Jason,
That must have been SOME CRACK! Just imagine two saw toothed pieces of metal meshed - the amount of metal parallel to the direction of the mated surfaces is virtually identical to that of a solid piece of metal. So I still contend that except in VERY unusual circumstances, x-ray will not work.
Bev Christian
Research in Motion
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: January 27, 2003 9:06 AM
To: TechNet E-Mail Forum.; Bev Christian
Subject: Re: [TN] BGA micro cracks
Bev,
One X-ray system/technology that WILL see these cracks is the Agilent 5DX.
Due to it's scintillator technology, it will see cracks in BGA's. I have
used it for this before. One can "slice" through the joint at micron level
and see voided areas where the crack is. As far as the fancy scope, I'm not
sure, but think you may be referring to an Ersascope or something like the
new Metcal system.
Jason Gregory
SMT Production Supervisor
LaBarge Inc.
(918)459-2367
(918)459-2221 fax
[log in to unmask]
Bev Christian <[log in to unmask]>@ipc.org> on 01/27/2003 07:52:12 AM
Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
to Bev Christian <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
To: [log in to unmask]
cc:
Subject: Re: [TN] BGA micro cracks
David,
Let me try and use an analogy to explain why you cannot use x-rays to find
micro-cracks or intermittent full cracks (opens), as Werner has aptly
called them. Imagine being at the base of the Rockies on the east side
and looking west. You can't see to the other side obviously because the
mountains are in the way. If you go up the east face of the first
mountain in front of you, 4900 feet of the 5000 height, you still can't
see west. Just consider, for the purposes of cracks, that x-rays need a
visual line of site. Don't have that? Then x-rays aren't going to help
you. Period. The mass of stuff in front of the x-rays is almost the same
with or without the crack, even if the beam is parallel to the
micro-crack.
What MIGHT help you is use one of those fancy microscopes/boroscopes that
let you peek under array devices and use one of those calibrated
torque-limited screw drivers that Celestica (Bruce Houghton and co.)
talked about in a committee meeting at the last APEX. Now that might
work, unless you are talking about one open in the middle surrounded by
solid joints.
regards,
Bev Christian
Research in Motion
-----Original Message-----
From: David Harman [mailto:[log in to unmask]]
Sent: January 24, 2003 8:45 PM
To: [log in to unmask]
Subject: [TN] BGA micro cracks
Here is my issue.
We have a CM that x-rays 100% of the BGAs on our product and notes no
abnormalities. We might have some micro cracking at the ball joints.
(This was discovered because the product electrical properties are
intermittent when we press the BGA down.). In addition to having our CM
x-ray the board we had an outside company perform this inspection with the
same results. If it is not micro cracking we are un-clear what else can
be causing this abnormality.
Any suggestions on how and what we can do to capture this abnormality in
production?
What type of screening can be done after production? (We have performed a
static thermal testing (-0 to 125 degrees) with no failures after testing.
What other type of testing or inspection can be performed to evaluate ball
joints on BGAs?
Thanks David.
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