I. classification of PCB board
1, Single panel: Single panel (Single - SidedBoards) on the most basic of PCB, parts on one side, the conductor is focused on the other side (have SMT components with lead to one side, the plug-in device to the other side). Because wire only appear on one side, so this kind of PCB is called Single panel (Single sided). Because in the design of Single panel lines, there are many restrictions (because only one side, wiring must around the path alone cannot cross between), so only use this kind of early circuit board.
2, Double panel, Double panel (Double - SidedBoards) to both sides of the circuit board wiring, but it took two wires, must have the appropriate circuit connection between two sides. The "bridge" between the circuit is called guide hole (via). The guide hole is on the PCB, small hole filled with or coated with metal, it can be connected to both sides of the wire. Because the area of the Double panel a times larger than a single panel, Double panel solved because wiring of the difficulty in the single panel (conduction through hole to the other side), it is more suitable for use in more complex than a single panel circuit.
3, a multilayer sandwich plate (Multi - LayerBoards) in order to increase the area of the wiring, sandwich plate with more single or double wiring board. With a double lining, two one-way for outer layer or two double lining, two blocks of single outer layer of the printed circuit board, through the positioning system and alternate insulation adhesive materials and conductive graphics interconnection according to design requirement of printed circuit board becomes four, six layer printed circuit board, also known as multilayer printed circuit board.
The number of layers of the board does not mean that there are several independent wiring layers. In special cases, empty layers will be added to control the thickness of the board
PCB. Large supercomputers are used quite layers of the motherboard, but because this kind of computer can replace with many ordinary computer cluster, super sandwich plate has not been used gradually. Because each layer of PCB are closely combined, general is not easy to see the actual number, but if you look closely at the motherboard, can still see it.
Ii. Features of PCB board
1. High density: for decades, the high density of printed circuit board has been developing with the improvement of integrated circuit integration and installation technology.
2. High reliability. Through a series of inspection, testing and aging test, PCB board can ensure long-term and reliable work.
3. Designability: PCB design can be realized through design standardization and standardization for various performance (electrical, physical, chemical, mechanical, etc.) of PCB, with short time and high efficiency.
4. Productiveness.adopting modern management, it can carry out standardization, scale (quantity), automation and other production to ensure the consistency of product quality.
5. Testability: relatively complete test methods, test standards and various test equipment and instruments have been established to detect and identify the PCB product qualification and service life.
6. Assemblability: PCB products are not only convenient for standardized assembly of various components, but also can be automated and mass-produced on a large scale. At the same time,PCB and various component assembly parts can also be assembled to form larger parts, systems and even the whole machine.
7. Maintainability. As PCB products and various component assembly parts are designed and manufactured in a standardized and large-scale way, these parts are also standardized. Therefore, in case of system failure, they can be replaced quickly, conveniently and flexibly to quickly restore the system to work.