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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:
Thu, 10 Apr 2008 13:44:17 -0500
Content-Type:
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text/plain (84 lines)
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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