Storage, cleaned surfaces

The stability and maintenance of a cleaned surface is often more critical than the final surface state which is achieved after the cleaning process. Storage in an ultraclean, controlled environment, a very expensive but most effective measure is usually seldom required. Instead of using a universal protection device, it is often easier and cheaper to identify the undesirable contaminants and to eliminate them from the storage environment. Such contaminants are usually the airborne ones, including various types of dust particles, atmospheric condensates of chemical vapours, and, last but not least, water vapour. The use of some preventive measures is, therefore, well worth considering. Contact with dust may be reduced drastically by storing the parts in a closed container or in a clean bench. 

Typical exposure times for UV/O3 cleaning are from a few minutes to remove a few MLs of hydrocarbon contamination to hours, days, or weeks for storage of cleaned surfaces. The UV/O3 cleaning technique has the advantage that it can be used as a dry, in-line cleaning technique at atmospheric pressure. It is also useful for cleaning holes (vias) in surfaces. 

Cleaned surfaces should be stored in a non-recontaminating environment. Often, surfaces to be stored are held in clean fixtures to reduce the necessity for handling the surfaces directly. The fixtures must be compatible with the storage environment"... 

Cleaned parts can be stored under liquids to exclude reactive gaseous agents. Metals stored in anhydrous liquids such as anhydrous alcohol or anhydrous acetone do not re-oxidize as rapidly as if they are exposed to the atmosphere. Storage of surfaces in degassed (boiled) water decreases the oxidation of the surface compared to water containing dissolved air. 

Housekeeping (contamination control) Efforts to minimize contamination in the processing area. Examples include cleaning surfaces, reducing clutter, storage in closed cabinets, no dust-catching surfaces such as the tops of cabinets or spaces under cabinets that are hard to clean, etc. 

Fish which is frozen in air blast will often be dipped into clean water afterwards, resulting in a layer of ice on the surface. This glazing process protects the fish from the effects of dehydration in subsequent storage. 

---