Supply Layers, Power Planes, Polygons in Inner Layers – What is what?
If you would like to use copper planes in inner layers you should be aware of several things and know how this works: EAGLE uses so-called Supply layers, that will be generated automatically and lead one single signal. And there are the quite “normal” inner layers that use polygons for copper planes. EAGLE considers its Supply layers as a special kind of inner layer. Supply Layer: This one can be activated with the Supply option in the DISPLAY menu, Change button. The layer name determins the signal that will be lead in this layer: If you use, for example, the name GND, and activate the Supply option, the resulting layer name is $GND. The $ character is the identifying mark for a Supply layer. This can be done also with the help of the LAYER command, for example: LAYER 3 $GND Specials of a Supply layer a) The layer is displayed inverted, i. e. everything drawn in this layer is non-copper on the real board. b) This layer does not work with Pads and Vias. Connected elements will automati