MacBook Pro temps drop with thermal paste makeovers

“Any PC enthusiast knows that thermal paste is something to be applied in precise amounts. Maybe Apple could take a lesson from all of us out there who have tacked a cooler onto a CPU. Apparently, the recent rash of toasty MacBooks can be attributed to excessive amounts of silicon thermal paste applied between chips and heat sinks. A number of MacBook users have, in heated desperation, resorted to cracking open their MacBooks only to find minuscule amounts of thermal silicon between the chip and sink, but massive amounts of silicon paste spilling out around the edges. Now, if the silicon thermal paste had been applied properly all these MacBooks wouldn’t be cooking themselves to death,” J. Micah Grunert reports for Neoseeker.

“Some MacBook users had cried that their computer was running at just over 50 Degrees Celsius. But once a better thermal paste replaced the silicon, temperatures dropped to roughly human body temperatures, some 35 to 39 Degrees Celsius,” Grunert reports.

Full article here.

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58 Comments

  1. is this what the new commercial will be about?

    “The Mac Book Pro: the best notebook in the world can even make your breakfast” (Show two eggs sunny-side up sizzling on a flipped over MBP)

    ::sigh::

  2. I noticed that many MacBook Pro users reported in the Apple forums that resetting the PMU fixed their heat issues.

    In fact, it may well be that taking your MacBook Pro apart enough to re-apply heat sink compound has the side-effect of resetting your PMU, which actually fixes the heat issue.

  3. I doubt that a tiny bit of extra paste will matter that much in this case. This is a Core Duo, not an Athlon64. When they apply the heat sink, it squishes the paste pretty thin anyways, and the paste around the chip doesn’t matter at all – only between the CPU and heatsink.

  4. I’m a mechanical engineer who’s designed plenty of power supplies and other printed circuit boards. HERE’S HOW IT WORKS:

    1) Thermal paste has MUCH poorer conductivity than solids such as ceramic, metal and plastic.

    2) Thermal paste is applied between plastic or ceramic chips and metal heatsinks to improve thermal conductivity between them.

    3) Isn’t this an oxymoron? No. Because the interface between the two flat surfaces is imperfect. It is neither perfectly flat nor is it perfectly smooth. Consequently, there are areas that touch (fabulous heat conduction), and areas (both macro and micro) that have air between them. Air is a much poorer conductor of heat than thermal heat sink grease (“silicone” grease) so the compound improves conductivity only if it replaces air without diminishing solid-to-solid contact area.

    4) You only want a small, nearly transparent coating of the thermal heat sink compound before mating the surfaces. You want the compound that would otherwise interfere with the perfectly touching areas to easily squeeze out of the way and only stay in the areas where there are macro-size debonds and micro-size (surface roughness) spots.

    5) If one has applied too much compound before mating the parts, you can float the heat sink atop a couple-mil-thick layer of “thermally-conductive” heat sink compound. Again, the stuff has better conductivity than air but it’s much worse than solid-to-solid conductivity. So floating the part is bad.

    6) If the chip runs hotter, it heats up its local area of the printed circuit board and the nearby case rather than shed it’s heat into the heatsink (which, in turn, sheds its heat into the fan-forced air).

    7) If you have good chip-to-heatsink conductivity, the chip is cooler, the case is cooler, the heatsink is hotter, and it means the air coming out of the ventilation ports is hotter. This is good.

    8) Proper heat sink compound application is the most poorly understood thing on the world’s assembly lines and even some line supervisors still think that if “some’s good, more’s gooder”.

  5. Jon:

    Interesting question. Perhaps Apple will be able to utilize the heat energy produced by the chips to also power the CPU. You know, like cold fusion, so battery life can be extended for weeks and weeks. What we need is a little civil disobedience and violate the laws of thermodynamics.

  6. Oh, and notwithstanding some pooh-poohs from others about hot chips aren’t bad, they’re wrong.

    If an engineer added a heatsink, it was done to keep something from overheating (most likely the chip). There is a logarithmic relationship between chip life and temperature. An over-capcity heatsink costs more money and takes up more space (a serious constraint in a laptop computer) so it’s not like there is excess heatsink capacity; engineers almost NEVER get excess heatsink capacity. If the heat isn’t getting into the heatsink at the “advertised” rate (under ideal conditions with the proper application of heatsink grease), then something’s getting too hot and that’s not good.

  7. Jon: See Greg’s post – hot laptop case = poor thermal dissipation.

    MacBook Pro owners – go get some Arctic Silver thermal paste, apply thin transparent layer between heat sync and CPU. Then see temperature drop 10-20 degrees as a minimum.

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