About Cleanrooms

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Introduction to Cleanrooms and Cleanroom Products

A cleanroom is a controlled environment where concentration of airborne particles is controlled to specified limits. These contaminants are found in our environment or generated by people, process, facilities and equipment. The air in a typical office building contains from 500,000 to 1,000,000 particles (0.5 microns or larger) per cubic foot of air. A Class 100 cleanroom is designed to never allow more than 100 particles (0.5 microns or larger) per cubic foot of air. Class 1,000 and Class 10,000 cleanroom are designed to limit particles to 1,000 and 10,000 respectively. The level to which these particles need to be removed depends upon the standards required. The commonly used standards are the ISO 14644 and the Federal Standard 209E. Attached table shows the classification of cleanroom standard against particles found in it.

ISO 14644-1 Cleanroom Standards

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Note: 1M3 is approx 35.2 ft3

To appreciate the stringent standard of a cleanliness in cleanroom, it is useful to note that 0.5um is about 1/200 the diameter of human hair. Cleanrooms are planned andmanufactured using strict protocol and methods. They are frequently found in electronics, pharmaceutical, biopharmaceutical, medical device industries and other critical manufacturing environments. They are kept clean and standard maintained by controlling and eliminating possible sources of contaminants (things that go into a cleanroom); and to control the total environment via air flow rates and direction, positive pressurization, temperature, humidity and used of specialized filtrations.

Once a cleanroom is built it must be maintained and cleaned to very high standards. There must be also set protocols and standards to personnel and products entering a cleanroom.

Sources of Contamination

Contamination is a process or act that causes materials or surfaces to be soiled with contaminating substances. Generally the sources of contamination can be traced to the following:

sources

Products use for Contamination Control in a Cleanroom

Generally there is confusion between cleanroom classification and cleanroom products. Class 10, class 100 or class 1000 refer the cleanliness requirement of the cleanroom and not directly related to cleanroom products used. Cleanliness level of the products used should be determined by the users and consistent with the manufactured products requirement. For example it may not be helpful to use a very clean gloves with a non-cleanroom wiper. User should ask for products specifications to ensure that they meet their requirements.

It is necessary to implement rules and standard to ensure that cleanroom protocols are maintained. Some of the best practices and products use for contamination control are as follows:

1. For Facilities

Furniture used inside a cleanroom is generally made from good grade stainless steel or non-shedding plastic material. Cushion cleanroom chairs should be cover with non-contaminating PVC leather with build in air filter. Furniture should be grounded to prevent build up of static charges.

Sticky mat is also recommend to be placed at doorway to staff entrances, changing room etc to prevent dirt from entering the cleanroom.

2. For People (Operators, technicians, visitors etc)

The human body is one of the biggest generators of cleanroom contaminants. The skin flaks, the hair, body fluid, cosmetics and dirt can cause serious contamination. The following products are generally used to prevent such contamination.

a) Cleanroom apparels

Jump suit, hood, booties and safety booties

  • Generally recommended for Class 10,000 or better cleanroom use. The cloth material used in construction is usually polyester with conductive ESD yarn stripe or grid to discharge statics from the human body.  Among other things, a good cleanroom uniform is one that uses breathable fabric with good carbon yarn, interlocking panels and all edges sealed.
  • Booties are worn together with jump suit. Sole of booties are usually made of non-marking PVC or PU material. PU sole material is softer, lighter and helps reduce fatigue.
  • Safety booties are booties with steel toecap embedded. They are recommended for foot protection when heavy parts or machinery are being handled in the cleanroom.
  • Smock, jacket, lab coat, cleanroom shoes, cleanroom safety shoes and sandals.
  • Smock, jacket and lab coat are generally recommended for class 100,000 and above cleanroom. Fabric used for smock is generally similar to cleanroom jumpsuit albeit less stringent.
  • Cleanroom shoes, safety shoes or sandals are usually used together with smock and jacket. They are clean and used indoor to differentiate from outdoor wear shoes.  . PU soles shoes are softer, lighter and help reduce fatigue.
  • For less critical area, PP or CPE shoecover can be used over walking shoes to reduce dirt from entering production area.

b) Facemasks

  • Nonwoven 3 ply face masks are usually used in critical cleanroom. They come with a melt-blown filter layer to prevent large particles and fluid from coming out of the month.
  • Elastic band type of mask is preferred for easy donning while 4 ties type are recommended for its snug fit.
  • Nonwoven 2-ply face masks are also used for good breathability and long duration use.
  • Sometimes paper face mask is use in less stringent environment.

c) Gloves and finger cots:
The hands are the most likely parts of the body to come into contact with the products. Therefore the type of gloves and their cleanliness is very important in the selection process.

  • Cleanroom gloves: Cleanroom gloves should be used only once and disposed off. Cleanroom gloves, unlike examination gloves, do not contain fillers, chemicals that cause outgassing, or polymers coating that may leave stains on products. Commonly used disposable gloves in cleanroom include Latex gloves, Nitrile gloves and Vinyl gloves.
    • Both Nitrile and Latex gloves can be chlorinated and washed with de-ionized water (DIW) to remove surface particles and metallic contents to very low level and are suitable to very stringent cleanroom uses.
    • Latex gloves provide good fit and elasticity, but have a strong latex smell and may be unsuitable to individuals with latex allergies.
    • Nitrile gloves provide a fairly good fit and elasticity and do not cause allergy. It also has some static dissipative properties that is critical for products that are ESD sensitive.  Nitrile gloves also tend to have better chemical resistant properties than Latex gloves.
    • Vinyl gloves can be fairly clean if manufactured in a clean environment. It does not have very good fit or elasticity compared to Latex or Nitrile gloves.  Its main advantage is its cost effectiveness.

It is always advisable to ask for product specifications and test reports for cleanroom gloves.

  • Woven gloves: Woven gloves are usually used for packaging or assembling work in Class 10k or more cleanroom. These gloves include polyester gloves, nylon gloves, ESD nylon gloves, and cotton gloves.  Some of these gloves have special coating for example PU coated, nitrile coated, PVC dot coated etc to give extra grip, abrasion or puncture properties.
  • Specialty gloves: Specialty gloves are gloves that are customized for particular function. Examples of such gloves are cleanroom chemical resistant gloves, cut resistant gloves, cleanroom heat resistant gloves, cold resistant gloves etc.
  • Finger cots: finger cots are commonly used in less critical cleanroom environment when only the fingers touch the products. Finger cots are usually made from latex or nitrile material. Cleanroom used finger cots are chlorinated and DI water washed to reduce particles and ionic contents.

4.Indirect Materials

Many indirect materials are used in the cleanroom to facilitate the manufacturing process. Some of the common indirect materials are:

  1. Packaging bags: Finished or semi finished products need to be packaged before moving out of the production area.  Commonly used packaging materials include PE bags, static shielding bags and moisture barrier bags. These packaging materials are specially selected, made and packed in cleanroom to ensure that they do not contaminate the products that are being packed.
  2. Wipers: Cleanroom wipers are used in the cleanroom to clean or dry products.  Wipers are generally divided into woven and nonwoven wiper.

Woven wipers:  Made from polyester material with the edges sealed to prevent particles generation from the end of the yarns. Clean room wipers are washed with DIW to remove particles and ionic contents.  Polyester micro denier wipers are specially knitted wipers with high particle removal property for critical cleaning.

Nonwoven wipers: Made from poly-cellulose, rayon or cotton material.  They are usually not as clean as the polyester wiper but have superior absorbency. Generally they are used in less critical applications and for the wiping of tools and equipment before entering the cleanroom.

Presaturated wipers:  Wipes are pre-mixed with certain % of IPA and DI water such that they can readily be used for wiping and cleaning. These pre-saturated wipers can be packed in canisters, pouches or individual sheets for the convenience of the end users.

Cleaning and mopping of cleanroom is very important for the cleanliness and maintenance of cleanroom. Mops used in cleanroom are usually made from micro denier wiper material.

  1. Cleanroom stationery includes cleanroom paper, notebooks, computer form, labels and pens and many others. Cleanroom papers are specially processed paper to minimize particle generation on the surface of the paper.  It also has low extractable and low metallic contents to prevent contamination of the cleanroom.  Cleanroom papers are use for notebooks, labels, computer forms and other paper items. Cleanroom pens are pens with ink that has low sodium and other metallic content.  Cleanroom labels use adhesive that contains low ionic content and does not leave stains or marks when removed.
  2. Tools like tweezers and pliers should be used to handle products to prevent contamination. Such tools are usually made of high quality stainless steel or special materials to prevent rust or other contaminants.

The above are just some of many products used inside cleanroom, for more products and information, kindly visit our products section or contact us directly at gsg@gsg-ultra.com