Process and Information Document#A-103
Cleanroom Facility, Liquid Crystal Institute, Kent State University, Kent, Ohio
Glass Storage
There are multiple glass storage locations.
For raw stock glass, typically one opened pack of 14” by 14” glass sheets is available on the bench of the login computer. These sheets of glass cost about $12 each so excessive use will be charged out to appropriate accounts. This glass should not be handled at any time unless gloves are worn.
Additional stock glass is located in the cleanroom stock room. Only facility staff are allowed to remove glass from the stockroom in order to maintain an appropriate check on inventory. If the stock glass at the login desk is depleted, please contact facility staff for restocking. Note, that there are many different types of glass in the stockroom. Some of them cost as much as $50-100 per sheet and have different scribing and etching parameters. If the wrong glass is selected by users, excessive costs will be incurred and damage to machinery could result.
Uncleaned glass may be stored in carriers inside the cleanroom as long as the carriers are labeled with the person’s name and date and condition of the glass, i.e., ‘uncleaned’. There is a black cabinet for storing partically processed glass. This is not a ‘clean; cabinet so only store glass there that you intend to clean as soon as it is removed, prior to any further processing. Do not cover the glass with Saran wrap or aluminum foil. This does not help to help the substrates clean and in most cases makes them less clean. Remember, Saran wrap and aluminum foil are not clean in the first place and come off of cardboard rolls and out of cardboard boxes. Saran wrap also carries a substantial electrostatic charge and acts as a particle magnet.
Cleaned glass may be placed in the drying oven until dry, but may not be stored there. Damage to boats could result with prolonged exposure to 80C. Also, the drying overn is not a ‘clean’ oven, and substrates left in there longer than 30 minutes will probably have to be recleaned before subsequent processing.
Cleaned glass may be stored in ‘clean ovens and chambers, but only if they are not in use by others and only if they are labeled appropriately with name, date, condition of the glass, and expected date of removal. The coating ovens are clean and supplied internally with filtered air. They may be used to store cleaned glass at no heat overnight if not is use for baking. However, they must be labeled and ‘tagged out’ so that someone will know not to turn on the oven to preheat it for their own use, not knowing that substrates and carriers are inside. The fire department visits us about once a year when someone turns on an oven thinking it is empty and smokes a carrier. Ovens are ruined beyond the ability to clean them when this happens.
Cleaned glass may also be stored in the vacuum ovens on no heat if the same labeling as above is followed. Substrates may be stored under vacuum if the condition of the surface is critical for the next processing step. Allow the vac chamber to pump down to lowest pressure and then close the vacuum valve to isolate it from the line. This is the proper way to store substrates in a vac oven. There is no need to leave the line open and if the vac pump fails due to a power outage, air and possibly pump oils will be sucked back into the line and vac chamber ruining your substrates. Always isolate the unit before leaving it unattended for long periods of time (more than an hour).
Substrates may not be stored in unlabelled carriers or on general room use tables. Labelled boats left out will be put in the black storage cabinet. Unlabelled boats will be discarded without warning.