I believe that many people are not unfamiliar with PCB circuit boards, because there are many fields involved in daily life, such as the computers we often use, and most of the current electronic products on the market, as well as smart phones, smart wearables, etc. that all need circuit boards.

PCB is the abbreviation of Printed Circuit Board, also known as printed circuit board. It is an important electronic component, a support of electronic components, and a provider of electrical connections for electronic components. Because it is made by electronic printing, it is also Called "printed" circuit boards.
PCB history
The inventor of the printed circuit board was Paul Eisler, an Austrian, who used a printed circuit board in a radio device in 1936. In 1943, the Americans used this technology extensively in military radios. In 1948, the United States officially recognized this invention for commercial use. Since the mid-1950s, printed circuit board technology has only begun to be widely adopted.

Before the advent of printed circuit boards, the interconnection between electronic components was achieved through direct connection of wires. But now, the circuit breadboard only exists as an effective experimental tool; the printed circuit board has occupied an absolute dominant position in the electronics industry.
Printed circuit board (PCB) will appear in almost every electronic device. If there are electronic parts in a certain device, they are all mounted on PCBs of different sizes. In addition to fixing various small parts, the main function of the PCB is to provide the mutual current connection of the upper parts. As electronic devices become more and more complex, more and more parts are needed, and the circuits and parts on the PCB are getting denser.
Before the advent of the PCB, the circuit was composed of point-to-point wiring. The reliability of this method is very low, because as the circuit ages, the rupture of the circuit will cause the circuit node to open or short circuit. Winding technology is a major advancement in circuit technology. This method improves the durability and replaceability of the circuit by winding small-diameter wires on the poles at the connection point.
The unique characteristics of PCB are summarized as follows:
1. High wiring density, small size and light weight, which is conducive to the miniaturization of electronic equipment.
2. Due to the repeatability and consistency of the graphics, it reduces wiring and assembly errors, and saves equipment maintenance, debugging and inspection time.
3. It is conducive to mechanization and automatic production, which improves labor productivity and reduces the cost of electronic equipment.
4. The design can be standardized to facilitate interchangeability.
PCB classification
According to the number of circuit layers, it can be divided into single-sided boards, double-sided boards, four-layer boards, six-layer boards and other multilayer circuit boards.
(1) Single panel
On the most basic printed circuit board, 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 type of printed circuit board is called a single panel. Because single-sided boards have many strict restrictions on the design of the circuit (because there is only one side, the wiring cannot cross and must be around a separate path), so early circuits used this type of circuit board.
(2) Double panel
This kind of circuit board has wiring on both sides. In order to connect the wires on both sides, there must be a proper circuit connection between the two sides. This kind of connection between circuits is called via. A via is a small hole filled with or coated with metal on a printed circuit board, which can be connected with wires on both sides. Because the area of ​​the double-sided board is twice as large as that of the single-sided board, and the wiring can be interleaved (it can be wound to the other side), the double-sided board can be used in more complicated circuits than the single-sided board.
(3) Multilayer board

The manufacturing method of the Multilayer PCB board is generally made by the inner layer pattern first, and then the single-sided or double-sided substrate is made by printing and etching, and placed in the designated interlayer, and then heated, pressurized and bonded. As for the subsequent Drilling is the same as the plated through hole method of double-sided board