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Hi team - I agree with Phil - where is the pad? It appears to be missing.
Any additional photos?
Dave
From: Phil Bavaro <[log in to unmask]>
To: <[log in to unmask]>
Date: 04/23/2013 12:44 PM
Subject: Re: [TN] QFN Pad Corrosion?
Sent by: TechNet <[log in to unmask]>
Steve,
I don't see a pad at all in the picture....much less a corroded pad.
I find it highly unlikely that only one pad had any kind of plating
problem on the part.
If the picture is actually showing a pad without any solder wetting to it,
even after removal, that raises my eyebrows more.
I would want to see the part.
Phil
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Tuesday, April 23, 2013 10:12 AM
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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