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October 2009

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Subject:
From:
Victor Hernandez <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 6 Oct 2009 13:04:48 -0500
Content-Type:
text/plain
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text/plain (142 lines)
Restrict the aperture on the solder stencil.   Slightly lift the corner
edge of one BGA carrier.  This action will provide HOP.

Victor,

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Tuesday, October 06, 2009 12:41 PM
To: [log in to unmask]
Subject: Re: [TN] BGA X-Ray Defect Detection Capabilities

Apply epoxy such as red Loctite chipbonder over the board pads. The BGA
sphere will not wet to the pad with the Loctite on it.
My hearing aid is off. Yell all you want. 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke
Sent: Tuesday, October 06, 2009 12:16 PM
To: [log in to unmask]
Subject: Re: [TN] BGA X-Ray Defect Detection Capabilities

It is very difficult to find co-planar board surface defects on Xray.
The
system relies on a visual interpretation for example an elongated joint
profile suggests some level of co planarity issue such as component
warpage
- If all joints are good except one or two non wets the X-ray system may
have issues resolving this.

The reason is that the "pull down" of the good joints will compress the
molten solder on the open joint that cannot wet to the pad and it will
not
look too much different from the joints around it.

If you want to manufacture such a joint you could deliberately
contaminate
one or two BGA pads, reflow the BGA and then go take a look on the Xray
system to see if you can resolve it.

I am not going to tell you how to contaminate those pads (you should not
have an issue) as there are people here that will yell at me.........8-)


John Burke
(408) 515 4992


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Tuesday, October 06, 2009 8:56 AM
To: [log in to unmask]
Subject: [TN] BGA X-Ray Defect Detection Capabilities

Everyone,

I just came back from an X-ray vendor qualification trip, and of course,
have a few questions for my professional peers.

Both vendors experienced problems reliably detecting opens and non-wets.
I really didn't expect to see this, as I thought these would be two of
the
most common defects seen among BGA users.  We had to leave boards at
both
facilities so they could further develop their algorithms.

We were not able to create a head-in-pillow defect, and thus, were not
able
to check their machines for this.  They also had no sample boards that
carried such an anomaly.  Is this another defect that is difficult to
detect, and must one utilize a 3D machine in order to find it (assuming
the
machine is capable of both 2D and 3D inspections, and there are no
components beneath the BGA)?

Are there any other caveats you might be able to provide?  Our list of
questions and qualification efforts were extensive, but I'm certain we
missed something.  I just hope whatever it was fell outside of being a
critical item...

Thanks in advance,

Leland

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