My guess is that those pins are ground pin so they didn't reach the same
temperatures as the other pins which are probably signal pins. Lower
temperature means less propensity to volatilize the co-deposited organics.

Dave

On Fri, Mar 6, 2015 at 9:41 AM, Stadem, Richard D. <[log in to unmask]
> wrote:

> Just curious. Why did the two pins in the middle of the picture not
> display that condition also? The answer to that question would point to a
> mitigation strategy.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
> Sent: Friday, March 06, 2015 9:38 AM
> To: [log in to unmask]
> Subject: Re: [TN] bright electroplated tin, versus immersion matte tin
>
> Hi Dave!
>
> Ahh yes, remember a while back when I was working in Tulsa the time I had
> issues with a AMP Densipac connector that I had posted about that you
> answered for me? You were thinking that it was bright tin. Below are the
> photos and the email thread...
>
> Steve
>
> http://stevezeva.homestead.com/files/AMP_Connectors.jpg
>
> http://stevezeva.homestead.com/files/Connector_Blumpies.jpg
>
> ********************************************************
>
> Steve Gregory <[log in to unmask]
> <
> http://listserv.ipc.org/scripts/wa.exe?LOGON=A3%3Dind0906%26L%3DTECHNET%26E%3Dquoted-printable%26P%3D4384754%26B%3D--%26T%3Dtext%252Fplain%3B%2520charset%3Dus-ascii%26header%3D1
> >>
> Sent by: TechNet <[log in to unmask]
> <
> http://listserv.ipc.org/scripts/wa.exe?LOGON=A3%3Dind0906%26L%3DTECHNET%26E%3Dquoted-printable%26P%3D4384754%26B%3D--%26T%3Dtext%252Fplain%3B%2520charset%3Dus-ascii%26header%3D1
> >>
> 06/23/2009 06:49 AM
> Please respond to TechNet E-Mail Forum <[log in to unmask] <
> http://listserv.ipc.org/scripts/wa.exe?LOGON=A3%3Dind0906%26L%3DTECHNET%26E%3Dquoted-printable%26P%3D4384754%26B%3D--%26T%3Dtext%252Fplain%3B%2520charset%3Dus-ascii%26header%3D1
> >>;
>
> Please respond to Steve Gregory <[log in to unmask] <
> http://listserv.ipc.org/scripts/wa.exe?LOGON=A3%3Dind0906%26L%3DTECHNET%26E%3Dquoted-printable%26P%3D4384754%26B%3D--%26T%3Dtext%252Fplain%3B%2520charset%3Dus-ascii%26header%3D1
> >>
>
>
> Subject [TN] "Blumpie" looking connector leads...
>
> Morning all!
>
> Trying to stay cool here! Broke 100 degrees yesterday and Sunday, and it's
> probably going to break 100 degrees today. Summer has come with a
> vengeance! Ran across something yesterday that I've never seen before. We
> build a board that uses this AMP Densipac SMT connector. We've built a lot
> of these boards before without any issues at all. This latest run we have
> something going on with these particular connectors.
>
> Here's a photo of them on the PCB:
> http://stevezeva.homestead.com/files/AMP_Connectors.jpg You can probably
> see that the leads have this "Blumpie" look to them...both bumpy and lumpy.
> This is fresh out of the reflow oven. Here's a closer look:
> http://stevezeva.homestead.com/files/Connector_Blumpies.jpg
>
> If you notice the two pins either side of the white line look fine. They
> are the anchor pins that are for mechanical strength for the
> connector...they are not I/O pins. The rest of the board looks absolutely
> fine too. Not a bit of problem. It's just the I/O pins. We have noticed
> that connectors with certain date codes don't have this problem. Also,
> before reflow the connectors look okay. Luckily we've only built a few
> boards, and we're stopping until we can get to the bottom of this... Have
> any of you ever seen "blumpie" connectors like these before?
>
> Steve
>
> *********************************************************
>
> From: [log in to unmask]
> <
> http://listserv.ipc.org/scripts/wa.exe?LOGON=A3%3Dind0906%26L%3DTECHNET%26E%3Dquoted-printable%26P%3D4384754%26B%3D--%26T%3Dtext%252Fplain%3B%2520charset%3Dus-ascii%26header%3D1
> >
> [mailto:[log in to unmask]
> Sent: Tuesday, June 23, 2009 7:22 AM
> To: TechNet E-Mail Forum; Steve Gregory Cc: [log in to unmask] <
> http://listserv.ipc.org/scripts/wa.exe?LOGON=A3%3Dind0906%26L%3DTECHNET%26E%3Dquoted-printable%26P%3D4384754%26B%3D--%26T%3Dtext%252Fplain%3B%2520charset%3Dus-ascii%26header%3D1
> >
>
> Subject: Re: [TN] "Blumpie" looking connector leads...
>
> Hi Steve - ah, the beauty of being a materials engineer is that the
> industry doesn't seem to learn from past material mistakes so I really
> don't need to learn anything new! I recommend you check with your connector
> vendor to confirm that the connector surface plating is bright acid tin.
> The photos appear to show a bright acid tin surface finish that has
> blistered during the solder reflow process due to excessive co-deposited
> organic material. Bright acid tin finishes (plated correctly) look very
> nice but have terrible solderability characteristics and are a known tin
> whisker generation source. It appears that you may have had a surface
> plating change from what you normally had been procuring. Good luck.
>
> Dave Hillman
> Rockwell Collins
>
>
>
> On Thu, Mar 5, 2015 at 9:01 PM, David Hillman <
> [log in to unmask]> wrote:
>
> > Hi Guy - ok, here is the short list and yes, I have a HUGE dislike for
> > brite acid tin:
> >
> > Brite acid tin (electroplated)
> > 1) grows tin whiskers like a chia pet due to the co-deposited organics
> > in the plating. The same co-deposited organics "boil" during a
> > soldering process causing lots of voids and generally poor solder
> > joints. Very short shelf life - three months is not uncommon. Doug and
> > I have some great pictures of the bubbling in one of our tutorials
> >
> > Matte tin (electroplated)
> > 1) one of the most common component finishes on components today.
> > Lacks thermal excursion robustness but will pass JSTD-002/003
> > solderability testing from good plating processes. Can also tin
> > whisker, less prone than brite acid tin, but also not zero tin
> > whiskers. Good for corrosion issues in some product use environments.
> > Fewer soldering ability issues with stronger fluxes
> >
> > Immersion tin
> > 1) Has poor thermal excursion robustness but will pass JSTD-003
> > solderability testing. Much less propensity to tin whisker when
> > plating formulation includes specific inhibitors. Good for corrosion
> > issues in some product use environments. Very flat and good for SMT
> > assembly. Because it is deposited by a galvanic reaction, typical much
> > thinner than electroplated tin systems. This plating system is covered
> > by the IPC-4554 specification.
> >
> > Take a look in the IPC AJ 820 or the IPC -7095 standards as they both
> > have good sections on surface finishes including some tin plating
> comparisons.
> > And remember, the initiation of tin whiskers is a characteristic of
> > tin itself so all pure tin finishes, regardless of their deposition
> > process, can have tin whisker issues. Hope this helps.
> >
> > Dave Hillman
> > Rockwell Collins
> > [log in to unmask]
> >
> > On Thu, Mar 5, 2015 at 7:51 PM, Guy Ramsey <[log in to unmask]> wrote:
> >
> > > Can anyone give me a nutshell difference between immersion tin for a
> > solder
> > > finish and electroplated tin?
> > > Advantages, disadvantages as a surface finish more than the chemical
> > > and plating process differences.
> > > Thanks,
> > > Guy
> > >
> > >
> > >
> > >
> > >
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