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Do you really understand the PCB board?

Do you really understand the PCB board?
There is a very critical component in the electronics industry called PCB. Isn't it familiar? Especially in Shenzhen, a city where giant electronics companies such as Huaqiangbei, DJI, and Goose Factory gather, even if they are not in the electronics industry, I believe everyone can often hear about PCBs in their lives.

PCB (Printed circuitboards), also known as printed circuit boards, is a provider of electrical connections for electronic components. People usually use "PCB" to express, so it is also called "PCB board".

1. The birth of PCB board

The development of PCB boards has a history of nearly a hundred years. Before the advent of the PCB board, the circuit was composed of point-to-point wiring, but the reliability of this method was very low, and with the aging of the circuit, the rupture of the circuit would cause the circuit node to open or short circuit.

Later, winding technology was adopted, which is a major advancement in circuit technology. This method improves the durability and replaceability of the circuit by winding small-diameter wires on the pillars of the connection points.

As the electronics industry develops from vacuum tubes and relays to silicon semiconductors and integrated circuits, the size and price of electronic components are also falling. Electronic products appear more and more frequently in the consumer field, prompting pcb manufacturers to find smaller and more cost-effective solutions. Thus, the PCB was born.

2. PCB board structure and substrate type

If you put the cross-section of the PCB board to a large enough multiple, you will find that it is like a wafer sandwich biscuit. During the production process, layers of different materials are pressed together by heat and adhesive. Today we will talk about the base material of the intermediate layer first.

The different differences between commonly used reinforcement materials can be divided into:

Paper substrate (FR-1, FR-2, FR-3)

Epoxy glass fiber cloth substrate (FR-4, FR-5)

Composite substrate (CEM-1, CEM-3)

HDI board (RCC)

Special substrates (metal substrates, ceramic substrates, thermoplastic substrates, etc.)

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Therefore, in most cases, the epoxy glass fiber cloth substrate FR-4 is the most used because it has higher mechanical and dielectric properties, better heat resistance and moisture resistance, and good mechanical processing. Sex, it has become the main reason why most manufacturers choose.

Of course, what kind of substrate PCB the company chooses in the end will have to be comprehensively considered and decided in combination with the final application scenario of the product.

3. Classification of PCB boards

Then according to the number of circuit boards, it can be divided into single-sided PCB boards, double-sided circuit boards, multi-layer circuit boards (four-layer boards, six-layer boards, eight-layer boards and other multi-layer circuit boards).

Single-sided circuit board

On the most basic PCB, the parts are concentrated on one side, and the wires are concentrated on the other side. Because the wires only appear on one side, this kind of PCB is called single-sided

(Single-sided). Because single-sided boards have many strict restrictions on the design of the circuit (because there is only one side, the wiring cannot cross and must be around a separate path), so only early circuits use this type of board.

Double-sided circuit board

This kind of circuit board has wiring on both sides, but to use wires on both sides, there must be a proper circuit connection between the two sides. The "bridge" between such circuits is called a via. A via is a small hole filled or coated with metal on the PCB board, which can be connected with the wires on both sides. Because the area of the double-sided board is twice as large as that of the single-sided board, the double-sided board solves the difficulty of the single-sided circuit board due to the staggered wiring (it can be connected to the other side through via holes), and it is more suitable for use in more complicated circuits than the single-sided board. On.

Multilayer circuit board

In order to increase the area that can be wired, multi-layer boards use more single or double-sided wiring boards. Use one double-sided as the inner layer, two single-sided as the outer layer, or two double-sided as the inner layer and two single-sided as the outer layer of the printed circuit board. The positioning system and the insulating bonding material alternately together and the conductive pattern Printed circuit boards that are interconnected according to design requirements become four-layer and six-layer printed circuit boards, also known as multilayer printed circuit boards.

The number of layers of the PCB does not mean that there are several independent wiring layers. In special cases, empty layers are added to control the thickness of the board. Usually, the number of layers is even and includes the two outermost layers. Most motherboards have a 4 to 8 layer structure, but technically it can be a PCB circuit board of nearly 100 layers. Most large supercomputers use fairly multi-layered motherboards, but because these types of computers can already be replaced by clusters of many ordinary computers, super-multilayered boards have gradually ceased to be used. Because the layers in the PCB board are tightly integrated, it is generally not easy to see the actual number, but if you look closely at the motherboard, you can still see it.

In the past ten years, my country's printed circuit board (PCB) manufacturing industry has developed rapidly, and its total output value and total output have both ranked first in the world. Due to the rapid development of electronic products, price wars have changed the structure of the supply chain. China has both industrial distribution, cost and market advantages, and has become the world's most important printed circuit board production base.

Printed circuit boards have developed from single-layer to double-sided circuit boards, multilayer circuit boards and flexible boards, and continue to develop in the direction of high precision, high density and high reliability. Continuously shrinking volume, reducing costs, and improving performance have enabled printed circuit boards to maintain strong vitality in the development of electronic products in the future.

The future development trend of printed circuit board manufacturing technology is to develop in the direction of high density, high precision, fine aperture, fine wire, small pitch, high reliability, multilayer, high-speed transmission, light weight, and thinness in performance.