Thermal grease and the MacBook

Thermal grease and the MacBook

Summary: Readers of this blog remember the recent issue about the amount of thermal grease (or paste) that Apple applies to the chips in the MacBook Pro. There's pretty decent evidence that over-application of the paste is causing the machine to run hotter than it should. It appears that the same may be true for the MacBook...


macbook-thermal-grease.jpgReaders of The Apple Core remember the recent issue about the amount of thermal grease (or paste) that Apple applies to the chips in the MacBook Pro. There's pretty decent evidence that over-application of the paste is causing MacBook Pros to run hotter than they should. It appears that the same may be true for the MacBook.

A picture (right) from the official MacBook service manual posted on the MacNN forums clearly shows a MacBook being assembled with too much thermal paste on top of the chips.

To make matters worse, page 94 of the MacBook (13-inch) Take Apart manual says:

Although the amount shown appears to be plenty of grease, this is the correct amount that has been tested and verified on the production line.
This over application of thermal grease on the MacBook and MacBook Pro flies in the face of the conventional wisdom about the correct procedures for use of the product. According to Wikipedia:
Because the thermal conductivity of heatsink compounds is so poor in comparison to the metals they couple, it's important to use no more than is necessary to exclude any air gaps. Excess grease separating the metal surfaces further will only degrade conductivity.

Heat Sink Guide also confirms the less-is-more approach to installing thermal grease:

You should apply a very thin (paper thin) layer on the heatsink with your finger before installing it. Don't use too much - the thinner the layer, the better.

It's not yet clear how many MacBooks are assembled with this much thermal grease or what the impact is on operating temperatures but it is clear that Apple is telling their service technicians to apply too much of the goop.

Topic: Apple

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  • Maybe its doing its job?

    According to the very same guide you linked to:

    "Why does my CPU get hotter after I used thermal compound?

    It doesn't - in no case your CPU get hotter after you applied
    thermal compound. However, you might think that it gets hotter,
    because the heatsink gets hotter. A hotter heatsink means better
    thermal conductivity between the CPU and the heatsink. The CPU
    itself will be cooler."

    So maybe its actually doing its job after all, and carrying the heat
    away from the processor and into the case. Remember, just
    beacause the case is hot, doesn't mean the processor is over
    • I guess time will tell

      Agreed. Others have said this as well.
      There's no denying the evidence that's been posted that re-applying the compound much thinner than what is shown can _dramatically_ reduce operating temperature by as much as 20 degrees Celcius.

      I guess we'll have to wait for the die hards to re-apply the grease on their MacBooks.

      Personally, my MacBook runs hotter than the sun, although a little better after installing the SMC firmware update.

      - Jason
      Jason D. O'Grady
      • no need to wait

        <i>I guess we'll have to wait for the die hards to re-apply the grease on their MacBooks.</i>

        it really doesn't matter what cpu and even what heatsink you're talking about, so we dont have to use a macbook specifically to know the end result of applying the grease properly.

        the results aren't processor specific, it's an issue of thermal conductivity and metal transferring heat, not amd/intel/ibm
        Valis Keogh
    • negative, we have a decade worth of experience on this

      too much thermal paste is a BAD THING

      period. end of discussion.

      there is a huge wealth of information on the subject and thousands if not millions of overclockers out there with years of experience on cpu heat issues. people who have run test after test and graph after graph, not because their boss told them to, but because they were curious and wanted to find out.

      i myself have some extensive graphs that show the difference between my stock intel cooler that came with my 3.2 gig northwood processor and then graphs showing the change in temperature of that processer when using a new cooler from gigabyte (3d cooler ultra btw), and also shows temperature graphs over time and under full load while at different overclocked speeds as well as standard speed.

      many utilities out there can monitor the thermal die on various cpu's and tell you exactly what temp the actual cpu is running at. too much grease and the cpu will run hotter, sometimes you have to clean the cpu off and re-apply to get the right spot.

      the amount of grease shown in that picture is the amount of grease that i personally would use on at least a DOZEN cpu's, not just one.

      Valis Keogh
    • Uh, no....

      Gee, unless Apple is using some kind of Larry Niven Ringworld type of super conducting material....

      The CPU should be approximately the same temp as the area of the heat sink closest to the CPU - in the ideal you should see max temp in the CPU core and the area of the heat sink that directly connects to the CPU core - after which the heat should radiate to the fins and then get exchanged as thermal radiation to the surrounding air. The thermal grease is only supposed to be there to fill in any air voids between the CPU and the heat sink - air acts as an insulator, it conducts heat poorly as compared to a direct metal to metal contact.

      What's happening is the gobs of thermal compound are acting as insulation between the CPU core and the heat sink surface - the grease is acting as an energy store until it's capacity to absorb thermal energy has been exhausted and it can convect the heat from it's own area to the heat sink. Not only that, but since the pictures show oozing from the CPU onto the other areas surrounding the CPU socket - heat is getting transferred away from the heat sink and to inappropriate areas such as the CPU socket and the motherboard. Luckily for the end user Apple is NOT using a product like Artic Silver - the metal in the product would shunt electricity between the CPU and the motherboard. BZZZZZAAAP - usually followed by a smoking hole in a now worthless motherboard.

      Expect to see early CPU failures with these production procedures in place.
  • Apply with your finger?!?!?!!!

    "You should apply a very thin (paper thin) layer on the heatsink with your finger before installing it."

    Applying thermal paste with your finger is a very bad idea. You are supposed to clean the surface of the processor with acetone and a lint free cloth. Then use alcohol and a lint free cloth to clean it. Then you are supposed to apply a thin layer of termal paste, usually with a clean razor blade. Applying the paste with your finger would introduce oils into the compound and onto the surface of the processor, which would be a bad thing.
  • Thermnal Grease is outdated!

    Why is Apple still using thermal grease? Of course it has a poor thermal characteristic. Thermal grease is lower thermal transfer coefficeint (by its very nature!)

    All they need to do is buy a sil-pad material like Bergquist Company's and solve the problem! Peel and stick! But they rather keep the 3 cent price differnence and let the consumer enjoy the pain of replacing equipment! Apple, visit and fix your problems!
    (from an ex-employee of Bergquist).
  • RE: Thermal grease and the MacBook

    Excess paste will act as an insulator - I have an electronics company and am always telling the staff to go easy on the stuff. If the clamping force is high most of it will be squeezed out anyway. It is there to fill any gaps, if the heatsink is badly machined or is slightly concave/convex/pitted. If you 'zoom' into to the surface the mollecular structure will make it rough anyway, even if it feels smooth. It is these small imperfections it is there to fill as well. Thermal grease over a sil pad anytime unless you need electrical insulation then themal grease is no good at all!
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