Released in February of this year, Version C of the moisture sensitive device handling standard includes more recognition than previously of desiccant cabinet technology and its use in preventing damage from moisture absorbed into components and boards. However, it is still considerably behind European manufacturers’ processes that have significantly eliminated high temperature baking of components and boards in favor of ultra low RH exposures (0.5%) at 25C or 40C. The oxidation and inter-metallics induced by higher temperatures are eliminated, improving solderability and joint reliability. Components and PCBs can be dried back to full floor life numerous times if necessary, something that’s impossible to do with baking and still be solderable.
J-STD-033C also accurately cautions about desiccant cabinet recovery time capabilities. Recovery time is the ability to return to set point after a door opening. 033C suggests that “the cabinet must be capable of recovering to its stated humidity rating within one hour from routine excursions such as door opening/closing.” Manufacturers need be aware of how many times their storage cabinets are being accessed in the course of a normal day, because with 60 minute recovery times, a cabinet can easily be averaging in excess of the 5% RH necessary to inhibit further moisture absorption. Current technology has again moved faster than the IPC JEDEC standards, with 4 minute recovery times now readily available.