Hi Bev,

Another important factor to consider is how often your operators will open
and close the doors of the cabinet. The gas flow will dictate how long it
takes to get back to the desired level inside the cabinet (i.e. less than
10% as per the current IPC/JEDEC guidelines). If the flow is not high enough
and the doors are opened frequently it is possible that the actual RH level
will never be within specifications. Once you have a cabinet in place you
can easily determine the optimal gas flow by using a small hygrometer. I use
one model that can record the RH level over time and you can download this
data on your PC to get it in a chart format.

By the way there are some dry cabinets manufacturers that offer complete RH
control. One model includes an automatic purge at a higher flow rate for 30
seconds, every time a door is opened, followed by a lower flow rate when the
doors are closed. I can provide you with the vendor information if you are
interested.

The desiccant-based cabinets are also effective but they tend to take a
longer time to return to the desired level after the doors have been opened.
In any case, it is highly recommended that you frequently monitor the RH
level inside your cabinets.

Francois Monette
Cogiscan Inc.
Tel : 450-534-2644


Date:    Mon, 8 Jul 2002 09:25:18 -0400
From:    Bev Christian <[log in to unmask]>
Subject: Moisture Sensitive Component Cabinets

Good morning Technetters!

One supplier of cabinets for moisture sensitive components states that for a
1200 L cabinet that a dry gas flow of 1200 L/hr  is needed.  Would you agree
with this number?  I know of course that the number is predicated to a
certain extent on the tightness of the cabinets, but right now I just want
to know if this is a ballpark figure that people agree on.
regards,
Bev Christian
Research in Motion

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------