With the rapid development of electronic technology, printed circuit board is widely used in various fields, almost all electronic equipment contains the corresponding printed circuit board. Today, I’d like to introduce the composition of PCB and its advantages.
What is PCB?
Printed circuit board (PCB) is also known as printed circuit board. The so-called printed circuit board refers to the assembly board that selectively processes mounting holes, connecting wires and pads for assembling and welding electronic components on the insulating base plate, so as to realize the electrical connection between components.
The current circuit board is mainly composed of the following：
- Circuit and pattern: circuit is a tool for conducting between components. In design, large copper surface will be designed as the grounding and power layer. Lines and drawings are made at the same time.
- Dielectric layer: used to maintain the insulation between lines and layers, commonly known as substrate.
- Through hole / via: the through hole can make the lines above two levels open to each other, the larger through hole is used as the part plug-in, in addition, the non through hole is usually used as the surface mounting location, and the screws are fixed during assembly.
- Solder resist / solder mask: not all copper surfaces need to eat tin parts, so the non tin eating areas will be printed with a layer of substance (usually epoxy resin) to prevent the short circuit between non tin eating lines. According to different processes, it can be divided into green oil, red oil and blue oil.
- Legend / marking / silk screen: This is an unnecessary component. Its main function is to mark the name and position box of each part on the circuit board, which is convenient for maintenance and identification after assembly.
- Surface finish: because the copper surface is easy to oxidize in general environment, so it can’t be tinned (poor solder tin ability), so it will be protected on the copper surface to be tinned.
The surface technology includes:
- Hasl board, specifically, dip PCB into the molten solder pool, so that all exposed copper surfaces will be covered by solder, and then remove the excess solder on PCB through hot air cutter, because the surface of PCB after spraying tin and solder paste are the same material, so the welding strength and reliability are better;
- Plating gold board, what is plating gold? We call the whole plate gold plating. The principle is to melt nickel and gold (commonly known as gold salt) into chemical solution, immerse circuit board in electroplating cylinder and connect current to generate Immersion gold coating on the copper foil surface of circuit board. The advantages of high hardness, wear resistance and non oxidizability of nickel gold coating are widely used in electronic products;
- Immersion Gold board, immersion gold is through the chemical oxidation-reduction reaction to generate a layer of coating, generally thicker, is a chemical nickel immersion gold method, can achieve a thicker gold layer.
- For the carbon oil board, some customers require to print carbon oil on the printed circuit board, and use the screen printing technology to print carbon oil at the designated position of the PCB board. After the oven curing test is OK, a qualified carbon film with a certain resistance value is formed to replace the original PCB pad;
- Gold finger board, gold finger board is actually a copper clad board covered with a layer of gold through a special process, because gold has a strong antioxidant and conductivity.
The main advantages are:
- Due to the repeatability (reproducibility) and consistency of the graphics, the wiring and assembly errors are reduced, and the maintenance, debugging and inspection time of the equipment are saved;
- It can be standardized in design to facilitate interchange;
- High wiring density, small volume and light weight, which is conducive to miniaturization of electronic equipment;
- It is beneficial to mechanized and automatic production, improves labor productivity and reduces the cost of electronic equipment.
- In particular, FPC flexible board bending resistance, precision, better application to high-precision instruments (such as camera, mobile phone, camera, etc.)
Can be high-density:
For decades, high-density PCB can develop with the improvement of IC integration and installation technology.
Through a series of inspections, tests and aging tests, PCB can be guaranteed to work reliably for a long time (generally 20 years).
For PCB performance (electrical, physical, chemical, mechanical, etc.), PCB design can be realized through design standardization, standardization, etc., with short time and high efficiency.
Adopt modern management, can carry on the standardization, the scale (quantity), the automation and so on production, guarantees the product quality consistency.
A relatively complete test method, test standard, various test equipment and instruments are established to test and identify the qualification and service life of PCB products.
PCB products are not only convenient for standardized assembly of various components, but also for automatic and large-scale mass production. At the same time, PCB and various component assembly parts can also be assembled to form larger parts, systems, and even the whole machine.
Because PCB products and various component assembly parts are designed and produced in a standardized way, these parts are also standardized. Therefore, once the system breaks down, it can be replaced quickly, conveniently and flexibly, and the system can be restored quickly. Of course, there are more examples. Such as miniaturization, lightweight, high-speed signal transmission and so on.