Hi Svend,

I have been wrestling quite a bit with moisture sensitive devices (MSD)
lately in our shop. We keep all MSD parts vacuum sealed when in storage. We
keep track of the "open hours" on a label attached to every MSD bag
containing MSD components. When a part is within 4 hours of the recommended
open time provided by the manufacturer, we bake the parts prior to the next
usage at 125 C for 24 hours (as recommended by IPC-SM-786A). We have not
had solderability problems following this procedure. It is imperative that
operators keep track of the open time for any parts that are not used for a
particular run and are resealed in the MSD bag before being put back on the
shelf. We use an A-VAC nitrogen resealer with desiccant in each MSD
container, and seal any unused components in their respective MSD bag.
Generally the silver MSD bag that the parts are received in  can be
resealed at least few times if the operator cuts a minimal amount off the
end when they open it.

The A-VAC is simple to use and only uses a very small amount of nitrogen to
reseal a bag. I did not purchase our resealer but I imagine it was not a
very costly item. It first pumps nitrogegn into the bag, then evacuates the
bag providing a pretty good vacuum and heat-seals the bag.

My problem is that some of our MSD parts are only available on tape and
reel. Most of our MSD parts are tray parts and can be processed per our MSD
precedure pretty easily. Supposedly moisture and be baked out of tape/reel
parts  at 40 C for one week so as not to damage the cover tape. I posted a
querie on Tech-Net asking if anybody had any actual experience with baking
out moisture with tape and reel parts and I didn't get a single reply!!


At 01:11 PM 6/17/98 +0200, you wrote:
>How to store moisture sensitive SMD-ICs in a decent and economic way ?
>
>On delivery some SMD-IC's are packed carefully in drypacks with silica
>gel and humidity indicator card. The supplier states that the parts
>after unpacking have to be used in a more or less rapid way - sometimes
>even within hours.
>However, the problem shows when not all parts are used at once so some
>of them have to be stored for a while.
>The supplier states that the problem can be overcome by baking the parts
>prior to reflow soldering. But baking takes time and may damage the
>solderability.
>
>So I would prefer to store the unpacked not-yet-to-use parts in a
>moisture controlled environment.
>We look at nitrogen storage - knowing the costs of implementing and
>running the thing. Is there a way to keep the nitrogen usage at a low
>level ?
>
>Or should we go for some form of "dry air environment" ? ... Who builds
>such things ? ... At what costs ?
>
>Or perhaps we could store parts in reusable dryboxes ?
>
>
>Best regards
>Svend
>
>################################################################
>TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
>################################################################
>To subscribe/unsubscribe, send a message to [log in to unmask] with
following text in the body:
>To subscribe:   SUBSCRIBE TechNet <your full name>
>To unsubscribe:   SIGNOFF TechNet
>################################################################
>Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional
information.
>For technical support contact Hugo Scaramuzza at [log in to unmask] or
847-509-9700 ext.312
>################################################################
>
>
>
----

Jeffrey C. Guynn <[log in to unmask]> Phone: (219) 429-6345
Lead SMD Manufacturing Engineer        Fax: (219) 429-4688
Raytheon Systems Company M/S 25-31
1010 Production Road, Fort Wayne, IN 46808-4106

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################