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February 2002

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Subject:
From:
"Sauer, Steven T." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 21 Feb 2002 08:26:07 -0500
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Hey Earl,
This subject brings back a time of trials and tribulations concerning solder
joint crack propogation using LCCCs and "like" devices.  Beginning with the
Coffin-Manson Law and the Engelmaier (Sir Werner's) equation, it was
determined that solder joint volume needed to be increased and the
"acceptable geometry" needed to be modified, almost to point of "the bigger
the blob the better the job".  Without getting into too many specifics, the
pad dimensions for these parts require augmentation from the norm by
increasing the pad length that extends outward from the device periphery to
a length equal to the pad length that is under the part.  The idea is to
increase the solder joint volume up the castellation and outward to the pad
creating a "bulbous" fillet -- this portion of the joint contributes to 85%
of the solder joint life with respect to crack formation and propogation.
The attained solder joints do go against general Rf rules of thumb (the
shortest path is best) but I was unaware of any performance issues with
applications below 2gHz.  As one Rf designer told me years ago, ..."don't
put a stress relief bend on that ribbon, just add more solder..."
Hope this helps, if not, sorry for adding clutter to your cave!

Steve Sauer
Manufacturing Engineer
Northrop Grumman, Xetron

-----Original Message-----
From: Earl Moon [mailto:[log in to unmask]]
I have another board/adventure requiring simple coplanaty issues be resolved
and I know how to do this so don't need advice. Need to know, from R/F
folks, if anyone is using the following:

EM Research Inc. LX-2050-05
EM Research Inc. LX-1450-01

These parts are castellated, are gold plated castellations, are PCB material
interposer types requiring very flat surfaces on which to be mounted. No
problems but for leadless and gold plating. Wondering if anyone out there
has experience with the aforementioned parts and results.

MoonMan

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