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From: firstname.lastname@example.org (Bob Wilson)
Subject: Re: Thermal resistance--does this sound right?
Date: Sat, 07 Sep 2002 03:06:46 -0000
Organization: Your Organization
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References: <3D781177.email@example.com> <3D78ECA4.4FAAE397@SpamMeSenseless.us.ibm.com>
In article <3D78ECA4.4FAAE397@SpamMeSenseless.us.ibm.com>,
>Bob Wilson wrote:
>> Nearly ANYTHING will give you less than 1 degree per Watt, for the large
>> area you are referring to (assuming the heat is evenly distributed). Even
>> grease at all (just air) will do it. So if you want to get a value of
>> less than 1 degree/Watt, use anything you want; grease, sil-pads
>It's fortunate that this is so, because the simple calculations people
>use (based on 1-D thermal resistances) become seriously inaccurate at
>small thicknesses. There's a poorly understood "interfacial thermal
>resistance" that becomes dominant for thicknesses less than 10 microns
>or so--it can easily be 0.1 K*cm**2/W. It's sensitive to the history of
>the surfaces and to the exact makeup of the joint materials. This is
>very inconvenient sometimes--I ran into it trying to figure out why
>multistage Peltier coolers aren't better than they are.
>Thermal transfer materials suppliers also peddle a lot of snake oil.
Yeah, like SilPads are as good as a greased mica joint!
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