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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