Leo:

It depends to some extent on the type of components you plan to 
store. IPC-SM-786A, "Procedures for Classification and Handling of 
Moisture/Reflow Sensitive ICs" (published 1/95), is fairly clear on what 
a supplier or user needs to do to prevent part damage due to moisture 
absorption. Generally, dessicant is the preferred method. Test methods
are included. It also gives historical background on the problem. 
Nevertheless, the parts in question are plastic encapsulated ICs. No 
provisions have been made (yet) for passives, connectors, or parts with low 
thermal masses such as BGAs.

The document is available from IPC: $15 members/$30 nonmembers.

Mike Buetow
IPC Technical Staff
7380 N. Lincoln Avenue
Lincolnwood, IL 60646
P: 708-677-2850, ext 335
F: 708-677-9570
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 On Wed, 13 Sep 1995, Leo Reynolds wrote:

> 
> The problem we are facing is that a customer is having us hold SMT 
> devices for next years production.  We have some materials in storage 
> for 6 months already and by the time the material is in use, some may be 
> over one year.  In the past one customer who held material, for 15 
> months and then found it was unsolderable, scrapped over $100,000 worth.
> 
> Has the IPC issued any guidelines for storage times?  Are there 
> recommneded techniques such as vapor bags with dessicants or storage in 
> inert gas environments, etc that are practical?
> 
> Any comments on this topic would be greatly appreciated.
> 
> Leo Reynolds
> Electronic Systems, Inc.
> P.O. Box 5013
> Sioux Falls, SD  57117
> 
> Ph 605-338-6868
> Fax 605-338-5061
> 
>