PCBs finish are ENIG?
May be black pads?
Reuven

On Tue, Apr 23, 2013 at 8:12 PM, Steve Gregory <[log in to unmask]> wrote:

> 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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*Reuven Rokah*

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