Yup you got that right, as usual, Werner.
The failure modes change between survivability and reliability testing
in response to the heating rates and high end temperatures, but weak
boards fail either way; just not the same way. If it is understood that
the failure mode may be affected by the testing, and it is agreed to by
AABUS, the method is useful. Survivability testing does not produce an
elegant degradation that allows and analysis of damage accumulation over
thermal cycles. Survivability testing is much more aggressive, where
"good" vs. "bad" is just a matter of a few thermal excursions.
We shall keep the methods and applications separate even though they are
run on the same equipment. Each does serve a very useful, but separate,
function.
Best regards,
Paul
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Tuesday, June 03, 2008 8:27 AM
To: [log in to unmask]
Subject: Re: [TN] Reflow specifications for PCB
Hi Paul & All,
It is proper to use different names- Reliability Testing vs.
Survivability Testing, for these tests, because they do not test the
same thing, even if the failure modes observed are the same. The loading
conditions and the material responses to them are not.
To say: " One effect is to increase testing throughput by a factor of
~10:1 if the product is robust and survives to end of test. Weak product
fails in just minutes which in effect increased through put by a factor
of ~40:1." is correct in terms of the through-put but not in terms what
is measured.
That is a problem with all those 'highly accelerated' tests, they do
accelerate the time to failure, but they do not typically accelerate the
pertinent damage mechanism.
So, lets keep the two tests, Reliability Testing and Survivability
Testing, separate, because each serves a very useful function.
Werner
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