Thankyou, Werner and all who replied to this question.
This application is expected to see temperature variation from -20C to 100C.
However, this will be operating environment changes at low rate of change.
From what you say, the main concern is rate of change/ frequency of cycle
that will reduce reliability, rather than the high maximum temperature.
regards,
Phil.
At 08:49 5/09/00 -0400, you wrote:
>Hi Phil,
>Some of the responses you received do not answer your question.
> >We are designing a Printed Board Assembly that will be required to operate
> >in an ambient temperature up to 100 degrees Centigrade.
> >There have been concerns expressed about the strength of solder joints at
> >that temperature.
>The answer is no, the strengths of solder joints, provided they are properly
>wetted and not sufficiently damaged by fatigue, is never an issue. The
>strength of the solder joints is adequate even in severe vibration and
>mechanical shock loading. The 'stress due to thermal mismatch' is also not an
>issue, since solder joint fatigue is strain-driven, not stress-driven. That
>means that the total creep-yield plastic deformation in solder joints will be
>the same for equal delta-Ts, but at higher Ts the creep process will be
>completed faster. This has a consequence in accelerated testing, but not for
>product in functional use.
>As Dave Hillman pointed out however, if you cycle from some lower T to this
>high T of 100C, you will get more creep-fatigue damage per cycle than for
>T-excursions to lower maximum temperatures; thus, earlier fatigue failures
>would occur in your situation. Whether this will give you adequate
>reliability depends on the design and use details.
>
>Werner Engelmaier
>Engelmaier Associates, L.C.
>Electronic Packaging, Interconnection and Reliability Consulting
>7 Jasmine Run
>Ormond Beach, FL 32174 USA
>Phone: 904-437-8747, Fax: 904-437-8737
>E-mail: [log in to unmask], Website: www.engelmaier.com
>
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Phil Dutton C.I.D.
Senior CAD Technician
IPC Certified Interconnect Designer
Tenix Defence Systems Pty Ltd
Systems Division - Adelaide
Second Avenue, Technology Park,
Mawson Lakes. SOUTH AUSTRALIA 5095
================================
Phone: (08) 8300 4400 (reception)
Fax: (08) 8349 7420
email: [log in to unmask]
Internet Page: http://www.tenix.com
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