Cleanroom

A cleanroom or clean room is a facility ordinarily utilized as a part of specialized industrial production or scientific research, including the manufacture of pharmaceutical items, integrated circuits, CRT, LCD, OLED and microLED displays. Cleanrooms are designed to maintain extremely low levels of particulates, such as dust, airborne organisms, or vaporized particles. Cleanrooms typically have a cleanliness level quantified by the number of particles per cubic meter at a predetermined molecule measure. The ambient outdoor air in a typical urban area contains 35,000,000 particles for each cubic meter in the size range 0.5 μm and bigger in measurement, equivalent to an ISO 9 cleanroom, while by comparison an ISO 1 cleanroom permits no particles in that size range and just 12 particles for each cubic meter of 0.3 μm and smaller.

History

The modern cleanroom was invented by American physicist Willis Whitfield. As employee of the Sandia National Laboratories, Whitfield created the initial plans for the cleanroom in 1960. Prior to Whitfield's invention, earlier cleanrooms often had problems with particles and unpredictable airflows. Whitfield designed his cleanroom with a constant, highly filtered air flow to flush out impurities. Within a few years of its invention in the 1960s, Whitfield's modern cleanroom had generated more than US$50 billion in sales worldwide (approximately $406 billion today).
The majority of the integrated circuit manufacturing facilities in Silicon Valley were made by three companies: MicroAire, PureAire, and Key Plastics. These competitors made laminar flow units, glove boxes, clean rooms and air showers, along with the chemical tanks and benches used in the 'Wet Process' building of integrated circuits. These three companies were the pioneers of the use of Teflon for airguns, chemical pumps, scrubbers, water guns, and other devices needed for the production of integrated circuits. William (Bill) C. McElroy Jr. worked as engineering manager, drafting room supervisor, QA/QC, and designer for all three companies and his designs added 45 original patents to the technology of the time. McElroy also wrote a four-page article for Micro Contamination Journal, wet processing training manuals, and equipment manuals for wet processing and clean rooms.

Overview[edit]

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, solar panel, rechargeable battery, LED, LCD and OLED display Manufacturing, biotechnology, the life sciences, and other fields that are very sensitive to environmental contamination. There are also modular cleanrooms.
The outside air entering a cleanroom is filtered and cooled by several outdoor Air handlers using progressively finer filters to exclude dust, and the air inside is constantly recirculated through fan filter units containing high-efficiency particulate air (HEPA), MERV 17-20 and/or ultra-low particulate air (ULPA) filters to remove internally generated contaminants. Special lighting fixtures, walls, equipment and other materials are used to minimize the generation of airborne particles. Plastic sheets can be used to restrict air turbulence.The air temperature and humidity levels inside the cleanroom are tightly controlled. Static electricity may be controlled using ionizing bars. Cleanrooms may also have numerous seismic base isolation systems to prevent costly equipment malfunction.
Staff enter and leave through airlocks (sometimes including an air shower stage), and wear protective clothing such as hoods, face masks, gloves, boots, and coveralls. This is to minimize the carrying of particulate by the person moving into the cleanroom.
Equipment inside the cleanroom is designed to generate minimal air contamination. Only special mops and buckets are used. Cleanroom furniture is designed to produce a minimum of particles and is easy to clean.
The selection of material for the construction of the cleanroom should not generate any particle hence monolithic epoxy or polyurethane floor coating is preferred. Buffed Stainless steel or Powder-coated MS sandwich partition panels & ceiling panel are used. Corners like the wall to wall, wall to floor, wall to ceiling are avoided by providing coved surface and all joints need to sealed with epoxy sealant to avoid any deposition or generation of particles at the joints.
Common materials such as paper, pencils, and fabrics made from natural fibers are often excluded, and alternatives used. Cleanrooms are not sterile (i.e., free of uncontrolled microbes); only airborne particles are controlled. Particle levels are usually tested using a particle counter and microorganisms detected and counted through environmental monitoring methods. Polymer tools used in cleanrooms must be carefully determined to be chemically compatible with cleanroom processing fluids  as well as ensured to generate a low level of particle generation.
Some cleanrooms are kept at a positive pressure so if any leaks occur, air leaks out of the chamber instead of unfiltered air coming in.
Some cleanroom HVAC systems control the humidity to such low levels that extra equipment like air ionizers are required to prevent electrostatic discharge problems.
Low-level cleanrooms may only require special shoes, with completely smooth soles that do not track in dust or dirt. However, for safety reasons, shoe soles must not create slipping hazards. Access to a cleanroom is usually restricted to those wearing a cleanroom suit.
In cleanrooms in which the standards of air contamination are less rigorous, the entrance to the cleanroom may not have an air shower. An anteroom (known as a "gray room") is used to put on clean-room clothing.
Some manufacturing facilities do not use fully realized cleanrooms, but use some practices or technologies typical of cleanrooms to meet their contamination requirements.
In hospitals, theaters are similar to cleanrooms for surgical patients' operations with incisions to prevent any infections for the patient.