Sign in with
Sign up | Sign in

Interaction Of The Heat Spreader And Heat Sink

Thermal Paste Comparison, Part One: Applying Grease And More
By

Uneven Surfaces

A microscope will show you that neither the surface of a heat spreader nor the surface of a heat sink are really smooth. What looks even to the  bare eye is full of pits and grooves.

When you press both surfaces together, only parts of the metal touch each other. Without a thermal compound, air fills the gaps. But air is a bad heat conductor. It's more of an insulator, actually. Thus, without thermal paste, much of the engineering that goes into heat spreaders and CPU coolers is wasted, as heat is only conducted where the metal surfaces touch.

Heat-Conducting Materials to the Rescue! Pastes and Pads

Clearly, the insulating air needs to be displaced by some thermal compound. Obviously, any thermal paste, pad, or liquid metal will conduct heat less effectively than the two metal surfaces involved. So, you want the application to be thin enough to not impose a lot of thermal resistance, but thick enough to overcome the surface imperfections of the heat spreader and sink.

Display all 136 comments.
This thread is closed for comments
Top Comments
  • 37 Hide
    rolli59 , October 10, 2013 9:29 PM
    Nice article and bookmarked for reference. Looking forward for the next part.
  • 10 Hide
    alidan , October 10, 2013 9:35 PM
    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.
Other Comments
  • 37 Hide
    rolli59 , October 10, 2013 9:29 PM
    Nice article and bookmarked for reference. Looking forward for the next part.
  • 10 Hide
    alidan , October 10, 2013 9:35 PM
    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.
  • 7 Hide
    The Von Matrices , October 10, 2013 9:36 PM
    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
  • 3 Hide
    thasan1 , October 10, 2013 9:40 PM
    a really nice and helpful article!
  • 2 Hide
    stickmansam , October 10, 2013 9:44 PM
    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
  • 9 Hide
    slatts1024 , October 10, 2013 9:47 PM
    One of the best articles I've read on Tom's in years and that's saying something. Looking forward to part 2.
  • 6 Hide
    BigMack70 , October 10, 2013 9:48 PM
    ooooooooooh such a tease

    can't wait for part 2 - this was a great read!
  • 2 Hide
    Shankovich , October 10, 2013 9:49 PM
    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
  • 4 Hide
    nukemaster , October 10, 2013 9:51 PM
    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
  • 2 Hide
    jimmysmitty , October 10, 2013 9:55 PM
    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.
  • 6 Hide
    stickmansam , October 10, 2013 9:57 PM
    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.
  • 2 Hide
    rmpumper , October 10, 2013 10:09 PM
    I always spread the paste manually. Never had issues with overheating.
  • 0 Hide
    smeezekitty , October 10, 2013 10:44 PM
    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.
  • 8 Hide
    SteelCity1981 , October 10, 2013 11:07 PM
    "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...
  • 1 Hide
    JimmiG , October 10, 2013 11:24 PM
    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.
  • 0 Hide
    giovanni86 , October 11, 2013 12:10 AM
    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.
  • 2 Hide
    urimiel , October 11, 2013 12:19 AM
    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.
  • 1 Hide
    zyky , October 11, 2013 12:36 AM
    2.66Ghz Q0 Q6600? What planet did I stumble upon? Hopefully one that still has Indigo Xtreme.
  • -9 Hide
    James Hood , October 11, 2013 1:27 AM
    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.
  • 6 Hide
    4Ryan6 , October 11, 2013 2:26 AM
    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
Display more comments