caprojects
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Raspberry Pi 4 Cooling Testing

Fri Aug 16, 2019 11:00 pm

This subject may have been discussed to death already however i would like to share my testing i have done so far with more testing still need to be done. I do need to wait on deliveries before further tests can be done. I also bought a Rasberry Pi 4GB for a testing Pi as i am waiting on the pi-top 4 being release for a project I will be working on.

The hardware I chose to use for this test is as follows:-
  • Raspbery Pi 4 4GB
  • ZkeeShop Aluminum Case Alloy Armor with Cooling Heatsink - found on Amazon https://www.amazon.co.uk/gp/product/B07VDYF41Q
  • Noctua NF-A4x10 40mmx10mm Fan 5V
  • Noctua NF-A4x20 40mmx20mm Fan 5V
  • Alphacool Eisschicht Light thermal pad - 7W/mK - 1mm
Noctua fans where chosen as they are fantastic fans in general and one of the best brands for PC cooling so these where my go to fans of choise

Testing Procedure
  • Cool CPU to Idle Fan Temperatures for 20 mins
  • Start Stress test run for 30 mins
  • create log of temperatures every 6 seconds over 1 min at 20 min mark
  • Cool CPU to Idle
  • Swap hardware if needed
Further steps when switching Thermal Pads
  • Cool CPU to Fan Idle Temps
  • Dissemble Heat sink case
  • Remove Thermal Pad
  • Clean CPU IHS and hea tsink with Isopropyl aclohol
  • apply new Thermal Pad
  • Assemble Heat sink case
  • Power on and start over
I done these steps so ensure that the CPU is cooled down after stress test runs and before logging the data, it ensured that the operating temperature had stabilized and stopped increasing. I did clean the CPU IHS before i even powered on the Raspberry Pi to ensure it was clean between thermal pad applications.

Tests Performed
  • Out the box no heat sink with and without a fan - Idle, Stress test and cpuburn-a53 test
  • Heat sink with packaged thermal tape with and without a fan - Idle, Stress test and cpuburn-a53 test
  • Heat sink with Alphacool 7W/mK thermal tape with and without a fan - Idle, Stress test and cpuburn-a53 test
CPU remained at stock clock of 1.5GHz while ambient temperature was 22°C, the fans where operated of the GPIO and at 5V. Only thing i done to the OS was install it from the SD card that i got with the Raspberry Pi and updated via command line and installed the stress test and cpuburn-a53

Results

All results can be found here https://1drv.ms/x/s!AnduNu9ZFdCnpzMHNlOgjrcV1n3e

Out the box with no heat sink
I started testing without the heat sink case as the heat sink case only come with 2 small squares of thermal pads. I started with Idle temps first straight out the box then used the 10mm thick fan followed by 20mm thick fan.

Code: Select all

Out the box     - Idle Avg:  56.124°C, Stress Test: 77.463°C, cpuburn-a53: Failed due to thermal throttling
Noctua NF-A4x10 - Idle Avg:  44.436°C, Stress Test: 59.843°C, cpuburn-a53: 64.713°C
Noctua NF-A4x20 - Idle Avg:  42.399°C, Stress Test: 57.363°C, cpuburn-a53: 62.056°C
I was expecting the out the box temperatures to be around what my results where. When it come to the fans, i was unsure the cooling performance would be between the 10mm thick and 20mm thick fan was going to be. the 20mm thick fan performed better

Heat sink case with packaged thermal pads
This was an interesting tests due to accidental findings. While recording the temp data to a spreadsheet i put the fan on it's side and it was blowing against the side of the Raspberry Pi on the GPIO side then i noticed the idle temperature drop below what i recorded so I decided to run an additional test for each senario, that being with the fan on top of the heat sink case and the fan to the side (GPIO side). I shose the GPIO side as it gave the best result.

Code: Select all

Heatsink stock thermal pad                 - Idle Avg: 45.808°C, Stress Test: 61.481°C, cpuburn-a53: 69.716°C
Heatsink stock thermal pad + NF-A4x10 Top  - Idle Avg: 43.418°C, Stress Test: 56.212°C, cpuburn-a53: 61.702°C
Heatsink stock thermal pad + NF-A4x10 Side - Idle Avg: 42.266°C, Stress Test: 54.087°C, cpuburn-a53: 57.319°C
Heatsink stock thermal pad + NF-A4x20 Top  - Idle Avg: 41.957°C, Stress Test: 54.663°C, cpuburn-a53: 59.843°C
Heatsink stock thermal pad + NF-A4x20 Side - Idle Avg: 40.451°C, Stress Test: 52.051°C, cpuburn-a53: 54.530°C
The results between the fan being on top to the fan being to the side was an accidental find and glad that i found this out as its shows that with the packaged thermal tape the fan seated to the side outperformed the fan being seated on top of the heat sink case with the 20mm thick fan being the best performer.

Heat sink case with Alphacool Eisschicht Light thermal pad 1mm - 7W/mK
Things got even more interesting in this test. When i switched the Raspberry Pi on and started my temp monitor script i instantly noticed the temps idling lower than the packaged thermal pads by a significant margin

Code: Select all

Heatsink Alphacool 7W/mK thermal pad                 - Idle Avg: 40.628°C, Stress Test: 48.420°C, cpuburn-a53: 54.707°C
Heatsink Alphacool 7W/mK thermal pad + NF-A4x10 Top  - Idle Avg: 37.618°C, Stress Test: 43.860°C, cpuburn-a53: 45.631°C
Heatsink Alphacool 7W/mK thermal pad + NF-A4x10 Side - Idle Avg: 37.795°C, Stress Test: 43.727°C, cpuburn-a53: 46.295°C
Heatsink Alphacool 7W/mK thermal pad + NF-A4x20 Top  - Idle Avg: 36.777°C, Stress Test: 42.222°C, cpuburn-a53: 44.746°C
Heatsink Alphacool 7W/mK thermal pad + NF-A4x20 Side - Idle Avg: 36.688°C, Stress Test: 41.691°C, cpuburn-a53: 43.772°C
I found these results fascinating and quite eye opening as all these heat sinks on the market they seem to be using the cheapest of cheap thermal pads which makes me believe that they are more like thermal adhesive than thermal pads.

The Alphacool Eisschicht Light thermal pad - 7W/mK, out performed the packaged thermal pads by a significant margin of between 9.3% to 26.05% (calculated on the averages) with the largest gains found on the more stress put on the CPU. A single 120mm x 10mm x 1mm Alphacool 7W/mK thermal pad strip only cos £6.99 and with this much of a margin compared to the thermal pads that come in the box with the case, its worth considering switching to a better thermally conductive pad especially when you want to keep the CPU cool.

I had an idea that the thermal pad that was packaged with the case was going to be a poor performer and the results are eye opening

Conclussion
The Noctua NF-A4x20 pefromed the best in every test involving fans and its really quiet at 5V but you can quieten it more by using 3.3V which i have not done any testing at 3.3V but with a quick check, at 3.3V it idles at 37°C-38°C and is extremely quiet.

When it comes to thermal pads, the provided thermal pads for the ZkeeShop case does not perform well to the point where cooling the case from the side was better than cooling it from the top. I believe this happens as there is direct airflow to the part of the case that contacts the thermal pad. With switching to a better performing thermal pad, cooling between the top or the side of the case showed negligible between 0.24% and 2.1% (less than 1°C). The data demonstrated that the packaged thermal pads has a lot lower thermal conductivity than that of the Alphacool Eisschicht Light thermal pad - 7W/mK

All data from my tests can be found here https://1drv.ms/x/s!AnduNu9ZFdCnpzMHNlOgjrcV1n3e

Testing to Continue
For now my testing has come to a halt but not finished as i do want to test 2 other thermal pads from Alphacool, 11W/mK and 14W/mK thermal pad and once i am done with thermal pads i do want to try some thermal paste as well. Thermal paste testing will require some modification of the heat sink case in order to reduce the gap between the case and CPU so that the case contact area is just touching the CPU.

The last ting i would like to do after testing between thermal pads and thermal pastes is to design my own custom heat sink case for the Raspberry Pi. The ZkeeShop heat sink case does perform well, its not a bad case but i have my own ideas when it comes to cooling the Raspberry Pi and would like to see if i could find a better design to improve cooling performance.

Sorry for the post being rather long, i just thought this was rather interesting, If you have any ideas on how to improve the testing, i am willing to hear it. I am thinking of doing all the tests again and log the temps every second for a more detailed test from idle to stress test for a set time back to idle again and maybe with overclocking as well to see how far it can be pushed with different thermal pads before throttling, but i can only do the tests 1 more time as i only have 1 thermal pad left that was included with the case. if you have any ideas, i would love to hear them.

Thanks for your time

trejan
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Re: Raspberry Pi 4 Cooling Testing

Sat Aug 17, 2019 3:43 am

That heatsink is sold under multiple names but they all seem to bundle 2 thermal pads that are a bizarre combination of a thermal pad and some regular double sided adhesive tape. They didn't bother to get real thermal adhesive tape which is why you're seeing such a big difference. The pad material looks reasonable but hard to test as it is nearly impossible to remove the adhesive tape without tearing the pad itself.

pica200
Posts: 152
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Re: Raspberry Pi 4 Cooling Testing

Sat Aug 17, 2019 4:12 pm

I have the same case and saw the same improvement after replacing the china pad with Arctic Thermal Pad. Last night i tried a stresstest again but this time with the 64 bit version of cpuburna53 and way lower ambient temperature + open window. Got stable 59°C. Last time on Raspian it was 68°C but i did not record the ambient temp.

As for the test of other pads: I bet you will not see nearly as high of a difference for them since the heat dissipation of the SoC is not very high anyway. 6-7 W/mK is cheap and does the job ;)

caprojects
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Re: Raspberry Pi 4 Cooling Testing

Wed Sep 04, 2019 11:49 pm

I bought some cheap thermal pads that is approximated to be between 1.2W/mK to 2W/mK and the results where extremely close to that of the packaged thermal pad with acceptable margin of error of +/- 0.5°C so i can only assume that for the heatsink case that i have the stock thermal pads are some where in the range of 1.2W/mK to 2W/mK and upgrading to 7W/mK thermal pad is worth it to keep the temps under more control.

The design of the case is one with some flaws and there is only contact with the CPU and not anything else that can benefit from some cooling

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Imperf3kt
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Re: Raspberry Pi 4 Cooling Testing

Thu Sep 05, 2019 12:42 am

caprojects wrote:
Wed Sep 04, 2019 11:49 pm

The design of the case is one with some flaws and there is only contact with the CPU and not anything else that can benefit from some cooling
The SoC is the hottest part of the Pi.
Chances are that if you connect the case to 'other things that can benefit from cooling', you'll instead heat them up until they match the SoC temperature, achieving the opposite goal
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viktorp2600
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Re: Raspberry Pi 4 Cooling Testing

Sat Sep 14, 2019 5:10 pm

The subject of properly cooling Raspberry Pi 4 is very interesting to me, so I would like to add another twist:
I tried to use better heatsinks, not just better fans and thermal tape.
I did try the set of Enzotech copper heatsinks on all hot components: CPU, RAM, USB and Ethernet - (Enzotech has small heatsink witch fits on Ethernet chip). For the CPU and RAM I used a pair of Enzotech BCC9 (14mm x 14mm x 9mm), but they have taller BMR-C1 (14mm x 14mm x 14mm) heatsink, if needed. I also used cheap 30mm x 10mm 5v fan.
Using ExplainingComputers test stress script from https://www.youtube.com/watch?v=AVfvhEJ9XD0 I got following results:
temp=35.0'C
temp=45.0'C
temp=45.0'C
temp=47.0'C
temp=47.0'C
temp=45.0'C
temp=47.0'C
temp=48.0'C
It looks like having better heatsink may drastically improve RPi4 cooling results even with the cheap fan.

pica200
Posts: 152
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Re: Raspberry Pi 4 Cooling Testing

Sun Sep 15, 2019 3:39 pm

If you want to try and get rid of the adhesive from the cheap pads you can try isopropyl alcohol. It dissolves it but it takes a bit. Acetone may be faster but unsure if the pad survives it.

graphicw
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Re: Raspberry Pi 4 Cooling Testing

Tue Sep 17, 2019 12:12 am

Thanks for all the testing and very useful information for the Pi community as whole. When more people begin using their Pi 4 as DTRs, this information will prove invaluable to them.

neilshep50
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Re: Raspberry Pi 4 Cooling Testing

Fri Sep 27, 2019 1:47 pm

I've done some tests with various combinations of cooler and fans. Ambient temperature was 20 degrees.
Results were:
1) Idle 50 deg, stressed 80 deg No cooling, just Pi4 bare board
2) idle 35 deg, stressed 49 deg Pi4 + Pimoroni fan shim
3) Idle 38 deg, stressed 51 deg Pi4 + Armor fan case with supplied "thermal" pads
4) Idle 32 deg, stressed 41 deg Pi4 + Armor fan case + 0.5mm copper shims and thermal grease, fans on
5) Idle 38 deg, stressed 53 deg As 4) but fans OFF
( The Armor case is: http://www.raspberrypiwiki.com/index.php/Armor_Case_B )

6) Idle 33 deg, stressed 71 deg Pi3B+, small heatsink
7) Idle 31 deg, stressed 49 deg Pi3B+, small heatsink + pimoroni fan shim

So my conclusions are, from tests 2 and 7, Pi4 is comparable to Pi3B+ when fan cooled.
Armor fan case, when using supplied pads, is no better at cooling than the Pimoroni fan shim.
Armor case is awesome when using a copper shim and thermal grease.

All tests done with Cristopher Barnatt's script on his Explaining Computers channel.

LTolledo
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Re: Raspberry Pi 4 Cooling Testing

Fri Sep 27, 2019 11:29 pm

neilshep50 wrote: Armor case is awesome when using a copper shim and thermal grease.
Good to know someone used my idea.... and is happy with it. :D
https://www.raspberrypi.org/forums/view ... 8#p1530798

am currently exploring some other ideas for cooling the RPi4B.... this is just one of my test being done on the RPi3B+ (dont have spare RPi4B for testing...)
here's the image. am using an piece of aluminum frame, 30x30.
RPicoolingtest-1.jpg
RPicoolingtest-1.jpg (201.35 KiB) Viewed 1443 times
RPicoolingtest-2.jpg
RPicoolingtest-2.jpg (177.64 KiB) Viewed 1443 times
with fan OFF, max temp I got was 45C
with fan ON, I get 35C
my test is just my simple use-case, GIMP with 5 images + VLC playing 1080p video in window mode + 5 tab-Chromium (news sites and this forum) + 5GB file transfer to RPi3B+...

will test on RPi4B when I get another one.... and hopefully soon.... ;)

Edit: below is the "improved" version of the heatsink prior to installation
RPicoolingtestheatsink.jpg
RPicoolingtestheatsink.jpg (158.69 KiB) Viewed 1437 times
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Come to me with 'problems' and I'll help you find solutions"

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al.lm
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Re: Raspberry Pi 4 Cooling Testing

Tue Nov 19, 2019 1:01 pm

neilshep50 wrote:
Fri Sep 27, 2019 1:47 pm
4) Idle 32 deg, stressed 41 deg Pi4 + Armor fan case + 0.5mm copper shims and thermal grease, fans on
What sizes of copper shims did you use?

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Imperf3kt
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Re: Raspberry Pi 4 Cooling Testing

Tue Nov 19, 2019 8:15 pm

al.lm wrote:
Tue Nov 19, 2019 1:01 pm
neilshep50 wrote:
Fri Sep 27, 2019 1:47 pm
4) Idle 32 deg, stressed 41 deg Pi4 + Armor fan case + 0.5mm copper shims and thermal grease, fans on
What sizes of copper shims did you use?
It says right there in your quote.
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al.lm
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Re: Raspberry Pi 4 Cooling Testing

Tue Nov 19, 2019 9:43 pm

Imperf3kt wrote:
Tue Nov 19, 2019 8:15 pm
I mean the sizes (length and width) of coppers shims.

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Imperf3kt
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Re: Raspberry Pi 4 Cooling Testing

Tue Nov 19, 2019 10:57 pm

Probably the same size as the SOC, 11 or 12 millimetres if I recall.
There isn't much point in going bigger and you just risk shorting out against SMD components
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al.lm
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Re: Raspberry Pi 4 Cooling Testing

Wed Nov 20, 2019 9:57 am

Ok, thank you!

jahboater
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Re: Raspberry Pi 4 Cooling Testing

Wed Nov 20, 2019 12:06 pm

I did wonder if its possible to grind 0.5mm off the mounting posts to avoid having to use the copper shim?

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Imperf3kt
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Re: Raspberry Pi 4 Cooling Testing

Wed Nov 20, 2019 8:44 pm

jahboater wrote:
Wed Nov 20, 2019 12:06 pm
I did wonder if its possible to grind 0.5mm off the mounting posts to avoid having to use the copper shim?
A copper shim isn't used for height in these situations, you use it to draw the heat out of the soc faster than aluminium does.
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neilshep50
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Re: Raspberry Pi 4 Cooling Testing

Thu Nov 21, 2019 11:27 am

Imperf3kt wrote:
Tue Nov 19, 2019 10:57 pm
Probably the same size as the SOC, 11 or 12 millimetres if I recall.
There isn't much point in going bigger and you just risk shorting out against SMD components
Spot on!

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davidcoton
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Re: Raspberry Pi 4 Cooling Testing

Thu Nov 21, 2019 10:44 pm

Imperf3kt wrote:
Wed Nov 20, 2019 8:44 pm
A copper shim isn't used for height in these situations, you use it to draw the heat out of the soc faster than aluminium does.
Think about that for just a moment. Yes, you may get better heat transfer from the SOC to a copper shim. The shim, however, has very low thermal mass, so it heats up. It can only continue to "draw" heat from the SOC if it passes the heat on to ... the aluminium heatsink.

In any case, the limiting factor for heat transfer are the boundaries, where the "hear transfer coefficient" is the significant parameter. The thermal conductivity of the shim and heatsink is, IIRC, orders of magnitude higher. Eliminating the shim by closing the gap replaces two transfer coefficients with one.

The gapshim is there to allow for manufacturing variances with leaving an enormous air gap. And don't forget the heat transfer paste that reduces the trnasfer coefficient between the two surfaces.

School physics exercise -- work out how a metal door can keep heat in a room at 20C while it is freezing outside, without a massive heat supply in the room....

Edited so it makes sense!
Last edited by davidcoton on Sat Nov 23, 2019 4:13 pm, edited 1 time in total.
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Imperf3kt
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Re: Raspberry Pi 4 Cooling Testing

Thu Nov 21, 2019 11:43 pm

There are some studies that show using copper and aluminium to be superior to aluminium alone.
School physics exercise -- work out how a metal door can keep heat in a room at 20C while it is freezing outside, without a massive heat supply in the room....
Simple, you fill the door with insulating material.
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emma1997
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Re: Raspberry Pi 4 Cooling Testing

Fri Nov 22, 2019 12:01 am

Even a solid metal door will keep heat in better than no door at all. Convection vs conduction.

I can confirm what davidcotton says from experience with to220 heatsinks. Also surprising to know that so called thermal paste can be worse than none at all. The less in between sink and chip the better.

Nothing at all is best but not possible if there's voltage difference. Then the thinner the insulating pads the better. Until too thin then sparks fly. Don't ask how I know.

Not the Pi though which I assume has no connection on that metal cap.

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davidcoton
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Re: Raspberry Pi 4 Cooling Testing

Fri Nov 22, 2019 5:44 pm

Imperf3kt wrote:
Thu Nov 21, 2019 11:43 pm
There are some studies that show using copper and aluminium to be superior to aluminium alone.
Citation?
Simple, you fill the door with insulating material.
No. You do the maths and physics and show that a solid metal door's heat conduction (in the scenario described) is limited by something other than the door's thermal conductivity.
emma1997 wrote: Even a solid metal door will keep heat in better than no door at all. Convection vs conduction.
See above. You are missing the point.
I can confirm what davidcotton says from experience with to220 heatsinks.
davidcotton has not contributed to this thread yet.
Also surprising to know that so called thermal paste can be worse than none at all. The less in between sink and chip the better.
Yes, in that case because thermal paste in itself does not have a high thermal conductivity. But it does increase the contact area, so reducing the thermal transfer loss between the heat source and the heatsink.
Not the Pi though which I assume has no connection on that metal cap.
There is a thermal path (on the Pi3B+ and Pi4B) from the SOC through its packaging to much of the exposing metalwork of the various ports. I assume it is therefore all electrically connected to 0V (this theory not tested by me).
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bjtheone
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Re: Raspberry Pi 4 Cooling Testing

Sat Nov 23, 2019 3:55 pm

davidcoton wrote:
Fri Nov 22, 2019 5:44 pm
Imperf3kt wrote:
Thu Nov 21, 2019 11:43 pm
Simple, you fill the door with insulating material.
No. You do the maths and physics and show that a solid metal door's heat conduction (in the scenario described) is limited by something other than the door's thermal conductivity.
emma1997 wrote: Even a solid metal door will keep heat in better than no door at all. Convection vs conduction.
See above. You are missing the point.
Thermal was a long long time ago but I am going with boundary layers and skin effect, assuming relatively laminar convection flow on both sides of the door.

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davidcoton
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Re: Raspberry Pi 4 Cooling Testing

Sat Nov 23, 2019 4:27 pm

bjtheone wrote:
Sat Nov 23, 2019 3:55 pm
Thermal was a long long time ago but I am going with boundary layers and skin effect, assuming relatively laminar convection flow on both sides of the door.
It's the transfer of heat from one material to another at any material discontinuity, as summed up by "heat transfer coefficient".

In the door example, heat has to get from the air to the metal and back to outside air. Boundary layer may be involved, skin effect IDK.

When cooling a Pi, the chip designer has to get heat from the silicon (itself a non-uniform material, in case that matters) to the metal case, without simultaneously providing electrical conductivity. The board designer provides paths for the heat to get from the metal chip case to available metal connector shells that act as radiators, almost inevitably that is electrically conductive. The user has to ensure heat can escape beyond that, either with a larger mass of metal with exposed radiating surface (heatsink), or by increasing the supply of (cooler) air to the existing radiator surfaces, or both. Whatever technique is used, the limiting parts of the thermal path are the material boundaries (solid to solid or solid to air).

It's like the EU Schengen agreement -- eliminate boundaries to enhance the free flow of people.
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emma1997
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Re: Raspberry Pi 4 Cooling Testing

Sat Nov 23, 2019 11:29 pm

davidcoton wrote:
Fri Nov 22, 2019 5:44 pm
davidcotton has not contributed to this thread yet.
oops! Sorry, I suspect this may not be the first time. lol Note to self: not only remember to cross the 't's but get the count right.
davidcoton wrote:
Fri Nov 22, 2019 5:44 pm
I assume it is therefore all electrically connected to 0V (this theory not tested by me).
This theory has been tested by me and guaranteed the metal cap is not grounded. As an EE and former semiconductor product engineer I could go into some of the reasons why. But this is getting a bit long so maybe not smart considering managements tendency to lock technical discussions.
davidcoton wrote:
Fri Nov 22, 2019 5:44 pm
Imperf3kt wrote:
Thu Nov 21, 2019 11:43 pm
School physics exercise -- work out how a metal door can keep heat in a room at 20C while it is freezing outside, without a massive heat supply in the room...
emma1997 wrote: Even a solid metal door will keep heat in better than no door at all. Convection vs conduction.
See above. You are missing the point.
Aside from the fact that what I said is true, maybe not far off point if Imperf3k's thought experiment related to heat transfer. Can I at least get a B-?

Anyway my comment was an attempt to explain that conduction is not the only factor in keeping chips cool. Convection and radiation can also play a role although conduction is usually the major one in heat transfer between sink and chip. Admittedly those two play a bigger role in sink to air but not exclusively.

Also to revisit the heatsink compound subject maybe worth mentioning this is a recurring topic over on the eevblog forum. More than one new thread per week on average and I'm active in a few.

Top professionals and hobby gurus there generally agree lapping and polishing with no compound at all produces measurably better result than slopping on even the best Magic-Gold-Arctic-Silver-Diamond $100/gram brands. Not generally a subject of argumentation these days.

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