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April 2008

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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, 11 Apr 2008 07:50:07 -0500
Content-Type:
text/plain
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text/plain (172 lines)
Mornin' Steve!

Yep, solder dipping the connector sounds like a good idea, but I hope
you have better luck than I did with my connectors. I still have some
sitting in my office after I sent them out to see if they could be
pre-tinned. Here's what I got back:

http://stevezeva.homestead.com/files/Pre-tinning.jpg

I called on two places; Corfin, which no-bid them, and Tintronics which
gave it a go but didn't have any luck and resulted in what you see in
the picture.

My connector leads comes in two finishes, flash gold and matte tin, our
customer doesn't want any pure tin finishes, so we were stuck with what
we have.

These are the kinds of parts that I've found it difficult to comply with
the gold removal statement in the J-STD. I mean you could tin everything
by hand and solder wick it off by hand, but is that practical? I know
there's a statement in the standard that the requirement for gold
removal may be eliminated if there is documented evidence that there are
no gold related solder embrittlement issues associated with the
soldering process being used. If you call Samtec and ask for that,
they'll tell you; "We've not heard anything from any of our customers
about solder embrittlement issues...", but to get that documented from
them is another story.

So we inform our customers that we're putting these down without
removing the gold, and they tell us to continue on. So far so good.
We've yet to hear of any embrittlement problems...

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Sauer, Steve
(Xetron)
Sent: Friday, April 11, 2008 5:55 AM
To: [log in to unmask]
Subject: Re: [TN] Samtec QMSS-DP Series Differential Pair Connectors

Thanks for your insight Steve, as always!
Yep, Samtec continually provides challenges for the simple man! 
I've taken steps to increase the apertures as you and GA Tan have
suggested.  The other attribute that needs correction is the soldermask
webbing between the pads --> designer said it was easier to create a
window around each set of pads --> which caused some gasketing issues.
The other thing that I'm thinking about is having the leads hot solder
dipped by Corfin Industries because we all know "nothing solders better
than solder with Pb".
As far as rework, if you don't have a bottom side heater, you're
screwed.
Thanks again.

Steve 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Thursday, April 10, 2008 2:44 PM
To: [log in to unmask]
Subject: Re: [TN] Samtec QMSS-DP Series Differential Pair Connectors

Hi Steve!

Don't you just love Samtec connectors? Seems like they design a
connector that looks good on paper, but more or less throw it over the
wall when comes to manufacturing with it.

We build some boards that use some Samtec connectors that are very
similar, they're from the QTE series:

http://www.samtec.com/ftppub/cpdf/QTE-XXX-XX-X-D-XXX-MKT.pdf

These are a little longer than yours and I ran into the same
issues...unsoldered pins. Here's a picture of the ones we put down:

http://stevezeva.homestead.com/files/Samtec_QTE.jpg

We put these on two assemblies, one has .062" thick PCB, the other has a
.093". We have far more problems with the .062" thick board than we do
with the thicker one...something to consider.

I had the stencils re-made after we built the boards the first time
because of the open solder joints. There's a bunch of 0402's on these
boards so I'm using a .005" thick stencil. When I had the second stencil
made, I had them open up the apertures for the connectors to 1-mil over
in the X/Y dimension of the pads, And that seemed to help quite a bit.
The overprint wicks back into the pad during reflow and gives a little
more solder volume to help compensate for any coplanarity.

One thing I can tell you is that these are a BEAR to rework! The thing
that makes it tough is the grounding strip down the middle of the
footprint. It can be done though. I have a Hakko FR-1012 IR preheater
that I've had to use, and let me tell you I don't think I could have
reworked one of these connectors without it.

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Sauer, Steve
(Xetron)
Sent: Wednesday, April 09, 2008 1:24 PM
To: [log in to unmask]
Subject: [TN] Samtec QMSS-DP Series Differential Pair Connectors

Good Afternoon,
Does anyone have any experience with the subject connectors?
I'm currently evaluating these connectors (the mate is QFSS series) for
a new application and am experiencing issues with coplanarity of the
leads resulting in random nonsoldered pins.  The coplanarity is listed
on the spec sheet as .004" (.10mm) max and I'm using a 6mil stencil with
1:1 apertures (as recommended by the mfr).
Thanks in advance for your assistance.

Steve

Steve Sauer, CEPM
Sr. Project Engineer
Northrop Grumman Xetron
Cincinnati, OH
513-881-3368
[log in to unmask]

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