Hi Ofer,
I have been through this discussion recently with a large OEM that wanted to
know if they could use a warehouse full of old components (a result of the
sharp decline in orders two years ago).
In addition to the solderability concern that has already been mentioned,
you really need to pay special attention to all component categorized as
Moisture Sensitive Devices (MSD).
As you may be aware, MSDs are normally delivered from the suppliers in dry
packs with a moisture sensitivity label. This label should include a bag
seal date. By definition this seal date is only an indication relative to
the minimum shelf life of the bag which is 12 months when stored in a
non-condensing atmospheric environment of <40C/90%RH. This is based on the
fact that a Moisture Barrier Bag (MBB) is never perfectly hermetic. Over
time the ambient humidity will permeate through the bag, eventually
saturating the desiccant and ultimately the components may absorb too much
moisture before the bag is open.
According to the latest industry standard, excessive humidity in the dry
pack is determined strictly based on the status of the Humiditity Indicator
Card (HIC) when the bag is opened, whether or not the one year shelf life
has been exceeded. Ref J-STD-033A, section 5.5.
By the way I am not sure where your dehydration profile comes from but it
does not seem to be consistent with the latest standard revision which
specifies 3 to 48 hours at 125C, based on the MS level, body thickness and
saturation factor (Ref: J-STD-033A, table 4-1).
There are other concerns and potential pitfalls associated with older MSDs.
If you want more information on this subject feel free to contact me
offline.
Regards,
Francois Monette
Cogiscan Inc.
Tel : 450-534-2644
Fax : 450-534-0092
[log in to unmask]
www.cogiscan.com
Date: Tue, 10 Jun 2003 08:35:11 -0400
From: "Blair K. Hogg" <[log in to unmask]>
Subject: Re: Receiving old components
Hi Ofer,
We impose similar requirements on our suppliers, TH components no older than
18 months and SMT components no older than 12 months. I approve about 5
waivers each week (maybe I shouldn't publish that, in case any of my
suppliers are on Technet) for component age. We've been lucky so far, and
haven't seen our defect rate go through the roof. We don't use BGAs in our
process, but do have a fair amount of fine pitch QFPs in our designs.
I've considered changing our requirement to be either the age restriction or
a recent third party solderability test, but haven't gone anywhere with that
idea. In this forum a while back (at least a year) there was a short thread
about component age restrictions and a link to a publication by the NEDA
(electronic distributors association) regarding better controls on component
stock, storage methods and all by the distributors and suggested that age
restrictions were no longer necessary. Check the archives for that thread.
I'm still skeptical, and if, as the paper suggested, removed these
restrictions altogether would be compelled to audit all my component
suppliers (distributors) for their handling and storage methods of
components.
I thought that Jack Crawford may have been looking into this from an IPC
perspective. I believe he posted the original article from NEDA.
Blair Hogg
Quality Manager
GAI-Tronics Corporation
Date: Tue, 10 Jun 2003 14:16:21 +0200
From: Ofer Cohen <[log in to unmask]>
Subject: Receiving old components
Hello, Technetters,
Although we have decided (and documented in our procedures) that the age of
the components during the income inspection will be 18 months max, the
market situation, jobbers plea (and consecutively - pricing) and time to
market (and the purchasing department) are twisting my hand, to approve
reception of old components.
Given that:
a) we do not have a lab;
b) all we can do before the assembly is visual inspection (especially of
BGAs);
c) components dehydration profile is 120 degC for 8 hours min;
d) components age is 3 years and more,
I am trying to find the best process by making visual inspection of the
components (flatness and corrosion of balls/pads), dehydration and thorough
electrical testing.
Have any suggestions?
Regards
Ofer Cohen
Quality Assurance Manager
Seabridge Ltd.
---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
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
-----------------------------------------------------
|
