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Why are PCBs layered

2021-12-23

Why are PCBs layered

Detailed analysis of PCB layering principle

Classification of PCB circuit layers: it is divided into single panel, double-sided board and multilayer board. The multilayer board we often see is generally 4-layer board or 6-layer board, and the complex multilayer board can reach dozens of layers. The principle of PCB layering is analyzed in detail below:

Folding single panel

Single sided boards are 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 sided. Because single panels have many strict restrictions on the design circuit (because there is only one side, the wiring cannot cross and must go around a separate path), only early circuits used this kind of board.
Folding double-sided board
Double sided boards this kind of 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 kind of "bridge" between circuits is called guide hole (via). 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 that of the single panel, the double panel solves the difficulty of staggered wiring in the single panel (it can be connected to the other side through the hole), which is more suitable for more complex circuits than the single panel.
Folding multilayer board
Multilayer board (multi layer boards) in order to increase the area that can be wired, multi-layer boards use more single or double-sided wiring boards. One printed circuit board with both sides as the inner layer, two printed circuit boards with one side as the outer layer, two printed circuit boards with both sides as the inner layer and two printed circuit boards with one side as the outer layer are formed by alternating them through positioning system and insulating bonding materials, and the conductive graphics are interconnected according to the design requirements It is 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 main boards have a 4-8-layer structure, 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.