Single panel
On the most basic PCB, the parts are concentrated on one side and the wires are on the other side. Because the wires only appear on one side, the PCB is called single-sided. Because there are many strict restrictions on the design of the single-sided board (because only one side, the wiring can not cross and must be around the path), so only the early circuit to use such a board.
Double panel
This circuit board has two sides of the wiring, but to use the two sides of the wire, must be between the two sides have the appropriate circuit connection Caixing. The "bridge" between such circuits is called via. The guide hole is a small hole filled with metal on the PCB, which can be connected to both sides of the wire. Because the area of the double panel is twice as large as that of the single panel, the double panel solves the difficulty of interleaving in a single panel (which can pass through the guide hole to the other side), which is more suitable for use on more complex circuits than single panels.
Multilayer board
In order to increase the area that can be routed, the multilayer board uses more single or double-sided wiring boards. With a double-sided inner layer, two single-sided for the outer layer or two double-sided for the inner layer, two single-sided for the outer printed circuit board, through the positioning system and insulation bonding materials alternately and conductive graphics According to the design requirements of the interconnection of the printed circuit board has become a four-story, six-layer printed circuit board, also known as multi-layer printed circuit board. The number of layers of the board does not represent a few layers of separate wiring layers. In special cases, the voids are added to control the thickness of the plates, which are usually even numbers and contain the outermost layers. Most of the motherboards are 4 to 8 layers of the structure, but the technical theory can be done nearly 100 layers of PCB board. Large supercomputers use quite a lot of motherboards, but because such computers can already be replaced with a lot of ordinary computer clusters, ultra-multi-layer board has been gradually not used. Because the PCB in the layers are closely combined, generally not easy to see the actual number, but if you carefully observe the motherboard, or can be seen.