Thermal compound has been used on heatsinks ever since they were first used. No matter what type of cooling method for your processor (air, water, phase-change, liquid nitrogen), there will always be some microscopic space between the chip and heatsink, which are filled with air. A “dry joint” does not transfer heat very well, as there is more air between the two surfaces than actual physical contact. Even with a mirror finish there are still microscopic pockets of air which hinder heat transfer away from the processor.
Thermal compound is used to fill these microscopic gaps with a material that conducts heat, but is pliable enough to fit in all the nooks-and-crannies, creating a complete physical surface that heat can pass through. Over the past few years there have been several different thermal paste technologies, each of them trying to efficiently transfer heat away from the processor. One of the best electrically conductive metals is silver followed slightly by copper.
Notable characteristics of silver and copper *
A chunk of silver is a very ductile and malleable (slightly harder than gold) univalent coinage metal with a brilliant white metallic luster that can take a high degree of polish. It has the highest electrical conductivity of all metals, even higher than copper, but its greater cost has prevented it from being widely used in place of copper for electrical purposes. Pure silver also has the highest thermal conductivity, whitest color, the highest optical reflectivity (although it is a poor reflector of ultraviolet), and the lowest contact resistance of any metal. Silver halides are photosensitive and are remarkable for the effect of light upon them. This metal is stable in pure air and water, but does tarnish when it is exposed to ozone, hydrogen sulfide, or air with sulfur in it. The most common oxidation state of silver is +1; a few +2 compounds are known as well.
Copper is a reddish-coloured metal, with a high electrical and thermal conductivity (among pure metals at room temperature, only silver has a higher electrical conductivity). Copper may well be the oldest metal in use, as copper artifacts dating to 8700 BC have been found. Besides being part of various ores, copper can be found in the metallic form (i.e. native copper) in some locations. In Greek times, the metal was known by the name chalkos. In Roman times, it became known as aes Cyprium (”aes” being the generic Latin term for copper alloys such as bronze and other metals, and because so much of it was mined in Cyprus). From this, the phrase was simplified to cuprum and then eventually Anglicized into the English copper.
Because silver is the highest electrical and thermal conductor, manufacturers have used it as the magic ingredient in high-performance thermal compounds. Silver, as we all know, is expensive, and so are compounds based on silver. More advanced forumulas exist, as the current King of Thermal Compounds (Arctic Silver Ceramique) contains no silver at all. There is still room for inovation and competition on the thermal battlefield, and one of the newest heirs to the Throne is TherMax Tech’s XFlux-GA Thermal Compound.
TherMax Tech claims the compound is an electrical insulator, but one should still be conservative with the it. While the compound is not electrically conductive, it should still be kept away from electrical traces, pins, and leads. The compound is slightly capacitive and could potentially cause problems if two electrical paths are bridged. The compound is absolutely stable and will not seperate, run, migrate or bleed up to 200 degrees Celcius. No toxic substances are present in the compound or were used in its creation. The compound also cleans up easily with rubbing alcohol.