What are the classifications of PCB circuit boards? Below I will give you a detailed analysis.

One. Classification according to the number of layers

Classification according to the number of circuit layers: divided into single-sided, double-sided and multi-layer boards. Common multi-layer boards are generally 4-layer boards or 6-layer boards, and complex multi-layer boards can reach dozens of layers. There are three main division types of PCB boards:

1. Single panel:

The single-sided board 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 SMD components, it is 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 a single-sided (Single-sided). Because the single board has many strict restrictions on the design of the circuit (because there is only one side, the wiring cannot cross and must go around a separate path), so only early circuits used this type of board.

2. Double panel:

The double-sided circuit board has wiring on both sides, but to use the wires on both sides, there must be a proper circuit connection between the two sides. Such "bridges" between circuits are called vias. Vias are small holes on a PCB, filled or painted with metal, that can be connected to wires on both sides. Because the area of ​​the double-sided board is twice as large as that of the single-sided board, the double-sided board solves the difficulty of interleaving the wiring in the single-sided board (it can be conducted to the other side through the hole), and it is more suitable for use in more complex circuits than the single-sided board.

3. Multilayer board:

In order to increase the area that can be wired, multilayer boards use more single or double-sided wiring boards. A printed circuit board with a double-sided inner layer, two single-sided outer layers, or two double-sided inner layers and two single-sided outer layers, alternated together by a positioning system and insulating bonding materials, and conductive patterns. Printed circuit boards that are interconnected according to design requirements become four-layer and six-layer printed circuit boards, also known as multi-layer 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 will be added to control the thickness of the board. Usually, the number of layers is even and includes the outermost two layers. Most motherboards are 4 to 8-layer structures, but technically, nearly 100-layer PCB boards can be achieved. Most large supercomputers use fairly multi-layer motherboards, but because such computers can be replaced by clusters of many ordinary computers, ultra-multi-layer boards have gradually fallen out of use. Because the layers in the PCB are tightly combined, it is generally not easy to see the actual number, but if you look closely at the motherboard, you can still see it.

Second, according to soft and hard classification

Divided into rigid circuit boards, flexible circuit boards, and rigid-flex boards. Generally, the PCB shown in the first picture below is called a rigid (Rigid) PCB, and the yellow connecting line in the second picture is called a flexible (or flexible) PCB. The intuitive difference between rigid PCB and flexible PCB is that flexible PCB can be bent. Common thicknesses of rigid PCBs are 0.2mm, 0.4mm, 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.6mm, 2.0mm, etc. The common thickness of flexible PCB is 0.2mm, and a thickened layer will be added behind it where the parts are to be welded. The thickness of the thickened layer varies from 0.2mm to 0.4mm. The purpose of knowing these is to provide structural engineers with a spatial reference when designing. Common rigid PCB materials include: phenolic paper laminate, epoxy paper laminate, polyester glass felt laminate, epoxy glass cloth laminate; common flexible PCB materials include: polyester film, polyimide Amine film, fluorinated ethylene propylene film.

The above is the classification of PCB circuit boards, I hope to help you understand.