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Subject:
From:
Steve Gregory <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steve Gregory <[log in to unmask]>
Date:
Fri, 6 Mar 2015 08:38:02 -0700
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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

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06/23/2009 06:49 AM
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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

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Sent: Tuesday, June 23, 2009 7:22 AM
To: TechNet E-Mail Forum; Steve Gregory Cc: [log in to unmask]
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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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