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April 1997

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Subject:
From:
Mike Buetow <[log in to unmask]>
Date:
Wed, 16 Apr 1997 11:34:09 -0500 (CDT)
Content-Type:
TEXT/PLAIN
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TEXT/PLAIN (55 lines)

On Tue, 15 Apr 1997, Ely Mercado wrote:

> 1. Where can I get the specfication or criteria on IC SMD
>    shelf life?

This is really two questions. Component susceptibility to moisture 
absorption is determined by the vendor, who classifies it to 1 of 6 levels.
These levels are generally per J-STD-020, a standard jointly developed by 
IPC and JEDEC.

Shelf life is affected by moisture susceptibility. Of course, parts come 
with date codes, and typically assemblers must get special approval to 
use parts with old date codes. I'm not aware of any standard that 
specifically indicates how "long" a component is reliable, solderable, 
etc. No doubt many of the large military contractors, and probably the 
parts suppliers, have data on this. Whether they are willing to share it 
is another issue altogether.

> 2. I understand there's the IPC-SM-786A but it's more oriented
>    to specific IC moisture/reflow sensitivity.

This is correct.

> 3. Is there a criteria for how long for an IC or SMD parts
>    for that matter can be stored prior to reflow.

Yes. J-STD-020.

Note that IPC-SM-786A (published January 1995) and J-STD-020 (published 
October 1996) are almost identical in terms of classification criteria. The 
difference is that IPC-SM-786A includes handling procedures. IPC and 
JEDEC plan to develop a joint spec on handling, too (J-STD-021, 
perhaps?).

Mike Buetow
IPC Staff
2215 Sanders Road
Northbrook, IL 60062
P: 847-509-9700, ext. 335
F: 847-509-9798
[log in to unmask]

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