This really is a fun discussion, I'm enthralled!

Ahne, you missed one thing in your statement about the laptop in the
Pacific Northwet, (throw it, shake it, cool it, SOAK IT, etc.)

KennyB
Redmond, Wa.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ahne Oosterhof
Sent: Wednesday, November 16, 2005 12:48 PM
To: [log in to unmask]
Subject: Re: [TN] [LF] Reliability prediction of LF soldering

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.

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