Circuit boards are divided into three categories according to the number of layers: single-sided, double-sided and multilayer circuit boards.

The first is a single panel. On a basic PCB, the parts are concentrated on one side and the wires are concentrated on the other side. Because the wires only appear on one side, this kind of PCB is called a single-sided circuit board. Single panels are usually simple to manufacture and low cost, but the disadvantage is that they cannot be applied to overly complex products.

The double-sided board is an extension of the single-sided board. When single-layer wiring cannot meet the needs of electronic products, double-sided boards should be used. There are copper wires on both sides, and the wires between the two layers can be connected through vias to form the required network connections.

Multi-layer board refers to a printed board with more than three conductive pattern layers and insulating material between them laminated at intervals, and the conductive patterns between them are interconnected as required. Multilayer circuit boards are the product of the development of electronic information technology in the direction of high speed, multi-function, large capacity, small volume, thinner and lighter.

How to distinguish between multi-layer circuit boards and single-layer circuit boards:

1. Pick up and face the light. If the inner core is opaque, it is a multi-layer board, on the contrary, it is a single and double board. Single-sided board, only one layer of wiring, no copper in the hole. There are lines on the front and back of the double-sided board, and there is copper in the vias.

2. In the production process of multilayer circuit boards, the production process of inner lamination will be added on the basis of single and double panels. Distraction using slices can also be analyzed.　　

Application advantages of multilayer circuit boards:

1. The assembly density is high, the volume is small, and the weight is light, which meets the needs of lightweight and miniaturization of electronic equipment;

2. Due to the high assembly density, the wiring between components (including components) is reduced, the installation is simple, and the reliability is high;

3. Due to the repeatability and consistency of graphics, errors in wiring and assembly are reduced, and equipment maintenance, debugging and inspection time are saved;

4. The number of wiring layers can be increased, thereby increasing design flexibility;

5. It can form a circuit with a certain impedance, and can form a high-speed transmission circuit;

6. Circuit and magnetic circuit shielding layer can be set, and metal core heat dissipation layer can also be set to meet the needs of special functions such as shielding and heat dissipation.

With the continuous development of electronic technology and the continuous improvement of electronic equipment requirements in computer, medical, aviation and other industries, circuit boards are developing in the direction of reducing size, reducing quality, and increasing density. Due to the limitation of available space, single- and double-sided printed boards have been impossible to achieve further increase in assembly density. Therefore, it is necessary to consider the use of multi-layer circuit boards with more layers and higher packing density. Multilayer circuit boards have been widely used in the manufacture of electronic products with their flexible design, stable and reliable electrical performance and superior economic performance.