Dave,
You're "too kind" when you say a 20 microinch thick Sn63 finish on a Dip
component is going to "age" less gracefully than a 60 microinch thick
Sn63 finish. The way I see it a 20 microinch Sn63 finish is going to
"suck" by the time you get the part and try to use it.
Regards,
George
George M. Wenger (908)-546-4531 [log in to unmask]
Celiant Corporation
40 Technology Drive
Warren, New Jersey 07059
-----Original Message-----
From: David Hillman [mailto:[log in to unmask]]
Sent: Tuesday, December 11, 2001 4:08 PM
To: [log in to unmask]
Subject: Re: [TN] Shelve life for SMT/PTH components
Hi Peter! Steve Sauer did a great job of covering the most important
basics
so I'll just add few other details. Based on many of the discussions
which
occur within the JSTD-002A committee, you should expect that your
component
shelf life should be a minimum of 6 months and very typically 12 months
from date of fabrication. You can expect that components with
Sn63/Sn62/Sn60 finishes retain their solderability better than Sn85 or
Sn100 finish. There is also one general rule - the thicker a finish the
better it retains its solderability. A 20 microinch thick Sn63 finish on
a
DIP component is going to "age" less gracefully than a 60 microinch
thick
Sn63 finish on the same component. Humidity has the greatest impact on
the
loss of solderability so if you can control the humidity in your
component
storage area then you will be better off (most people have typical
controls
of 30%-60% RH). Lastly, always relate your solderability expectations
with
the type of flux chemistry you are using in assembly. Typically, the
JSTD-004 type M or H fluxes are more robust to solderability variations
than the type L fluxes. The JSTD-002A specification, in conjunction with
a
good logistics plan (as Steve recommended), can serve as a good tool for
solderability management. Good Luck.
Dave Hillman
Rockwell Collins
[log in to unmask]
Peter Lee <[log in to unmask]>@ipc.org> on 12/11/2001 02:12:15 AM
Please respond to "TechNet E-Mail Forum." <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
To: [log in to unmask]
cc:
Subject: [TN] Shelve life for SMT/PTH components
Hello,
In general, what is the standard shelf life for the normal PTH and SMD
components like DIP IC's, SOIC's, PLCC's?
Assuming that they are non-MSD critical, what would be the proper
storage method to ensure good solderability is being preserved (such as
nitrogen storage chamber)?
How significant is the impact of storage conditions (e.g. humidity,
expose to ambient) and shelf life have on the solderability of component
leads?
Rgds,
Peter
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