I wanted to hear how fellow Technet people are processing surface mount
potentiometers.

I have experienced some field failures recently in this area.  Water has
leaked into a "Sealed" potentiometer.  When power is applied an
alternate circuit grows inside the pot causing the part to fail.

We are processing this part using an OA solder paste through a normal
pick and place operation.  Reflow profile takes this through a normal
reflow curve Max. Peak temperature of 195-205 degrees C with a Ramp rate
of 2-2.5 Degrees C.  We then add on a few through hole parts through
progressive assembly then  wave solder and clean the assembly.

We are utilizing an Electrovert Aquastorm 100.  We process the boards
through at 4 feet per minute.  Water temperature is 145 degrees F.

We have been cleaning boards (and potentiometers) for over eight years
with never a problem.  This one has sure surprised me.  Just wondering
if anyone else has had any experience with this and what they have done
to fix this other than hand soldering the pot on in final.


--
Paul Truit, Mfg. Eng.
RBB Systems, Inc.
4265C E. Lincolnway
Wooster, OH  44691
Ph. (330) 567-2906 ext 514
Fax (330) 263-5324
Email: [log in to unmask]

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