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Date: | Tue, 23 Apr 2013 12:45:08 -0500 |
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Higher mag would be great to discern anomaly. You have to see it to call it, baseball
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Tuesday, April 23, 2013 12:12 PM
To: [log in to unmask]
Subject: [TN] QFN Pad Corrosion?
Hi All,
I have another question about the QFN16 that I was talking about last week. I was sent a photo of the bottom of one of the devices after it had been removed from a failed board. It is here:
http://stevezeva.homestead.com/QFN16_Corrosion.jpg
It's pointing out a pad that seemed to have a lot of corrosion on it and I was told that solder would not wet to it. I was asked what might cause this?
My first thoughts are that the appearance might have been caused by the rework when it was removed, and that a un-solderable intermetallic has formed on pad but I can't say that for sure. The part is finished with matte tin when it is supplied. When a part is tin finished, they have a barrier nickel plate beneath the tin right?
I don't have the part in front of me, I only got sent the photo. I was asked what my thoughts were, so I thought I'd ask my TechNet friends too... :o)
Thanks,
Steve Gregory
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