Viktor,
many years ago, I made calculations for cooling wafers to a super computer.
We needed a transconductance <<0.1 K/W. At the end I realized the need for
Helium to fill every single gap, but before that I learned some interesting
things. Often, we regard a air gap as a disaster because we want metal to
metal for best cooling. However, even a cooler fixed wiht metal filled
cooling mat has indeed a lot of air space, If you calculate with lambda (air
molecular free path) for air (many gases as you know), you get the
surprising result that there is a signifcant heat transportation across the
air gap. So, if the requirements are not too high, a airgap is not
necessarily a catastroph. But we talk single micrometers of course.
Furthermore we got radiation, which is much dependent on what materials we
have on both sides of the gap. The guy who did a lot of work on heat
transportation through various media was named Prandtl. If you still have
you old school books, you may find his formulaes.
--------------------------------------------------
From: "Victor Hernandez" <[log in to unmask]>
Sent: den 19 April 2010 06:03
To: <[log in to unmask]>
Subject: Re: [TN] Best way to measure "actual" themal pad compression
> Explain further on this method/technique.
>
> Victor,
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Technet Legg
> Sent: Monday, April 19, 2010 7:58 AM
> To: [log in to unmask]
> Subject: Re: [TN] Best way to measure "actual" themal pad compression
>
> Probably too late to be relevant to the original poster, but;
>
> If the issue is distance between surfaces of the thermal interface, then a
> capacitive measurement is probably the simplest method. This often avoids
> the question of real dissipator surface area as well.
>
> RL
>
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