Well, if there is so many factors in (like flux ; preheats etc.) in play ;
it's not much use to try to come up with universal standard ; is it ?
Solderability (therefore life) is tied to the process .
Than , would the interpolation I described from your 785 cycling ; Werner ;
give pretty accurate results ?
I backed off when Jim mentioned the steams; thought of it O/Nite ;
came back the same :
working with specific substrate (flash); specific flux (no clean); and
specific components ;
what is any test going to tell me ?
Apart from the parallels from aged to fresh ; meaning actual soldering on
aged and fresh boards and comparing them (hope you find a year ol' empty
card around); I can't see a way around .
Standards are jolly good aids, still we should be able to develop internal
tests addressing much better our SPECIFIC processes (nothing general to
"agree" on ; is it ?)
Being old enough to remember from telecom days we did have to come up with
our own (likes Bell's); it's not that difficult ; unless you've been born
with calculator dependency .
Nowadays everybody punches function button having no clue why and what that
"cosin" works.
I'd say ; that's why.
Gettin' from A to B can be:
chore;standartised;inventive;dangerous;wealwaysdiditthisway;learning;etc.=an
ything YOU (or other madman on the road) makes it . The out of square
agility is essential .
It is actually interesting for example FDA recognises internal validations
as a must ; provided the roots are tied up = how do you know 100'C is a
boiling point ?
answer = it's not where you stand . ETC,etc.
(all in light humour ok ?; as Bev says ; one never knows how and who takes
it) .
Paul Klasek
http://www.resmed.com
-----Original Message-----
From: Werner Engelmaier [mailto:[log in to unmask]]
Sent: Thursday, 6 May 1999 8:01
To: [log in to unmask]
Subject: Re: [TN] Simulation of PCB ageing
In a message dated 5/5/99 11:37:37, [log in to unmask] writes:
>Which is an interesting experimental concept. Why hasn't this been done?
>If we can't agree on acceleration factors, why doesn't the industry do a
DOE
>with a leg or 2 being actual life and other legs being acceleration tests
to
>determine factors for different constructions/components/surface
finishes/.....
>Or has this been done?
Hi Steve,
This has been done-with mixed success, thus 'we can't agree on (or do not
know) acceleration factors' in many cases. Some degradation mechanisms are
only active at (highly) accelerated (read: more severe) test conditions,
e.g., CAF. Others are dependent on such a complex interaction of different
parameters, that nobody has been able to properly model them. Still others
degrade in ways not easily measured. And others, like solder joint and
PTH/PTV reliabilty have been successfully modeled and acceleration factors
can be determined.
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com
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