SMTA International Conference Proceedings


AN EXAMINATION OF 'DRY BOX' DESICCANT STORAGE WITHIN THE PCB MANUFACTURING ENVIRONMENT

Author: Kevin McCarten
Company: Lizem Technologies, Inc.
Date Published: 9/21/2003   Conference: SMTA International


Seika Machinery, Inc.

Abstract: The discussion regarding ‘dry box’ or desiccant storage of MSD’s (Moisture sensitive devices) has increased over the past years with the introduction of new IPC Joint Industry Standards. More and more resources on the topic, many contradictory are available over the internet. Manufacturers are becoming aware of the possible benefits of Ultra-Low humidity storage, however there are many misconceptions and uncertainties regarding the proper use and functionality of these devices, including exaggerated expectations for results.

Dry boxes can be implemented at various points within the Mfg. environment; for med-long term inventory, or for short term handling on the production floor, and in some cases (with certain conditions) as a process replacement for baking. Bare boards, raw components and partially assembled PCB’s can benefit from ultra-low humidity storage.

Depending on the application (ie; short term, long term, ‘bake-out’), the items stored within, and their condition as they enter dry storage, various loads will be placed on the storage cabinets; however in all cases user expectations will remain the same; short recovery time after door open, and a constantly maintained ultra-low humidity (1 % - 5% RH) environment. Without the proper assessment of the load that will be placed on a particular dry box application, and an examination of the dry box variations available (ie N2 ‘trickle’, N2 Purge, Multi-desiccators, addition of heating, or a combination of any thereof, etc) it’s almost certain that manufacturers will not be satisfied with their observed results, and will not be storing their devices safely.



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