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PCB Fabrication

The principle of PCB Fabrication

When we open the keyboard of a general-purpose computer, we can see a piece of soft film (flexible insulating substrate) printed with silver-white (silver paste) conductive patterns and healthy bit patterns. Because the general screen printing method obtains this kind of pattern, we call this kind of PCB a flexible silver paste PCB. The PCB on the various computer motherboards, graphics cards, network cards, modems, sound cards and household appliances that we saw in the Computer City were different. The substrate used in it is made of paper base (usually used for single-sided) or glass cloth base (usually used for double-sided and multilayer), pre-impregnated with phenolic or epoxy resin, one or both sides of the surface layer are glued with copper clad film and then laminated Become. This kind of circuit board copper clad sheet material, we call it rigid board. Then make a printed circuit board, we call it a rigid PCB. We call single-sided PCB with printed circuit patterns on one side, and PCB on both sides with printed circuit patterns on both sides. The PCB formed by double-sided interconnection through hole metallization are called double-sided boards. If 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 PCB, the positioning system and the insulating bonding material alternate together and The PCB with the conductive pattern interconnected according to the design requirements becomes a four-layer or six-layer PCB, also called a multilayer PCB. There are now more than 100 layers of practical PCB.

PCB FabricationThe introduction of PCB Fabrication process

The PCB Fabrication process is more complicated, and it involves a wide range of processes, from simple mechanical processing to  complex mechanical processing, common chemical reactions, photochemical, electrochemical, thermochemical and other processes, computer-aided design CAM and many other aspects of knowledge . Moreover, there are many process problems in the production process and new problems will be encountered from time to time. Some of the problems disappear without finding out the cause.  Because PCB Fabrication process is a discontinuous assembly line form, any problem in any link will cause the entire line to stop production. Or as a consequence of a large number of scraps, if PCB are scrapped, they cannot be recycled and reused. The work pressure of process engineers is relatively high, so many engineers have left the industry and turned to PCB equipment or material vendors to do sales and technical services.

The substrate of the board itself is made of a material that is insulated and not easy to bend. The small circuit material that can be seen on the surface is copper foil. The copper foil is originallycovered on the entire board, and part of it during the PCB Fabrication process. After being etched away, the remaining parts become net-like small circuits. These circuits are called conductor patterns or wiring, and are used to provide circuit connections for parts on the PCB.

In order to fix the parts on the PCB, we solder their pins directly to the wiring. On the most basic PCB (single-sided board), the parts are concentrated on one side, and the wires are concentrated on the other side. So we It is necessary to make holes in the board so that the pins can pass through the board to the other side, so the pins of the parts are soldered on the other side. Because of this, the front and back sides of the PCB are called Component Side and Solder Side.

If there are some parts on the PCB that need to be removed or reinstalled after the production is completed, then the socket will be used when the part is installed. Since the socket is directly soldered on the board, the parts can be disassembled and assembled at will .

At present, in the electronic product processing industry, PCB board as one of the key electronic components indispensable. At present, PCB board has a variety of types, such as high frequency PCB board, microwave heating PCB board and other types printed PCB board in the sales market has made a certain reputation. PCB Fabrication companies have a special manufacturing process for each type of sample. But generally speaking, the following three factors must be considered in PCB board production and processing.

                                  PCB Fabrication                         PCB Fabrication 

1. The selection of PCB boards

The PCB board can be divided into organic chemical raw materials and inorganic raw materials. Each raw material has its unique advantages. Therefore, the type of PCB board need to consider following factors clearly: the performance of dielectric gas, the type of copper foil, the thickness of base groove, Production and processing characteristics and so on. Among them, The surface thickness of copper foil is the primary condition to endanger the characteristics of PCB. Generally speaking, the thinner the thickness is, the more convenient the etching process is and the higher the precision level of the drawing is.

2. The setting of production process
The natural environment of PCB Fabrication workshop is a very critical side. Also, the control of working temperature and air relative humidity is a particularly important factor. If the working temperature transition is too obvious, may cause the plate on the rotary hole rupture. If air relative humidity is too large, the characteristic that nuclear power generation has bad harm to the plank with strong ability to absorb water, basically behave in performance plane of dielectric gas. Therefore, it is necessary to maintain appropriate natural environment standards during PCB Fabrication.

PCB Fabrication

3. The selection of production process

PCB Fabrication is very vulnerable to the damage of various elements. The production and processing processes, such as the number of layers, caving processing technology and surface coating solution, may cause damage to the finished product quality of PCB. Therefore, in the natural environment of this production process, PCB Fabrication is carried out by integrating the characteristics of manufacturing machinery and equipment. Considering that, flexible adjustment can be carried out according to different PCB board types and production and processing requirements.

In general, PCB Fabrication must take into account the selection of the plate, the production process setting, and the selection of the production process. In addition, the solution of PCB board construction materials and the way of opening materials are a level that must be carefully selected, which is closely related to the glossiness of the finished products of printed board of power circuit packaging

What are the common mistakes of PCB board during PCB Fabrication and how to avoid them?PCB Fabrication

1. Overlap of welding plates.

a. Create heavy holes, which are broken and damaged by multiple boreholes in one place during drilling.

b. In the multilayer board, there are both connection plates and isolation plates at the same position. The board is shown as • isolation and connection error.

2. The use of graphics layer is not standard

a. The violation of conventional design, such as component surface design at the Bottom layer and welding surface design at the TOP layer, is misleading.

b. There are a lot of design garbage on each layer, such as broken lines, useless borders, labels, etc.

3. Unreasonable characters

a. Characters covering SMD welding sheet will bring inconvenience to PCB on-off detection and component welding.

b. The characters are too small to make screen printing difficult, and the characters are too large to overlap each other, making it difficult to distinguish. The fonts are generally >40mil.

4. Set aperture of single welding plate

a. The single-side welding plate generally does not bore holes, and its aperture should be designed to be zero; otherwise, when borehole data is generated, the coordinates of holes will appear at this position. Special instructions should be given for drilling holes.

b. If the single-side bonding pad needs to be drilled but the aperture is not designed, the software will treat the bonding pad as SMT bonding pad during the output of electricity and formation data, and the isolation plate will be lost in the inner layer.

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