route the signals and power tracks.
  2. Add a GND zone on the front and on the back (the zone tool, or the zone add command) over the whole outline.
  3. Put a few vias between the two pours, especially near chips and along the edges (“stitching”).

Pitfalls#

  • Islands. Copper cut off by tracks becomes an unconnected island. Add a via to the other layer or reroute the track that splits it.
  • Cuts under fast signals. A track on the back that slices the pour under a USB pair forces the return current around it. Keep the back pour solid under such signals.
  • Antennas. Keep all copper, including pours, out of the keep-out area of an ESP32 module’s antenna.