I was not able to open the provided links. We experience die cracks before.
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: Friday, February 12, 2010 11:57 AM
To: [log in to unmask]
Subject: Re: [TN] Die cracks
Chris,
I looked at your photos. The first two links reference Die Crack 01, the
last two reference Die Crack 02, so there are only two pics to look at.
Die Crack 01, I played with the exposure a bit and it appears that the crack
runs to the right, to the edge of the die and stops. The corner of the
device appears to be pretty badly chewed up, although the image is slightly
out of focus at higher zoom. Would be nice to see the entire chip, to see
what is going on over on the left side as well. Enhancing the contrast did
not appear to show any delamination between the device and over-mold
compound, therefore I am inclined to believe that it is NOT a popcorn
situation.
Die crack 02 also did not appear to show and separation between the
over-mold and the device. This crack appears to terminate on the right side
of the chips surface before even reaching the edge of the device, but what
does the left side look like?? The terminus of the crack on the right side
appears to stop at the surface of the chip and not enter the over-mold.
Both of these would likely have shown up quite well with a low frequency
thru transmission acoustic scan - thinking of my days on my good old Sonix
acoustic scope...
I would like to see more info, but my knee-jerk reaction at this point [with
caveat] is that this is a die packaging/handling related issue, not an issue
related to your assembly/reflow. Need to see both ends of the cracks and
some clear high-mag looking for delam in the structures.
FWIW
Steve C
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Mahanna
Sent: Friday, February 12, 2010 11:45 AM
To: [log in to unmask]
Subject: [TN] Die cracks
Hi TN
We are in desperate need of QUICK expertise and/or opinions wrt the die
cracks that can be seen from the links below. Sorry Steve, didn't want to
circumvent you but I've got to come up with an opinion by EOD. BGA/CSPs
were encapsulated in slow cure epoxy prior to excision. We section BGAs
everyday and rarely see die cracks.
I've got to decide whether we should recommend that the CM build up a few
more for NDT (acoustics, CT..)
I know: max cool-down was probably 2.2-2.8C/ second; ICT was not strain
engineered or tested; SAC305 balls, paste; parts passed ICT, ..but cracks
don't look to reach active circuitry
Don't know: laminate, peak reflow
Can't say: pretty much anything else
Thanks!
Chris
https://robisan.sharefile.com/d-s7b37c04078d4889b
https://robisan.sharefile.com/d-sc19f7716a0645489
https://robisan.sharefile.com/d-sb215d22cbf54972b
https://robisan.sharefile.com/d-s22d269ff34d4018a
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