Leland,
I think there are many on TN that can give you recommendations but before they do they probably will have several questions for you.
My questions would be:
1. What is the PCB surface finish? Is it ENIG?
2. What is the pitch of the BGA and how large (# of I/O) is the BGA?
3. When you say you've isolated the problem to an intermittent BGA contact, have you isolated the intermittent to a particular ball or location on the BGA? Is the intermittent at the corners or on outer rows or near the perimeter?
4. When you say X-Ray didn't detect a flaw how close (what magnification did you look at the BGA balls) did you examine the BGA? Did you look at the over all BGA or go ball by ball? If you went ball by ball and were able to see evidence of solder paste filleting on all balls that it probably wasn't a plugged stencil but may be a fractured solder joint.
Regards,
George
George M. Wenger
Senior Principal Reliability / FMA Engineer
Andrew Corporation - Wireless Network Solutions
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 Office (732) 309-8964 Mobile
E-mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Thursday, December 02, 2010 10:36 AM
To: [log in to unmask]
Subject: [TN] BGA Failure Analysis Recommendations
Good morning, everyone!
I'm looking for some advice on how to best analyze a BGA problem. We
had an assembly to fail in a reliability test, and have isolated the
problem to an intermittent contact on the BGA device. When downward
pressure is applied to the component it will pass. Without the
pressure, it won't.
That tells me we have either fractured a joint, had a ball to separate
from the package, or had a head in pillow (or non-wet) condition.
We don't have a BGA inspection scope in house, and I can only see two of
the four outside edges with the equipment I have. Of course, nothing is
wrong with those.
We have both 2 and 3D xray machines, but neither detect a flawed
condition.
At this point, do I go with dye and pry, or conduct a series of cross
sections?
What's the recommendations of the pros out there that have dealt with
this? Your suggestions are sincerely appreciated!
Leland Woodall
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