Thermal Paste Comparison, Part One: Applying Grease And More

The Differences Between AMD And Intel Heat Spreaders

Convex and Concave Heat Spreaders

To make matters worse, heat spreaders are not merely rough, but due to the way they're manufactured, they aren't level, either. The following diagram exaggerates the problem for the purpose of illustration:

AMD’s heat spreaders are slightly higher in the center and Intel’s have higher edges. From my perspective, AMD's approach is better-suited for cooling. Due to the mounting pressure of the CPU cooler, the thermal compound is thinnest where most of the heat needs to be transferred. Thus, Intel CPUs deserve perhaps a touch more thermal paste, and you should take care that no air gaps form in the center.

How Thermal Paste Spreads under Pressure

The following animation illustrates how thermal paste escapes to the sides when pressure is applied. Later, we’ll discuss the relationship between a paste’s fluidity (how "liquid" it is, the opposite of viscosity) and the maximum mounting pressure in detail. For now, let’s just say that a paste with low viscosity is more suitable for low-pressure mounting methods, like Intel’s push pin method, than a "hard" paste.

The technical specifications of a thermal paste’s thermal resistance do not necessarily predict its real-world performance for a specific combination of CPU, paste, and cooler. A good heat sink can be crippled by a mismatched thermal compound. A good match between cooler and paste can achieve more than just blindly choosing an expensive thermal compound.

Create a new thread in the US Reviews comments forum about this subject
This thread is closed for comments
136 comments
    Your comment
    Top Comments
  • rolli59
    Nice article and bookmarked for reference. Looking forward for the next part.
    39
  • 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.
    10
  • Other Comments
  • rolli59
    Nice article and bookmarked for reference. Looking forward for the next part.
    39
  • 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.
    10
  • 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 http://forums.anandtech.com/showpost.php?p=34053183&postcount=566
    7
  • thasan1
    a really nice and helpful article!
    3
  • 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
    2
  • slatts1024
    One of the best articles I've read on Tom's in years and that's saying something. Looking forward to part 2.
    9
  • BigMack70
    ooooooooooh such a tease

    can't wait for part 2 - this was a great read!
    6
  • 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 http://www.youtube.com/watch?v=EyXLu1Ms-q4
    2
  • 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
    4
  • 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.
    2
  • 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.
    6
  • rmpumper
    I always spread the paste manually. Never had issues with overheating.
    2
  • 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.
    0
  • 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...
    8
  • 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.
    1
  • 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.
    0
  • 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.
    2
  • zyky
    2.66Ghz Q0 Q6600? What planet did I stumble upon? Hopefully one that still has Indigo Xtreme.
    1
  • 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.
    -9
  • 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!

    Ryan
    6