There are a lot of different pieces of conformal coating equipment.  Each one of them has their own unique purpose and drying cabinets are no different.  The three main uses of drying cabinets are to extract air from around the assemblies, hold the assembly still during curing, and to protect the card from damage.

Drying cabinets are mainly used to extract air from around the assemblies to aid the drying process and to remove any dangerous fumes that are out-gassing during the curing process.  These fumes contain harmful solvents that are flashing off from the spraying or dipping process.

Another specific use of the drying cabinet is to ensure the assembly will be held still and prevent the uncured coating from flowing into areas that it should not be in.  Because all of these conformal coatings are liquid, they are quite susceptible to the laws of gravity.  If they are not held still and level, coating can run into connectors or other sensitive areas.

While coating is still uncured, they are particularly sensitive to damage from touch or particles in the air.  Much like curing concrete, there is much possibility to damage the integrity of the coating during this fragile stage.  Using a drying cabinet eliminates the possibility of any damage or contamination from the atmosphere.

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