Cleanrooms are spaces that maintain low levels of airborne particulate and viable micro-organisms; any liquids and gases entering a cleanroom are purified to maintain the cleanliness level. Textiles may be used to prevent contaminants from entering, remove contaminants, prevent contamination by people and from new materials entering the clean space.
By Robert McIlvaine
Preventing contaminants from entering the clean space
Air filters installed in the ductwork ensure that clean air enters the cleanroom; most air is recirculated and filtered upon re-introduction. There can be multiple filters: the prefilter removes particles larger than a few microns and protects the downstream high-efficiency particulate (HEPA) filter. The prefilter can be wetlaid glass, as can be the HEPA filter, but in the HEPA filter the glass fibers are very small in diameter. Polyester airlaid nonwovens are often used in prefilters.
All water used in cleanrooms must be highly filtered. In the case of water for injection (WFI), the water must be especially pure because it will be used in drugs that will be injected into the human body.
Removing contaminants in the clean space
Textile wipes and swabs are used on surfaces within the cleanroom to remove particles, but when impregnated with disinfectants, they also kill micro-organisms. Materials used in wipes require special nonparticulate shedding qualities, so conventional wipes are not suitable for cleanroom applications.
Preventing contamination by people in the clean space, and by new materials entering the clean space
Some functions within a cleanroom cannot be handled economically with robotics, so people have to be able to function in a clean space. However, humans shed hundreds of thousands of particles every hour. Their contamination is minimized by essentially encapsulating them in a filter: gowns, masks, gloves and other apparel act as a barrier to prevent particles generated by the wearer from contaminating the air. In the ultra-cleanrooms used for semiconductor manufacturing, breath is also filtered in a design similar to a diver’s helmet.
To prevent contamination from new materials, gowns, gloves, filters and other products used in cleanrooms must be manufactured in cleanrooms and then packaged prior to transport.
Businesses that operate cleanrooms may include manufacturers of pharmaceuticals, semiconductors, food products, flat panel displays and memory storage. Operators of cleanrooms, including those manufacturingÂ pharmaceuticals, semiconductors, aseptically packaged food, flat panels and solar cells, will spend $7.5Â billion in 2015 for consumables. This is projected to include gloves, laundering of reusable garments, disposable clothing and reusable clothing, wipes and additional supplies.
The largest single purchasedÂ product is disposable gloves—universally used in all classes of cleanrooms and in all types of industries. Gloves must be changed each time a worker leaves or enters a cleanroom and must meet requirements for minimal particle shedding and VOC off-gassing. Packaging of gloves to prevent contamination during shipment from the ultraclean environment where they are manufactured to the ultraclean environment where they are unpackaged adds to the cost.
Reusable garments are often rented; laundries or processors also have to clean these garments in ultraclean environments. Garments are frequently disposed of or cleaned after each exit from the clean space.
The supplies market includes special mops, mats and furniture, which have to be built so they do not shed particulate or volatile organic compounds. Two-thirds of the supplies market consists of cleaning chemicals and disinfectants used in cleanrooms.
East Asian purchases of cleanroom consumables are not only larger than other regions, but are growing at a faster rate. This is due to the expansion of the flat panel, semiconductor, solar cell and medical device industries in that region.
Growth and trends in cleanroom markets
The semiconductor industry is on a growth spurt, and that is reflected in revenues for new rooms and in the amount of additional space. The Semiconductor Industry Association (SIA) reported the worldwide sales of semiconductors reached $78.47 billion during the first quarter of 2014, marking the industry’s highest-ever first quarter sales. Total semiconductor revenue in 2013 reached $318.1 billion, up from $303 billion in 2012.
The use of textiles in cleanrooms is growing due to the expanding industries where cleanrooms are essential, and industries are more willing to invest in products to reduce contamination. There is, however, a trend to replace people in cleanrooms with robotics. This is expensive and only applicable in certain situations, so it
is not likely to impact cleanroom textiles’ bright future.