Hi Ruby,
[1] The Coffin-Manson equation is not applicable to a metal at temperatures
where it significantly creeps, e.g. solder in typical use temperatures.
[2] For solder joints the failure mechanism is thermo-mechanical
creep-fatigue, not thermal fatigue.
[3] "The only stress taken into account in the equation is temperature range"
does not make any sense, there are many other parameters that need to be
considered.
[4] The temperature transition rate is not of real consequence in actual
solder joint reliability. It only becomes an issue at rates that also produce
thermal shock, and than the temperature transition rate is the least of your
worries, since the solder joint loading is dominated by a wholly different
mechanism.
Please get yourself a copy of the industry documents IPC-SM-785, Guidelines
for Accelerated Reliability Testing of Surface Mount Solder Attachments, and
IPC-D-279, Design Guidelines for Reliable Surface Mount Technology Printed
Board Assemblies, to familiarize yourself with the underlying issues.

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

In a message dated 07/31/0 18:51:38, [log in to unmask] writes:
>Hello all:
>We're using Coffin-Manson equation to calculate the acceleration factor
>(AF)of solder joint. The failure mechanism is thermal fatigue. The only
>stress taken into account in the equation is temperature range. I have a
>question: is it possible to include the temperature transition rate in that
>equation? And what's the relationship between AF and temperature rate?
>Ruby

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