PCB Blog - Introduction of PCB manufacture

PCB, also known as printed circuit board, is one of the important components in the electronic industry. Almost every type of electronic device, from electronic watches and calculators to computers, communication electronics, and military weapon systems, requires the use of printed boards to electrically interconnect electronic components such as integrated circuits.

PCB manufacture

The printed circuit board is composed of an insulating base plate, connecting wires, and a solder pad for assembling and welding electronic components, which has the dual function of conducting wires and insulating base plates. It can replace complex wiring and achieve electrical connections between various components in the circuit, not only simplifying the assembly and welding work of electronic products, reducing the workload of traditional wiring methods, and greatly reducing the labor intensity of workers; Moreover, it reduces the overall volume, reduces product costs, and improves the quality and reliability of electronic equipment.

PCB have good product consistency and can adopt the standardized design, which is conducive to achieving mechanization and automation in the production process. At the same time, the entire assembled and debugged printed circuit board can serve as an independent spare part, facilitating the exchange and maintenance of the entire product. At present, printed circuit boards have been widely used in the production and manufacturing of electronic products.

PCB characteristics

The reason why PCB has been increasingly widely used is that it has many unique advantages, roughly as follows

1. PCB can be high-density

For many years, the high density of printed boards has been able to develop correspondingly with the improvement of integrated circuit integration and the advancement of installation technology.

2. PCB high reliability

Through a series of inspection, testing, and aging tests, it is possible to ensure that PCBs can work reliably for a long time (usually with a lifespan of 20 years).

3. PCB designability

The requirements for various properties of PCBs (electrical, physical, chemical, mechanical, etc.) can be achieved through design standardization and standardization. This design has a short time and high efficiency.

4. PCB producibility

PCB adopts modern management, which can achieve standardization, scale (quantity), and automated production, thereby ensuring the consistency of product quality.

5. PCB testability

We have established relatively complete testing methods and standards, which can be used to detect and evaluate the qualification and service life of PCB products through various testing equipment and instruments.

6. PCB assemblability

PCB products are not only convenient for the standardized assembly of various components but also for automated and large-scale mass production. In addition, assembling a PCB as a whole with various other components can also form larger components, systems, and even the entire machine.

7. PCB maintainability

Due to the standardized design and large-scale production of the components assembled as a whole with various components in PCB products, these components are also standardized. So, once the system malfunctions, it can be quickly, conveniently, and flexibly replaced to quickly restore the system's operation.

PCB has other advantages, such as miniaturization, lightweight, and high-speed signal transmission.

The functions of PCBs in electronic devices

(1) Provide mechanical support for fixing and assembling various electronic components such as integrated circuits, achieve wiring and electrical connections or insulation between various electronic components such as integrated circuits, and provide the required electrical characteristics.

(2) Provide solder mask graphics for automatic welding, and identification characters and graphics for component insertion, inspection, and maintenance.

(3) After using printed boards in electronic equipment, due to the consistency of similar printed boards, manual wiring errors are avoided, and electronic components can be automatically inserted or pasted, soldered, and inspected, ensuring the quality of electronic products, improving labor productivity, reducing costs, and facilitating maintenance.

(4) Provide the required electrical characteristics, characteristic impedance and electromagnetic compatibility characteristics for the circuit in the high-speed or high-frequency circuit.

(5) The printed circuit board with embedded passive components provides certain electrical functions, simplifies electronic installation procedures, and improves product reliability.

(6) In large-scale and ultra-large-scale electronic packaging components, it provides an effective chip carrier for miniaturized chip packaging of electronic components.

PCB design principles

Firstly, consider the size of the PCB. PCB size is too large, printed lines are long, impedance increases, noise resistance decreases, and cost also increases; If it is too small, the heat dissipation is poor, and adjacent lines are easily disturbed. After determining the PCB size, determine the position of special components. Finally, lay out all components of the circuit according to its functional units.

When determining the position of special components, the following principles should be followed

① Try to shorten the wiring between high-frequency components as much as possible, and try to reduce their distribution parameters and electromagnetic interference with each other. Components that are susceptible to interference should not be too close to each other, and input and output components should be kept as far away as possible.

② There may be a high potential difference between certain components or wires, and the distance between them should be increased to avoid accidental short circuits caused by the discharge. Components with high voltage should be arranged in areas that are not easily accessible by hand during debugging.

③ Components weighing over 15 g should be fixed with brackets and then welded. The components that are large, heavy, and generate a lot of heat should not be installed on the printed circuit board, but on the chassis bottom plate of the entire machine, and heat dissipation should be considered. The thermal element should be kept away from the heating element.

④ For the layout of adjustable components such as a potentiometer, adjustable inductance coil, variable capacitor, microswitch, etc., the structural requirements of the whole machine shall be considered. If it is adjusted internally, it should be placed above the printed board for easy adjustment; If it is adjusted externally, its position should match the position of the adjustment knob on the chassis panel.

When laying out all components of a circuit based on its functional units, the following principles should be followed

① Arrange the positions of each functional circuit unit according to the circuit flow, making the layout convenient for signal flow and keeping the signal in the same direction as much as possible Layout around the core components of each functional circuit as the center. The components should be evenly, neatly, and tightly pulled onto the PCB, minimizing and shortening the leads and connections between each component as much as possible.

③ For circuits operating at high frequencies, consideration should be given to the distribution parameters between components. The general circuit should arrange the components in parallel as much as possible. In this way, not only is it aesthetically pleasing, but it is also easy to assemble and weld, making it easy for mass production.

④ The components located at the edge of the circuit board are generally not less than 2 mm away from the edge of the circuit board. The optimal shape of a circuit board is a rectangle. The aspect ratio is 3:2 or 4:3. Circuit board surface size greater than 200 mm × At 150 mm, the mechanical strength of the circuit board should be considered.

PCB circuit boards are important sub-components of electronic components and are also interconnected substrates. PCB circuit boards are crucial interconnecting components in electronic products. Without them, the assembly of electrical components cannot be properly connected and assembled. The industry chain is derived from PCB circuit boards and its business coverage is very extensive.