I also suspect that Joyce is correct, but for a slightly different reason in that the tin oxide is coming from the flux left behind on the belly pad.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
Sent: Thursday, December 10, 2015 7:45 AM
To: [log in to unmask]
Subject: Re: [TN] What else it can be
Hi Vlad - I agree with Joyce, the SEM signature looks like tin oxide suspended in an organic (note the C peak). I sometimes see this as SnOx in the flux residue after soldering.
Dave
On Wed, Dec 9, 2015 at 6:55 PM, Vladimir Igoshev <[log in to unmask]
> wrote:
> No underfill or any other fancy stuff
>
> ---- On Wed, 09 Dec 2015 16:53:28 -0800 Yuan-chia Joyce Koo<
> [log in to unmask]> wrote ---- > tin oxalyate used for epoxy
> catalyst... there were works for flux/ > underfill one step stuff
> utilize flux by product as catalyst for > curing... (can't remember
> which group did that...)
> > jk
> > On Dec 9, 2015, at 7:03 PM, Vladimir Igoshev wrote:
> >
> > > Hi Dave,
> > >
> > > Not really. It doesn't "burn" or "curl" much under the beam, so
> > > it's solid.
> > >
> > > Vladimir
> > >
> > > ---- On Wed, 09 Dec 2015 15:51:29 -0800 David > >
> Hillman<[log in to unmask]> wrote ---- > >> Thank you
> Steve!
> > >>
> > >> Vlad - does the substance slightly charge in the SEM?
> > >>
> > >> Dave
> > >>
> > >> On Wed, Dec 9, 2015 at 5:46 PM, Steve Gregory
> <[log in to unmask]> > >> wrote:
> > >>
> > >>> Hi Dave and Vlad,
> > >>>
> > >>> I have it up here:
> > >>>
> > >>> http://stevezeva.homestead.com/What_else_it_can_be.pdf
> > >>>
> > >>> Steve
> > >>>
> > >>> On Wed, Dec 9, 2015 at 4:34 PM, David Hillman < > >>>
> [log in to unmask]> wrote:
> > >>>
> > >>>> HI Vlad - we can't open Dropbox here due to firewall > >>>>
> restrictions so can > >>>> you have Steve G. post the pictures?
> > >>>>
> > >>>> Dave Hillman
> > >>>> Rockwell Collins
> > >>>> [log in to unmask] > >>>> > >>>> On Wed, Dec
> 9, 2015 at 4:59 PM, Vladimir Igoshev < > >>>>
> [log in to unmask] > >>>>> wrote:
> > >>>>
> > >>>>> HI everyone,
> > >>>>>
> > >>>>> I'm attaching a link to a file showing something I'd
> appreciate > >>>>> your > >>>>> thoughts on. It's a cross-section of
> a QFN on an IAg board; > >>>>> Pb-free/no-clean process. As you can
> see from the EDS spectrum, > >>>>> that > >>>>> greyish stuff
> between pins has pretty much only Sn and O in its > >>>> elemental >
> >>>>> composition.
> > >>>>>
> > >>>>> I know there is burn flux residue around solder joints but
> that > >>>>> stuff > >>>>> doesn't have any C in it. The question I
> have is what is it.
> > >>>>>
> > >>>>> I spoke to Bev and both of us are still puzzled.
> > >>>>>
> > >>>>> Here is the link:
> > >>>>>
> > >>>>
> https://www.dropbox.com/s/3wbj62vqjyhvj2y/What%20else%20it%20can%
> > >>>> 20be.pdf?dl=0
> > >>>>>
> > >>>>> Thank you very much in advance.
> > >>>>>
> > >>>>> Regards,
> > >>>>>
> > >>>>> Vladimir
> > >>>>>
> > >>>>> SENTEC
> > >>>>>
> > >>>>>
> > >>>>>
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