Hi Pete,
It's a well known thing and it's been around for a while. :-) I took a
look at the images you sent and the ball with a crack is a CORNER one.
Corner balls cracks first as a result of bending (or the board being
dropped).
By the way, you didn't mention what triggered the investigation?
Regards,
Vladimir
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Wednesday, November 01, 2006 1:36 PM
To: Vladimir Igoshev
Cc: (Leadfree Electronics Assembly Forum); Pete Houwen
Subject: RE: [LF] need some SEM/EDX BGA images
Vladimir,
Interesting that you should mention that. I just finished reading a
study
done by Altera that found that failures induced by bending stress can
appear similar to black pad failures. I have been trying to get
information about the pin location of the failed joints on the BGA, but
the
answer is taking a while. These boards are depanelized after assembly,
and
they do get moved around the shop quite a bit. We have also found
boards
that passed functional test, only to fail after shipping, though none of
these were analyzed.
http://www.altera.com/literature/cp/altera-panpac-2005.pdf
Pete
"Vladimir
Igoshev"
<vladimir.igoshev
To
@amd.com> "\(Leadfree Electronics Assembly
Forum\)" <[log in to unmask]>,
"Pete
11/01/2006 10:03 Houwen" <[log in to unmask]>
AM
cc
Subject
RE: [LF] need some SEM/EDX BGA
images
Hi Pete,
Is there any chance that the boards were bent during the
assembly/handling?
I'll send you a few images later on, so you can compare them with what
you've got.
Regards,
Vladimir
Vladimir Igoshev, Ph.D.
Physical FA Laboratory Manager
Advanced Micro Devices Inc.
Ph: 905-882-2600, x 6611
Fax: 905-882-5536
Cell: 416-300-4203
E-mail: [log in to unmask]
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Pete Houwen
Sent: Tuesday, October 31, 2006 4:00 PM
To: [log in to unmask]
Subject: Re: [LF] need some SEM/EDX BGA images
A couple of notes to the original post:
Our board vendor is a known high quality vendor that we've used
flawlessly
for many years. We have another assembly location building these same
boards, same vendor, no problems at all.
The images I have do not show classic black pad. I'm looking for black
pad
images (SEM/EDX) for comparison. They do show P-rich zones, but also Ni
in
the solder bals, and bumps of solder on top of the NiP, in the partially
fractured area.
These boards may be getting heated 4 or 5 times. I can't get an
official
report from them, but I understand the initial 2 reflows use a peak of
265
with an undetermined by extended TAL. I believe may be drawing too much
Ni
out of the bulk pad.
If I have a PCB problem, I want to address it. I think it's more likely
I
have an assembly problem, and they want to dismiss that immediately.
And at the same time, in a separate effort, I'm trying to stop them from
changing to a known poor quality vendor to save a few dollars.
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