A printed circuit board (PCB, Printed Circuit Board) is the basic component used to connect and support electronic components in an electronic device. It allows electronic components such as resistors, capacitors, integrated circuits, etc. to be connected in a circuit in a predetermined manner through a series of conductive paths, pads, and other features. The following is a basic introduction to PCB circuits, including their structure, production process and application areas.

I. Composition of PCB

PCB is usually composed of the following main parts:

1. substrate:

The substrate of PCB generally uses resin glass fibre (FR-4) material, which possesses good mechanical strength and electrical insulation. Other types of materials such as aluminium substrates and polyimide are also used for special applications.

2. Conductive Layer:

The conductive layer is generally made of copper and is etched to form the circuit wiring. The thickness of the copper layer usually depends on the current carrying capacity, with common thicknesses such as 1 ounce, 2 ounces, and so on.

3. Insulating Layer:

 The insulating layer is located between the conductive layer, playing the role of electrical insulation and support. For multi-layer PCB, the insulation layer is separated from the different conductive layers, usually using epoxy resin material.

4. surface treatment:

In order to improve soldering performance and prevent oxidation, the surface of the PCB is often treated, common surface treatment methods are hot air levelling (HASL), tin spraying, gold plating and so on.

5. Hole and over-hole:

PCBs can be set up with different sized holes, which can be used for component insertion as well as signal transmission and heat dissipation. Through-holes are used to connect different layers of circuits.

Second, the classification of PCB

According to different needs and processes, PCBs can be divided into the following categories:

1. Single-sided PCB:

Only one side has conductive lines, suitable for simple circuits such as calculators and certain household appliances.

2. Double-sided PCB:

Both sides have conductive lines and are connected to each other through perforations, suitable for circuits of higher complexity, such as communications equipment.

3. Multilayer PCB:

Composed of three or more conductive layers, suitable for high-density, high-complexity circuits, such as computer motherboards, mobile phones.

4. Flexible PCB (FPC):

Printed circuit boards with flexibility, suitable for devices with space-saving requirements and complex shapes.

5. Rigid-Flexible PCB:

Combines the characteristics of rigid and flexible PCBs, widely used in portable electronic devices.

Third, the production process of PCB

PCB production generally experience the following steps:

1. design:

The use of PCB design software (such as Altium Designer, Eagle, etc.) for circuit design, generate the corresponding PCB layout and circuit diagram.

2. Lithography:

Transfer the design pattern to the copper-clad board to form a conductive layer. The photopolymer is first applied and then the pattern is developed by UV exposure.

3. etching:

The copper layer not protected by photoresist is removed and the excess copper is etched away by chemical etching, leaving the desired circuit pattern.

4. Punching and Forming:

Punch holes in the PCB to facilitate the insertion and connection of individual components. For multilayer boards, it is necessary to reserve holes for interlayer connection.

5. surface treatment:

 Treat the surface of the PCB to prevent oxidation and improve solderability.

6. Testing and Inspection:

After production is completed, electrical tests and visual inspections are performed to ensure that the functionality and quality of the PCB meets the standards.

Fourth, the application areas of PCB

PCB is widely used in various industries, its main application areas include:

1. consumer electronics:

Mobile phones, tablet PCs, TVs, audio systems, home appliances, etc.

2. Computer and network equipment:

Computer motherboards, routers, switches, servers, etc.

3. automotive electronics:

Used for various control systems in automobiles, such as engine control units (ECUs), navigation systems, etc.

4. medical equipment:

 Medical monitoring instruments, imaging equipment, testing equipment, etc.

5. communication equipment:

Base stations, signal transmission equipment, wireless communication products, etc.