Semiconductors, integrated circuit chips and packages, liquid crystal displays, high-precision circuit boards, optoelectronic devices, various electronic devices, microelectronics industry, large-scale, ultra-large-scale integrated circuits require large amounts of high-purity water and ultra-pure water to clean semi-finished products and finished products. The higher the integration of integrated circuits, the higher the requirements for water quality. At present, the Ministry of Electronics Industry of China divides electronic-grade water quality technology into five industry standards, namely 18MΩ.cm, 15MΩ.cm, 10MΩ.cm, 2MΩ.cm, 0.5MΩ.cm, to distinguish different water quality.
1. The traditional water treatment method of preparing ultrapure water by ion exchange resin, the basic process flow is: raw water → sand carbon filter → precision filter → raw water tank → positive bed → negative bed → mixed bed (complex bed) → pure Water tank → pure water pump → rear precision filter → water point
2. The combination of reverse osmosis water treatment equipment and ion exchange equipment is adopted. The basic process flow is: raw water → sand carbon filter → precision filter → raw water tank → reverse osmosis equipment → mixed bed (complex bed) → pure water Box → pure water pump → rear precision filter → water point
3. Adopt the method of matching reverse osmosis water treatment equipment and electrodeionization (EDI) equipment. This is the latest process for making ultrapure water, and it is also an environmentally friendly, economical and ultra-pure water preparation with great development potential. Process, the basic process flow is: raw water → sand charcoal filter → precision filter → raw water tank → reverse osmosis equipment → electrodeionization (EDI) → pure water tank → pure water pump → rear precision filter → water point
At present, the processes for preparing ultrapure water for the electronics industry are basically the above three, and most of the remaining process flows are derived from different combinations and collocations based on the above three basic process flows. Now their advantages and disadvantages are listed below:
1. The first type of ion exchange resin has the advantages of less initial investment and less space, but the disadvantage is that it requires frequent ion regeneration, consumes a lot of acid and alkali, and has a certain degree of damage to the environment.
2. The second type uses reverse osmosis as a pretreatment and is equipped with ion exchange equipment. Its feature is that the initial investment is higher than that of ion exchange resin, but the regeneration period of ion equipment is relatively long, and the acid and alkali consumption is more than that of ion The resin method is much less. But it is still destructive to the environment.
3. The third type uses reverse osmosis as a pretreatment and is equipped with an electrodeionization (EDI) device. This is currently the most economical and environmentally friendly process for making ultrapure water. It does not require acid or alkali. The regeneration can continuously produce ultrapure water, which is not destructive to the environment. The disadvantage is that the initial investment is too expensive compared to the above two methods.