Jack,
Here are a few more practical considerations :
The white paper states the following : "...Product does not wear out,
deteriorate or age on the shelf to an extent that could adversely affect
performance..." I am not sure if this statement can apply to ICs categorized
as moisture-sensitive, which probably includes the majority of them. In this
case, the shelf life of components in sealed moisture barrier bags is not
indefinite. Since the bags are never perfectly hermetic, some amount of
moisture will be absorbed through the bag over time and eventually can
saturate the desiccant and make its way into the components. I am aware of
at least one instance where components exceeded their critical limit and
popcorned right out of the bag (i.e. went straight to reflow after being
removed from their dry bags, well within their specified floor life, and
failed due to internal delamination).
As you may be aware the dry pack specifications found in J-STD-033 are based
on a minimum shelf life of one year from the bag seal date, in a
noncondensing atmospheric environment of < 40C/90%RH. This is why the bag
seal date must be written on the MS label on the outside of the dry bag. Of
course when the one year limit is exceeded it does not necessarily mean that
the parts are not good anymore. However, special care should be taken to
verify the status of the HIC when the bag is opened. I am also aware of some
distributors and users who will systematically open bags after one year to
replace the desiccant and re-seal. Either way this concern should be
addressed somewhere in that paper.
As far as traceability is concerned, there are also some practical issues
that should be considered. I understand that the date codes will still be
marked on the components and that is certainly a requirement for many users.
However, it is important to note a very strong trend right now in the
industry from some of the leading OEMs to require component lot traceability
all the way to the board serial number, and eventually to the final assembly
serial number. This is almost standard practice in some high rel industries
such as medical and aerospace and it is becoming more common in the high end
telecom and automotive. This is a requirement that is placed on their CEMs
by companies like Sun Microsystems, EMC and others. For component lot
traceability the problem has always been to find a practical way for the
assembler to keep track of this data. Given the fact that the component
vendors and distributors are already allowed to mix multiple date codes in
the same batch of parts (i.e. within the same reel or tray), it becomes
extremelly dificult to automate this process. The standard solution today is
to have a bunch of people visually inspecting each board down the assembly
line, reading the date code of each IC and typing that data into a computer
!!! This is of course extremelly time consuming and prone to human error.
Some of the assemblers who have been looking at ways to automate this data
collection process have decided to sort the date codes and re-package all
components in their stockroom before releasing them to the assembly line. It
is obvious in this case that this task could have been accomplished much
better by the component vendor. What I am saying is that we might be getting
ourselves in trouble if we further relax the requirements for maintaining
visibility on the lot codes through the supply chain. We might be only
pushing an issue further down the line where it gets more and more expensive
to fix it.
I hope this is helpful,
François Monette
Cogiscan Inc.
Tel : 450-534-2644
Fax : 450-534-0092
E-mail : [log in to unmask]
www.cogiscan.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Jack Crawford
Sent: Monday, April 29, 2002 4:54 PM
To: [log in to unmask]
Subject: [TN] Proposed lifting of component date code restrictions
IPC has become aware that the National Electronics Distributors
Association (NEDA) has posted a white paper discussing the proposed lifting
of date code restrictions and they have requested comments from end users as
well as component suppliers and distributors. The paper can be viewed at
http://www.nedassoc.org/whitedat.html.
Comments can be provided to me on or off net; we'll compile them and
forward to NEDA. If you comment to NEDA directly [log in to unmask], please
cc: me on your reply [log in to unmask]
Cordially
Jack
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