Put a "pellet" of something like playdo on the pedestal but don't make it
too big -  if your gap is supposed to be 30 mils make the playdo (or
similar) into very small pieces sat 100 mils diameter. Place one or two of
these on the pedestal. Assemble the components to the chassis. Dis -
assemble everything. The playdo (or similar will stick to either the chassis
or the component - it doesn't matter which.

Examine the component or pedestal surface with a microscope on a boom stand
under high ish magnification with a dial guage connected between the
microscope holder and the focussing assembly. Zero the focus sharply on the
top of the playdo and zero the guage, then focus sharply on the component or
pedestal to which it is connected, the difference will be the air gap. Put 3
or 4 of these in each position and take an average.

Best regards


John Burke
(408) 515 4992


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joe Macko
Sent: Tuesday, February 16, 2010 12:34 PM
To: [log in to unmask]
Subject: [TN] Best way to measure "actual" themal pad compression

All,

 

I am looking for some proven ways to measure the actual air gap (e.g., 5 to
30 mils) between a component and its mating thermal pad pedestal located on
a Chassis without cutting up the hardware so I can determine the actual
thermal pad compression once a pad is installed.  Using a model, the
theoretical gap can be calculated but I would like to empirically
measure/verify what the gap is and the subsequent pad compression.
Visually, it is hard to tell and not all locations are visible and, I do not
have access to any hardware to cut up, etc.. so I am looking for a tried and
proven method. Some have suggested using a soft material like putty that
will compress and could then be subsequently measured after disassembly. I
have heard rumors of material designed for this purpose but are unable to
find such material.  thx

 

Best Regards,

-Joe M.

 


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