PCB board

The circuit board can be called a printed circuit board or a printed circuit board. The English name is (Printed Circuit Board) PCB, (Flexible Printed Circuit board) FPC circuit board (FPC circuit board is also called flexible circuit board). It is a highly reliable and excellent flexible printed circuit board made of 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 boards, PCB boards, aluminum substrates, high frequency boards, thick copper boards, impedance boards, PCBs, ultra-thin circuit boards, ultra-thin circuit boards, printed (copper etching technology) circuit boards, etc.

working principle

The working principle of the circuit board is to use the board-based insulating material to isolate the surface copper foil conductive layer, so that the current flows in various components along the pre-designed route to complete tasks such as work, amplification, attenuation, modulation, demodulation, coding, etc. Function.

composition

The circuit board is mainly composed of pads, vias, mounting holes, wires, components, and connectors. The main functions of each component are as follows:

Pad: A metal hole for soldering component pins.

Vias: There are metal vias and non-metal vias, where metal vias are used to connect component pins between layers.

Mounting holes: used to fix the circuit board.

Wire: An electrical network copper film used to connect component pins.

Connector: A component used for connection between circuit boards.

Filling: The copper used for the ground network can effectively reduce the impedance.

Electrical Boundary: Used to determine the size of the circuit board, and all components on the circuit board must not exceed this boundary.

Figure 2 Via structure of the circuit board

Classification

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

Multilayer board: refers to a printed board with three or more conductive pattern layers and insulating materials in between, 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.

Single-sided: On the most basic PCB, parts are concentrated on one side and 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 panel is usually simple to make and low cost, but the disadvantage is that it cannot be applied to too complicated products.

Double-sided: It 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.

Circuit boards are divided into flexible boards (FPC), rigid boards (PCB), and rigid-flex boards (FPCB) according to their characteristics.

working level

The circuit board includes many types of working layers, such as 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 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; Top Solder and Bottom Solder are the solder paste protection layer and the bottom solder paste protection layer respectively.

(2) 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.

(3) Silk screen layer: It is mainly used to print the serial number, production number, company name, etc. of the components on the circuit board.

(4) Internal layer: mainly used as a signal wiring layer, Protel DXP contains a total of 16 internal layers.

(5) Other layers: mainly include 4 types of layers.

Drill Guide (drilling orientation layer): mainly used for the location of drilling holes on the printed circuit board.

Keep-Out Layer: Mainly used to draw the electrical border of the circuit board.

Drill Drawing (drilling drawing layer): mainly used to set the drill shape.

Multi-Layer: Mainly used to set multi-layers.