According to the number of layers, the PCB can be divided into three categories: single sided board, double sided board, and multilayer circuit board.
The first is single sided board. On the basic PCB, the components are concentrated on one side and the wires on the other side. Because wires appear only on one side, the PCB is called single sided circuit board. Single sided board is usually simple and inexpensive, but they can’t be used in complex products.
Double-sided is an extension of single-sided. When single-layer wiring cannot meet the needs of electronic products, double-sided is used. Both sides have copper cladding and traces, and the lines between the two layers can be conducted through vias to form the required network connections.
A multi-layer board refers to a circuit board with more than three layers, the conductive pattern layer 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, thinning and light weight.
According to the characteristics of the circuit board, the circuit board is divided into FPC, Rigid PCB, and FPCB. Circuit board includes many kinds of working layers, such as signal layer, protective layer, silk screen layer, internal layer, etc.
The functions of various levels of circuit boards are briefly described as follows:
⑴ Signal layer: mainly used to place components or wiring. Protel DXP usually contains 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 copper.
(2) Protective layer: It is mainly used to ensure that the places on the circuit board that do not need tin plating are not tinned, so as to ensure the reliability of the operation of the circuit board.
Among them, Top Paste and Bottom Paste are the top solder mask layer and bottom solder mask layer, respectively, and Top Solder and Bottom Solder are the solder paste protection layer and the bottom solder paste protection layer, respectively.
(3) Silk Screen layer: it mainly used to print components on the circuit board, production number, company name, etc.
(4) Internal layer: it mainly used as signal routing layer, Protel DXP contains a total of 16 internal layers.
(5) Other layers: it mainly includes four types of layers.
Drill Guide: it mainly used for drilling position on printed circuit board.
Keep-Out Layer: it mainly used to draw the electrical frame of the circuit board.
Drill Drawing (drilling drawing layer): mainly used to set the drill shape.
Multi-Layer: Mainly used to set multi-layers.
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