Hello Werner. Do you have any links to papers that you wrote or could share with usa alittle more about the ramp and dwell stresses that you talk about in your E-mail? Looks interesting.
Thanks J Goulet
----- Original Message -----
From: "Werner Engelmaier" <[log in to unmask]>
To: [log in to unmask]
Sent: Thursday, November 12, 2009 1:30:07 PM GMT -05:00 US/Canada Eastern
Subject: Re: [TN] Engelmaier expression etc.
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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