I've done a bunch of cooling stuff over the years; here's some of the stuff I've picked up.
Start with the easy stuff; Here's a table for thermal conductivity of metals:
Note the top four are Silver, Copper, Gold, and Aluminum, in that order. I've never seen a gold heatsink, but they exist; for use in boiling acid, apparently.
That's why good thermal compound is filled with Silver dust, in a binder material; the Silver powder does all the work.
Note Nickel is about 1/5 as good as silver; I lap the nickel layer off heat sinks I use. Copper won't oxidize covered with silicone oil.
I also lap the top of the Processor heatspreader; why settle for less, and it's easy. I write the processor type on a sheet of paper, and tuck it in the machine, if it laps the info off.
You shouldn't really have to go that far, but some are worse than others; I use an optical Flat to test the surfaces.
en.wikipedia.org
The smoothest surface transfers the most heat; the compound is just to fill any air voids, as air is a pitiful heat conductor by comparison.
You don't need to go any lower than the minimum grain size of the compound you use; liquid metal can take advantage of extreme flatness.
With silver based compound, going to optically flat actually hurts, because now there's no gaps to fill with silver particles; it leaves them sitting on the surface, like sand between two plates of glass.
Best case is voids slightly smaller than the grain size, so the particles fill the voids, and stick up, allowing other particles from the other side to intermingle slightly.
The higher the surface area of the contact points, the more heat can be transferred.
Thinner layers are always the best; Smooth, thin layers without leaving air voids will give a minimum working temperature for a given heat transfer.
Anyone who tells you to "rough up the HS surface" doesn't know what they're talking about.
Some things I've used:
Gallistan has a thermal coefficient of about 16.5
W/m
K (liquid metal thermal compound is mostly this, with varying amounts of indium)
AS5 is about 8.7
W/(m·
K) , Noctua is about 8.5 W/mK ; both are Silver filled Silicone oil. (Expect ~7W/mK as installed, you never get what they say.)
IC diamond lists
4.5 W/m-K, which is worse than what I've measured AS5 at, lol. I've never used thi$.
NaK is a terrible thermal interface material.
(It's been tried; not good for humid locations, lol.)
99% of my computers use AS5 or equivalent, since it first became available.
Earlier ones used the white goop, lol. Don't bother, it sux, by comparison.
If you want to start with the
best cooling solution, I'd start here:
The cuplex kryos NEXT marks a new milestone in CPU water block development. Every detail has been analyzed, optimized and tested to achieve perfection in cooling performance, installation procedure and product features. The result is not...
www.aquatuning.us
The Solid Silver one is listed at $275.
Someone else may make these; the hard part is the skived inner fins for transfer to the water, if that's not done well, then the performance will be poor regardless.
Skived fins:
(Stolen from Ebay)
Some people advertise CNC'ed fins, I'd want to know how they're connected to the plate. Skived is shaved, so it's direct metal.
Getting the heat to the ambient is also very important; water moves heat very well, but Heat Pipes do too, and don't leak.
The bigger the radiator surface area, whether it's mounted on a Heat Pipe or a water loop, works the best, and makes all the difference.
There, you want the maximum area of thermal contact as well; cheap fins loosely coupled to the heat pipes suck, as do "multi-pass" copper tube type radiators.
Fin and plate type radiators are the best; they have water flowing thru thin tubes from one side to the other, like good transmission coolers do.
I've seen heat pipe radiators filled with water (and Ammonia, and NaK) to move heat across the plates; they're a bit pricey and problematic for home computer use, though.
All of these tweaks are only going to give you a few degrees; If lapping, Diamond, or liquid metal give you a 10 degree improvement at the top end, you probably did something wrong before, and corrected it when you redid it.
These days I personally just buy a big copper heat pipe cooler from a reputable place, lap the surfaces, and use AS5; everything else on a system I want to actually use is kind of frivolous.
They rarely fit in the case, though.
I had one of these on a P4, lol.
That's 2.2 kilos of solid copper, lol.
Also, thermal pads are gap fillers; replacing them with a properly sized copper shim, and putting compound on both sides will Always be better.
I only use them where there's no choice.
