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When working as intern at an Apple store more than 10 years back the instructions from Apple for reassembly would always tell to put a huge amount of thermal gr

When working as intern at an Apple store more than 10 years back the instructions from Apple for reassembly would always tell to put a huge amount of thermal grease on the CPU. So much that it would be squirted out from under the heatblock in large blobs. I always found it odd as I was used to add just as much as was needed without spilling over. Never read any research on it though so I'm curious what was the right approach. I can't image Apple just getting this part of the thermal puzzle wrong when everything else is fully optimized. Or them just skimping a few cents on better grease.

rozenmd 8y ago
Came here to say this. Former employees of Apple I know recommend reapplying the thermal paste immediately after getting a MacBook Pro.
- Fnoord 8y ago
  They recommend I open up the device myself? Thereby voiding warranty? Isn't that getting more and more difficult?
  - thinkythought 8y ago
    This may have changed, but for years the apple warranty was "as long as you don't damage anything, you're allowed to open it". I did some research and at least the manual for my machine still states this, but mine is also from 2012
    - ktsmith 8y ago
      I took a 2011 model in since I just needed a replacement battery due to bulging. The Apple employee was flabbergasted that I had removed the screws and bottom plate saying I had voided the warranty... on a severely out of warranty device. He was insistent that any device that had screws in it would have the warranty voided if those screws were removed and the device opened, even after showing him the manual which instructs the user on how they can open the device to replace the hard drive in the section labeled "Boost your MacBook Pro" starting on page 35. https://manuals.info.apple.com/MANUALS/1000/MA1602/en_US/macbook_pro_15inch_late_2011.pdf https://manuals.info.apple.com/MANUALS/1000/MA1602/en_US/mac...
      - rozenmd 8y ago
        They're getting a bit sloppy with the people they hire recently it seems. I had someone from AppleCare basically tell me I had 90 days after a repair to find an issue with it (violating Australian Consumer Law, which gives you 2 years) - mortified staff in-store gave me my refund though.
masklinn 8y ago
"Better grease" makes a fairly limited difference over standard[0], and it requires way more care if it's a silver-based compound (as that's electrically conductive). I'm guessing their thinking is they want to avoid air at all costs, so requiring way excessive amounts ensures it will never be lacking, which they probably think is significantly worse than excesses. [0] the difference in thermal conductivity between an entry-level thermal grease and a high-quality one is 2x~3x (entry level is ~2W/(m.K) while top-of-the-line might reach ~8W/(m.K)). The difference between air and a low-end thermal grease is 2 orders of magnitude (~0.025 W/(m.K) versus ~2)
- philjohn 8y ago
  It also causes structural breakdown of aluminium, so if there's any of that anywhere nearby (or in the heatsink) it's a no-go.
paulmd 8y ago
If a bare-die CPU or GPU is not fully covered, the uncovered portions will rapidly become hot and the chip may die (especially if the thermal sensors are covered and cannot detect this). This is different from modern desktop processors where there is an IHS to help spread the heat around - there is a very real danger to insufficient paste application on a bare die. In contrast, since modern thermal pastes are non-conductive, there is no real downside to an enthusiastic application of paste except for making a mess, so you want to default to putting too much on rather than having some dumb intern kill a PC with an insufficient application. There is virtually no effect on thermals. https://www.youtube.com/watch?v=rAid5G30-WM https://www.youtube.com/watch?v=rAid5G30-WM LM is conductive, so you need to be much more careful with the application, as over-application will kill the chip. It also can migrate over time, especially if you put a bit too much on, and is particularly unsuitable for laptops that are going to be moved around a lot. Putting LM on a laptop is a gimmick, and one with fairly considerable risk to the hardware, not something that is suitable for mass production.
- aequitas 8y ago
  I think that might be the reason indeed. It's better to err on the safe side.
- lvillani 8y ago
  > since modern thermal pastes are non-conductive, there is no real downside to an enthusiastic application of paste except for making a mess I recently re-applied thermal paste (an old Arctic MX-2 I had lying around) on a late 2013 MacBook Pro which has bare-die CPU and GPU. The first time I did it, I applied too much paste and it had an observable negative effect on thermal dissipation. Once I applied the correct amount, I got slightly better results than stock paste.
  - andromeduck 8y ago
    That's strongly mitigated by mounting pressure which is very high in macbooks.
- tjoff 8y ago
amelius 8y ago
> So much that it would be squirted out from under the heatblock in large blobs. Is this stuff electrically conductive?
- blattimwind 8y ago
  No
  - astrodust 8y ago
    Here's a typical warning from a manufacturer: http://www.arcticsilver.com/as5.htm http://www.arcticsilver.com/as5.htm > While much safer than electrically conductive silver and copper greases, Arctic Silver 5 should be kept away from electrical traces, pins, and leads. While it is not electrically conductive, the compound is very slightly capacitive and could potentially cause problems if it bridges two close-proximity electrical paths.
  - slantyyz 8y ago
    The correct answer is "it depends on which paste you use". If you're using a "liquid metal" compound, you probably want to be very careful, as it is conductive.[1] [1] https://www.ekwb.com/blog/thermal-compound-guide/ https://www.ekwb.com/blog/thermal-compound-guide/
    - blattimwind 8y ago
      > The correct answer is A correct answer takes context into account. In this case, "vendors that always tell to put a huge amount of thermal grease on the CPU".
woliveirajr 8y ago
The best scenario is full contact between the CPU/GPU/whatever makes the heat and the heatsink. No product that is put between those elements will make heat dissipation get any better, as it won't change the composition of the heatsink or of the CPU/GPU surface. Now, in real life, CPU, GPU and heatsink don't have the perfect, more-than-mirror finished surface. There are small gaps and small peaks that prevent a full contact. And those gaps are filled with air. Air is a bad heat conductor. So, to reduce this bad, bad air effect, you fill the gaps with thermal paste. Thermal paste will be better than air pockets. Thermal paste will be worst than metal/metal (CPU/GPU/heatsink) contact. So, put as little as thermal paste as needed, just to fill the gaps. But put too few paste, or don't cover everything, and you'll end up with more gaps: the paste will prevent those metal/metal peaks contacts and if not spread evenly it will leave bigger gaps. If you can't know the ideal, it's better to have a little more paste (but covering everything) than to few or badly spread (leaving bigger gaps).
- andromeduck 8y ago
  It's even better to add more paste and high mounting pressure which is what Apple does. https://www.overclockers.com/heatsink-mounting-pressure-vs-performance/ https://www.overclockers.com/heatsink-mounting-pressure-vs-p...

rozenmd 8y ago

Came here to say this. Former employees of Apple I know recommend reapplying the thermal paste immediately after getting a MacBook Pro.

Fnoord 8y ago
They recommend I open up the device myself? Thereby voiding warranty? Isn't that getting more and more difficult?
- thinkythought 8y ago
  This may have changed, but for years the apple warranty was "as long as you don't damage anything, you're allowed to open it". I did some research and at least the manual for my machine still states this, but mine is also from 2012
  - ktsmith 8y ago
    I took a 2011 model in since I just needed a replacement battery due to bulging. The Apple employee was flabbergasted that I had removed the screws and bottom plate saying I had voided the warranty... on a severely out of warranty device. He was insistent that any device that had screws in it would have the warranty voided if those screws were removed and the device opened, even after showing him the manual which instructs the user on how they can open the device to replace the hard drive in the section labeled "Boost your MacBook Pro" starting on page 35. https://manuals.info.apple.com/MANUALS/1000/MA1602/en_US/macbook_pro_15inch_late_2011.pdf https://manuals.info.apple.com/MANUALS/1000/MA1602/en_US/mac...
    - rozenmd 8y ago
      They're getting a bit sloppy with the people they hire recently it seems. I had someone from AppleCare basically tell me I had 90 days after a repair to find an issue with it (violating Australian Consumer Law, which gives you 2 years) - mortified staff in-store gave me my refund though.

masklinn 8y ago

"Better grease" makes a fairly limited difference over standard[0], and it requires way more care if it's a silver-based compound (as that's electrically conductive). I'm guessing their thinking is they want to avoid air at all costs, so requiring way excessive amounts ensures it will never be lacking, which they probably think is significantly worse than excesses. [0] the difference in thermal conductivity between an entry-level thermal grease and a high-quality one is 2x~3x (entry level is ~2W/(m.K) while top-of-the-line might reach ~8W/(m.K)). The difference between air and a low-end thermal grease is 2 orders of magnitude (~0.025 W/(m.K) versus ~2)

philjohn 8y ago
It also causes structural breakdown of aluminium, so if there's any of that anywhere nearby (or in the heatsink) it's a no-go.

paulmd 8y ago

If a bare-die CPU or GPU is not fully covered, the uncovered portions will rapidly become hot and the chip may die (especially if the thermal sensors are covered and cannot detect this). This is different from modern desktop processors where there is an IHS to help spread the heat around - there is a very real danger to insufficient paste application on a bare die. In contrast, since modern thermal pastes are non-conductive, there is no real downside to an enthusiastic application of paste except for making a mess, so you want to default to putting too much on rather than having some dumb intern kill a PC with an insufficient application. There is virtually no effect on thermals. https://www.youtube.com/watch?v=rAid5G30-WM https://www.youtube.com/watch?v=rAid5G30-WM LM is conductive, so you need to be much more careful with the application, as over-application will kill the chip. It also can migrate over time, especially if you put a bit too much on, and is particularly unsuitable for laptops that are going to be moved around a lot. Putting LM on a laptop is a gimmick, and one with fairly considerable risk to the hardware, not something that is suitable for mass production.

aequitas 8y ago
I think that might be the reason indeed. It's better to err on the safe side.
lvillani 8y ago
> since modern thermal pastes are non-conductive, there is no real downside to an enthusiastic application of paste except for making a mess I recently re-applied thermal paste (an old Arctic MX-2 I had lying around) on a late 2013 MacBook Pro which has bare-die CPU and GPU. The first time I did it, I applied too much paste and it had an observable negative effect on thermal dissipation. Once I applied the correct amount, I got slightly better results than stock paste.
- andromeduck 8y ago
  That's strongly mitigated by mounting pressure which is very high in macbooks.
tjoff 8y ago

amelius 8y ago

> So much that it would be squirted out from under the heatblock in large blobs. Is this stuff electrically conductive?

blattimwind 8y ago
No
- astrodust 8y ago
  Here's a typical warning from a manufacturer: http://www.arcticsilver.com/as5.htm http://www.arcticsilver.com/as5.htm > While much safer than electrically conductive silver and copper greases, Arctic Silver 5 should be kept away from electrical traces, pins, and leads. While it is not electrically conductive, the compound is very slightly capacitive and could potentially cause problems if it bridges two close-proximity electrical paths.
- slantyyz 8y ago
  The correct answer is "it depends on which paste you use". If you're using a "liquid metal" compound, you probably want to be very careful, as it is conductive.[1] [1] https://www.ekwb.com/blog/thermal-compound-guide/ https://www.ekwb.com/blog/thermal-compound-guide/
  - blattimwind 8y ago
    > The correct answer is A correct answer takes context into account. In this case, "vendors that always tell to put a huge amount of thermal grease on the CPU".

woliveirajr 8y ago

The best scenario is full contact between the CPU/GPU/whatever makes the heat and the heatsink. No product that is put between those elements will make heat dissipation get any better, as it won't change the composition of the heatsink or of the CPU/GPU surface. Now, in real life, CPU, GPU and heatsink don't have the perfect, more-than-mirror finished surface. There are small gaps and small peaks that prevent a full contact. And those gaps are filled with air. Air is a bad heat conductor. So, to reduce this bad, bad air effect, you fill the gaps with thermal paste. Thermal paste will be better than air pockets. Thermal paste will be worst than metal/metal (CPU/GPU/heatsink) contact. So, put as little as thermal paste as needed, just to fill the gaps. But put too few paste, or don't cover everything, and you'll end up with more gaps: the paste will prevent those metal/metal peaks contacts and if not spread evenly it will leave bigger gaps. If you can't know the ideal, it's better to have a little more paste (but covering everything) than to few or badly spread (leaving bigger gaps).

andromeduck 8y ago
It's even better to add more paste and high mounting pressure which is what Apple does. https://www.overclockers.com/heatsink-mounting-pressure-vs-performance/ https://www.overclockers.com/heatsink-mounting-pressure-vs-p...