1. Printed Circuit Board (PCB)
Printed Circuit Board (Printed Circuit Board), because it is printed by electronic printing, so it is called "that Printed Circuit Board". The Printed Circuit Board(PCB) is a substrate used to assemble electronic parts. It is a Printed Circuit Board(PCB) that forms a connection between the point and the printed element according to a predetermined design on the general substrate. The main function of this product is to make various electronic components form a predetermined circuit connection, play the role of relay transmission, is the key electronic interconnection of electronic products, known as the "mother of electronic products". The printed circuit board is the substrate and key interconnect of electronic parts and should be equipped with any electronic device or product.
2. PCB manufacturing principle
When we open the health disk of a general-purpose computer, we can see a silver-white (silver paste) conductive and healthy pattern on the soft film (flexible insulating substrate). Due to the general screen leakage printing method to obtain this pattern, we call this printed circuit board flexible silver paste printed circuit board. We went to Computer City to see all kinds of computer motherboards, video cards, network cards, modems, sound cards and printed circuit boards for home appliances. The substrate used consists of a paper base (often used for one side) or a glass cloth base (often used for two sides and multiple layers), prepreg phenolic resin or epoxy resin, the surface layer is glued to one or both sides of the copper book, and then cured by lamination. This kind of circuit board copper book board, we call hard board. When we make printed circuit boards, we call them rigid printed circuit boards. We call it a printed circuit board, a printed circuit board with a printed circuit board on both sides, and a printed circuit board formed by hole metalization, we call it a dual panel. If a double-sided printed circuit board is used as the inner layer and two single-sided as the outer layer, the printed circuit board, which is alternately connected by the positioning system and the insulating bonding material, interconnects the conductive graphics according to the design requirements and becomes a four-layer six-layer printed circuit board, also known as a multi-layer printed circuit board. There are now more than 100 functional printed circuit boards.
3. PCB production process
PCB production process is more complex, involving a wide range of processes, from simple processing to complex processing, ordinary chemical reactions, photochemical electrochemical thermochemistry, computer-aided design, CAM and other aspects of knowledge. Moreover, there are many technical problems in the production process, and new problems will be encountered from time to time, some of which disappear without finding out the cause. Because its production process is a discontinuous assembly line, any link of the problem will lead to the whole line to stop production or a large number of scrap consequences. If the printed circuit board is wasted, it can not be recycled, and the work pressure of process engineers is greater. As a result, many engineers have left the industry and turned to PCB equipment or material suppliers for sales and technical services.
The substrate of the circuit board itself is made of insulating and inflexible materials. The surface can see that the thin wire is copper foil, the original copper foil covers the entire circuit board, and in the production process, part of the etching treatment is the remaining part of the small wire network. These lines are called conductorpatterns, or wiring, and are used to provide circuit connections to various components on the PCB.
In order to secure the parts to the PCB, we welded their pins directly to the wire. On the most basic PCB(single panel), the parts are concentrated on one side and the wires are concentrated on the other side. This way, we need to punch a hole in the circuit board so that the pin can go through the board to the other side, so the pin of the part is welded on the other side. Therefore, the positive and negative sides of the PCB are called the component surface (ComponentSide) and the welding surface (SolderSide).
If there are some parts on the PCB that need to be disassembled or installed after the production is completed, the Socket is used during installation, because the socket is directly welded to the board, and these parts can be disassembled and assembled at will.
If we want to connect two PCBS together, we usually use an edgeconnector (edgeconnector). Commonly known as the "golden finger". The Golden finger contains many exposed copper pads that are actually part of the PCB wiring. Usually, when connecting, we insert the gold finger on one PCB into the appropriate Slot on the other PCB (generally called expansion Slot). In computers, such as video cards, sound cards, or other similar interface cards, they are all connected to the motherboard through their golden fingers.
Green or brown on the PCB is the color of welding paint (soldermask). This layer is an insulating protective layer that protects the copper wire and prevents parts from being welded to incorrect places. Another silkscreen printing surface (silkscreen) will be printed on the resistance welding layer. Text and symbols (mostly white) are usually printed on it to indicate the location of parts on the board. The silkscreen printing surface is also known as the legend surface.
The printed circuit board is carefully planned to etch the copper wire between the parts and the parts on the circuit board, providing the main support for the installation and interconnection of electronic components, which are the essential components of all electronic products.
A plate made of a non-conductive material with pre-drilled holes commonly used to mount chips and other electronic components. The assembled holes help connect predefined metal channels on the board surface and, after passing through the PCB, form a circuit by connecting conductive metal electrodes to the PCB.
4. Brief history and development direction of PCB
In China, the development of single-sided printed circuit boards (PCBS) began in the mid-1950s, initially applied to semiconductor radios. In the 1960s, China's foil-coated substrate was developed by itself, making copper foil etching the leading process for PCB production in China, and a large number of veneers were produced in the 1960s. Small batch production of double-sided metallized hole printing, and in a few units began to develop multi-layer printing plates. In the 1970s, the graphic electroplating etching process was popularized in our country, but due to various disturbances, special materials and equipment for printed circuits could not keep up with The Times, and the overall production technology level lagged behind the advanced level of foreign countries. In the 1980s, with the approval of reform and opening up, a large number of foreign advanced single-sided, double-sided, multi-layer PCB production lines were introduced in the 1980s, and after more than a decade of digestion and absorption, China's printed circuit board production technology has rapidly improved.
Development direction: In recent years, China's electronic industry has become one of the main pillars of domestic economic growth. With the rapid development of the computer, communication equipment, consumer electronics and automotive industries, the PCB industry has also achieved rapid development. With the development of printed circuit products, people put forward higher requirements for new materials, new technologies and new equipment. While expanding the output of China's printed electronic materials industry, we should pay attention to the improvement of performance and quality, and the printed circuit special equipment industry is no longer a low-level imitation, but the development of production automation, precision, multi-function and modern equipment. PCB production integrates the world's high-tech, printed circuit production technology will use liquid photosensitive imaging, direct plating, pulse plating, laminated multilayer board and other new processes.
5. PCB and its upstream and downstream characteristics and classification
PCB has six characteristics: high density, high reliability, designability, producibility, assemblability and maintainability.
In general, the more complex the function of electronic products, the longer the loop distance, the more contact, the more PCB layer is needed, such as advanced consumer electronics, information and communication products, etc., soft board is mainly used for laptop computers, cameras, automotive instruments and other products that need to bend. According to the number of layers, PCB can be divided into single board (SSB), dual panel (DSB) and multi-panel (MLB); According to flexibility can be divided into rigid printed circuit board (RPC) and flexible printed circuit board (FPC). In the industrial research, according to the basic classification of the above PCB products, the PCB industry is divided into six categories: single-board, double-layer board, conventional multi-layer board, flexible board, HDI(high-density sintering) board, packaging substrate, etc.
The PCB upstream industry includes PCB substrate raw material suppliers and PCB production equipment suppliers, and the downstream industry includes consumer electronics, computers and peripheral products, automobiles and mobile phone industries. According to the industrial chain can be divided into raw materials - copper printed circuit board - electronic product applications. The analysis is as follows:
Fiberglass cloth: Fiberglass cloth is one of the raw materials of copper laminate, made of fiberglass yarn, accounting for about 40% of the cost of copper laminate (thick plate) and 25%(sheet). Fiberglass yarn is calcined from silica sand and other raw materials in the kiln into a liquid, the fiberglass is pulled through a very small alloy nozzle into very fine fiberglass, and then hundreds of fiberglass fibers are twisted into fiberglass yarn.
Copper foil: Copper foil accounts for the largest proportion of the cost of copper foil raw materials, accounting for about 30% of the cost of copper plate (thick plate) and 50%(sheet), so the price rise of copper foil is the main driving force for the price rise of copper foil.
Copper laminate: With epoxy resin as the flux, the glass fiber cloth and copper foil pressed, is the direct raw material of PCB, after etching, electroplating, multi-laminate, made of printed circuit board.
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