In accordance with the number of circuit layers to points, the PCB can be divided into a single panel, double-sided boards and multilayer boards, common multilayer boards are generally 4 or 6 layers of boards, complex and even up to dozens of layers.
1, single-panel (Single-Sided Boards) in the most basic PCB, the parts are concentrated on one side, the wire is concentrated on the other side. Because the wires appear only on one side, so this PCB is called a single panel (Single-sided). Because single-sided boards have many strict limitations in designing the wiring (because there is only one side, the wires can't cross each other but must go around a separate path), only early circuits used these boards.
2, double-sided board (Double-Sided Boards) Both sides of this board have wiring, but to use both sides of the wire, you must have a proper circuit connection between the two sides. This "bridge" between circuits is called a via. A via is a small hole in the PCB, filled or coated with metal, which can be connected to the wires on both sides. Because a double-sided board is twice as large as a single-sided board, and because the wiring can be interleaved (wrapped around to the other side), it's better suited for more complex circuits than a single-sided board.
3, multi-layer boards (Multi-Layer Boards) In order to increase the area that can be wired, multi-layer boards with more single or double-sided wiring board. With a double-sided for the inner layer, two single-sided for the outer layer or two double-sided for the inner layer, two single-sided for the outer layer of the printed circuit board, through the positioning system and insulating bonding material alternating with the conductive pattern according to the design requirements for interconnecting printed circuit boards have become four-layer, six-layer printed circuit boards, also known as multilayer printed circuit boards. The number of layers on a board indicates how many separate wiring layers there are, usually an even number of layers and including the two outermost layers. Most mainframe boards are constructed with 4 to 8 layers, although it is technically possible to theoretically do PCB boards with nearly 100 layers. Most large supercomputers use fairly multilayer motherboards, although because such computers have been able to be replaced by clusters of many ordinary computers, ultra-multilayer boards have fallen out of use. Because the layers in a PCB are so tightly packed together, it's generally not easy to see the actual number, but if you look closely at the motherboard, you can still see it.
In accordance with the classification of hardness and softness, it can be divided into hard circuit board (Rigid PCB), soft circuit board (also known as flexible circuit board) (Flexible PCB), and hard and soft combination of board (Rigid-Flex PCB).
The thickness of a rigid PCB is usually 0.2mm up to 7.0mm, while a flexible PCB is usually 0.2mm, and then thickened where it needs to be soldered. The emergence of flexible circuit boards is mainly due to the limited space of the organization, so it is necessary to use the PCB can be bent to achieve the space requirements. Flexible circuit board materials are mostly polyester film, polyimide film and fluorinated ethylene propylene film, etc. The birth and development of FPC (flexible board) and PCB (rigid board) have given rise to the new product of flexible-rigid combination board. Therefore, the combination of hard and soft board, is a flexible circuit board and hard circuit board, after pressing and other processes, according to the relevant process requirements are combined together, the formation of FPC characteristics and PCB characteristics of the circuit board.
To material classification:
1, organic materials: phenolic resin, glass fiber / epoxy resin, Polyimide, BT / Epoxy and so on belong to.
2, inorganic materials: aluminum, Copper-invar-copper, ceramic and so on belong to. The main function is to dissipate heat.
To categorize the use: communication, power consumption electronics, military, computer, semiconductor, electrical test boards and so on.