How toxic is thermal paste and is there a safer version?

gdr · **Joined:** Sun Jan 06, 2013 4:39 pm **Posts:** 26

Just what the topic says, I'm wondering if what type of thermal compound is safest for both humans and computers. Wikipedia has a few clues:

Quote:

Thermal greases use one or more different thermally conductive substances:

Ceramic-based thermal grease has generally good thermal conductivity and is usually composed of a ceramic powder suspended in a liquid or gelatinous silicone compound, which may be described as 'silicone paste' or 'silicone thermal compound'. The most commonly used ceramics and their thermal conductivities (in units of W/(m ·K)) are:[4] beryllium oxide (218), aluminum nitride (170), aluminum oxide (39), zinc oxide (21), and silicon dioxide (1). Thermal grease is usually white in colour since these ceramics are all white in powder form. These figures are for bulk material, not thermal grease.
Metal-based thermal grease contain solid metal particles (usually silver or aluminum). It has a better thermal conductivity[citation needed] and is more expensive than ceramic-based grease.
Metal-free thermal compound does not allow electrical conduction and therefore it eliminates the risk of short circuit and keeps the components safe. This type of thermal conductor is often used in computer systems to increase the thermal conductivity of the CPU or GPU. Besides, it is very easy to remove comparing with other types of thermal grease.[5]
Carbon based. There are products based on with carbon-based conductors, using diamond powder,[6][7][8] or short carbon fibers [1], they have the best thermal conductivity[citation needed] and are generally more expensive than metal-based thermal grease.
Liquid metal based. Some thermal pastes are made of liquid metal alloys of gallium. These are rare and expensive.
Phase Change Metal Alloy (PCMA) is not a "grease" but another type of Thermal interface material. The design consists of a sealed alloy metal pad that needs to be "reflowed" under high heat (typically 90-100C.) The alloy on the inside of the seal will change phases, and fill all the micro-voids. Since this material is made of mostly metal alloy, the thermal properties of this interface material are very good.

All but the last classification of compound usually use silicone grease as a medium, a heat conductor in itself, though some manufacturers prefer use of fractions of mineral oil.[citation needed]

All these compounds conduct heat far better than air, but far worse than metal. They are intended to fill gaps that would otherwise hold air, not to create a layer between component and heatsink—this will decrease the effectiveness of the heatsink. Ideally perfectly smooth and flat metallic surfaces would not need heatsink compound.

So far I can tell that avoiding thermal paste containing beryllium is a good idea, but I hope someone have provide more information about the rest of the types.

Ralf Hutter · **Posted:** Mon Jan 07, 2013 7:23 am

If you're actually worried about it, use Vegemite instead. Or this.

edh · **Posted:** Mon Jan 07, 2013 7:43 am

Pretty much any metal or synthetic has a big environmental footprint in being made. There may be very little in it when you consider the frankly tiny quantities involved compared to say, manufacturing all of the components of your system.

As for chemical risk, the stuff is disolved in a paste so is only likely to harm the user if it is ingested. If these chemicals enter a water course in any REAL amount then you might be worried about local wildlife but the quantities being realistically used are tiny.

Is it perhaps a problem that so much gets wasted? I have probably about 10 tubes of thermal paste that have come free with something and a small fraction of it is actually required, therefore I have lots of tubes building up and not all of it cheap stuff. I'm sure in our throw away soceity many people will just bin it. I personally am unlikely ever to have to buy thermal paste again!

gdr · **Joined:** Sun Jan 06, 2013 4:39 pm **Posts:** 26

Ralf Hutter wrote:

If you're actually worried about it, use Vegemite instead. Or this.

Haha, it's too bad Vegimite would eventually dry out. In any case, I bet it would make your computer smell like burn Vegimite after a while.

Any idea where to find the White Ice 510FGfrom the second link? I searching for the stuff, but it looks like the stuff is mainly sold to larger commercial operations by larger vendors. It might be possible to special order the stuff from a hardware store or lab equipment retailer though, I'll look around.

On the other hand, silicone grease looks like an interesting choice. According this site, it works fine on CPUs. Perhaps silicone grease was originally used as heat sink compound before people started adding other stuff to the mix? Pure silicone grease intended for use in diving applications might do the trick too. However, it would be important to make sure the grease doesn't melt and wind up all over the motherboard.

As far as safety is concerned, the nano particles that are used in some heat sink compounds scare me. Here's a quote from Wikipedia.

Quote:

Nanoparticles present possible dangers, both medically and environmentally.[46] Most of these are due to the high surface to volume ratio, which can make the particles very reactive or catalytic.[47] They are also able to pass through cell membranes in organisms, and their interactions with biological systems are relatively unknown.[48] A recent study looking at the effects of ZnO nanoparticles on human immune cells has found varying levels of susceptibility to cytotoxicity.[49] There are concerns that pharmaceutical companies, seeking regulatory approval for nano-reformulations of existing medicines, are relying on safety data produced during clinical studies of the earlier, pre-reformulation version of the medicine. This could result in regulatory bodies, such as the FDA, missing new side effects that are specific to the nano-reforumlation.[50]

edh · **Posted:** Tue Jan 08, 2013 2:15 am

gdr wrote:

As far as safety is concerned, the nano particles that are used in some heat sink compounds scare me. Here's a quote from Wikipedia.

Quote:

Nanoparticles present possible dangers, both medically and environmentally.[46] Most of these are due to the high surface to volume ratio, which can make the particles very reactive or catalytic.[47] They are also able to pass through cell membranes in organisms, and their interactions with biological systems are relatively unknown.[48] A recent study looking at the effects of ZnO nanoparticles on human immune cells has found varying levels of susceptibility to cytotoxicity.[49] There are concerns that pharmaceutical companies, seeking regulatory approval for nano-reformulations of existing medicines, are relying on safety data produced during clinical studies of the earlier, pre-reformulation version of the medicine. This could result in regulatory bodies, such as the FDA, missing new side effects that are specific to the nano-reforumlation.[50]

Yes but are you ingesting thermal paste? You don't need to be worried about this for your own sake. For wildlife, ingestion could be a real risk but should be mitigated by safe disposal.

How toxic is thermal paste and is there a safer version?

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