Werner,
If you regard a solder joint as a function, how many are there in
laptop? Let's say 5,000. And let's regard all gates and transistors etc
as functions. There are millions. If a failure occurs, isn't the
probability that failures will appear in these first? I don't say
against your opinion about bad solder joints, just try to figure out
what is most likely to make trouble the one or two years, which is
typical before you buy a new laptop.
Inge
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Werner Engelmaier
Skickat: den 30 maj 2007 00:09
Till: [log in to unmask]
Ämne: Re: [TN] RoHS compliant laptop with early failure
Hi Inge,
Unfortunately, for solder joints the MTBF-concept makes little sense
because
they fail as the result of wear-out.
If you look at the wear-out of solder joints of a large population, you
see
almost a 2-order of magnitude between first failure and last failures,
since
the Weibull shape factor is about 3.
For some laptops rhyming as the one previously mentioned, out-of-the-box
failures have been reported with most failure having occurred in ghe 12
to 24
months range--depending on usage, of course.
The problem is a design issue with large component, large delta-CTE,
large
on/off T-difference, little lead compliancy—a textbook case of how not
to do it.
Werner
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