Briefly describe the relationship between screen printing and printed circuit board 5

b. Note Method 80-150 mesh screen is recommended. The ink and curing agent should be used within 48 hours after mixing. When using manual printing, the force should be uniform and the speed of squeegee printing should not be too fast. Dry film thickness is preferably 20-25 m. The printing environment must be clean and dust free, operate under yellow light and avoid direct sunlight.
The printed pcb should be dried in a 70-75°C hot air oven to remove the solvent.
Single panel: 70～75°C/10～15min
Double panel: 70-75°C/8min on the first side
The second side is 70-75°C/10-20min
Hot air drying temperature can not be too high or too low, not to dry naturally, when the temperature is too high or the drying time is too long, the thermal cross-linking reaction of the ink film occurs, resulting in difficulty in development (residual glue), and the resolution is reduced; Low or time is too short, the solvent in the ink film does not completely evaporate. When the film is exposed, there will be a phenomenon that the photosensitive film sticks to the negative film. When developing, the cured film has poor resistance to development, and the film surface is dull or peeling off. The dried pcb should be cooled to Exposure can be done at room temperature.
The development performance of a developing machine with a spray pressure of 2.5-3.0 kg/cm2 is undoubtedly superior to that of immersion development. It is recommended that the production unit should use an automatic developing device as much as possible.
After the development of pcb must be heated at 140 ~ 150 °C temperature for more than 30min, in order to improve the overall heat resistance and other comprehensive properties.
7 Light-Soluble Solder Resist Ink is suitable for manufacturing rigid pcb solder resist pattern, fast photo-solidity, smooth printing, excellent heat resistance, strong adhesion, and can meet the requirements of single and double-sided pcb solder resist. Type 2 and Type 3 are suitable for Flexible PCB solder mask production, cured film is good flexibility, strong adhesion to the substrate.
Precautions Ink should be fully stirred for 15 minutes before it can be used to improve the rheological properties of the ink.
The screen is preferably 250-350 mesh.
8 Thermosetting solder mask ink two-component thermosetting solder mask ink, ink and curing agent mixed for a long period of use, high hardness of the cured film, strong adhesion, bright color, excellent heat resistance, low curing temperature, the plate is not easy Warp, and can be cured immediately after printing, suitable for manufacturing single, double-sided and multi-layer pcb solder resist pattern.
Instructions for use Before using the ink must be fully stirred for more than 5min, to prevent ink from the upper and lower components inconsistent, resulting in poor performance of the cured film. The ratio of curing agent to ink should be 3 to 5:100, too much curing agent, too high temperature or too long time will cause the cured film to easily fall off. Conversely, the hardness of the cured film will become low.
(4) Computerized plate making Screen printing plate making, the most common one at present is the computer design → laser photoplotter out screen printing plate making film (photographic film). Another way is to use the computer inkjet technology (without a digitized platemaking system) to directly image the screen plate coated with a photosensitive material, and use this technology to directly challenge the platemaking film (photographic film), not only in the plate making process. The camera was eliminated from the technology, and the darkroom process and silver salt base (platemaking film) were eliminated. This new technology from the computer to the screen has been commercialized, and its complete set of equipment has been put on the market. At present, the only drawback of this technology is that the system is extremely expensive. However, it can be foreseen that this high-priced state of screen-printing high-tech equipment cannot be maintained for a long time. It is inevitable that prices will be reduced drastically. This point can be made clear from the fact that computer and other information industry products have been significantly reduced in price year by year. What is even more gratifying is that the new advanced technology, which directly supports the production of screen printing plates, has been put into use.
(5) Parametric programming of screen production control With the introduction of the above new technologies, it has become possible to automate the control of screen printing prepress parameters, and because of this, modern screen printing will completely or farewell to the past. The full reliance on the workshop production mode. Screen printing will become a controllable and easily controlled production process. How are the production/production parameters controlled in the pcb screen production process?
1 Screen tension Screen tension is a very important factor in ensuring the quality of screen printing production. If we only pay attention to the high-techization of screen printing prepress equipment and printing equipment and post-processes in the production process and neglect the importance of screen tension, then all our efforts will be futile. According to experts' research, screen tension will directly affect the consistency of the screen thickness, the uniformity of exposure, the durability of the screen, the stability of the network spacing, positioning, size, the pressure of the blade, the speed of the blade, the flow of the ink. Sex, ink consumption, energy consumption.