Hello members of TechNet,

We use IGBTs in TO-247 packages and diodes in TO-220 packages mounted to
heatsinks using a spring steel clip.  There is a great deal of discussion
regarding the amount of pressure the clip puts on the device (or lack of
pressure), what size fastener to use to mount the clip and how tight the
fastener should be.  We are currently using a spring clip made by AAVID
which when "tightened" we find that the tab the screw goes through does not
sit flush with the heatsink.

I need info on recommended screw sizes, screw torques, and pressure applied
to the devices to produce proper thermal transfer.   How much pressure on
the device is enough?  What is my best way to measure the force to prove the
assemblies are working to Engineering's satisfaction?

Thanks in advance for your help.

Phil Nutting
Manufacturing Engineer
Kaiser Systems, Inc.
126 Sohier Road
Beverly, MA 01915
ph: 978-922-9300
fx: 978-922-8374
[log in to unmask]

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