Jim,

It's not very hard to see that you have a coplanarity issue here.  That's why the lead did not wet.

Leland
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From: TechNet [[log in to unmask]] on behalf of Jim West [[log in to unmask]]
Sent: Tuesday, November 18, 2014 3:12 PM
To: [log in to unmask]
Subject: [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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