Parylene (poly paraxylylene) is a generic name for polymers that belong to a unique chemical family and are used as conformal coatings in protective applications.
Water vapor trapping with a cryogenic surface was a concept developed by Dale Meissner in the 1970's as a way to speed pump down of vacuum chambers and to reduce the base pressure to enhance vacuum coating.
During laboratory evaporation, the main function of the Cold Trap is to collect harmful vapors before they enter the vacuum pump. For a vacuum pump that requires oil, collection of solvent vapors is essential to prevent them from collecting in the vacuum pump’s oil. Also, if corrosive or water vapors collect in pump oil, the vacuum pump will be damaged and eventually the vacuum pump will cease beyond repair.
On parylene vacuum coating equipment, a low-temperature trap is required between the coating chamber and the vacuum pump. See the following figure.
In large vacuum systems, the vacuum acquisition assembly may be composed of many types of vacuum pumps, and must include the front stage vacuum pump with roots pump.