By definition “A ‘Cleanroom’ or ‘Clean Room’ is a guarded environment specially designed and maintained with minor level of atmosphere contaminant such as dust, airborne microbes, aerosol particles, and microorganisms, and chemical vapours for the purpose of manufacturing pharmaceutical & bio-pharmaceutical products, biomedical & electronic devices or scientific research and other critical manufacturing.” ISO 14644-1, FS209E, BS 5295, GMP EU Cleanroom Standards define and explain specification & standards for controlled environment and Data Centre Cleaning. The Federal Standard 209E which defines standard classes of air cleanliness for airborne particulate levels in cleanrooms is the most widely adopted standard among all. Eliminating or reducing pollutant to the specified standards to achieve clean zone is a serious process and procedure which requires special skills and knowledge.
What is Cleanroom definition & meaning | Classifications Cleaning Standards?
All aspects of contamination and environment conditions i.e. Air flow rates and direction, pressurization, temperature, humidity, and specialized filtration influence the Cleanroom Class & standard of cleanness. To achieve the desired cleanroom class all elements of contamination and environment conditions must strictly be controlled. To maintain the class and standard of a cleanroom a stuck cleaning regime is followed. Highly quality filters are used to removing impurities and fine air dust particles from air entering a cleanroom. The enclosed clean air inside a cleanroom is continuously recirculated and filtered through the high-efficiency particulate air (HEPA) or ultra-low particulate air (ULPA) filtering machines to filter and remove any contamination that may have been created internally. Physical access to the cleanroom is strictly controlled, any person entering the room wears clothing such as hoods, face masks, gloves, boots, and coveralls to reduce the chances of bringing contamination and dust from outside.
A particle (0.5 microns) 200 times smaller than a human hair (75-100 microns in diameter) may create a serious defect in cleanness class and grade of a cleanroom. Even the very minor level of contamination may cause costly downtime which costs a loss of productivity and revenue. Cleanness in a cleanroom is the very important factor not only during its construction phase but throughout its life-cycle.
Significance of the Clean Room
The clean room and the elaborate steps taken before entering it are vital to the success of every Hubble mission. Even a speck of dust or a fingerprint could severely damage the sensitive telescope components and instruments, so the clean room must filter out these harmful contaminants. Unlike personal digital cameras, a smudge or speck of dust on Hubble’s optics and sensors can’t be easily cleaned, especially once the instruments have reached orbit, Weiss says.
Besides being extremely clean, this facility is also the only place large enough to house Hubble’s components and simulators, as well as all the equipment needed to prepare the components for launch. In fact, the Goddard clean room is big enough to house two space shuttle payloads at the same time.
Because of its size and sanitary conditions, Weiss says all the components taken to Hubble on the four previous servicing missions (SM1, SM2, SM3A and 3B) made their way through Goddard’s clean room.
Metrics and Benchmarks
Cleanrooms are among the most energy-intensive types of facilities. This is primarily due to the cleanliness requirements that result in high airflow rates and system static pressures, as well as process requirements that result in high cooling loads. Various studies have shown that there is a wide range of cleanroom energy efficiencies and that facility manager may not be aware of how energy efficient their cleanroom facility can be relative to other cleanroom facilities with the same cleanliness requirements. Metrics and benchmarks are an effective way to compare one facility to another and to track the performance of a given facility over time. This article presents the key metrics and benchmarks that facility managers can use to assess, track, and manage their cleanroom energy efficiency or to set energy efficiency targets for new construction. These include system-level metrics such as air change rates, air handling W/cfm, and filter pressure drops. Operational data are presented from over 20 different cleanrooms that were benchmarked with these metrics and that are part of the cleanroom benchmark dataset maintained by Lawrence Berkeley National Laboratory (LBNL). Overall production efficiency metrics for cleanrooms in 28 semiconductor manufacturing facilities in the United States and recorded in the Fabs21 database are also presented.
Cleanroom Classifications Cleaning Standards
US FED STD 209E Cleanroom Classifications & Standards
ISO 14644-1 Cleanroom Classification & Standards
BS 5295 Cleanroom Classifications & Standards
GMP EU Classification & Standards
The Types of Contaminants
The entryway vestibules and suit-up process help counteract particulate debris, one of two contaminating offenders. Particulate debris includes tiny bits of dirt or dust workers might track in, such as loose fabric lint or flakes of dead skin. A robust ventilation system and an entire wall of air filters provide further protection.
The clean room ventilation system circulates almost one million cubic feet of air every minute through 9,000 square feet of HEPA filters located along one wall. The filters are not your typical off-the-shelf HEPA variety from the local home improvement store. These are specially designed to last several decades, Weiss says.
Combined, all these features afford the Goddard clean room a Class-10,000 rating. That means any cubic foot of air in the clean room has no more than 10,000 particles floating around in it larger than 0.5 microns.
How small is that? A micron is one-millionth of a meter, and typical “outside” air has millions of such particles. (A human hair is between 20 and 200 microns wide.) If an inch ballooned to the size of the Empire State Building, a 0.5-micron bit of dust would still be smaller than a penny on the sidewalk.
Molecular contaminants, the second offender, are a little more difficult to describe. Most people are familiar with “new car smell.” Over time that smell fades away because molecules in the car’s plastics and leather vaporize, or “boil off.” Exposure to the heat of a summer day speeds up the process.
The optics and sensors inside Hubble and other spacecraft go through a similar process. Orbiting Earth every 97 minutes, Hubble passes through the intense heat of the sun a whopping 15 times a day. Those higher temperatures can cause materials inside Hubble to boil-off molecules.
The loss of some molecules poses no threat to a car, but this molecular damage can devastate sensitive optical equipment. To prevent this, all of Hubble’s new components and instruments are put into a vacuum chamber and literally baked at high temperatures. This process eliminates potentially damaging molecules in one fell swoop, so they do not cause problems after the components are installed on Hubble.
What does Contamination mean in Cleanroom?
Contamination is a process or act that causes materials or surfaces to be soiled with contaminating substances. There are two broad categories of surface contaminants: film type and particulates. These contaminants can produce a “killer defect” in a miniature circuit. Film contaminants of only 10 nm (nanometers) can drastically reduce coating adhesion on a wafer or chip. It is widely accepted that particles of 0.5 microns or larger are the target. However, some industries are now targeting smaller particles.
A partial list of contaminants is found below. Any of these can be the source for killing a circuit. Preventing these contaminants from entering the cleanroom environment is the objective. It requires a commitment by everyone entering the Cleanroom to make it happen. Professional cleaning personnel need to be aware of the importance of controlling contaminants. Strict procedures should be followed whenever entering or cleaning a cleanroom. Compromise is not acceptable when cleaning in a Clean Room.
Sources of Contamination
This is a partial list of some of the commonly known contaminants that can cause problems in some cleanroom environments. It has been found that many of these contaminants are generated from five basic sources. The facilities, people, tools, fluids and the product being manufactured can all contribute to contamination. Review this list to gain a better understanding of where contamination originates.
Facilities: Walls, Floors, Ceilings, Paint, Coatings, Construction material (sheetrock, sawdust etc.), Air conditioning debris, Room air and vapours, Spills. and Leaks.
People: Skin flakes, Oil, Cosmetics, Perfume, Spittle, Clothing debris (lint, fibres etc.), and Hair.
Tool Generated: Friction, Wear particles, Lubricants, Emissions, Vibrations, Brooms, Mops, and Dusters.
Fluids: Particulates floating in air, Bacteria, Organics, Moisture, Floor Finishes, Coatings, Cleaning chemicals, Plasticizers (outgasses), Deionized water, Product generated, Silicon chips, Quartz flakes, Cleanroom debris, and Aluminum particles
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