Single panel
Single-Sided Boards On the most basic PCB, the parts are concentrated on one side, and the wires are concentrated on the other side (when there are chip components, the same side as the wire, and the plug-in device is on the other side). Because the wires only appear on one side, this type of PCB is called Single-sided. Because the single panel has many strict restrictions on the design circuit (because there is only one side, the wiring cannot cross and must go around its own path), only early circuits used this type of board.
Double panel
Double-Sided Boards This type of circuit board has wiring on both sides.To use two-sided wires, 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 filled or coated with metal on the PCB. It can be connected to the wires on both sides. Because the area of the double-sided board is twice as large as the single-sided board, the double-sided board solves the difficulty of wiring interleaving in the single-sided board (which can be conducted to the other side through the hole), and it is more suitable for more complicated circuits than the single-sided board.
Multilayer board
Multi-Layer Boards In order to increase the wiring area, multiple layers
The board uses more single or double-sided wiring boards. A printed circuit board with one double side as the inner layer, two single sides as the outer layer, or two double sides as the inner layer, and two single sides as the outer layer. The conductive pattern is alternately connected together through a positioning system and an insulating bonding material. The printed circuit boards that are interconnected according to design requirements become four-layer and six-layer printed circuit boards, also known as multilayer printed circuit boards. The number of layers of the board does not mean that there are several independent wiring layers. In special cases, an empty layer is added to control the thickness of the board. Usually, the number of layers is even, and it includes the two outermost layers. Most motherboards have a structure of 4 to 8 layers, but technically it can achieve nearly 100 layers of PCB boards. Large supercomputers mostly use fairly multilayer motherboards. However, because such computers can already be replaced by clusters of many ordinary computers, ultra-multilayer boards have gradually become unused. Because the layers in the PCB are tightly coupled, it is generally not easy to see the actual number, but if you look closely at the motherboard, you can still see it.