FPC circuit board can be divided into single panel, double-sided board and multilayer board according to the number of circuit layers. The common multi-layer board is generally 4-layer board or 6-layer board, and the complex multi-layer 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 elements on the other side, the wires are on the same side, and the plug-in devices are on the other side. Because the wires only appear on one side, this PCB is called a single panel. Because there are many strict restrictions on the design circuit of a single panel, because there is only one side, and the wiring cannot cross and must follow a separate path, only early circuits use this type of board.
Double sided board
Wiring is provided on both sides of the dual panel circuit board. However, to use the wires on both sides, proper circuit connection must be provided 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 in the single panel due to the staggered wiring and can be connected to the other side through the hole. It is more suitable for use in more complex circuits than the single panel.
Multilayer board
Multilayer board in order to increase the area that can be wired, multilayer boards use more single or double-sided wiring boards. The 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 by the positioning system and the insulating adhesive material and the conductive pattern is interconnected according to the design requirements, becomes a four layer and six layer printed circuit board, also known as a 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 4-8-layer structure, but technically, nearly 100 layers of PCB can be achieved theoretically. Most large supercomputers use quite a few layers of mainboards. However, because this type of computer can be replaced by many clusters of ordinary computers, the super multi-layer boards are gradually not used. Because the 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:
The reason why PCB can be more and more widely used is that it has many unique advantages, which are summarized as follows.
And the density can be increased. For decades, the high density of printed boards has developed with the improvement of integrated circuit integration and the progress of mounting technology.
High reliability. Through a series of inspections, tests and aging tests, the PCB can be ensured to work reliably for a long time (the service life is generally 20 years).
Designability. To meet the requirements of PCB performance (electrical, physical, chemical, mechanical, etc.), the 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 not only facilitate the standardized assembly of various components, but also can be automated 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. Since PCB products and various component assembly parts are designed and produced in a standardized manner, these parts are also standardized. Therefore, once the system fails, it can be replaced quickly, conveniently and flexibly, and the system can be restored quickly. Of course, we can give more examples. Such as miniaturization and lightweight of the system and high-speed signal transmission.