Heatsink Mod for MBA

[ayeying]

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?

[g808]

http://forums.macrumors.com/showthread.php?t=471266

[wordy]

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.

[ayeying]

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.

[wordy]

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.

[ayeying]

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)

[drstupid]

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.

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

[evsp341995]

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

[ayeying]

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

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

[evsp341995]

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

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.

[chopper dave]

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.

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.

[evsp341995]

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.

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.

[ayeying]

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.

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.

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.

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.

[evsp341995]

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.


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?

[ayeying]

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?

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.

[MacModMachine]

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.

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....

[evsp341995]

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....

What about using copper to attach the original heatsink to the aluminum bottom of the mba and use the bottom as the radiator

[coast1ja]

What about using copper to attach the original heatsink to the aluminum bottom of the mba and use the bottom as the radiator

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!

[ayeying]

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....

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.

What about using copper to attach the original heatsink to the aluminum bottom of the mba and use the bottom as the radiator

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!

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

[evsp341995]

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

[ayeying]

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

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.

[evsp341995]

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.

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.

[ayeying]

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.

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

[evsp341995]

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

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

[ayeying]

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

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.

[evsp341995]

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.

How does the hot air leave the system now? You said that air flows accross the heatsink, but there's nothing on the far side of the heatsink to blow the air out of the vents. When the fans running 7200 rpm, I can't feel much air coming out of the vents

[ayeying]

How does the hot air leave the system now? You said that air flows accross the heatsink, but there's nothing on the far side of the heatsink to blow the air out of the vents. When the fans running 7200 rpm, I can't feel much air coming out of the vents

The air being blown across the heatsink when its at 100% load for both GPU and CPU is approx 70-80 deg C. However, since the ambient air is cooler, the exiting air wouldn't be near that temp, closer to 40-50 deg C but it can build up.

What happens is the heat generated by the diode is being pushed to the edge of the heatsink, like how you have water on a desk and you're scraping it off the edge. The air just takes a ride across the heatsink then exit at the vents in the back. I'll post a diagram of the heatsink air flow later in the day when I have access to a scanner.

The fan blows air horizontally across the heatsink instead of directly out of the vents. Thats why air flow seems very small, then again, we only have a very small fan running at 6200RPM which is not fast at all.

[evsp341995]

The air being blown across the heatsink when its at 100% load for both GPU and CPU is approx 70-80 deg C. However, since the ambient air is cooler, the exiting air wouldn't be near that temp, closer to 40-50 deg C but it can build up.

What happens is the heat generated by the diode is being pushed to the edge of the heatsink, like how you have water on a desk and you're scraping it off the edge. The air just takes a ride across the heatsink then exit at the vents in the back. I'll post a diagram of the heatsink air flow later in the day when I have access to a scanner.

The fan blows air horizontally across the heatsink instead of directly out of the vents. Thats why air flow seems very small, then again, we only have a very small fan running at 6200RPM which is not fast at all.

How is tghe hot air leaving the system? If thre is little airflow from the vent, then isn't the air just circulating around inside the system?

[mac jones]

Thanks for the very informative original post (and follow ups)

I work with aluminum all the time. It's great stuff for projects because it's easily bendable and it's easily cut.

fantastic material and it's even a good conductor (cheap also).

I have some sheets that would be perfect for this so i'm going to try it. I've got an idea that this may work a bit.

It's odd though, I was afraid to do any kind of mod like this as these things are so expensive, but now that some time has (reduced the value) I feel fine about it :D

should be fun.

Note: Got the slop in hinge. Do they still replace these defective parts at the Apple stores? (I heard it was a ongoing commitment , but you know how that goes :rolleyes: )

[evsp341995]

Thanks for the very informative original post (and follow ups)

I work with aluminum all the time. It's great stuff for projects because it's easily bendable and it's easily cut.

fantastic material and it's even a good conductor (cheap also).

I have some sheets that would be perfect for this so i'm going to try it. I've got an idea that this may work a bit.

It's odd though, I was afraid to do any kind of mod like this as these things are so expensive, but now that some time has (reduced the value) I feel fine about it :D

should be fun.

Note: Got the slop in hinge. Do they still replace these defective parts at the Apple stores? (I heard it was a ongoing commitment , but you know how that goes :rolleyes: )


what are you going to do? are you just going to lay more sheets of aluminum down on top of the original heatsink?

[mac jones]

what are you going to do? are you just going to lay more sheets of aluminum down on top of the original heatsink?

I've been inside and poked around a lot when swaping out SSD's and doing the paste at one time.

I'll try what the OP did as thankfully now we have measurements ( and the old adage applies "If it ain't broke....." )

If I can think of a better options I will try it and post.

Everyone else do the same.

note: As I mentioned above, I used to be nervous about this, but I imagine that it would be pretty hard to screw this up if you don't break anything as the heat sink in there now is a joke. They went for extreme weight reduction, which is nice but maybe not what I want, presently.

[chopper dave]

Ayeying, I think you have a lot of good ideas, but I'm going to have to be a science stickler and correct some common misconceptions you have spread about heat transfer.

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.

Actually, they are equally good radiators. The ability of a metal to radiate heat is entirely dependent on its surface area, geometry, fluid type, and fluid velocity. See the following article for a description of how engineers approximate heat transfer from a solid to a fluid/gas, and notice how there is lots of attention paid to the fluid, and NONE to the material of the solid.

http://en.wikipedia.org/wiki/Heat_transfer_coefficient

You are correct of course that copper is a good conductor, and has a greater heat capacity than aluminum. In the steady-state case, heat capacity does not enter into the equation, though it definitely changes the time required to reach steady-state conditions. These factors may have obscured what was really causing the results of your trials.



What happens is the heat generated by the diode is being pushed to the edge of the heatsink, like how you have water on a desk and you're scraping it off the edge.

Heat always flows from a hot area to a cold area, that's just the 2nd law of thermodynamics, so your analogy of heat being pushed is incorrect. A better one would be of water flowing downhill, with the higher ground symbolizing the hot area of the heatsink around the diode.

[ayeying]

Ayeying, I think you have a lot of good ideas, but I'm going to have to be a science stickler and correct some common misconceptions you have spread about heat transfer.

I welcome anyone to question my theories, that's how we learn. Considering I never took physics in College (yet) or even in High School (Seriously, I never took it), I'm doing this through logic and wiki pages and Google.

Actually, they are equally good radiators. The ability of a metal to radiate heat is entirely dependent on its surface area, geometry, fluid type, and fluid velocity. See the following article for a description of how engineers approximate heat transfer from a solid to a fluid/gas, and notice how there is lots of attention paid to the fluid, and NONE to the material of the solid.

http://en.wikipedia.org/wiki/Heat_transfer_coefficient

You are correct of course that copper is a good conductor, and has a greater heat capacity than aluminum. In the steady-state case, heat capacity does not enter into the equation, though it definitely changes the time required to reach steady-state conditions. These factors may have obscured what was really causing the results of your trials.

I'm a bit confused here. For the sake of argument, if both metals of same density and mass were in a controlled environment and both were required to dissipate heat, which would go faster? I understood that Aluminum would dissipate faster?

Heat always flows from a hot area to a cold area, that's just the 2nd law of thermodynamics, so your analogy of heat being pushed is incorrect. A better one would be of water flowing downhill, with the higher ground symbolizing the hot area of the heatsink around the diode.

Yeah, I kinda figured that one was a bit off.

Here's a picture that I randomly drew up that shows the air flow of the stock heatsink/fan. I'm not an artist so screw my crappy drawing but it shows how the air enters and exits out of the MacBook Air (This applies to the Rev A models also, just a different heatsink style but same concept)

From 1) It draws in cold air from the environment
2) The fan pushes the air to a horizontal exit of the Fan assembly
3) The warmed up air exits through the vents in the back

The air flow works because there are foam based walls directing the air flow on the heatsink.

[evsp341995]

I'm still confused as to what the proper material for this heatsink would be, copper or aluminum. I plan to cnc cut a much better heatsink with some short fins on it to replace the shoddy apple one. Does anyone have measurements of how much space is between the bottom case and the heatsink when the bottom is on the computer? I estimate about 2mm. I also still haven't gotten a clear answer as to whether attaching the. Heatsink to the bottom case (so the bottom could act as a radiator) would be benefitial.

[chopper dave]

I'm a bit confused here. For the sake of argument, if both metals of same density and mass were in a controlled environment and both were required to dissipate heat, which would go faster? I understood that Aluminum would dissipate faster?


Interesting question. It is not very useful to compare Al and Cu and say they have the same density- it defeats the purpose of a comparison. Let's say they are both the same geometry. It is important to distinguish between short-term and long-term (steady-state) performance. It is also important to define "dissipate." Do you mean watts from the chip, or watts from the heatsink?

In the very short term, the Cu sink will probably take more watts from the chip because it has more heat capacity and better conduction. it is possible for the Al sink to dissipate more heat to the air at first, though, because it will heat up faster due to its low heat capacity.

In the long term, steady state solution heat capacity does not enter into the equation (it is like a mass in a physical system, the conductivity like a spring). Heatsinks usually have a maximum temperature determined by the processor they are cooling. The tradeoff is that the hotter the sink gets, the more heat it can dissipate. You can imagine then that an ideal heatsink will be uniformly hot, enabling maximum dissipation to the air across its entire geometry.

Cu will almost always work better because its high conductivity will keep the heatsink temperature more uniform, while the Al sink will tend to be cooler at its extremes. We choose Al over Cu when weight, cost, or corrosion is a concern.

to evsp341995: I have had a hard time machining copper- it is very gummy and you need to get the right alloy for it to be easy to work with. Still, if you have the experience and don't mind the extra few ounces, it is probably the superior material. I think a lot of manufacturers treat their Cu heatsinks with a thin film to protect against corrosion- you might want to look into this as well. No coatings are necessary for Al and as long as you choose a 6 or 7000 alloy it will machine nicely.

I think attaching the sink to the bottom, probably through a thermal interface pad, is a good idea, as long as your lap doesn't mind the extra heat. It is hard to measure spaces when you can't get a micrometer in there. I would put shims in between the heatsink and bottom and just keep adding them until you feel some resistance putting the bottom back on. Measure the shims and plan for that distance.

[ayeying]

I'm still confused as to what the proper material for this heatsink would be, copper or aluminum. I plan to cnc cut a much better heatsink with some short fins on it to replace the shoddy apple one. Does anyone have measurements of how much space is between the bottom case and the heatsink when the bottom is on the computer? I estimate about 2mm. I also still haven't gotten a clear answer as to whether attaching the. Heatsink to the bottom case (so the bottom could act as a radiator) would be benefitial.

I would say at best there's approx 1.5 to 2mm max of clearance between the heatsink itself and the bottom enclosure. Remember, the bottom plate actually warps slightly when it's screwed on in a non ordered fashion so the clearance would be slightly different +/- 0.02mm.

I'd say a combination of Copper and Aluminum would be the best since those are the 2 mostly used metals in conventional heatsinks for all computer hardware.

Attaching the heatsink to come in contact with the bottom panel will increase radiation of heat and mass, but if you block the airflow, wouldn't that just make the fan literally useless since it's being blocked from exiting the warm air?

[evsp341995]

Interesting question. It is not very useful to compare Al and Cu and say they have the same density- it defeats the purpose of a comparison. Let's say they are both the same geometry. It is important to distinguish between short-term and long-term (steady-state) performance. It is also important to define "dissipate." Do you mean watts from the chip, or watts from the heatsink?

In the very short term, the Cu sink will probably take more watts from the chip because it has more heat capacity and better conduction. it is possible for the Al sink to dissipate more heat to the air at first, though, because it will heat up faster due to its low heat capacity.

In the long term, steady state solution heat capacity does not enter into the equation (it is like a mass in a physical system, the conductivity like a spring). Heatsinks usually have a maximum temperature determined by the processor they are cooling. The tradeoff is that the hotter the sink gets, the more heat it can dissipate. You can imagine then that an ideal heatsink will be uniformly hot, enabling maximum dissipation to the air across its entire geometry.

Cu will almost always work better because its high conductivity will keep the heatsink temperature more uniform, while the Al sink will tend to be cooler at its extremes. We choose Al over Cu when weight, cost, or corrosion is a concern.

to evsp341995: I have had a hard time machining copper- it is very gummy and you need to get the right alloy for it to be easy to work with. Still, if you have the experience and don't mind the extra few ounces, it is probably the superior material. I think a lot of manufacturers treat their Cu heatsinks with a thin film to protect against corrosion- you might want to look into this as well. No coatings are necessary for Al and as long as you choose a 6 or 7000 alloy it will machine nicely.

I think attaching the sink to the bottom, probably through a thermal interface pad, is a good idea, as long as your lap doesn't mind the extra heat. It is hard to measure spaces when you can't get a micrometer in there. I would put shims in between the heatsink and bottom and just keep adding them until you feel some resistance putting the bottom back on. Measure the shims and plan for that distance.

Thanks for the very informative post. I don't have any experience machining copper, I just read a few forums about it. So you think I should use aluminum? Do you have any experience machining aluminum? What bit should I use? Carbide? Do I need any cooling?

I would say at best there's approx 1.5 to 2mm max of clearance between the heatsink itself and the bottom enclosure. Remember, the bottom plate actually warps slightly when it's screwed on in a non ordered fashion so the clearance would be slightly different +/- 0.02mm.

I'd say a combination of Copper and Aluminum would be the best since those are the 2 mostly used metals in conventional heatsinks for all computer hardware.

Attaching the heatsink to come in contact with the bottom panel will increase radiation of heat and mass, but if you block the airflow, wouldn't that just make the fan literally useless since it's being blocked from exiting the warm air?

We won't be blocking airflow. Were only going to cover a small area of the original heatsink with the heat transfer pads.

[PinkyMacGodess]

I'm still confused as to what the proper material for this heatsink would be, copper or aluminum. I plan to cnc cut a much better heatsink with some short fins on it to replace the shoddy apple one. Does anyone have measurements of how much space is between the bottom case and the heatsink when the bottom is on the computer? I estimate about 2mm. I also still haven't gotten a clear answer as to whether attaching the. Heatsink to the bottom case (so the bottom could act as a radiator) would be benefitial.

Intel started using a solid copper core surrounded by a finned aluminum structure a number of years ago because the copper would draw the heat out and the aluminum would radiate it out through the air moving through the vanes.

I replaced the heat sinks in our 1U Sun Fire server and it also used a copper slab with an aluminum finned structure to diffuse the heat. It was a rather interesting find. After seeing no copper in any heat sinks and now seeing a lot of uses of it.

Could someone machine a groove into the existing heat sink, slip a copper piece into position and then use either thermal paste or a thermal pad to transfer the heat to it. I'd think that should work wonders for keeping things cooler. Hiding it from the prying eyes of an Apple surgeon would be far more difficult...

[evsp341995]

Intel started using a solid copper core surrounded by a finned aluminum structure a number of years ago because the copper would draw the heat out and the aluminum would radiate it out through the air moving through the vanes.

I replaced the heat sinks in our 1U Sun Fire server and it also used a copper slab with an aluminum finned structure to diffuse the heat. It was a rather interesting find. After seeing no copper in any heat sinks and now seeing a lot of uses of it.

Could someone machine a groove into the existing heat sink, slip a copper piece into position and then use either thermal paste or a thermal pad to transfer the heat to it. I'd think that should work wonders for keeping things cooler. Hiding it from the prying eyes of an Apple surgeon would be far more difficult...

We couldn't machine a groove into the original one as it is WAY too thin. It is about .2mm thick.

[ayeying]

Yeah, machining Copper that's barely a mm thick isn't possible. I actually ended up cutting it with scissors and flattening it out as much as I can.

Your idea of using thermal pad or something to transfer the heat from the heatsink to the lower panel is interesting. I'll see if I can find some extra materials and try it out.

[phogstenjr]

Hello,

Has anyone had any luck with a working heatsink modification for the 1st Generation MacBook Air?

Paul

[Drag'nGT]

A better heatsink would do really well on the forums. Anyone able to make these to sell?

[nicklausi]

Hi there,
i just registered to participate in this discussion. Btw: I think its really interesting!
I also thought about many possible ways, improving my mba's heatsink.
As i read the whole thread and some other threads, i came to the conclusion, that it would be the best attempt to concentrate on the airflow and how to make use of it the most efficient way.

How would it be, if you just take a thin layer of aluminum - but with the double size of the actual heatsink. So you cut out a piece of aluminum with the same thickness, the same width - but at least the doubled height.
Then you bend it over 180°, where the height exceeds the former heatsink.

This new heatsink touches the bottom of the aluminum macbook body, but doesn't get into the way of the airflow.
At last you could cut some fins at the end, for fitting it between the airflow openings.

I will make a small drawing and attach it, as my english is not sufficient enough to explain it properly.

[nicklausi]

the draft