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March 2006

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Subject:
From:
"Braddock, Iain" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Braddock, Iain
Date:
Mon, 20 Mar 2006 09:18:26 +0000
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Hi Colin,

Component long term storage was an investigation the NPL covered a few years
ago. Check out their website for report titled 'Shelf life & Solderability
ageing', It's is on free issue.

Regards,
        Iain.

-----Original Message-----
From: Colin Weber [mailto:[log in to unmask]]
Sent: 20 March 2006 04:33
To: [log in to unmask]
Subject: [TN] Component Long Term Storage


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Hello Folks,

Could anyone please advise on what realistic long term storage (many years)
can
be achieved, and how to achieve it, for components such as integrate
circuits?
Any articles or guidelines would be helpful.

We are facing some obsolete component issues and do not have resources to
redesign many boards for incompatible replacements or new devices.

After searching the archives I have ascertained that it seems the
hygroscopic
nature of the packages is not a great problem. J-STD-033 should help with
determining storage requirements for this issue. Would it be true to say
baking
the components can eliminate any absorbed moisture, even after many years of
long term storage?

A bigger problem appears to be intermetallic growth on the legs, between the
coating (tinning) and the actual leg material.  The intermetallic can grow
over
time, eventually causing the legs to lose solderability.  I suspect the
growth
rate is temperature dependent and could be slowed by cooling.



Regards,

Colin Weber

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