What Are Cleanroom Classifications?

Clean room refers to a well-closed space where air cleanliness, temperature, humidity, pressure, noise and other parameters are controlled as required.

The development of clean rooms is closely linked to modern industry and cutting-edge technology. Due to the environmental requirements of the precision machinery industry (such as processing of gyroscopes and miniature bearings) and the semiconductor industry (such as large-scale integrated circuit production), the development of clean room technology has been promoted. Domestic statistics have shown that the qualification rate of producing MOS circuit dies in an environment without a clean level requirement is only 10% to 15%, and 64 is only 2% of the memory. At present, the application of clean rooms in precision machinery, semiconductor, aerospace, atomic energy and other industries has become quite common. ^[1]

To achieve cleanliness in a clean room, there must be comprehensive measures, including process layout, building planes, building structure, building decoration, personnel and material purification, air cleaning measures, maintenance management, and so on. Among them, air cleanliness measures are the fundamental guarantee for achieving cleanliness levels. In terms of air cleanliness, there are the following specific measures ^[1]

(1) When the product requires cleanliness of level 100, select the laminar flow type; when the product requires cleanliness of level 1000 ~ 100,000, select the turbulent flow type.

(2) Reduce eddy currents and avoid bringing pollutants outside the work area into the work area.

(3) In order to prevent the second flying of dust, the air velocity should not be too high. The air return of the turbulent clean room should not be located in the upper part of the work area. It should be arranged on the floor or under the side wall evenly.

(4) The airflow in the work area should be uniform, and the flow rate must meet the requirements of process and sanitation. The clean airflow should cover the working part as much as possible, so that the pollutants will flow to the air outlet before spreading.

(5) The working equipment should be arranged with a certain interval to create conditions for the layout of the air supply and return air outlets and the unobstructed air flow: the design of the air flow organization must consider the impact of tall equipment on the air flow organization.

(6) Clean benches should not be placed in laminar clean rooms. When placed in a turbulent clean room, it should be placed on the upwind side of the airflow in the work area to improve the indoor air cleanliness.

(7) When there is a fume hood in the clean room, it should be placed on the downwind side of the airflow in the work area to reduce indoor pollution. ^[2]

In general, the energy consumption of a purified air conditioning system is much larger than that of a general air conditioning system. The reason is that the load characteristics are different between the two. As far as clean rooms, especially semiconductor industry clean rooms, their load characteristics are:

(1) The clean environment serves the production process, and the clean room design must meet the environmental requirements of the production process, which is a matter of course. Therefore, in the design of the clean room, the environmental parameters of the production process should be realistic. Its area, floor height, temperature, humidity, cleanliness, etc. should be high to high, low to low, not higher. Under the premise of not affecting the normal operation of the production process, reduce the parameter requirements as much as possible, control the purification area, reduce the scope of the high-purification level clean zone, and strictly control the area of 100 and higher unidirectional flow clean zones. ^[3]

(2) Place the clean rooms of the same level as much as possible during the division of the production process. Set the processes with high cleanliness requirements on the upwind side, and process that generates fly ash, toxic, harmful, flammable and explosive gases Equipment and containers should be placed outside the clean area as much as possible. If it must be placed in the clean area, airtight measures should be taken to reduce the emissions of dust and exhaust gas. ^[3]