What is an appropriate method to determine the amount of desiccant to pack with a VME assembly which is populated with moisture sensitive plastic encapsulated microcircuits? The packaged assembly may sit in shipboard and landbased spare inventory for 15 or more years. The packaging technique is as specified in MIL-STD-2073-1C Method 51 (formerly IIc) with ESD protection. The formula in MIL-STD-2073-1C for calculating the quantity of desiccant to use does not have a storage time component and I have not found a storage duration mentioned in the standard. The similar industrial specification is EIA/JEP124. The method for calculating desiccant quantity does have a storage time multiplier. I plan on using an ESD, vapor barrier bag per MIL-B-81705C Type I, Class 1 which measures about 12"x16". The MIL-STD calculation would require 4.2 units of desiccant. The EIA/JEP calculation would require 3.5 units of desiccant for a 12 month storage duration. The slide rule calculator provided by the desiccant supplier says to use 1/2 unit of desiccant. If I use the EIA/JEP method for the 15 year duration then I would need to include 53.5 units of desiccant which would require more space than the VME card. This larger amount seems extremely impractical. The 1/2 unit quantity seems too little for the anticipated storage time. I would appreciate comments and ideas regarding this issue. Jim Baker Principal Hardware Design Engineer General Dynamics Defense Systems 100 Plastics Ave., Room 2154 Pittsfield, MA 01201 413-494-7152 email: [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************