# Making an iMac GPU heatsink



## fifthmanstandin (Oct 17, 2008)

This is sort of a wierd premise but here goes. I have an iMac. I'm having overheating problems. One thing that gets me about the design is that the heatsink on the gpu is actually on the outside and there's no direct fan blowing across it. The CPU and hardrive stay plenty cool but poor little gpu just sits there by itself overheating and being lonely. So here's what I want to do and before I explain it just let me say that I have good experience in metalsmithing so working in copper is not an issue. 

I want to take a heatsink with a fan on it, something to the effect of a stock cpu fan and remove the factory heatsink and replace it with that. Problem I see is that the holes don't line up with a traditional fan. So what I see as a solution is to lap the bottom of the new heatsink and solder a 16-14 gauge sheet of copper right onto the new heatsink's contact point. I'd be using zinc based lead free solder and it'd be a good solid sweat solder where both pieces contact evenly. Generally speaking you can insure contact by using ridiculous amounts of solder between the two, which isn't an issue. From that 14/16 gauge sheet I will drill holes to match the current holes on the mobo and use plastic nuts and bolts to hold it in properly. After being thermal pasted of course. From that I'd unplug one of the fans in the case and plugin my new heatsink fan for my gpu. 

My basic question is : provided that the contact from gpu to copper sheet is good and that the solder connection from heatsink to sheet is good, will the thermal transfer properties be sufficient being that I have a thin layer of what is essentially zinc/copper/silver allow. I know the heat transfer properties of copper and silver are fine. But what about zinc? 
Any thoughts you guys might have would be nice. All I can say is I'm tired of my gpu hitting 63 Celsius when I play a game and locking the system down.


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## fifthmanstandin (Oct 17, 2008)

another thought is to cut a steel plate and drill the holes to fit and have it function kinda like a tension plate over a heatsink model like this
http://www.newegg.com/Product/Product.aspx?Item=N82E16835106061


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## magnethead (Mar 18, 2006)

******* me would just wire/zip tie/super glue an 80mm fan on it and call it good 

that said, i wouldnt risk damaging something expensive.


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## derek_jones_36 (Nov 9, 2008)

Perhaps atttempting to direct some outside air into the system might be a better bet. What does the system have inside it for cooling? Perhaps try working with what you have inside the system. It's a multi solution problem that seems to be fixable in any number of ways.


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## derek_jones_36 (Nov 9, 2008)

Have a look at this post from this forum...regarding mac gpu temps..

http://forums.worldofwarcraft.com/t...50837A1D931.app25_02?topicId=2288049437&sid=1


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## fifthmanstandin (Oct 17, 2008)

I've known for some time about imac's running hotter on the gpu's. SMC fan control has long been on my system and isn't taking care of the problem nor has completely disassembling the system and cleaning it. I've suspected that it's a soldering issue as I've heard the 2006 imac models had some soldering defects from the gpu chipset to the mobo since there's not a card and it's simply a chip on a board. I'm 99.9% positive that it's not solvable by internal methods. SMC has the fans set as high as they go. The heat sink paste has been changed not two months ago and still renders no solution. The next logical step that I can see is replacement of the fail *** heat sink on the mobo all together.


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