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November 2014

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From:
Guy Ramsey <[log in to unmask]>
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Date:
Tue, 25 Nov 2014 13:21:48 -0500
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: Friday, November 21, 2014 10:30 AM
To: [log in to unmask]
Subject: Re: [TN] AW: Solder defect

The see what Gunter is saying. I wonder if that reflection on the lead is an
artifact, and not really a flux deposit. I agree the solder volume seems
adequate to have provided an opportunity for the lead to have wetted. 
It does look like the lead is deflected, not co-plannar. It also looks like
it moved a little. This can be indicative of a solderability problem. These
parts can float until they wet. What kind of paste? Look carefully to
confirm that what Gunter says is true. Is there flux on the lead? 

If not the opposite could be true. The reflow temp is too high. The most of
the flux is burned of and this lead, which is not co-planer does not have
enough flux to promote wetting when it settles into the solder deposit.
Creating the foot in mud condition. 

Guy

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Grossmann, Günter
Sent: Wednesday, November 19, 2014 2:09 AM
To: [log in to unmask]
Subject: [TN] AW: Solder defect

Jim

As Dave already mentioned the two possible causes are coplanarity and
temperature. Looking at pictures 2 and 4 I'd rather go for coplanarity but
in picture 8 it seems to me as if the level of the solder is high enough to
wet the pin and the pin is covered by flux (which isn't the case in pictures
2 and 4). This looks like a low temperature issue. It's well possible that
you have a combination of several reasons for a failure.



Günter 




> -----Ursprüngliche Nachricht-----
> Von: TechNet [mailto:[log in to unmask]] Im Auftrag von Jim West
> Gesendet: Dienstag, 18. November 2014 21:13
> An: [log in to unmask]
> Betreff: [TN] Solder defect
> 
> Hi all,
> 
> Please see attached links. (Thanks Steve) 
> http://stevezeva.homestead.com/IMG00002.jpg
> 
> http://stevezeva.homestead.com/IMG00004.jpg
> 
> http://stevezeva.homestead.com/IMG00008.jpg
> 
> We have recently come across two failures that were the result of one
> (1) pin not soldered on a 144 pin QFP.  Looking at the pictures, 
> you'll see no wetting and the pin embedded in the solder.  We could 
> say it's contamination, but we had no issues with any other pins on 
> the QFP.  One more thing to add to the troubleshooting, the failure is 
> the same pin (36) on the QFP.  Do I have a warping issue?  The pin 
> doesn't appear to be bent, but I have not ruled that out until I have 
> better means of verifying.  If it's contamination, why only one pin?
> I would think that I would get at lease the heel or toe, or even the 
> sides to solder, but in this case no wetting.  You can see the pin has 
> made contact with the solder due to the indentation.  How does this 
> not solder if it has made contact with the solder paste?  I'm at a 
> loss
and we will probably end up sending this to a lab, but I'm not sure if we
will gain anything from a lab??
> 
> We are using leaded solder for this application.
> Photo IMG00002 and 00004 are from the same failure Photo IMG00008 is 
> the 2nd failure.
> 
> Your thoughts?
> 
> Thanks,
> Jim
> 
> 
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