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April 1998

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From:
Engelmaier <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Sat, 25 Apr 1998 06:07:33 EDT
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In a message dated 04/24/98 18:05:45, Heidi Jones wrote:

>Hi Werner,
>
>We use both, depending on the test specification, so I am curious, how do
>the damage and/or failure mechanisms differ between thermal cycling and
>temperature cycling?

Hi Heidi,
There is, of course, no difference between thermal cycling and
temperature cycling; however, there is a huge difference between
thermal/temperature cycling where the T-ramps do not exceed about 30C/minute
and T-shock. The prime difference between the two is, that T-schock sets up
transient thermal gradients that cause component and substrate warping, thus
loading solder joints in tension; whereas T-cycling is slow enough to avoid
warpages not occurring in product use and the solder joints are loaded in
shear dur to the expansion mismatch between component ans substrate as they
would be in most applications.

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]

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