Thermal Paste Comparison, Part One: Applying Grease And More

Applying Thermal Paste, Part One

A Philosophical Debate: The Application Method

It’s tough to pick a technique for applying paste. Any method only works well if paste quantity and viscosity is absolutely correct for the particular application. In light of the hot spot discussion, however, we believe that smearing paste on the whole CPU is quite pointless and a thing of the past. Instead, we want to focus on the particularities of the CPU, its heat spreader, the heat sink, and the mounting method (in particular the mounting pressure).

Brushes and Low-Viscosity Pastes

Liquid pastes like the Revoltec Thermal Grease Nano can be applied with a brush, and are consequently the easiest to use. However, low viscosity comes at the price of a high silicone content, which impacts thermal conductivity. These pastes typically fall to the bottom of our performance charts. When you try to apply semi-liquid pastes by brush, typically you wind up with too much, and that isn’t optimal, either.

Drop, Sausage, or Wall Painting?

In my opinion, spreading paste on the entire CPU is too tedious and runs the risk of applying too much material, or even causing air pockets. Furthermore, some pastes simply do not want to be smoothed. The more you try to even the surface out, the more it tears open.

Trying to spread a high-viscosity paste with a credit card is a fool’s errand. You'll waste a lot of time and won’t achieve a thin, smooth layer. Yes, you can try to put a latex glove on your hand and use your index finger. But even with this method, the risk of applying too much paste is significant, especially if you have no practice. The higher the viscosity, the less successful you can anticipate being trying to "paint the wall".

A Strip of Paste

When you imagine CPU die under the heat spreader, it may seem smart to put a strip of paste over that area. But don’t apply too much. Otherwise, the paste will ooze out on all sides. If your paste is electrically conductive, you can almost be assured of hardware damage.


When you apply the paste strip frugally, the result is better. Don’t worry too much about bare spots. The edges of the heat spreader don’t contribute much to thermal transfer anyway. If your cooler sports a back plate and applies lots of mounting pressure, the paste will spread further. As a rule of thumb, the lower the viscosity of the paste and the higher the heat sink's mounting pressure, the more your compound of choice will spread.

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  • rolli59
    Nice article and bookmarked for reference. Looking forward for the next part.
  • alidan
    please tell me yo are also going to do the solder the heatsink to the cpu method? i forget what its called, but that is what i want to use for my next computer and would love to see how it stacks up.
  • The Von Matrices
    In the second section about advanced cooling methods, are you planning on discussing delidding CPUs and replacing thermal paste? If you do it might be worth mentioning that the delidding won't improve temperatures because of improved thermal paste conductivity but because of reducing the thickness of the paste. See
  • thasan1
    a really nice and helpful article!
  • stickmansam
    Huh, I do turn my heatsinks sometimes for optimal alignment so the heat pipes are perpendicular to the die. Depends if I got the room in the case and what ram is being used. Also heatsink dependent
  • slatts1024
    One of the best articles I've read on Tom's in years and that's saying something. Looking forward to part 2.
  • BigMack70
    ooooooooooh such a tease

    can't wait for part 2 - this was a great read!
  • Shankovich
    Loving that DHT-based design overlay picture on the first page. I've been telling my friends for a while to just get coolers with plated covers because the pipes miss the hotspot on intel CPU's, but no I'm full of bs apparently. This video is awesome btw, shows how spreads happen
  • nukemaster
    How many volts does this "7 volt" unregulated power supply put out?

    Just curious. I have some 8/9/12 volt regulators that would eliminate the guessing games for resistor fan adapters(voltage depends on the fans current draw).

    I have seen unregulated 6 volt power supplies range from 8-over 12 volts at low loads.

    For a rather low price you can use a regulator to get whatever voltage you want :)

    ohh yeah and...
    I can't wait for the next part of this to be release
  • jimmysmitty
    From what I have seen it depends on the materials. AS5 was great for a while but thee are better ones out than that now such as Noctuas or Zalmans.

    I also enjoyed using the IC Diamond thermal paste as it proved to cool very well but since it has a diamond based substance it can scuff the heat spreader.
  • stickmansam
    Also would like to see an Ivy/Haswell test system since they run pretty hot and imo, they need more study on how to best cool them due to the TIM inside them.
  • rmpumper
    I always spread the paste manually. Never had issues with overheating.
  • smeezekitty
    I am using dirt cheap masscool fanner-420.

    My temps are quite good - really the choice of cooler is much much more important than the choice of paste.
  • SteelCity1981
    "don’t apply too much. Otherwise, the paste will ooze out on all sides. If your paste is electrically conductive, you can almost be assured of hardware damage."

    Tell this to OEM's ever seen a hp, dell, Lenovo, Asus, Acer cpu after you take off the heatsink with thermal paste on it? it's oozed all over he place...
  • JimmiG
    I experimented with different application methods when I built my 4770K-based system. Small dot, large dot, X, line. No real difference, but the small dot produced the best results by ~2C. I used MX-4, which is so easy to apply that you can't really mess up.

    When delidding and applying Liquid Pro between the IHS and die, I "painted" a very thin layer. It was very difficult until the surface tension broke, then it was easy from there.
  • giovanni86
    Nice article, you guys ripped me a new one with the spread all over cpu method. Been doing that for a long time hah. Based off what you guys said i feel like it need to reapply paste considering the hot spot on my ivy bridge processor. I feel as if that method works although its very tedious and takes a long time to apply a even surface, i used Arctic MX-2 and it seemed to apply easy with some resistance to spreading evenly flat.. 30 minutes later walaa.. haha painted flat all over.. But i like that pea method in the middle seems to cover the hot spot quite well. Will have to try that out. Can't wait for the next part.
  • urimiel
    Dude! this is great. This the first time since the Coppermine era that we started using thermal pastes widely that somebody put all the information together. Congrats guys great job. Well done.
  • zyky
    2.66Ghz Q0 Q6600? What planet did I stumble upon? Hopefully one that still has Indigo Xtreme.
  • James Hood
    Hey Tom's, I realize that you guys have limited time for these articles, and have to limit the scope. But I think it should be pointed out that not every one reading these articles are complete novices. In fact, I would wager those of us wanting to see the subtle differences between paste and cooler combinations are intermediate to advanced users. As such, in the future I think the risks involved should be left up to the reader. Having the comparison data to go with the risk would be helpful. Gaining .5C better temps for me would not be worth it. But if it dropped 2C on a GPU for my laptop... now that is tempting. As it stands, this data will not be available for those of us that would be interested.

    Otherwise, great article, can't wait to see the results.
  • 4Ryan6
    Nice Job Igor, You have your ambient controlled for the tests and very good illustrations of contact imperfections and CPU hot spot area!

    I know you're glad to be nearing the end as that was a lot of time invested to completion.

    Congratulations sir, on one of the best reviews I've seen come from Toms yet!

  • edlight
    Direct touch heat pipe heatsinks do not have air between the pipes where they contact the cpu. There's the block that they are set into. No mention was made of lapping heatsinks. 16 and 8 hour breakins for paste is way too little, so the fast breaking in paste will have an advantage.
  • Tass1234
    Hi, i would love to see tests done with a couple of the best pastes comparing the amount of cooling between the paste been applied spread with a credit card or similar and applied by the pressure done by the sink. Would be much better than just saying spreading is bad because you can create air bubbles because we can't compare by the sayings here what is better, if spread by pressure or spread by hand if is done well and without bubbles (and of course with an easy to spread paste like MX4). Thanks :D
  • m32
    I've bee trolled!!!! lol. I'm looking forward to part 2. This is an great read for us hardware geeks.
  • besterino
    IMHO Igor's articles are the best (any maybe not only on Tom's). Always a worthy read, sometimes even a funny one. :D And dammit, he's versatile (not only the nomral stuff, but also keyboards, speakers, you name it, he's got it covered - in detail.)

    Yeah, I'm a fanboi.