Change to elliptic pads with the major axis perpendicular to the axial centerline of the MELF...
The problems should go away forever..

Paul Edwards

Surface Art Engineering


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Gervascio, Thomas L
Sent: Friday, February 27, 2009 10:59 AM
To: [log in to unmask]
Subject: [TN] Rolling MELFs

Have a problem and curious to see if others have the same problem.
Misery loves company you know. We have some MELFs that are moving during
reflow. They are not tombstoning and the direction of movement is
perpendicular to the direction of travel . The parts are properly placed
prior to reflow but are sliding off the pads along the edges of the
pads. It seems like something is happening during reflow that is
disturbing the MELFs. No indications of any other parts being skewed.
The MELF pads are the U-shaped pads to help reduce tombstoning. Don't
think I can change to a non eutectic tin/lead solder paste (a paste with
a plastic range) but if the parts are indeed being disturbed by
vibration I don't know if that would help.



Tom




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