Dear TechNetters,

I have a situation involving a surface mount MELF Resistor, 270 ohm, 3W.
During environmental testing, one solder joint separated at the pad
causing intermittent failure.  Unfortunately, the technician repaired the
solder joint so I have nothing to evaluate.  Based on information given to
me, I suspect it was a mismatch of CTE between the MELF and the PCB
(FR4,.062).

Does anyone have any experience, pad design or CTE data,  with large,
cylindrical MELF's?  This part is .5" x .156" dia.  and is custom
manufactured by RCD.  We are stuck with this part in surface mount, as
someone got a great "deal" on 100,000 or so parts, so it critical that I
prove reliability (or lack of) with the solder joints.  In advance, I
appreciate any information that can point me in the right direction.

Howard Watson
Manufacturing Engineer
AMETEK/Dixson