PCB often see that there are several layers of what is the meaning of the circuit board is not only one layer?
In the early years, the production process was limited to a maximum of 8 layers and should now be much more than that
The circuit board layer must be an even number, in addition to a layer, there is little singular.
The board of the circuit board is not the board itself, is a layer of copper, is the conductor layer, usually one or two layers, multi-layer, then there is a conductive layer in the middle of the board
