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Reducing Cleanroom Dangers |
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Any unwanted material, particle, chemical or other substance can
taint, pollute, defile, make impure or unclean the process or
product of a cleanroom. Contamination can take many forms, and to reduce the risks it is imperative American Society of Testing Materials’ standard for “Cleaning and Maintaining Controlled Areas and Clean Rooms,” (E 2042-04). Specific routine cleaning instructions shall be generated for each cleanroom and that an effective cleaning program be implemented and maintained consistently throughout the life of a cleanroom. When a cleanroom is operational, a routine cleaning and maintenance plan should be established according to the provided to the appropriate maintenance and quality assurance organizations. The cleaning plan shall be modified, as required, to reflect the operational needs of hardware being processed in the cleanroom, since cleaning during critical operations could result in damage and contamination of the hardware. Janitorial responsibilities in cleanrooms shall include emptying and cleaning of trash receptacles, wiping of all installed facility items such as wall vents, garment racks, and ledges and cleaning of floors and equipment such as shoe cleaners. Non-facility equipment is the responsibility of the using organization and shall be cleaned on a schedule that reflects the product requirements and cleanroom cleaning schedule. This includes work stands, work tables, deliverable hardware items and ground support equipment. Because of the potential for damage and contamination of user equipment and hardware, janitorial personnel shall be instructed to avoid such items when cleaning the room. Facility Equipment — The responsibility for the scheduling of routine cleaning and maintenance operations of equipment such as cranes and handling fixtures shall be mutually agreed upon by the using and facilities organizations, as a part of the cleaning and maintenance plan. Contingency Operations — In the event of an equipment failure or other condition that requires unplanned cleaning or maintenance operations, the user personnel and the responsible facilities and janitorial personnel shall jointly develop appropriate plans and procedures. Verification — A log sheet/cleaning checklist shall be maintained for each cleanroom and facility equipment item. The log sheets shall be initialed and verified that all scheduled cleaning and maintenance procedures have been performed. The log sheets shall contain space for notes and comments. Any violations of procedures, out of specification conditions, and potential operating problems shall be noted and reported to the responsible supervision. Routine Cleaning Operations Cleaning shall proceed in the same order each day as specified in the cleaning plan and detailed instructions. The cleaning shall begin with the removal of trash. Cleaning shall progress through the facility starting with the upper levels and moving down to the lowest level and from the “cleanest” areas to the “dirtier” areas, usually the exit area. Shoe Cleaning Machines — Shoe cleaning machines should be cleaned as required in accordance with manufacturers’ recommendations. To prevent the risk of electric shock, shoe cleaners shall always be unplugged before cleaning. The lid shall be removed and the bag checked, if there is one, and replaced if required. The inside of the machine shall be wiped clean and any debris removed. The cover shall then be replaced and the outside wiped. Finally, the machine shall be plugged in and checked for proper operation. Trash Collection — All trash shall be collected before the start of cleaning. Plastic liners from receptacles shall be collected by slowly folding the top of each bag closed, removing it from the container. Personnel shall be instructed to never deflate or “punch down” the bags inside the cleanroom. If debris or dust has escaped into the container, the inside of the container shall be wiped and vacuum cleaned. A new liner shall be replaced by unfolding it inside the container. The outside of the receptacle shall be wiped down. Trash bags shall be removed through the cleanroom exit door. Cleaning Solutions and Wiping Procedure — Cleaning is typically performed with DI water or dilute IPA although periodic wiping with a cleanroom detergent is recommended to remove residual film buildup. Dilute the detergent in accordance with vendor recommendation. The following procedure is recommended: A two-compartment bucket should be filled with DI water in one and an appropriate cleanroom detergent in the other. Follow recommendations for detergent. Dip in detergent and squeeze dry. After wiping the mop in DI water, proceed by vacuuming or wiping. Change the water after wiping each 10 m2(100 ft2) of surface. The DI water or cleaning detergent may be dispensed from a TFE-fluorcarbon squeeze bottle for smaller surfaces such as bench tops. Wiping Procedure: Use wipers with low NVR in accordance with Specification E 1560 and which are non-linting and absorbent in the following way: • Wet the cleanroom wiper and gently squeeze to remove excess water; • Fold the wiper into quarters; • Wipe in a straight line across the surface; • With each stroke, overlap the previous stroke; • Do not scrub or wipe in a circular manner to prevent the spreading of dirt; • After each stroke, refold the wiper to expose a new, clean surface; • Discard the wiper after all clean wiper surfaces have been used; • Continue wiping until all surfaces have been cleaned; • If detergent is used, perform a final wipe with IPA to remove any NVR; • Remove the bucket from the cleanroom; and • Empty, clean, and dry wipe the bucket. Walls — Walls may be cleaned, us ing DI water, with a tacky roll mop, a damp mop head made of knit polyester or polyvinyl acetate, or a mop draped with a damp cleanroom wiper. (Warning— A tacky roll mop can generate a significant electric charge and shall not be used near hardware sensitive to Electrostatic discharges.) Horizontal Surfaces — Clean horizontal surfaces such as benches, tables and ledges using DI water and wipers as described above. Vacuum Cleaning of Floors — Vacuuming shall be performed using either the facility vacuum cleaning system or a portable, HEPA filtered vacuum cleaner. The cleaning and maintenance plan shall include vacuum cleaning systems to assure that they are in proper working order and dirt is routinely removed from the dust bag or exhaust port. The following procedure is recommended: Draw the vacuum head toward the worker with each stroke overlapping the previous stroke. Lift the cleaning head and place it at the beginning of each stroke. Avoid back and forth motion which will disturb dust and push dirt from the cleaner head. Take precautions to avoid damage to hardware from long, heavy vacuum hoses. Wet Mopping of Floors — The following wet mopping procedure is recommended: • Use two buckets or a two-compartment bucket. Fill one with DI water and the second with the approved detergent solution. Use the precise, recommended detergent concentration. Excess detergent may leave a residue on surfaces. • Dip the mop into the detergent solution and squeeze dry for each stroke. • Puddling shall be avoided. • Rinse the mop in DI water after each stroke. • Draw the mop toward the worker with each stroke overlapping the previous stroke. • Change to clean water after every 10 m2 (100 ft2) of floor area is covered or as specified in the cleaning procedure. The water shall not be allowed to become gray or visibly dirty. Frequency of Cleaning — The frequency of cleaning depends upon the cleanliness requirements of the product being processed in the cleanroom and the types of processing operations being performed. Cleaning schedules when hardware is being processed shall be coordinated with the hardware processing operations. Cleaning of Janitorial Equipment All janitorial equipment shall be cleaned at the end of each cleaning shift. Equipment shall be dedicated for use in the cleanroom and shall be stored in an approved, clean location in the facility. Cleanroom janitorial equipment shall not be used in non-cleanroom areas in the facility. Training — Personnel performing cleaning shall be trained and certified in cleanroom disciplines. Additional training shall be provided for personnel performing precision cleaning. Contract Personnel — Outside contractors are sometimes employed for cleanroom janitorial services. Contractors and their personnel shall have demonstrated prior training and experience in cleanroom janitorial operations. If Category I cleaning is required, experience with NVR control and handling of hazardous solvents is necessary. If contractor personnel do not have the requisite experience, additional training shall be provided. Personnel operational restrictions and gowning requirements shall conform to those required for operations in the area based on the cleaning plan and special program requirements during primary, final, and routine cleaning. For example, no cleaning should be done when sensitive equipment is exposed, or during critical operations. Garments shall be changed daily during primary and routine cleaning and in accordance with cleanroom operating procedures during normal operations. FSM |
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