Hi Vlad! Sorry to disagree but you are applying classic crack initiation
and growth theory on a material that doesn't follow those basic
principles. The voids in solder joint neither initiate crack growth nor
blunt crack growth. It would make a materials engineers life soooo much
easier if solder just behaved like steel. Richard Coyle published an
outstanding paper that covers this topic in great detail. I recommend that
folks read the following paper:
R. Coyle, et al, ?The Effect of Process Voiding on BGA Solder Joint
Fatigue Life Measured in Accelerated Temperature Cycling?, SMTAI
Conference Proceedings, September, 2007
Dave Hillman
Rockwell Collins
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"Igoshev, Vladimir" <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
02/22/2008 12:34 PM
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Re: [TN] Shrink hole voids
Hi David,
Think of rivets on a plane or ship. They are there to prevent a crack
from propagating. A hole (or void) will do the same trick. It does not
create a stress concentration (particularly in a ductile material like
solder) and therefore it can stop a crack ("swallowing" it). You can
take a look at the basics of Fracture Mechanics if you want to.
Regards,
Vladimir
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Tremmel
Sent: Friday, February 22, 2008 1:29 PM
To: [log in to unmask]
Subject: [TN] Shrink hole voids
Hello TechNet Gurus,
I read an article that say that a shrink hole void (hot tear or sink
hole)
is not a crack, does not impact reliability, does not continue to grow
under
thermo-mechanical stresses.
This seems to go against my common sense and would venture to say adds
to
solder creep fatigue.
Would anyone like to comment on my comment and/or offer a link to where
I
can find more information?
I am a poor country and your two cents goes a loooooong way.
As always, thank you in advance.
Thank you,
David Tremmel
Value Recovery
847 858-5540 - Cell
847 557-9574 - Office
847 557-9573 - Fax
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