Introduction & Overview
Several years ago, we published a round-up of thermal pastes that started with Thermal Paste Comparison, Part One: Applying Grease And More and concluded with Thermal Paste Comparison, Part Two: 39 Products Get Tested. Since it's so hot outside (at least in our U.S. labs), we're trying to cool so many new CPUs and GPUs, and readers keep asking for it, we decided to combine and update those stories, adding a range of new thermal pastes and pads.
In case you're wondering, toothpaste and denture cream aren't counted in our final tally of 85 contenders. Then again, you might surprised at what dental products can do on a CPU!
Not All Thermal Pastes Are Alike
Because thermal paste is a high-margin product, the market is crowded. While the exact composition of most solutions is a well-kept secret, a Google search makes it pretty easy to get a list of typical ingredients. The upper temperature limit is typically 150°C, though some pastes claim to withstand up to 300°C or more.
The composition of a paste determines its thermal conductivity, its electrical conductivity, its viscosity, and its durability. But what is a paste really made of? Basic compounds consist of zinc oxide and silicone as a binding agent. However, such simple combinations are barely sold anymore. Most vendors start with these ingredients and add other materials, like aluminum. Case in point, the Prolimatech PK1 sports 60-85% aluminum content, 15-25% zinc oxide, and 12-20% silicone oil, as well as an anti-oxidation agent. Some ingredient lists are more mysterious. For instance, the one printed on be quiet!'s DC 1 syringe ambiguously specifies 60% metal oxide, 30% zinc oxide (wait a second; since when is zinc not a metal?), and 10% silicone.
Some pastes, like Arctic Silver 5, even contain silver. Other pastes are based on graphite, like the professional-grade WLPG 10 by Fischer Elektronik. It foregoes the silicone and claims very high thermal conductivity (10.5 W/m·K), but is more difficult to apply and typically electrically conductive. There are also pastes that employ carbon nanoparticles, though they're not suitable for most enthusiasts due to their electrical conductivity and price. The number of copper-based pastes on the market has shrunk, but if you search, you can still find a few.
Silicone is a cheap binder, but it tends to spread. So manufacturers try to constrain this undesirable property or to dispense with silicone altogether in their products. This also applies to so-called "oiling," where the paste virtually dissolves into its base components and the silicone simply oozes away.
There are only a few actual thermal paste manufacturers. Third parties often adapt these bases to create new products with different consistency and color. As a result, many pastes end up almost identical, though they do differ significantly in price.
Pastes Don't Age Gracefully
You may not know this, but thermal paste has a shelf life. Manufacturers usually specify up to three years for unopened packages, but they often forget to tell you when your tube was produced. Thanks to the Tom's Hardware forum members for a reminder of this.
As an example, we tested Innovation Cooling's Diamond 7 Carat and Diamond 24 Carat, which differ only in package size. But the Diamond 7 Carat proved clearly inferior in our benchmarks. Their consistencies were also off. It could have been that such an expensive (bordering on exotic) product sat on the shelf for a long time. An unknowing enthusiast would buy it new, never knowing the compound had degraded.
As a preventative measure, purchase your thermal paste from a larger shop with faster turnover or find a local dealer who can tell you how long your paste of choice was sitting in inventory.
Are The Pastes Overrated?
The difference in quality between a celebrated third-party paste and what OEMs use on their builds is smaller than you might think. It's not uncommon to realize a performance improvement by simply bolting your hardware together more carefully. A lot of folks then erroneously attribute this betterment to their new paste.
Also, not so expensive silicone-based solutions despite being easy to apply and affordable, aren't worth the trouble they cause later as they deteriorate.
Liquid metal is suitable for more experienced power users; its application is difficult to master and you may run into trouble with hardware warranty claims, since these "pastes" can never be completely removed without some sort of leftover residue. Given the challenges posed by highly conductive pastes, we'll discuss them separately.
In the end, to achieve above-average performance that is measurably better than what you're already seeing, you need to use the pastes, and then apply them perfectly.
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