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January 2005

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Subject:
From:
Guy Ramsey <[log in to unmask]>
Reply To:
Date:
Wed, 12 Jan 2005 11:08:42 -0500
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I was not involved in the product evaluation. And I can't answer your
question. Perhaps Werner could give you an approach.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Simms, Michael
Sent: Wednesday, January 12, 2005 10:36 AM
To: [log in to unmask]
Subject: [TN] FW: [TN] FW: FW: Flexible vs. rigid substrates


Hello Guy,
Thank you for your response.  Our customer's concern is that
the solder joints involved are on a rigid substrate and the substrate is
flexed to some amount of curvature.  The concern rests on the presumption
that the solder joints are thus placed under some unknown but constant
stress.  Some of the engineers involved are concerned that no data
may exist for the reliability of solder joints placed under constant stress.
The solder joints may also be subjected to high temperature excursions
during
their service life.
Some of the engineers reviewing the application have questioned putting
solder joints
under constant stress during their service life.  The fear is that under
constant stress,
even without repeated flexing, reliability of the solder joints is
compromised and
their service life unpredictable and unknown.
Wouldn't the use of flex material eliminate the stress?
I was asked to review IPC documents to find what the industry position may
be regarding flexing of rigid assemblies.
So far, in my review of IPC documents and from some anecdotal responses from
TechNet,
it appears that the industry may not have addressed the acceptability of
this type
of application.
Regards,
Mike

Mike Simms
Chemist
Trace Laboratories - Central
1150 W. Euclid Ave.
Palatine, IL  60067

phone  847-934-5300
fax      847-934-4600
www.tracelabs.com

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