While taking a look at some other peoples PCB designs I noticed something that I haven't seen yet.

In some designs, I see regions marked by unconnected, small dots on the signal layers. Here are two examples from completely different projects:

Question: What is the purpose of these markings?

Example One Example Two


2 Answers 2


These schematics are created in Eagle. The dashed lines mark polygons for copper pours, which have marked out, but haven't been poured yet.

enter image description here

The image comes from this page, which also contains a detailed discussion about polygons in Eagle.


The dotted lines form an area, in eagle called a polygon, to form a copper pour. This means the area within the dotted lines will be filled with copper (actually: the copper will not be removed from this area when the pcb is fabricated). All traces crossing the area within the dotted lines will be surrounded by an open space so the traces will not be connected to the copper pour.

These copper pours are often found as ground plane or, as the red dotted line in the bottom picture, as heat conductor. The red copper pour in the bottom picture, together with the via, will create an area where heat can be dissipated.

As for the top picture, I don't know the benefit for the odd shape of the copper pour.

See picture for more info: enter image description here

  • 1
    \$\begingroup\$ Specifically, the dotted lines show the nominal borders of the pours as drawn. To see the actual pour that will be produced, issue a "ratnest" command. \$\endgroup\$
    – Dave Tweed
    Commented Mar 1, 2015 at 21:46

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