сleanroom (rus. чистoе помещение otherwise чистая комната) — The premises where the concentration of suspended particles (mist spray) does not exceed a standard level and the needed temperature, humidity and pressure is maintained as necessary.

Description

Cleanrooms are a key element in the infrastructure of specialised research centres, as well as of various high-tech production facilities in the aerospace, electronics, pharmaceutical and chemical industries.

Cleanrooms can be constructed within premises where the concentration of suspended particles (mist spray) does not exceed a standard level and where the required temperature, humidity and pressure are also maintained as necessary.

Cleanrooms are classified by purity grade, which determines the various maximum particle counts. The highest class can be 10 000 times purer than medical operating theatres, to ensure an average concentration of less than one dust particle per cubic decimeter of air. To achieve this level of purity, a complex set of engineering and technical solutions are required, as follows:

- the minimisation of the initial level of pollution during the construction phase;

- careful selection and correct installation of all the complex technological and auxiliary equipment;

- providing multistage cleaning of the air supplied to the room and efficient stale air extraction;

- ensure optimal internal division of space into various purity zones;

- perform constant (continuous or constant interval) monitoring of actual purity levels using particle counters;

- all personnel must strictly comply to cleanroom operation and maintenance requirements.

Micron-size contaminants that are a result of production and research activity can be removed efficiently by a stable laminar (in case of cleanrooms of the highest purity grades) ultrapure airflow within the entire room. In most cases, such air is supplied via ceiling ultrafine filters. The additional insulation of internal space to prevent external contamination is achieved through arranging a higher-pressure area for the clean space.

To maintain the required level of cleanliness, it is also necessary to ensure that all the components in the premises which have direct or indirect contact with a cleanroom, particularly, ceilings, floors, walls, furniture, process equipment and accessories, produce and retain as few contaminants as possible. In general, conventional paper, pencils, and natural fibre products are not allowed, special substitutes are used instead, and construction materials are selected primarily by their abrasion resistance and molecular evaporation over the entire range of operating conditions and loads.

One of the major sources of pollution in a cleanroom is the staff. Therefore, in general, they must use protective clothing made from special materials, and no make-up, jewellery and painted nails are allowed. Employees enter the cleanroom only through special airlocks, and lots of manufacturing processes are absolutely non-attended.

For security reason in some premises continuous gas monitoring has to be installed. Additionally, for particle control in most spaces there is a need for temperature and humidity control to a strict level and ESD (Electro-Static Discharge) and EMI (Electro Magnetic Induction) also have to be controlled, as they influence the process tool function. In some of the above activities it is also necessary to control vibration by special construction methods and anti vibration equipment.

Modern cleanrooms can be quite large, sufficient to house entire production lines with a footprint of hundreds or even thousands of square meters. The largest consumers of the technologies above are the manufacturers of semiconductor components, processors, memory cards and hard disks. Nevertheless, advanced technologies to be developed and commercialised in bio and nanotechnology industries can significantly increase the amount of cleanrooms to be constructed in the near future and set new requirements for cleanliness standards.

Authors

  • Nanii Oleg E.
  • Zelikov Vladimir V.

Sources

  1. Cleanrooms and associated controlled environments// Mezhgosudarstvennyjj standart GOST ISO 14644-1-2002. — M.: IPK, izd-vo standartov, 2003.
  2. Ljungqvist B., Reinmuller B. Clean Room Design: Minimizing Contamination Through Proper Design. — Interpharm Press, 1996.
  3. Whyte W. Cleanroom technology: fundamentals of design, testing and operation. — Wiley, cop., 2001.

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