Werner, Gary
Well our PhD Student Pascal Jud did work out a 2- Parametric Norton Law for the creep of SnAg3.8Cu0.7 and its parameters:
P.P. Jud, G. Grossmann, U. Sennhauser and P.J. Uggowitzer,
Local creep in SnAg3.8Cu0.7 lead-free solder,
Journal of Electronic Materials 34, 9 (2005) pp 1206-1214
Right now we work on some structural correction factors to accout for deviations between the measured resuts and the modell and the idea we had last week works surprisingly good.
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]
>>> [log in to unmask] 29.01.2006 14:24 >>>
In a message dated 1/28/06 7:35:02, [log in to unmask] writes:
> Hi Werner:
> Is that because the creep-fatigue models for lead-free solder are not
> fully developed yet? Or perhaps they are and I am not aware of the latest
> info.
> Would it be safe to assume that if you perform a temperature cycle test
> using an accelerated temperature range with lead-free solder, that you can
> reduce your risk of field problems but you cannot extrapolate a life for
> normal use? Assuming a test dwell time of approximately 10 - 15 minutes
> measure on the board.
> Are you teaching any courses in the North East this year?
> Gary Delserro
> www.desolutions.com
>
Hi Gary,
The creep-fatigue models for lead-free solder are not fully developed yet. We
know, that under most circumstances the LF-solders creep slower than SnPb.
Therefore, if you perform the exact same accelerated test for LF-and SnPb
solders and you do not get substantially [but we do not know what substantially
means in numerical terms] more cycles-to-failure for the LF-solders, they will
give you lower product reliability in most operational environments.
You missed my workshops in Boston December 5 and 6. The next time I give some
of them are at IPC EXPO/APEX in Anaheim on February 6 & 7, at the Naval
Surface Warfare Center in Crane near Indianapolis on February 27 & 28 (open to the
industry), and in Santa Clara, CA, on March 6 & 7 in conjunction with the
IPC/JEDEC Lead-Free Conference.
Not exactly the Northeast--sorry.
Regards,
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, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com
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