It looks like I need to defend that statement.  Somewhere in my files is a
an article comparing rate of change on soldered assemblies.  When a fast
rate of change was used, the assemblies survived.  When a slow rate of
change was used, failures occurred.  All else being equal with respect to
temperature limits and number of cycles.  The explanation was at a high rate
of change, the solder joints did not have the opportunity to "relax."  I'm
sure others can explain that better than me.

So, my point is, a slow rate of change would be more effective at testing
the solder joints than a high rate of change.  I think we're all saying the
same thing.  Heck, I learned this from you guys!

Glenn

-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Monday, March 11, 2002 10:15 AM
To: [log in to unmask]
Subject: Re: [TN] Thermal Shock


Hi Jim,
In a message dated 03/11/2002 7:59:02, [log in to unmask] writes:
>Glenn (or anyone else), could you elaborate on your statement that slow
>rates of change affect solder joints more than fast rates of change.
A: No, the statement is incorrect. The rate of change in temperature is more
detrimental when high due to possible component/PCB warping. What is more
detrimental is a longer hold times typically associated with slower heating
rates and not T-shock.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 386-437-8747, Fax: 386-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com