The establishment and development of any high and new technology now seems to obey the "3E principle." The so-called "3E" refers to Ecology, Energy, and Economy.
The increasing popularity of liquid photosensitive resist inks has made it one of the advanced technologies in the transfer of precision printed circuit boards. Many manufacturers in the world have continuously improved and improved their product performance to meet the increasing demands in production. High quality requirements and increasingly strict environmental restrictions. From the current application and future development trends, liquid photosensitive resist inks will continue to be researched and developed in the following areas [12–14]:
2. 1 Adapting to the requirements of environmental protection The rapid industrialization from the 1950s to the 1960s, pollutants emitted by human activities exceeded the capacity and self-purification of the earth and caused global pollution, causing public hazards that threatened the survival of humankind. In the 1980s, The global environment is further deteriorating and poses a great threat to the sustainable development of the economy. People gradually realize that volatile solvents cause the destruction of ozone in the atmosphere and cause harm to the environment. In the United States, California has restricted new processes from using volatile substances. Organic solvents; the United States and the European Community have legislation that allows solvents to evaporate into the atmosphere in volumetric quantities.
The basic components of the liquid photosensitive resist ink are organic compounds such as phenolic resin, epoxy resin, and photosensitive polymer. Now the solvents that cause ozone damage in the atmosphere are still used in resist inks, such as glycol ethers and binary Organic solvents such as alcohol esters. The liquid photosensitive resist inks in the market contain organic solvents or volatile organic compounds. The third-generation water-based liquid photosensitive resist film technology now developed has greatly reduced the volatile solvents. Application content.
The first generation of ink is developed with organic solvents, and the second generation is changed to a solvent carrier, developed with a low concentration of sodium carbonate or potassium carbonate solution. If the use of screen printing liquid photosensitive resist ink is reduced by the solvent carrier 390 ~ 400 g / L 120 to 150 g/L of the water carrier, and the ink applied by the curtain is reduced from 550 to 600 g/L of the solvent carrier to 70 to 120 g/L of the water carrier, and the environmental and human hazards are reduced. To a lesser degree, the new water carrier technology utilizes emulsification technology to disperse the polymer into many stable, small-point states suspended in water. These polymer dots are the dispersed phase in the emulsion while the water is continuous or stationary. These polymers are insoluble in water, and in the process of water evaporation, there is still a small amount of solutes and water left in the polymer to form a hard and inviscid film.
2. 2 Adapting to the Thin, Fine, and Thin Development Directions of PCBs Since PCBs are being developed in a thin and light-weight direction, for example, the surface mounting of printed circuit boards for high-speed circuits requires the control of characteristic impedance and the use of thinner materials. Liquid photosensitive resist inks are also suitable for thin substrates. However, due to the semi-transparent substrate of the printed board, if the thickness of the plate is less than 0.8 mm, the UV light will directly penetrate the substrate during double-side exposure. Affecting the other side of the exposure pattern, resulting in mutual interference between the two-sided exposure graphics. Therefore, for thin substrates can currently only use a single-sided production process, the first side after the first surface processing, the second side, so the production efficiency is lower by half. The developed product can be applied to the application of double-sided simultaneous exposure of thin substrates.
In accordance with the technical requirements of the surface mount printed circuit board and the multichip module (MCM), the centerline of the lead wire is reduced to 0.3175 mm or less by 0.15 mm, so that the land or lead pitch is also from 0.2 mm. To 0. 1 mm, even 0. 05 mm, which requires a higher accuracy of the resist pattern, the ability to handle 0. 05 mm welding pitch.
The ink should have good printability, such as proper shakiness adjustment and fluidity, and at the same time excellent defoaming ability; the wet weight of the ink, high solid content, screen printing should have a good shielding effect of the wire, both guaranteed The ink thickness at the edge of the circuit is thinner than the height of the SMD connector pad or pins. The resolution of the ink is high, the resolution is good, and the side walls of the developed ink are nearly vertical. There is almost no side etching and the requirement is very high. In line technology, printing lines between SMD pads or pins can prevent solder bridges or laps from welding.
3 Conclusions and Outlook
In general, the use of a new generation of liquid resists has the following advantages: 1 High fine line resolution; 2 Can realize PCB design with reduced or no pad; 3 Can make the best orthogonal rectangular pattern; 4 board line width and graphics height tolerance minimum. These advantages, can achieve PCB production of high line density, well-defined conductive patterns, and the short connection with the integrated circuit, forming a short and thin high-density area, reduce the line pairs The noise sensitivity and crosstalk signal interference can produce lighter and thinner printed circuits, and the effective utilization rate is high. The material cost is much lower than the dry film. In addition, the flatness of the surface of the copper clad laminate is not high. Even with scratches, it can still be fully covered by the resist, and the dry film requires that the board surface is flat, otherwise it will cause the circuit to be short-circuited or open circuit. Therefore, the use of liquid photoresist also helps reduce the cost and increase the yield. .
Liquid photosensitive resists have been applied to the production of printed circuit boards (PCBs) since the early 1980s and have been continuously improved. After entering the 1990s, the application of liquid photosensitive resists has undergone new development. Flexibility or flexibility The improvement has been applied to mobile phones and portable personal computers as an insulating layer for build-up multi-layer printed boards. It is believed that its use will increase, and it will provide high-density printed circuits. High-level, thin-type development provides the conditions. Due to the significant advantages of liquid photosensitive resists, it was widely welcomed by PCB manufacturers as soon as it became available, and its usage increased dramatically. In 1996, the world usage was about 4 000 tons. Among them, the Chinese market is about 200 t. The domestic demand rose to 300 t in 1998. In 2000, the domestic market demand exceeded 500 t. Therefore, with the rapid development of high-density PCBs in China, liquid photo resists will There are more attractive development prospects.
Source: China Sensitive Materials Network
tv cabinet,tv unit, tv stands,floating tv stand
Guangdong Planet Cabinetry Co., Ltd. , https://www.ptkitchencabinet.com