Hi Inge,
Well, you sure lay it on.


2.What is Norris-Landzberg equation? Has it to do with extrapolation of 
ccelerated test results?
A: Norris and Landzberg were 2 people working for IBM who published a paper with their equation,
developed for Pb but mis-applied for solders.
IBM distanced itself from the N-L model, and nobody ever heard from Norris or Landzberg again to
my knowledge. That has not stopped people from using N-L to extrapolate accelerated solder reliability 
test results, because it generally gives very optimistic answers. It biggest short-coming is thast dwell 
time is not considered.
3.About damage during ramp vs. damage during dwell (temp cycling), how do you 
ecide data which mirrors real operational conditions?
A: Ramp is only important if it is rapid enough to lead to build-up of stresses faster thqan creep can reduce them;
that mean thermal shock-type testing.
4.Is Matlab 7.6.0 useful for practical reliability calculation, or is it just 
esearch tool?
A: No idea.
5. What is the Engelmaier expression? Has it to do with Werner's face after a 
ouple of beer?
A: I do drink beer, but not enough to make any difference---single-malt scotch, no that is another matter.
But if you really want to change my expression, give me 50 cm of virgin powder snow on top of a nice slope---
now that is a paradign shift.
Now, I do have 2 equations with my name on it. One, for solder creep-fatigue behavior, the Engelmaier-Wild 
model [Roger wild was a researcher at IBM on who's data the model is based]; the other to relate tensile properties
to fatigue behavior for copper, aluminum, and the like.

Anything else I can help you with, Inge. Did some consulting for Saab last Summer---they said they would rather give me money than a ride on one of your jet fighters---bummer.
Werner


-----Original Message-----
From: Hernefjord Ingemar <[log in to unmask]>
To: TechNet E-Mail Forum <[log in to unmask]>; Werner Engelmaier <[log in to unmask]>
Sent: Thu, Nov 12, 2009 1:50 pm
Subject: Engelmaier expression etc.



 
articipated in a meeting about LGA/QFN/BGA reliability and life. Have a couple 
f qs.
1.NN (Neural Networks) often contain up to 20 parameters. Will these models 
eally be useful in practice? Seems a lot to complicated to me.
2.What is Norris-Landzberg equation? Has it to do with extrapolation of 
ccelerated test results?
3.About damage during ramp vs. damage during dwell (temp cycling), how do you 
ecide data which mirrors real operational conditions?
4.Is Matlab 7.6.0 useful for practical reliability calculation, or is it just 
esearch tool?
5. What is the Engelmaier expression? Has it to do with Werner's face after a 
ouple of beer?
/Inge=


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