So, it's been about 5 years since I was last fascinated by TIMs (HOPG in particular), much has been learned and unlearned (and probably forgotten) since I started ye olde Gettin Greasy ... thread.
As I understand it, the best-performing TIM available for processors is Indigo Xtreme. But:
- Available from only one manufacturer, in limited (hyperspecific) applications and at a considerable cost premium
- Application requires a thermal reflow procedure which places thermal stress on critical components, does not produce entirely consistent results, and is basically incompatible with large/heavy heatsinks - most PC users are actually confused, shocked, and intimidated at the procedure, which may be a contributing factor in randomly poor results
- Removal can also be difficult, and requires unusually strong, nasty solvents
The next best would be Coollaboratory Liquid Ultra/Pro products. Unlike Indigo, you can slather a bottle of this stuff on any part you like. But:
- Results (as reported online) appear highly variable, suggesting multiple applications may be necessary to obtain best performance. It may or may not be compatible with all heatsink/block geometries.
- Removal is difficult, typically requiring much chipping and carving and hours of mechanically subtractive frustrations.
Then there's the "conventional" TIMs, the semi-metallic pastes and greases and oils. A little bottle can last you a long time and cover many assorted parts, and most of them aren't very costly. The best of these (judging by online reviews, testing, and benchmarks) appear to be Prolimatech PK-3, Gelid GC Extreme, Phobya HeGrease Extreme, and Tuniq TX-4. To be honest, many of the reviews and tests and benchmarks tend to be a bit scientifically amateur, with low reproducibility, poor controls, little or no thought to isolating (or empirically eliminating) possibly significant variables. And, of course, they are as often as not influenced by subjective bias, opinion, expectations, and perceived popularity of certains brands and products. To be fair, it's not really reasonable to expect people to comprehensively and methodically test multiple batches of TIMs on multiple platforms and multiple configurations, etc, not always entirely to my exacting engineer-like expectations, and especially not for free!
Another new product, graphene-based Thermene, also has my attention with promising specification claims. But it is currently impossible to obtain any of the product nor even any believable comments from people who have used it.
And to be honest, I realize that pretty much any premium-grade TIM will do the job well enough. "Mediocre" performers like venerable Arctic Silver are basically good enough for the job, I suppose. But my interest is on pushing the extreme threshold, even if it really only means a practical difference of perhaps 1-3 degrees in processor cooling. Well, perhaps I should only say "semi-extreme" since I'm talking about air, liquid, and basic phase-change cooling; I'm not talking about LN2 and other exotics. I like computers which can actually do things in the real world, they need to coexist in the same room as their operators and they need to be able to run tasks for more than the few minutes it takes to screenshot a lucky overclocking world record.
One interesting consideration which I have not seen referenced on any of the online reviews/etc ... I want a no-maintenance no-hassle TIM which continues to perform for many months or even years. Not a TIM which performs miracles for a week or half a season and requires constant reapplication. I have some machines in which I constantly tinker and swap parts - but I also have machines which I expect to dust out no more than once or twice a year and otherwise leave alone.
Some interesting scholarly article stuff: US Patent 8081468 B2 (Memory modules including compliant multilayered thermally-conductive interface assemblies) and Graphite sheets and graphite gap pads used as thermal interface materials. I am impressed by graphite, graphene sheets, and - as always - HOPG. Incidentally, I'm also currently interested in thermal pads (of whatever sort) to use in RAM heatspreaders, motherboard heatsinks, and similar stuff.