According to circuit-level classification: is divided into single-sided, double-sided and multilayer. Common multilayer layer 4 or 6 layers Board, complicated multilayer up to dozens of layers.
Division of PCB Board has the following three main types:
Folding single panel
Single-panel (Single-Sided Boards) on the most basic PCB, components concentrated in the side, wire centres on the other side (with SMD components and wires for a plug-in device to the other side). Because wires only occurs on one side, this PCB is called single-sided (Single-sided). Because a single panel in the design line there are many severe restrictions on (because only one side, wiring can't cross paths that must be around alone), so only the earlier circuit using such boards.
Folded double panel
Double-sided boards (Double-Sided Boards) both sides of the circuit board and wiring, but you have to use both sides of the wire must have appropriate electrical connection lines in between the two sides. This "bridge" is called a pilot hole (via). Pilot hole is on the PCB, or coated metal-filled holes, it can work with both sides of the wire is connected. Because the double-sided Board 1 time times greater area than a single panel, double panel solved the staggered because of wiring difficulties of single-panel (you can pass to the other side by Kong Dao), it is more suitable for use in more complex than single-sided circuit.
MLB (Multi-Layer Boards) in order to increase the size of wiring, multilayer PCB used more single-or double-sided wiring boards. With a double, two single-sided as outer layer or two double-sided for inner, outer of two single-sided printed circuit boards through alternate positioning systems and insulation adhesive material and conductive pattern according to the design requirements for interconnected printed circuit boards became four-story, six-layer printed circuit board, also known as a multilayer printed circuit board. Layer does not mean the Board has several layers of independent wiring, in exceptional cases, adding an empty layer to control thickness, layers are usually even-numbered and contain two layers on the outside. Most of the motherboard is 4 to 8 layer structure, but technically theory can be done nearly 100 layer PCB Board. Large supercomputers mostly use quite a lot of motherboards, however, because the computer can already use many clusters instead of ordinary computer, Super multilayer PCB are not to be used. Because each layer of the PCB close bond, generally not so easy to see the actual number, but if you look at motherboard, can still be seen.