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Originally Posted by BillA
ask AS about AS stuff
heat transfer is primarily through the actual contact points as I understand the literature,
the flatter the surfaces the greater number of points and/or area of contact
a uniform film of 0.001" w/o any substrate contact would be a pretty good insulator, easily demonstrated by removing the film
"uniform film" is an (imaginary) assumption requiring 2 absolutely flat surfaces
TIM testing is a specialty of its own, lots of info on how to do it;
see Inco's testing for some TIM values, I defer to him
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If "a uniform film of 0.001" w/o any substrate contact [is] a pretty good insulator" then how can AS claim (low?) thermal resistance?
I must be missing something obvious. Else, why bother with thermal interface material at all?
"'uniform film' is an (imaginary) assumption requiring 2 absolutely flat surfaces"
Maybe a restatement would clarify:
1. If we knew the theoretical thermal resistance at 25 microns with perfectly flat metal -"uniform film"- perfectly flat metal or could establish real-life worst case thermal resistance at 25 microns
2. Then if could gurantee <10 microns variation per mating surface with thermal resistance filling the gap.(by reasonable means as yet unknown/discussed)
Would we then be better able to test anything? Assuming point 1 turns out to be arbitrarily small under most scenarios.
Edit:
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Originally Posted by BillA
EDIT
you said "need to be accounted for"
I'm not suggesting a calculation methodology which is what you seem to be driving at
rather an awareness that the number of variables not explicitly quantifiable necessitate temperance in the making of assumptions/conclusions
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Indeed.
Can we quantify a worst case variance and find it to be either negliable or account for a given (reasonable) size gap and make sure we do better than such a gap?
Will have to get back to this, need time to track down and digest Incoherent's posts and other relevant information. Maybe talk to AS. (HA!)
Real life commetments are also catching up with me, though.