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June 2004

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Subject:
From:
"Marsico, James" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 23 Jun 2004 07:33:33 -0400
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Thanks, Guenter, for your response, one more question, though.  If the
solder joints are allowed to stabilize at the temperature extremes, won't
the internal stresses diminish in time (creep)?  If so, will the strain rate
still have an affect? With that said, will the soak time have an affect on
solder joint reliability?

Jim Marsico
Senior Engineer
Production Engineering
EDO Electronics Systems Group
[log in to unmask] <mailto:[log in to unmask]>
631-595-5879


        -----Original Message-----
        From:   Guenter Grossmann [SMTP:[log in to unmask]]
        Sent:   Wednesday, June 23, 2004 3:28 AM
        To:     [log in to unmask]
        Subject:        [TN] Antw: [TN] Shock vs. Cycling

        James

        The results you will achieve will be totally different and specific
to
        the test.
        In thermal shock deformation and  degradation mechanisms will be
        activated that are irrelevant in thermal cycling and vice versa.
        - Degradation in solder joints depends on the strain rate
        - The degradation path in solder joints can be influenced by the
stress
        applied. And, the higher the strain rate the higher the stress.
        - Thermal shock can lead to the destruction of the components
something
        that will not occur in thermal cycling
        - Due to thermal shock the substrate will bend or warp and bring in
        additional stress into the component and the joints not occurring in
        thermal cycling

        If your application includes thermal shock you must test the
specimen
        accordingly if the stress is thermal cycling, thermal cycling is the
        test you have to do otherwise it is impossible to make any
connection
        between the test results and the real application. I do have even
doubts
        about the validity of comparative tests done with thermal shock if
no
        thermal shock occurs in the application (see above).

        Best regards

        Guenter

        EMPA
        Swiss Federal Laboratories  for Materials Testing and Research
        Centre for Reliability
        Guenter Grossmann,  Senior Engineer

        8600 Duebendorf
        Switzerland

        Phone: xx41 1 823 4279
        Fax :     xx41 1 823 4054
        mail:     [log in to unmask]

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