The circuit board can be called a printed circuit board or a printed circuit board, which is a highly reliable and excellent flexible printed circuit board made of polyimide or polyester film as the base material. The names of the circuit boards are: ceramic circuit board, alumina ceramic circuit board, aluminum nitride ceramic circuit board, circuit board, PCB board, aluminum substrate, high frequency board, thick copper board, impedance board, PCB, ultra-thin circuit board, ultra-thin Thin circuit boards, printed (copper etching technology) circuit boards, etc. \u0422\u0435\u0441\u0442\u043e\u0432\u044b\u0435 \u043d\u0430\u0431\u043e\u0440\u044bWorking principleThe working principle of the circuit board is to use the base insulating material to isolate the conductive layer of the surface copper foil, so that the current flows along the pre-designed route in various components to complete such as work, amplification, attenuation, modulation, demodulation, encoding, etc. Function.CompositionThe circuit board is mainly composed of pads, via holes, mounting holes, wires, components, connectors, etc. The main functions of each component are as follows:Pad: Metal hole used to solder component pins.Vias: There are metal vias and non-metal vias, among which metal vias are used to connect component pins between layers.Mounting hole: used to fix the circuit board.Conductor: The electrical network copper film used to connect component pins.Connector: A component used for connection between circuit boards.Filling: It is used for the copper covering of the ground network, which can effectively reduce the impedance.Electrical boundary: used to determine the size of the circuit board, and all components on the circuit board cannot exceed this boundary.ClassificationAccording to the number of layers, circuit boards are divided into three major categories: single-sided boards, double-sided boards, and multi-layer boards.Multi-layer board: refers to a printed board that has more than three conductive pattern layers and the insulating material between them are laminated at intervals, and the conductive patterns are interconnected as required. Multilayer circuit board is the product of the development of electronic information technology in the direction of high speed, multi-function, large capacity, small volume, thinner and lighter weight.Single panel: On the most basic PCB, parts are concentrated on one side, and wires are concentrated on the other side. Because wires only appear on one side, this PCB is called a single-sided circuit board. Single-sided panels are usually easy to manufacture and low in cost, but the disadvantage is that they cannot be applied to too complicated products.Double-sided board: It is an extension of a single-layer board. When single-layer wiring cannot meet the needs of electronic products, the double-sided boards should be used. There are copper clad and traces on both sides, and the lines between the two layers can be conducted through via holes to form the required network connection.Circuit boards are divided into flexible boards (FPC), rigid boards (PCB), and soft-rigid boards (FPCB) according to their characteristics.Working levelThe circuit board includes many types of working layers, such as the signal layer, protective layer, silk screen layer, internal layer, etc. The functions of various layers are briefly introduced as follows:(1) Protective layer: It is mainly used to ensure that the place on the circuit board that does not need to be tinned is not tinned, so as to ensure the reliability of the circuit board operation. Among them, Top Paste and Bottom Paste are the top solder resist layer and the bottom solder resist layer respectively; Top Solder and Bottom Solder are the solder paste protective layer and the bottom solder paste protective layer respectively.(2) Signal layer: mainly used to place components or wiring. Protel DXP usually includes 30 middle layers, namely Mid Layer1~Mid Layer30, the middle layer is used to arrange signal lines, and the top and bottom layers are used to place components or lay copper.(3) Silk screen layer: It is mainly used to print the serial number, production number, company name, etc. of components on the circuit board.(4) Internal layer: It is mainly used as a signal wiring layer. Protel DXP contains 16 internal layers.(5) Other layers: mainly including 4 types of layers.Drill Guide (drilling orientation layer): mainly used for the position of drilling holes on the printed circuit board.Keep-Out Layer (forbidden wiring layer): mainly used to draw the electrical border of the circuit board. WIFI \u043f\u043e\u0441\u043b\u0435\u0434\u043e\u0432\u0430\u0442\u0435\u043b\u044c\u043d\u044b\u0439 \u0441\u0435\u0440\u0432\u0435\u0440Drill Drawing (drilling drawing layer): mainly used to set the drilling shape.Multi-Layer (multi-layer): mainly used to set multi-layer.This article introduces the concept, working principle, composition, classification and working level of circuit boards. Depending on the design of the circuit board, the price will vary depending on the material of the circuit board, the number of layers of the circuit board, the size of the circuit board, the quantity of each production, the production process, the minimum line width and line spacing, the minimum hole diameter and the number of holes , special process and other requirements to decide.