From my "engineering" experiences:
I used the "scientific" method to calculate an MTBF before finishing a paper
design. Then changed the design if the number ended up too far out of the
desired ballpark.
The changes could be made (I thought) because for most components the
demonstrated MTBF depended a lot on how they are being used. A 1W transistor
dissipating 0.1W lives longer than one running at 1.0W. (Kind of like
comparing one solder joint on a 0402 resistor in a desktop modem (super
benign environment) to one on the corner of a BGA located close to the shear
edge of a board that is used in a portable computer by a forester in the
Pacific NW in the middle of winter (throw it, shake it, cool it, etc.).
After building engineering samples of the design I required life cylce tests
to find a 'demonstrated MTBF', a number that would go in the spec document
for customers to see.
This discussion is really "fun".
Ahne.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ingemar Hernefjord
(KC/EMW)
Sent: Wednesday, November 16, 2005 10:25
To: [log in to unmask]
Subject: Re: [TN] [LF] Reliability prediction of LF soldering
Agree, wasn't an answer on my question. We have complicated situation with
mixed technology, and we have few persons with a deep understanding in the
mystery of metallurgy and kinetics and so on. Perhaps someone else can give
a tip. The scientific reports are sometimes too academic, and my job is to
'strip' the report and make it understandable for those who work on the
'floor' (old fashioned expression, guess we are all standing on floor,
except for the high bosses, who are in the blue). So, again, can you omit
the variations of lead distribution or not? It's very important that I give
the soldering responible people a correct information.
Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of John Burke
Sent: den 16 november 2005 19:09
To: [log in to unmask]
Subject: Re: [TN] [LF] Reliability prediction of LF soldering
Sharp words for Technet..........................8-)
John
------------------------------------
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John Burke
Senior Manager RoHS Compliance
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Whittaker, Dewey
(AZ75)
Sent: Wednesday, November 16, 2005 10:04 AM
To: [log in to unmask]
Subject: Re: [TN] [LF] Reliability prediction of LF soldering
At least if he did that he could take it for granite that he was working
with cutting edge technology.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Wednesday, November 16, 2005 10:59 AM
To: [log in to unmask]
Subject: Re: [TN] [LF] Reliability prediction of LF soldering
Hi Ingemar,
Well, tell us--what choice do you have? Are you a 'scientist' or an
'engineer'? Shall we stop making product? Go back to the stone age--assuming
of course that the quartz is uniformly distributed in the blade of your
stone axe?
Since when do we live in a perfect world?
Werner
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