Cleanroom

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Clean_room.jpg
Nasa's Glenn Research Center cleanroom.
A cleanroom is a manufacturing environment that has a low level of environmental pollutants such as dust, airborne microbes, aerosol particles and chemical vapors. More accurately, a cleanroom has a controlled level of contamination that is specified by the number of particles per meter-cubed (ppm) and by maximum particle size.
Contents

Overview

Cleanrooms can be very large. Entire manufacturing facilities can be contained within a cleanroom with factory floors covering thousands of square meters. They are used extensively in semiconductor manufacturing, biotechnology, the life sciences and other fields that are very sensitive to environmental contamination.

The air entering a cleanroom from outside is filtered to exclude dust, and the air inside is constantly recirculated through high efficiency particulate air (HEPA) and ultra low penetration air (ULPA) filters to remove internally generated contaminants. Staff enter and leave through air locks (sometimes including an air shower stage), and wear protective clothing such as hats, face masks, boots and cover-alls. Equipment inside the cleanroom is designed to generate minimal air contamination. Common materials such as paper, pencils, and fabrics made from natural fibers are often excluded. Low-level cleanrooms are often not sterile (i.e., free of uncontrolled microbes) and more attention is given to airborne dust.

Cleanroom HVAC systems often control the humidity to low levels, such that extra precautions are necessary to prevent electrostatic discharges.

Cleanroom classifications

The following is adapted from Rockwell Automation (http://www.rockwellautomation.com/anorad/guide/cleanroom_criteria.html):

US FED STD 209E cleanroom standards

particle/ft³
Class 0.1 µm 0.2 µm 0.3 µm 0.5 µm 1 µm 5 µm
1 35 7 3 1    
10 350 75 30 10 1  
100   750 300 100 10 1
1,000       1,000 100 10
10,000       10,000 1,000 100
100,000       100,000 10,000 1,000

ISO 14644-1 cleanroom standards

particle/m³
Class 0.1 µm 0.2 µm 0.3 µm 0.5 µm 1 µm 5 µm
ISO 1 10 2        
ISO 2 100 24 10 4    
ISO 3 1,000 237 102 35 8  
ISO 4 10,000 2,370 1,020 352 83  
ISO 5 100,000 23,700 10,200 3,520 832 29
ISO 6 1,000,000 237,000 102,000 35,200 8,320 293
ISO 7       352,000 83,200 2,930
ISO 8       3,520,000 832,000 29,300
ISO 9       35,200,000 8,320,000 293,000

Cleanroom class comparison

ISO 14644-1 FED STD 209E
ISO 3 1
ISO 4 10
ISO 5 100
ISO 6 1,000
ISO 7 10,000
ISO 8 100,000

See also

de:Reinraum


Cleanroom (Software Engineering)

Cleanroom is also a term used in software engineering.

Meaning 1: The process is based on very careful design of functions. The implementation of these are then peer-reviewed to verify that they do what they are specified to. By analogy with cleanrooms in semiconductor fabrication which prevent the need for cleaning silicon wafers by making sure that they never get dirty, Cleanroom development removes the need for debugging by ensuring that bugs never get introduced. (see also Rational Unified Process).

Meaning 2: Another different use of the term "cleanroom" in software engineering is the use of separate teams to specify requirements, implement functionality, and to compare the two. Communication between the groups is usually carried out only in writing, with all communication being reviewed by lawyers.

This method can be used to develop software in a way that can be demonstrated not to have infringed legal restrictions by a third party. This form of clean-room development was used to develop the first non-infringing third-party PC BIOS implementations.

See also

zh:净室 ja:クリーンルーム

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