Graham,

You should be aware of the following information relative to dry storage for
moisture-sensitive devices:

Contrary to popular belief, it is not safe to assume that all MSDs can be
stored in a dry cabinet for an extended period of time. Over time the
components will saturate to the ambient conditions inside the dry box (10%
RH is common) and this actually exceeds the critical level for many devices.
The level of risk and the time required to exceed the critical level are
directly related to the MS level and body thickness of the components and to
the RH level in the dry box.

To account for this situation, the IPC/JEDEC standard J-STD-033 is currently
being revised to include a limit of 90 days maximum of storage in a dry
cabinet. (I can send you a copy of the proposed revision if you want).

A better option for long term dry storage is to keep MSDs inside a dry bag
with desiccant and optionally to place this dry bag in a dry environment. Of
course the bags are not perfectly moisture-proof but they will offer a drier
environment than a standard dry box for a longer period of time. They are
designed to protect the components for a minimum of 12 months in a
non-condensing environment of <40C/90%RH. The drier the environment around
the bags the longer it will take before too much moisture gets inside. When
you open the bag, the Humidity Indicator Card (HIC) inside will indicate if
parts need to be baked before processing.

I am in the process of putting the finishing touch to a technical paper on
the subject of MSD dry storage that will be presented at the upcoming APEX
technical conference. I would be glad to send you a copy of this paper if
you are interested.

Francois Monette
Cogiscan Inc.
50 De Gaspe, Suite A5
Bromont, Quebec, Canada, J2L 2N8
Tel : (450)534-2644
Fax: (450)534-0092
www.cogiscan.com


Date:    Tue, 27 Nov 2001 07:02:57 -0500
From:    Graham Collins <[log in to unmask]>
Subject: Re: BGA long term storage?

Hi Doug!
Indeed - not a new problem - and one we have faced on other programs.  =
It's just the BGAs that are new to us for this problem.

Nitrogen storage is available here and I expect that's what we will use =
(unless some other TechNet guru has a better idea!).

I've heard of ROSA, and in fact Dave was kind enough to send me a 35mm =
thick document describing some experiments and results with it.  Very =
interesting machine.  Do you know if anything ever come of the work to =
produce a commercial (non-lab) version of this?  Hmm... wonder what =
happened to Bev's?

Anyway - thanks to everyone for the responses.  Nitrogen storage was/is =
the plan, but it is always good to have a sanity check with some experts.

regards

Graham Collins
Process Engineer,=20
Northrop Grumman
Atlantic Facility of Litton Systems Canada
(902) 873-2000 ext 6215

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