I gotta jump on this, because I'm closer to real testing (gonna dump 'theoretical cooler'): this is about TIM variances, which has been concerning me for some time: how do I know that I can repeat the same TIM application one year from now? (hint: I dunno). See below, as it applies to me, twice.
As is known, I have considered acquiring TIM film (of the thinnest grade available, actually have samples), for the simple sake of repeatability. Many are available. Some require curing.
As is also known, I am capping my copper heat die with a real IHS; another TIM joint. (let's keep unrelated issues outside this thread, if anyone objects, ok?
) and taking temp measurements as follows: Intel style IHS groove, and 1 or 2 readings in the heat flux, Incoherent style. (I'm still working out the construction details). As a result, I ought to be able to detect 'unusual variations', and should have some very interesting data after several blocks, but I am not testing with Intel's Indium (unless I can source it, then I might consider it).
While it's been previously suggested that comparison tests be run between
real cpu and heat die, I know of no tester willing to go both routes (me included). That would have to be a collaborative effort. Anyone?
Back on topic.
If Tcase is measured with a groove on top of the IHS, couldn't we simply measure Tj with a groove
under the IHS? Hum, babbling again... I'd have to groove the top of my heat die, and slip the thermocouple under the TIM (1) joint. ... which I'm not going to do because I'm not comfortable with the impact on the measurement of Tcase, and I'm not building two heat dies (well I am, but they're different sizes). I will however have temp readings below what would be Tj...
So... order of magnitude (of the variation?)... TIM2 > TIM1 by a factor of (at the very least) 2? ... and of course, it isn't nearly as important as the flatness of the HSF/Block. ... so ... TIM1 is more reliable (than TIM2) because the IHS "spreads" the clamping pressure more equally than what TIM2 is subjected to, when the HSF/block is not flat (or more precisely, doesn't match the flatness of the IHS, when clamped).
(sorry, flexing out new "rambling" style)