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Subject:
From:
Amol Kane <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Amol Kane <[log in to unmask]>
Date:
Mon, 6 Dec 2010 09:36:05 -0500
Content-Type:
text/plain
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text/plain (165 lines)
I personally like the SMT tools mirror. The topline mirror is too flexible and you need to have a very steady hand to ensure that the mirror does not move when looking thru a scope. With the SMT tools mirror, you can securely place the mirror on the board and then pivot it to get different angle views on the BGA balls.

Amol

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman
Sent: Friday, December 03, 2010 1:38 PM
To: [log in to unmask]
Subject: Re: [TN] BGA Failure Analysis Recommendations

AABvoAAIn-Reply-To: <[log in to unmask]>
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5994

Richard,

How do the Topline mirrors compare to the SMT tools mirror?

http://www.smttools.com/mini_mirrors.html  (this seems to be more like what you described)

Bob 

-----Original Message-----
From: Stadem, Richard D. [mailto:[log in to unmask]] 
Sent: Friday, December 03, 2010 1:27 PM
To: Bob Landman; [log in to unmask]
Subject: RE: [TN] BGA Failure Analysis Recommendations

Actually I made a mistake, and it is Topline that carries the prisms.
Here is the link.
http://www.topline.tv/InspectionMirror.html

Someone emailed me to say they no longer carry them, but I am not sure that is because they were trying to get them from Practical. Sorry about the mistake.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman
Sent: Friday, December 03, 2010 12:23 PM
To: [log in to unmask]
Subject: Re: [TN] BGA Failure Analysis Recommendations

Richard,

I looked at Practical's website but couldn't find the small inspection prisms you mentioned.  Do you have a URL to the page where they have them?  Would be a "nice to have" device.

Bob Landman
H&L

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Thursday, December 02, 2010 11:02 AM
To: [log in to unmask]
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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