Single panel
On the most basic PCB, the parts are concentrated on one side, and the wire is on the other side. Because the wire only appears on one side, the PCB is called a single panel (Single-sided). Because the single panel in the design of the line there are many strict restrictions (because only one side, wiring can not cross and must be around the path of the individual), so only the early circuit to use this type of board.
Double sided board
The two sides of the circuit board are wired, but to use the two sides of the wire must be in the two sides have the appropriate circuit connection. The "bridge" between the circuits is called the pilot hole (via). The guide hole is a small hole filled with or coated with metal on the PCB, which can be connected to the two sides of the wire. Because the double sided board area than a single panel big double, double panel solves the single panel because of the staggered wiring difficulties can be mediated through hole which is communicated with a on the other side, it is more suitable for used in more complex than a single panel circuit.

Multilayer board
In order to increase the area of wiring, the multilayer board can use more single or double layer wiring board. A two-sided as inner layer and the second single for outer layer or two double as inner layer, two single-sided printed circuit board of the outer and the positioning system and insulation materials bonded together and conductive pattern according to the design requirements of interconnected printed circuit board becomes four layers and six layer printed circuit board the alternately, also known as multilayer printed circuit board. The number of layers of the board does not represent a few layers of independent wiring layer, in particular, will join the air layer to control the thickness of the board, usually the number of layers are even, and contains the outermost layer two. Most of the main board are 4 to 8 layers of structure, but the theory can be done in the 100 layer of the PCB board. Large supercomputers use a large number of layers of mainframe computers, but because this kind of computer can be replaced with a lot of ordinary computer clusters, over the plate has gradually not been used. Because all the layers in the PCB are closely combined, it is generally not easy to see the actual number, but if you look closely at the motherboard, you can see it.