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1. Because PCB eliminates most the large through-hole or buried hole interconnection technology, the wiring density on the printed board is improved and the area of the printed board is reduced (generally 1/3 of the insert installation), and the design layer and cost of the printed board can also be reduced.

2. Lighten the weight, improve the seismic performance. It adopts the glue solder and new welding technology, which improves the quality and reliability of the product.

3. Due to the increase of wiring density and shortening of lead length, parasitic capacitance and parasitic inductance are reduced, which improves the electrical parameters of PCB.

4. It is easier to automate than insert installation, it improves the pcb assembly speed and productivity, and reduces assembly cost accordingly.

From the above surface installation technology, we can see that the improvement of circuit board technology is increased with the improvement of chip packaging technology and surface mount technology. Now the surface sticking rate of computer cards is constantly rising. In fact, this circuit board can not meet the technical requirements by using the transmission network printing line graph. Therefore, for ordinary high-precision circuit board, its line graphics and solder resist graphics basically use photosensitive line and photosensitive green oil production process.

Development trend:

With the development trend of high density of PCB, the production requirements of PCB are getting higher and higher. More and more new technologies are applied to the production of PCB, such as laser technology, photosensitive resin and so on. This is only a superficial introduction. There are many other things in the production of PCB, such as blind hole, winding board, Teflon plate, lithography and so on. If you want to study in depth, you need to try harder.  

Soft and hard classification

It is divided into rigid circuit board and flexible circuit board, soft and hard joint board. The intuitive difference between rigid PCB and flexible PCB is that flexible PCB can be flexed. The common thickness of rigid PCB is 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.6 mm, 2.0 mm and so on. The common thickness of flexible PCB is 0.2 mm, where the parts to be welded will be thickened, and the thickness of the thickened layer will be 0.2 mm and 0.4 mm. The purpose of understanding these is to provide them with a space reference when the engineers are designing the structure. The rigid PCB materials include the phenolic paper laminates, the epoxy paper laminates, the polyester glass felt laminate and the epoxy glass cloth laminates. And the flexible PCB materials include polyester film, polyimide film, and fluorinated ethylene propylene film.

Raw material

Copper clad laminate is the substrate material for making printed circuit boards. It is used to support various components and realize electrical connection or electrical insulation among them.

PCB Fabrication

The PCB method of electronic enthusiasts mainly includes thermal transfer printing, photosensitive wet film method and photosensitive dry film method. Etchant has environment-friendly ferric chloride (FeCl3) and has fast hydrochloric acid plus hydrogen peroxide (HCl+H2O2). Commonly used PCB drawing softwares include Altium Designer 10 and other Altium Designer (predecessor Protel) series software. Photosensitive dry film plus ferric chloride is the best choice for amateurs.

Procedures

Choose a way to make the circuit board. The choice is usually based on the availability of the material required by this method, the level of technical difficulty of this method, and the quality level you want the printed circuit board to achieve. The following is the brief introduction to various methods and the main characteristics of these methods, which will help you to choose:

Acid etching: this method requires extreme safety measures and many materials, such as etchant. Also, this method is a bit slow. The quality of the printed circuit board obtained by this method depends on the material you use, but in general, it is a good way for a circuit with a simple or medium complexity.

UV etching: this method requires some more expensive materials, which may not be available everywhere. However, the method steps are very simple, it requires less security measures and can satisfy more sophisticated and complex computers.

Mechanical etching / wire fixing: this method requires special machines that can be mechanically etched out of the board, or to set off the spacer between the wires. If you want to buy a machine like this, it will be very expensive. If you want to rent one, you need a workshop nearby. However, if you want to make many copies of the circuit, it is a good way. This method can also make very precise pcb prototype.

Laser etching: this method is usually applied to large production companies, but it can also be found in some universities. The general concept of this method is similar to mechanical etching, but laser beams are used to etch the boards. It's usually hard to get this machine, if your local university is lucky to have such a machine, then you will have the chance to use it with their permission.

1. Choose the acid used for etching. Ferric chloride is the usual choice. But you can also use ammonium sulfate crystals or other chemicals. No matter which chemical etching agent you choose, these are dangerous materials. Besides the general safety precautions mentioned in this article, you also need to read and observe other safety instructions when etching.

2. Drawing prototype pcb layout. In order to carry out acid etching, you need to use anti etching materials to draw circuits. If you want to draw the circuit layout by hand (not suitable for medium or large circuits), you should make special marks according to different purposes. The commonly used material is laser printing ink. Using laser printing to draw the layout of the circuit has the following steps:

Print the layout of printed circuit boards on a white printed paper. Before making this, you should make sure that the layout is mirrored with your circuit (when printed, most PCB layout programs have this option). This is the only step that uses a laser printer.

Put the printed side of the paper on the copper plate.

The time required to iron the paper surface with a common iron depends on the type of paper and ink used.

Immerse copper and paper in hot water for a few minutes (up to 10 minutes).

Tear off the paper. If you can't tear any place, you can try to soak it a little longer. If everything is finished, there will be a layout of your PCB and a black marking line on the copperplate.

3. Prepare acid. There may be some additional instructions according to the etch acid you choose. For example, some crystalline acids need to be melted in hot water, while other acids do not.

4. The copper plate is immersed in the acid.

5. Stir it every 3-5 minutes.

6. When all the copper is not etched, remove the copper and clean it.

7. Remove the insulating material for drawing. A specific chemical solvent can remove any insulating material used to draw the layout of the circuit. But if you don't have the solvent, you can use sandpaper to remove them.

PCB circuit board, also known as printed circuit board, is the provider of electrical connections for electronic components. It has a history of more than 100 years and its design is mainly layout design. The main advantage of the circuit board is to greatly reduce the errors in wiring and assembly, and improve the level of automation and productivity.

According to the number of PCB layers, it can be divided into single panel, double-sided board, four layers, six layers and other multi-layer PCB.

As prototype PCB is not a general terminal product, the definition of the name is slightly confused, for example, the motherboard used by a personal computer is called a motherboard, but it can not be called a circuit board directly. Although there is a circuit board in the host board, it is not the same, so the assessment of the industry is not the same. Another example is that because the integrated circuit parts are loaded on the circuit board, the news media call it IC board, but in essence, it is not equivalent to printed circuit board. We usually say that PCB refers to bare boards, that is, circuit board without a device.