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July 2008

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Subject:
From:
Genny Gibbard <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Genny Gibbard <[log in to unmask]>
Date:
Mon, 21 Jul 2008 13:10:02 -0600
Content-Type:
text/plain
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text/plain (63 lines)
 Thanks for posting, Steve.
My concern?  IPC-2221, Table 6-1 minimum electrical conductor spacing.
For a low voltage assembly is 0.13mm.  These solder balls are hugging
one pad, so they aren't a problem.  I probably agree that I wouldn't
fail this particular board.  If this solder ball trapped itself in
between two pads, though, it is like a little stepping stone between the
pads - the space on either side is less than the minimum clearance spec.
Maybe I am applying this incorrectly?


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: July 21, 2008 11:54 AM
To: [log in to unmask]
Subject: Re: [TN] Solder balls

Hi Genny!

Sorry it's taken me a bit to get your picture posted, but I just got
back from 2-weeks vacation and a week in Colorado going to a
IPC-771/7721 instructor certification class, so I've been catching up on
things this morning. But here is your picture:

http://stevezeva.homestead.com/files/solderballs-QFN.jpg

Myself, I wouldn't worry about them tiny solderballs. They probably
aren't going anywhere, and besides if they did, they're so small what
problem could it cause?

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Genny Gibbard
Sent: Monday, July 21, 2008 10:52 AM
To: [log in to unmask]
Subject: [TN] Solder balls

Have you ever gotten a much better analytical tool available to you, and
have it cause major panic due to what you can see now that you never saw
before?
We got a major fancy dancy brand new X-Ray.
Now we see things like the attached picture.  Steve, could I trouble you
to post it for me?  
 <<solderballs-QFN.jpg>>
Our old X-Ray would have never seen this.
Would you fail these solder balls?

It is a QFN, 0.5mm pitch, 0.3mm pad width with a heat slug.
I think trying to replace this device by hand would cause more trouble
than we see right now.

Genny 

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