FPC circuit board can be divided into single panel, double-sided board and multilayer board according to the number of circuit layers. The common multilayer board is generally 4-layer board or 6-layer board, and the complex multilayer board can reach dozens of layers.
There are three main types of circuit boards:
Single panel
The single panel is on the most basic PCB. The parts are concentrated on one side and the wires are concentrated on the other side. When there are patch components, they are the same side as the wires, and the plug-in devices are on the other side. Because the wires only appear on one side, this kind of PCB is called single panel. Because there are many strict restrictions on the design circuit of single panel, because there is only one side, the wiring can not cross, but must go around a separate path, so only early circuits used this kind of board.
Double sided board
Dual panel circuit board has wiring on both sides, but to use wires on both sides, there must be appropriate circuit connection between the two sides. This "bridge" between circuits is called a pilot hole. The guide hole is a small hole filled or coated with metal on the PCB, which can be connected with the wires on both sides. Because the area of the double-sided board is twice as large as that of the single panel, the double panel solves the difficulty of staggered wiring in the single panel and can be connected to the other side through holes. It is more suitable for more complex circuits than the single panel.
Multilayer board
Multilayer board in order to increase the area of wiring, multilayer boards use more single or double-sided wiring boards. A printed circuit board with one double-sided as the inner layer, two single-sided as the outer layer, or two double-sided as the inner layer and two single-sided as the outer layer, which is alternately connected together through the positioning system and insulating bonding materials, and the conductive graphics are interconnected according to the design requirements, becomes a four layer and six layer printed circuit board, also known as multi-layer 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 board thickness. Usually, the number of layers is even and includes the outermost two layers. Most of the motherboards have a structure of 4 to 8 layers, but technically, nearly 100 layers of PCB can be achieved in theory. Most large supercomputers use multi-layer mainboards, but because such computers can be replaced by clusters of many ordinary computers, super multi-layer boards have gradually been abandoned. Because all layers in the PCB are closely combined, it is generally not easy to see the actual number. However, if you carefully observe the motherboard, you can still see it.
characteristic:
PCB can be more and more widely used because it has many unique advantages, which are summarized as follows.
High density. For decades, the high density of printed boards has developed with the improvement of integrated circuit integration and the progress of installation technology.
High reliability. Through a series of inspections, tests and aging tests, it can ensure the long-term (service life, generally 20 years) and reliable operation of PCB.
Designability. For various performance requirements of PCB (electrical, physical, chemical, mechanical, etc.), PCB design can be realized through design standardization and standardization, with short time and high efficiency.
Producibility. With modern management, standardized, large-scale (Quantitative) and automatic production can be carried out to ensure the consistency of product quality.
Testability. A relatively complete test method, test standard, various test equipment and instruments are established to detect and identify the qualification and service life of PCB products.
Assemblability. PCB products are not only convenient for standardized assembly of various components, but also for automatic and large-scale mass production. At the same time, PCB and various component assembly parts can also be assembled to form larger parts and systems until the whole machine.
Maintainability. Because PCB products and various component assembly parts are based on standardized design and large-scale production, these parts are also standardized. Therefore, once the system fails, it can be replaced quickly, conveniently and flexibly to quickly restore the system. Of course, more examples can be given. Such as miniaturization, lightweight and high-speed signal transmission of the system