Friday, July 10, 2009

Cleanroom Equipment and Materials

The following guidelines are suggested for proper handling of equipment and materials in the cleanroom:

All buckets should be made of plastic* or stainless steel and should be discarded when they become too scratched or worn.

Carts should have a stainless steel or smooth painted surface with wheels made of polyurethane, or covered with approved cleanroom tape.

Furniture constructed of Formica, stainless steel, or polypropylene with non-shedding surfaces on tops and bottoms and free of scratches, is acceptable.

Glove Box
A glove box may be used for the containment and handling of multi-page documents. The glove box is constructed of plastic with a clear cover for ease of viewing. Gloves are attached for movement of papers.

Lubricating Oils
Always use low-outgassing oils and wipe excess oils from all surfaces to prevent particle accumulation.

Packaging Material
Common packaging materials include nylon, polyethylene, polyethylene and nickel/Mylar laminate. These materials vary in level of cleanliness, with some as low as one particle per square foot. Others may need to be cleaned before being used for packaging.

Paint used in the cleanroom should be scratch and chip resistant and low-outgassing, such as two-part polyurethane or epoxy based paint.

Paper Products
Regular paper and cardboard should never be allowed in the cleanroom. Use only approved cleanroom paper such as Tyvek or paper that has been wrapped in cleanroom packaging.

Use only one-piece ball point pens. Click-type pens will generate metal and plastic particles whenever they are retracted. Do not use pencils as they will generate graphite particles.

Rubber Items
Rubber items can shed and should be contained in cleanroom packaging material. Also, certain solvents can attack rubber and break it down.

Shelves/Storage Cabinets
Shelves should be constructed with open grate stainless steel to minimize air turbulence. Keep shelves and cabinets away from critical process areas to reduce the formation of vortexes.

Keep solvents in safety approved containers. Cleaning and processing solvents should be filtered before use and should contain little or no soluble residue.

Storage Containers
Small containers with felt, foam, wood, or leather linings should be covered and sealed with cleanroom packaging material.

Vinyl, nylon, and Teflon tapes are appropriate for cleanroom use. Tapes should not leave adhesive residues behind when pulled up.

A cleanroom-dedicated tool set will eliminate the need for repeated cleaning to perform routing jobs. Tethering tools with a vinyl covered cable may be necessary at elevated heights. Whenever an abrasive tool, such as a drill or file is used, a vacuum should be utilized to catch particles generated by the tool.

Vacuum Systems
Some cleanrooms use a central vacuum system with internal hoses and attachments. HEPA filtered exhausts should be used on portable vacuum cleaners so the cleanroom is not contaminated during cleaning.

Vented Cooling Systems
Some equipment consoles may contain fans to cool electronic parts. Exhaust from consoles should either be vented to the outside or filtered within the cleanroom.

*Plastic Items
Plastic items are acceptable where particulation is concerned. Plastics are, however, outgassing substances since they contain plasticizers that make them pliable and flexible. The plasticizers can evaporate from the plastic and condense on nearby surfaces, possibly affecting product processing.

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