HI Jim - a couple of other possible root causes - (1) corner leads are
often the ground pins on packages so if the pin did not get hot enough then
solder won't wet to it; (2) As others have said, what about the corner lead
being bent?; (2) kind of a reach but what about the corner lead having poor
plating or poor solderability? Usually other pins would show the same issue
on this root cause.

Dave Hillman
Rockwell Collins
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On Tue, Nov 18, 2014 at 2:12 PM, Jim West <[log in to unmask]> wrote:

> 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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