Hi Leland,
That would point towards a weak interface or a Head-on-Pillow [ I sleep with my head 'on' not 'in' a pillow] situation.
Werner
-----Original Message-----
From: Leland Woodall <[log in to unmask]>
To: TechNet E-Mail Forum <[log in to unmask]>; Werner Engelmaier <[log in to unmask]>
Sent: Thu, Dec 2, 2010 2:53 pm
Subject: RE: [TN] BGA Failure Analysis Recommendations
Werner,
Actually the assembly failed a multi-cycle vibration test. The test details
were developed by a team of the customer's design and our R&D group. The test
itself is supposed to reflect a worst-case scenario of 10 years of product
usage.
Leland
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Thursday, December 02, 2010 2:13 PM
To: [log in to unmask]
Subject: Re: [TN] BGA Failure Analysis Recommendations
Hi Leland,
Most HALT tests are NOT accelerated reliability tests—the first tests for
robustness and for the second you should follow IPC-9701.
Werner
-----Original Message-----
From: Leland Woodall <[log in to unmask]>
To: [log in to unmask]
Sent: Thu, Dec 2, 2010 11:01 am
Subject: Re: [TN] BGA Failure Analysis Recommendations
Richard,
We've priced but not yet purchased a BGA inspection scope. I'll check
the one you've mentioned below from Practical. It might be thousands
cheaper than what we're considering, and yet perform the same function.
As far as the component, it was not reworked. The unit passed all our
in-house testing before being submitted to our HALT process.
The board finish is OSP.
Leland
-----Original Message-----
From: Stadem, Richard D. [mailto:[log in to unmask]]
Sent: Thursday, December 02, 2010 10:57 AM
To: TechNet E-Mail Forum; Leland Woodall
Subject: RE: BGA Failure Analysis Recommendations
Or you have an internal via barrel crack.
One way to tell is to purchase the small inspection prisms from
Practical Components. No BGA assembler/inspector should be without one.
You can use any standard microscope and the inspection mirror to see
under almost any BGA. The prism has a beveled edge so you can get right
down to the PWB, and you can angle the mirror to obtain the best view.
The prism is mounted on the end of a small wire that goes into a handle
much like an exacto knife handle. Imagine a 9-iron with a highly
polished face, but in miniature. To use it, you only need about .070"
clearance around the BGA periphery.
Back to the cause of the intermittent open.
If the BGA was previously reworked, and this did not fix the issue, then
it is probably an internal via separation. These are quite often
mistaken for a bad BGA solder connection. If it is a solder joint issue,
it is usually either BP or BF.
What is the circuit board finish?
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Thursday, December 02, 2010 9:36 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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