How to make a multi -layer PCB board

The double panel is a layer of medium in the middle, and both sides are wiring layers. The multi -layer plate is a multi -layer wiring layer. Each layer is a medium layer, and the intermediate layer can be made very thin. The multi -layer circuit board has at least three layers of conductive layers, two of which are placed on the outer surface, and the remaining layer is synthesized in the insulation board. The electrical connection between them are usually achieved through the plating holes on the horizontal side of the circuit board.
PCB multi -layer board production process process full solution

PCB multi -layer board production process process:
The production process of ordinary PCB boards is relatively simple, and the production process of PCB multi -layer circuit board is relatively complicated. The following is the full solution of the PCB multi -layer board production process:

1. PCB multi -layer board production process -layer pressure

1. Layer pressure takes the form of bonding the lines of each layer into the overall layer by the help of the B -level semi -solidified tablet. This bonding is done through the mutual diffusion and infiltration between the macromolecules on the interface, and then produce interweaving. The order semi -solitary tablets bond the process of each layer of lines into the overall process. This bonding is done through the mutual diffusion and infiltration between the macromolecules on the interface, and then produce interweaving.

2. Purpose: Press the discrete multi -layer board and sticky sheet into a multi -layer board required for the number of layers and thickness.

① The typesetting of copper foil, adhesion (semi -curing tablets), inner plate, stainless steel, isolation plate, leather paper, outer steel plate and other materials are superimposed according to process requirements. If the board of more than six floors is also a need, the pre -version is needed. Materials such as copper foil, sticky slices (semi -curing tablets), inner plates, stainless steel, isolation plate, leather paper, outer steel plate and other materials are stacked according to process requirements. If the board of more than six floors is also a need, the pre -version is needed.

② The layer pressure process sends the stacked circuit board into the vacuum heat compressor. Use the thermal energy provided by the machine to melt the resin in the resin tablet to bind the substrate and fill the gap.

③ For designers, layer pressure first need to consider symmetry. Because the board will be affected by pressure and temperature during the layer pressure, there will be stress existence by the board after the layer pressure is completed. Therefore, if the two sides of the layer pressure are uneven, the stress on the two sides is very different, causing the board to bend one side, which greatly affects the performance of the PCB multi -layer board.

In addition, even if in the same plane, if the distribution of copper is uneven, the resin flow of each point will be different, so that the thickness of the place with less copper will be slightly thinner, and the thickness of the places with more copper copper will be slightly thicker. Some. In order to avoid these problems, the factors of the uniformity of clothing copper, the symmetry of the overlapping layer, the design layout of the blind burial, and other aspects of the design must be detailed.

Second, PCB multi -layer board production process -the purpose of blackization and brownization

① Remove pollutants such as oil pollution and impurities on the surface;

② Increase the surface of the copper foil, thereby increasing the area of contact with the resin, which is conducive to the full spread of the resin and forming a large binding force;

③ turn non -polar copper surfaces into surfaces with polar CUO and CU 2 o, increase the combination of copper foil and polar bonds between copper foil and resin;

④ The surface of oxidized is not affected by moisture at high temperature, reducing the chance of layering of copper foil and resin.

⑤ The boards that are done in the inner line must be blackened or brown before layer pressure. It is oxidized on the surface of the lines of the inner plate. Generally generated CU 2 O is red and CUO as black, so CU 2 o in oxidation layers is mainly called brownization, CUO is mainly black.

 

Third, the production process of PCB multi -layer board -drilling and sinking copper

Objective: It will penetrate the metal of the hole

① The substrate of the circuit board is composed of copper foil, glass fiber, and epoxy resin. During the production process, the cross -section of the pores after the substrate drill is composed of the above three parts of the material.

② Pole metalization is to solve the metal copper covered with a uniform layer of uniform, heat -resistant shock on the section. Pole metalization is to solve the metal copper covered with a uniform layer of uniform layer on the cross section.

③ The process is divided into three parts: one drilling process, two chemical copper processes, and three thick copper processes (all board electroplated copper).

 

Fourth, PCB multi -layer board production process -outer layer dry membrane and graphic plating

The outer graphic transfer is similar to the principle of the inner graphic transfer. They are printed on the line graphics to the board with the method of light -sensitive dry membrane and taking photos. The difference between the outer layer of dry membrane and the inner layer of dry membrane is:

① If the reduction method is adopted, the outer dry film is the same as the inner dry membrane, and the negative sheet is used as the plate. The cured dry film on the board is a line. Remove the unskilled membrane and retreat after acid etching, and the line graphics remain on the plate because the membrane is protected.

② If the normal method is adopted, then the outer dry film is used as a plate. The cured part of the board is a non -line area (substrate area). After removing the non -solid membrane, the graphic plating is performed. There is no electroplating at the membrane, and there is no membrane. After the fascia, the alkaline etching is performed, and the tin is finally retreated. The line graphics remain on the board because of the protection of the tin.

③ Wet Filin (welding), the welding process is to add a layer of welded layer to the surface of the board. This layer of welded layer is called Solder Mask or welded ink, commonly known as green oil. Its role is mainly to prevent short circuits, insulation, insulation, and resistance to various harsh environments caused by the short circuit between the lines and other reasons, the short circuit between the lines, and the short circuit between the lines. The function of the printing board. Principles: At present, this layer of ink used by PCB manufacturers basically uses a liquid photosensitive ink. Its production principle is similar to that of line graphics transfer. It also uses Filin to cover the exposure and transfer the welding graphic to the PCB surface.

Fifth, PCB multi -layer board production process -Shen copper and thick copper

The metal of the hole involves a concept of ability, a thick diameter ratio. The thick diameter ratio is the ratio of the thickness of the plate to the aperture. , Thick diameter ratio. The thick diameter ratio is the ratio of the thickness of the plate to the aperture. When the board is continuously thickened and the pores are constantly decreased, chemical medicinal water is becoming more and more difficult to enter the depths of the drilling. Although the electroplating equipment uses vibration, pressurization, etc. The plating layer is still thin and still unavoidable. At this time, the drilling layer will be slightly open. When the voltage increases and the board is impacted under various bad circumstances, the defect is completely exposed, causing the lines of the board to disconnect and cannot complete the specified work.

Therefore, the designer needs to understand the processing capabilities of the manufacturer in a timely manner, otherwise the PCB designed will be difficult to achieve in production. It should be noted that the thick diameter than this parameter must not only be considered when designing through the hole, but also needs to be considered when the blind buried hole design.

 

Six, PCB multi -layer board production process -Wetfilin

① The process of wet Filin: Prelimable processing-> coating-> Pre -baking-> Exposure-> Show -> UV CITC -the SOLDMASK file associated with this process. Parameters such as welding -resistant pairing accuracy, the size of the green oil bridge, the production method of the pores, and the thickness of the welding resistance. At the same time, the quality of the welding ink will also have a great impact on the later surface treatment, SMT installation, preservation and service life. In addition, the entire process has a long production time and many production methods, so it is an important process for PCB production.

② The SOLDMASK file is associated with this process. The process capabilities involved include parameters such as welding -resistant pairing accuracy, the size of the green oil bridge, the production method of the pores, and the thickness of the weld. At the same time, the quality of the welding ink will also have a great impact on the later surface treatment, SMT installation, preservation and service life. In addition, the entire process has a long production time and many production methods, so it is an important process for PCB production.

③ The current design and production method of holes is a question that many design engineers are more concerned about. The optic problem brought by the welding is the project of PCB quality inspection engineers.

 

Seven, PCB multi -layer board production process -Chemical Shenxin

Chemical tin plating, also known as Shen Xi. The chemical tin plating process is to deposit tin to the PCB surface by chemical deposition. Its tin thickness is 0.8 μm to 1.2 μm, and it is gray -white to bright colors. It can well ensure the flatness of the PCB board and the coexist of the connector. Since the chemical tin plating layer is the main component of the solder. Therefore, the chemical tin plating layer is not only a protective coating of the connector, but also a direct welded layer. Because it does not contain lead and meets today’s environmental requirements, it is also the main surface treatment method in lead -free welding.

The new type of additive is added to the current chemical tin plating solution, and the reaction equation has also been completely changed, making the branches -like structure of the tin layer become granular crystals. Reduce the problem of copper tin alloy generation. Today’s chemical tin plating layer can experiment with weldability of welding and welding five times and show well. The current new problem is that Shenxi’s potion has a large impact on the welded ink, which is easy to cause welding stripping. However, many welded ink suppliers have been stepping up to improve their ink. Shen Xi’s potion is constantly improving, which can gradually meet the needs of the process.

 

Eight, characters

Because the accuracy of character requirements is lower than the line and welding, the characters on the PCB currently use the method of screen printing. The process is made by the printing board by the character Filin, and then the net is printed on the board with the net, and finally the ink is dried.

 

Nine, milling appearance

So far, the PCB we make has always belonged to the form of Panel, that is, a large board. Now that the production of the entire board has been completed, we need to separate the delivery graphic according to the large board (delivery or set) from the large board. At this time, we will use CNC machine tools to process in accordance with the advance procedures. The shape of the shape and strip mills will be completed at this step. If there are V-CUT, the V-CUT process is needed. The capacity parameters involved in this process include the tolerance, the size of the backward angle, and the size of the inner angle. The safety distance from graphics to the edge of the board should be considered when designing.

 

Ten, electronic test

Electronic testing is the PCB’s electrical performance test, which is usually also called the “pass” and “disconnection” test of PCB. In the electrical test method used by PCB multi -layer circuit board manufacturers, the most commonly used is two types: needle bed testing and flying needle test.

⑴ The needle bed is divided into general network needle beds and special needle beds. General needle beds can be used to measure the PCB of different network structures, but the price of its equipment is relatively expensive. The dedicated needle bed is specially formulated by a PCB, which is only suitable for the corresponding PCB.

The flying needle test uses the flying needle test machine. It tests the informant of each network through the mobile probes (multiple pairs) on both sides. Because the probe can be moved freely, the flying needle test is also a general -purpose test.