Heatsink Mod for MBA

Discussion in 'MacBook Air' started by ayeying, Apr 28, 2008.

  1. ayeying macrumors 601

    ayeying

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    Dec 5, 2007
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    Yay Area, CA
    #1
    Ok, right now I don't have a MacBook Air to play around with... but has anyone thought of doing a mod to the actual heatsink for better contact?

    I remember on my old Dell Inspiron 8600 Notebook PC, the ATi Radeon 9600 card constantly overheated due to bad heatsink contact. The fix was to use a piece of copper plating to add more mass + better contact for the heatsink.

    Since the air is thin, it is impossible to add a large piece of copper plating, but there are thin, maybe 0.13?mm thin pieces that can be added onto the CPU and Chipset using Thermal paste as a center gap for better contact.

    Anyone think of being the guinea pig to try this?
     
  2. wordy macrumors regular

    wordy

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    Toronto
    #3
    With recent discoveries, heat isn't so much of an issue, but you'd imagine that for a few more pennies, the heatsink could be copper instead of whatever it is. Fins are impossible if you see the actual space it has, but I think with proper thermal paste application a copper one would do some good.
     
  3. ayeying thread starter macrumors 601

    ayeying

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    #4
    well. Since I had some free time, I'd thought I mod my air. Right now, I took it apart and do a heatsink mod.

    I added a piece of aluminum that is about the same thickness as the original heatsink. I've also redone the thermal paste since I had to clean it out and all that. Anyways, needless to say, after this modification the air is EXTREMELY cooler and more efficent.

    Basically, the layering is like this:

    Original Heatsink --
    --Thermal Paste--
    Aluminum Plating
    --Thermal Paste--
    CPU/Chipset Diode

    I've done a stress test on the CPU using original the original voltage settings and here's the results, fans limited at 4000 rpm max.

    Terminal's Yes command:

    Original: 89 deg C for CPU, 59 deg C for Heatsink after 10 Minutes. Core shutdown every now and then
    Modded: 81 deg C for CPU, 61 deg C for Heatsink after 10 minutes. No core shutdown.

    VMWare Fusion Booting up 2 OS:

    Original: 81 deg C for CPU, 57 deg C for heatsink after completing boot. No core shutdown
    Modded: 69 deg C for CPU, 50 deg C for heatsink after completing boot. No core shutdown

    Right now Im typing this, I am getting a CPU temp of 39 deg C w/ 25% cpu usage. Maybe I'll get a more dense piece and redo this, but there is some advantages in adding more mass to this heatsink.
     
  4. wordy macrumors regular

    wordy

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    #5
    I don't doubt your results, but I think your goal is a little misguided. Heat sinks don't work by volume, i.e. adding more mass of metal. You're not trying to trap the heat in the metal.

    Heat sinks work by surface area. A good heat sink has lots and lots of surface area (that's why you see fins, they add lots of surface). The surface area allows the heat to dissipate into the surrounding air, and most importantly, moves heat away from the source (CPU/GPU/RAM, etc).

    A good mod would not consist of adding more depth, but rather more area. An ideal mod would just use a much larger piece of metal, not necessarily thicker, ideally made of copper, and also avoid using thermal paste as much as possible. Conduction through a solid piece would be better than through different media.
     
  5. ayeying thread starter macrumors 601

    ayeying

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    #6
    I understand where you're getting at, however, with what I'm trying to accomplish is to move a bit more heat from the CPU to the heatsink. The fan doesn't blow on the cpu die itself but rather the heatsink. Currently, the heatsink, when I took this system apart, had very little to no contact between the CPU and the Heatsink (pretty much the heat was trapped within the CPU cores). With more contact, heat is able to travel a bit better then before. Not as efficient as a desktop or even those within the other macbook models but its something. Our heatsink design is incredibly poor. Its not much better then just putting a piece of aluminum on the cpu.

    I don't plan on redesigning the air's heatsink anytime soon. I don't really think its possible with such a limited space available (and risk of contact with the logic board)
     
  6. drstupid macrumors newbie

    Joined:
    Apr 18, 2009
    #7
    hey ayeying! really keen to learn more about how you pulled this off. any photos at all? would love to see how you positioned the aluminium on the heatsink. cheers
     
  7. evsp341995 macrumors newbie

    Joined:
    Jan 7, 2010
    #8
    Cooling Mod

    Threads a bit old, but i want some advice on the mod I'm about to make. I am currently designing a copper heatsink that will be about .2 mm thick that i can attach to the current heatsink to diffuse the heat. Will this be too thick to use without modifying the bottom? could I make it thicker? I have already changed out the thermal paste, but it's still running too hot.

    Thx ~Ev
     
  8. ayeying thread starter macrumors 601

    ayeying

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    #9
    Attach how? You're working with very little clearance with about 2mm from the heatsink to the base panel.
     
  9. evsp341995 macrumors newbie

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    Jan 7, 2010
    #10
    I plan to thread the copper piece and screw up into it from the original heatsink, with some thermal paste between them. I would use a screw with a very small head and place it in the area between the processors where there is a gap.
     
  10. chopper dave macrumors regular

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    Jul 23, 2007
    #11
    I would give up trying to thread a 0.2mm plate- the pitch on even the tiniest screws would only give you 0.5-1 thread of contact. There is an L-bracket compressing the whole assembly together, so I would worry most about keeping the copper foil fold/wrinkle free and use some kapton tape (away from the CPU contact) to make sure it stays in place during assembly.

    I'm very curious to see how this goes. Are you tearing away the aluminum foil that the heat sink seems to be wrapped in? (that's what the revA that I have looks like)

    The name of the game here should be improving heat transfer between CPU and heat sink- the better that is, the lower the difference between sink and CPU temperature and the better your thermal performance will be.
     
  11. evsp341995 macrumors newbie

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    Jan 7, 2010
    #12
    My heat transfer between the processor and the heatsink seems to be pretty good. when the computer is idleing, the heatsink gets too hot to touch. I think the biggest problem is just the size of the heatsink. Aluminum isn't a great thermal conductor in the first place, expecially a piece that
    s as thin and flat as the one in the MBA. My goal is to actually cnc route a piece of copper that is somewhere between .5 and 1.5 mm thick with actual fins on it. I will mount the copper piece somewhere on the aluminum heatsink so it can take some of the heat away from the aluminum and dissapate it. I aggree with you on the screws, that that would be a bad idea; but what about some of that thermally conductive glue like arctic silver ceramique.
     
  12. ayeying thread starter macrumors 601

    ayeying

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    #13
    The heatsink is made from aluminum foil and thermal conducting "foam-like" material in the center. For the newer airs, the heatsink is made entirely out of aluminum.

    Okay, here's the deal. Aluminum is actually a great heat radiator and that's the primary reason it is used here. Copper is a great heat conductor, however, it's not good at all at radiating the heat away. It likes to store heat when Aluminum likes to get rid of it as fast as possible. However, Aluminum is light and has a lot less mass than a piece of copper of the same size so heat storage is obviously a lot less.

    You'll also run into the problem of air flow. The direction of air flow is not directed to the vents, its actually on a horizontal flow that flows across the heatsink plate. That's what draws the heat out of the vents.

    I understand what you're trying to do, I've actually created a prototype made from copper for the entire heatsink (also created a 2nd prototype with aluminum for makeshift fins to radiate the heat) but in the end, it didn't work for me because of the air flow. I could create a nice heatsink but the air flow limits the options entirely.
     
  13. evsp341995 macrumors newbie

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    Jan 7, 2010
    #14

    Why didn't your copper heatsink work if it was the same as the aluminum one?

    also, if there was enough copper in there, it could be solid state cooled (not that I would want to remove the fan)

    another idea i had was to just attach the heatsink to the aluminum back with copper and let the aluminum back dissapate the heat. Its large, and has alot of surface area. it would also allow the heat to leave the case. I suppose the downside to this would be that it would heat up everything else inside the computer, but how much would it really heat it up, and how much potential damage could that do?
     
  14. ayeying thread starter macrumors 601

    ayeying

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    #15
    I did several prototypes including a direct copy of the original heatsink but using Copper. The main reason it didn't work was cause the Copper kept storing the heat, rather than radiating it away. Even with the fans at 100%, it was hard for the copper to lose the heat. However, the upside is that the system stayed cooler for longer until the heat storage was full, then the entire system heated up faster than with the aluminum.

    If the system isn't stressed, a copper based heatsink can be used for passive cooling only.

    The next best thing using copper I would try is to apply a copper plate, thin but not foil, probably 0.15mm to the bottom of the heatsink, as you suggested. However, you need to make sure the copper is electrically shielded so it doesn't come into contact with any other parts of the board except the diode on the chips or you're asking for trouble. Electrical tape works great in this sense. Here, you got a storage of heat and a radiator of heat that might work but I haven't tried that method yet.
     
  15. MacModMachine macrumors 68020

    MacModMachine

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    Apr 3, 2009
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    Canada
    #16
    hmm...

    i was thinking the same, build a copper heatsink the same , but cutout a aluminum heatsink the same and double them up.

    like a heat sink sandwich....
     
  16. evsp341995 macrumors newbie

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    Jan 7, 2010
    #17
    What about using copper to attach the original heatsink to the aluminum bottom of the mba and use the bottom as the radiator
     
  17. coast1ja macrumors 6502

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    Jul 13, 2009
    #18
    I wondering what would happen if you just put a thermal pad in between the bottom case and the original heatsink... it would get hotter in your lap, but stay cooler inside!
     
  18. ayeying thread starter macrumors 601

    ayeying

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    #19
    That might work. I've only tried it small scale, aka, adding copper plates to the diodes directly. That seems to work a little better in drawing more heat out of the diode, store it in the copper while still allowing the original heatsink (aluminum) radiate it away.

    You'll block the Air flow... which is actually counter-productive rather than productive
     
  19. evsp341995 macrumors newbie

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    #20
    im not sure that it would block airflow as it would be on top of the original heatsink. wouldnt the air flow under it and around the attaching pieces. also, it would cool the attaching piece
     
  20. ayeying thread starter macrumors 601

    ayeying

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    #21
    No, air flows over the top of the heatsink. The air flow goes inbetween the heatsink and the bottom panel, which is why the panel gets hot/warm fairly quickly.
     
  21. evsp341995 macrumors newbie

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    #22
    Understood, but if the heat transferring piece between the original heatsink and the case didn't cover the entire original heatsink, air would still flow, and the fan would even cool the connecting piece which would be benefitial.
     
  22. ayeying thread starter macrumors 601

    ayeying

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    #23
    Yes, but the flow covers the entire heatsink, so I'm not sure how you'll allocate another part of the heatsink to allow transfer onto the panel
     
  23. evsp341995 macrumors newbie

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    #24
    I'm not suggesting that I allocate another part. I want too connect the original heatsink to the back case right in the middle of the original heatsink
     
  24. ayeying thread starter macrumors 601

    ayeying

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    #25
    I know, I mean how would you be able to transfer the heat from the heatsink to the panel.

    You can try that, but in theory that would be counter productive because again, the air flow is being blocked from exhausting the warm air into the outer environment. Instead, the warm air might just be pushed around and swirling around inside rather than exiting.
     

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