The appearance and development of printed circuit board (PCB) has brought about great changes to the electronics industry. It has become an indispensable component of various electronic equipments and instruments. With the continuous development of screen printing technology, the new screen printing materials, screen printing technology and testing equipment used in the PCB industry have been improved day by day. The current screen printing technology can adapt to high-density PCB production.
Screen printing material
1. wire mesh
The screen is the most important part of network printing, this is because it is the key to control the ink flow and print thickness, it determines the widely used durability and quality manufacturing technology in screen switch. In addition, the wire mesh and screen sensitive material has excellent combination, is also the production of high quality, high-precision screen printing plate is an important factor. In order to ensure a good combination of wire mesh and photosensitive material, the traditional method is to make new mesh roughening and degreasing, which can ensure the quality of the screen and prolong the service life of the wire mesh.
2. printing plate sensitive material
Printing plate photosensitive materials are commonly used diazo diazo, photosensitive diaphragm. In the process of screen printing, the diazo sensitive emulsion is widely used. The photosensitive film has uniform thickness controllable, high resolution, high definition, abrasion resistance, strong adhesion and screen and other characteristics, has been widely used in printed circuit board printing character.
3. nets frame
The material and cross section shape of the frame are very important. If the mesh frame is not strong enough, it can not guarantee the consistency of the tension. Now, the high tensile aluminum net frame is used.
4. screen printing ink
There are three general classification methods for screen printing ink:
First, according to the classification of printing materials can be divided into: paper screen printing ink (generally can directly use offset printing ink), plastic screen printing ink, fabric printing screen printing ink, glass screen printing ink, ceramic applique screen printing ink, etc..
Two, according to the components of the ingredients can be divided into oxidized conjunctiva drying resin material, volatile drying solvent ink, two component reactive ink and UV curing ink, etc..
Three, according to special use categories are: UV ink; luminescence, fluorescence, light storage ink; temperature ink, micro capsule ink (Braille, fragrance, foam, etc.); liquid crystal, conductive and magnetic ink; pearlescent ink, anti-counterfeiting ink, etc..
Application of PCB surface welding layer
The solder resist film of printed circuit board is a permanent protective layer. It not only has the function of preventing welding, protecting and improving the insulation resistance, but also has a great influence on the appearance quality of the circuit board. In the early stage of solder mask printing, it was first to use solder resist to make the screen pattern, and then to print the UV curable resist welding ink. Every time after printing, because of the deformation of wire mesh and inaccurate positioning, it will take a long time to scrape off the unwanted solder mask on the pad, which consumes a lot of manpower and time. Liquid photosensitive resist welding ink does not need to make halftone images, and uses empty screen printing and contact exposure. This process has the advantages of high accuracy, good adhesion, good weldability and high production efficiency, and has gradually replaced the photo bonded ink.
Application of corrosion resistant electroplated coating during PCB pattern transfer
In the process of making printed circuit boards, graphic transfer is the key process, and the transfer of printed circuit graphics has been commonly used in the past. At present, wet film is mainly used for making the inner layer line of multilayer printed board and making the outer line figure of double and multi layer board.
With the development of screen printing technology, printing technology plays more and more important role in PCB industry, its application, not only improve the PCB production efficiency, reduce the production cost of the printed circuit, but also improves the machining quality of printed circuit board. On the other hand, the research, development and application of screen printing materials, especially the development of functional inks, the application area of screen printing is more diversified, and has been expanding, such as membrane switch printing silver paste in the manufacturing technology and manufacturing; printing template paste SMT manufacturing technology; PCB Canbark the application of ink.