How pcb works？

Structure and working principle of PCB

What is PCB？

Printed Circuit Board (PCB for short), also known as circuit board, PCB board, aluminum substrate, high frequency board, ultra-thin circuit board, ultra-thin circuit board, printed (copper etching technology) circuit board, etc., is an important Electronic components are supports for electronic components and providers of circuit connections for electronic components. Traditional circuit boards use the method of printing etching resist to make circuit lines and graphic. So we call it printed circuit boards or printed circuit boards.

circuit board structure

The circuit board is mainly composed of pads, vias, mounting holes, wires, components, connectors, filling, electrical boundaries, etc. Common layer structures include single layer PCB (Single Layer PCB), double layer board (Double Layer PCB) and multilayer board (Multi Layer PCB). 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, the designer use this vias are 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: The filling means we use 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.

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 to ensure the part of the circuit board that does not need tinn, 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 protection layer and the bottom solder paste protection 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:

The silk print layermainly print the serial number, production number, company name, etc. of the components on the outermost layer of the circuit board.

(4) Internal layer:

The internal layer is the signal wiring layer, and 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.
Drill Drawing (drilling drawing layer): mainly used to set the drilling shape.
MulTI-Layer (multi-layer): mainly used to set multi-layer.

Design process of a circuit board

On the most basic PCB, the parts are concentrated on one side, and the wires are concentrated on the other side. Because wires only appear on one side, this PCB is called a single-sided board. For multi-layer boards, there are wires in multiple layers, and there must be an appropriate circuit connection between the two layers. The bridge between such circuits is called a via. The basic design process of a circuit board can be divided into the following four steps:

Design of circuit schematic diagram

The design of the circuit schematic diagram is mainly to use the schematic diagram editor of Protel DXP to draw the schematic diagram. A PCB schematic is a simple two-dimensional circuit design that shows the functions and connections between different components.

PCB design is a performance-related stage. Based on the PCB design, engineers build real components to test that the device is working properly. As mentioned earlier, anyone should be able to understand a PCB schematic, but looking at a prototype is not easy to understand its function.

Generate network report

The network report is a report that shows the link relationship between the circuit principle and each component in it. It is the bridge and link connecting the circuit schematic design and the circuit board design. Through the network report of the circuit schematic diagram, you can quickly find the relationship between components and components. Contact, so as to provide convenience for the subsequent PCB design.

So the PCB schematic is the first part of the printed circuit board design. It is a graphical representation, whether in written or digital form, that uses agreed symbols to describe circuit connections. It also hints at which components to use and how to connect them.

As the name suggests, a PCB schematic is a plan, a blueprint. That doesn’t mean where the components will be placed specifically. Instead, the schematic lays out how the PCB will ultimately achieve connectivity and forms a critical part of the planning process.

After the blueprint is complete, the next step is PCB design. A design is the layout or physical representation of a PCB schematic, including the layout of copper lines and holes. The PCB design shows the location of the above components and their connections to the copper.

Design of printed circuit board

The design of the printed circuit board is what we usually call the PCB design. It is the final form converted from the circuit schematic diagram. The related design of this part is more difficult than the design of the circuit schematic diagram. We can use the powerful design of Protel DXP Function completes this part of the design.

Generate printed circuit board report

After the design of the printed circuit board is completed, it is necessary to generate various reports, such as generating pin reports, circuit board information reports, network status reports, etc., and finally print out the printed circuit diagram.

working principle

The 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. Features.