How To: Make your own diamond Thermal Paste - Page 10

can you use QZs instead to save cash!?!?!

Just got the vial of diamond powder. Looking at it I've realized that possibly due to the higher density (== carat?) it's very 'heavy' as compared to air, so there's less of a worry for dust inhalation than I had at least expected, so long as it is not thrown about and a mask is used.

*addendum... Although a new difficulty of getting the dust to mix appropriately without clumping may also prove difficult, or at least getting the mixture to an equilibrium, has also revealed itself.

I'll be utilizing syringes and glass vials for mixing and degassing (as stated previously, by putting the vials in a spinner for a few hours / days...whichever is more needed), all in a relatively sterile room (one with consistent air flow for the purpose of the laser cutter that occupies the same space).

Only aspect left now is to get the silicone oil. Considering how much powder I got, I might try a few different types and measures of viscosity.

I was curious if anyone knew of non-silicone-based oils / greases that might be possible to use?
Edited by Thaipo - 9/2/09 at 10:49am

I am all done, finally. For those of you that just want to see random results without knowing what I did, skip to the bottom.

Testing rig:

To create the heater, I soldered 7 x 1.8 Ohm resistors together in series. I then wrapped the resistors with copper braid and soldered the braid to a small steel plate. The steel plate was purposely unpolished in order to see the performance of the TIM's. A power supply of 19v was attached to the resistors providing an output of 28.6W. This may seem small to some, but the results can be scaled up easily, and this was the maximum the resistors could handle. Using a multimetter, the exact values for voltage and resistence gave an output of 29.8W.

The heatsink is an old OCZ model that has three heat pipes passing through a copper block at the cpu end. The heat pipes then pass through aluminum fins at the fan end.

I actually didn't have a motherboard that could mount my heatsink so I used a piece of wood, I hallowed out a cavity in the wood for the resistors to fit into and then mounted the steel plate on top of the wood. I then made anchors for the heatsink to attach on either side of the steel plate. The contact area between the steel plate and the heatsink is 3.5cm X 3cm.

On the steel plate off to one corner was securely attached a thermocouple which ran to a multimeter to read its output. I drilled a small hole in the copper block of the heatsink and ran another thermocouple inside. This thermocouple was connected to a dedicated display module. I used a small amount of Ceramique on the thermocouples to ensure good contact. Each thermocouple was calibrated such the results at any given temperature differed by less than 0.3F.

Materials:

1. Air - I ran the system completely dry as a control.
2. AS5
3. Ceramique
4. Dow Thermal Fluid - Dow Corning make their own special TIM. It is just silicone oil and zinc, but it is very viscous (90,000cs).
5. Pure Silicone Oil - Also from Dow Corning but has a viscosity of 10,000cs. DC is very generous with their free samples.
6. Silicone and Diamond Slurry - This is the DC silicone oil with 100,000 mesh diamonds add with a ratio of 1:1 oil to diamind by weight.
7. Dow Fluid w/ Diamonds - This is the DC thermal fluid with 100,000 mesh diamonds add with a ratio of 3:1 fluid to diamond by weight.
8. Inventgeek.com Remake - Lastly, I attempted to follow the procedure of the inventgeek article. I used 100,000 mesh diamonds and for the silicone grease, I used one with PTFE particles already in it: click. The diamond to everything else ratio was 5:2 by weight.

Procedure:

To make the DIY TIM's, I placed a small glass container onto a scale, measured out the amount of diamond and grease, and then mixed it by hand using a toothpick. There was no danger of inhalation as mentioned in the inventgeek article. The particles were sufficiently dense and clumped together that they didn't go anywhere. I then finished the mixing using a dremel and a special attachment that made it like a batter mixer.

For all of the TIM's that I made for myself (except for the inventgeek batch), I placed them inside of my vacuum chamber to remove air bubbles. (warning, I'm going to get nerdy here) I wanted to know what pressure I need to pump my chamber down to in order for a majority of the bubbles to be removed. In order to do that you need to combine the Young-Laplace equation with the Ideal Gas Law. You end up with a third order polynomial. I solved the equation with matlab for different bubble radii. As you can see below, even with absolute zero pressure, some bubbles will only double in size. Meaning that in a very viscous fluid, they will not float out that much faster.



With the vacuum chamber I created, I can get down to 26 to 26.5 in Hg vacuum. This means that for my altitude most of the bubbles greater than 10 um will join and float out. When vacuuming the TIM's I left them in the chamber for an hour to get the majority of the bubbles out. (It is really cool when you pump down the chamber and your TIM looks like it's boiling. I actually did end up boiling water using the chamber to verify that the pressure readings were correct.)

For the actual testing, I first tried out all of the different fluids on the test rig to both see how each of them would spread and to thoroughly get the surface contaminated by all of them. I wanted to make sure that the order in which I did the experiments did not effect the results. The procedure for a standard test was to clean the steel plate and the heatsink with a dry rag. Then I would clean both surfaces using rubbing alcohol and a lint free cloth. I would place a dime sized amount of the TIM in the center of the steel plate, and then press down on it with the heat sink until it could be attached to the wood. Once the heatsink was attached, the fan was turned on and allowed to run for 30 mins to cool down the entire system. The test rig was positioned in the center of an air conditioned room. The ambient air temperature was taken to be the average of the two thermal couples after the 30 min cool down. This was consistently ~71 F and was used as the starting temperature in the data. The heater was then turned on and a stopwatch was used to track the time. Measurements were taken at 1,2,3,4,5,10,15,20,25,30,and 60 mins. Each TIM was tested three times and the average of all three runs was used. The order of the testing was random with each of the three runs for a particular TIM spread out over the course of all testing.

In the preliminary testing, I experimented with spreading the TIM across the entire heatsink with a razor before attaching it. That always caused an drastic decrease in performance. For this reason, that method was not used.

Results:
T1 is the steel plate temperature.
T2 is the heatsink temperature.
The margin of error is +- 0.3 F.

The first figure shows the temperature difference between the heat sink and the ambient air temperature. As you can see for all the runs that even though the different TIM's caused different delays in reaching an equilibrium temperature, they all reached the same equilibrium temperature. This is expected since the amount of the heat it is outputting (31W) is the same regardless of the TIM used. The time axis is graphed in log form in order to see all the data points. The lines in between the data points are just for continuity.




Next is a figure showing the the temperature difference between the steel plate and the ambient air temperature. The worst performing TIM is obviously air. Next is the mixture mimicking the directions from inventgeek. It was the only DIY TIM that was not put in the vacuum chamber.




Lastly, we have the temperature difference between the heatsink and the steel plate. I've excluded the air run so that we can distinguish the results better. As you can see at equilibrium, AS5, Cermaique, and the Dow Corning Thermal Fluid were all very close to one another with AS5 being the best out of the group. For pure silicone oil, you can see that it is better than the inventgeek mixture. This is most likely because of the air trapped inside of the mixture. It could have also been because the mixture was so viscous that it did not thin as much as the oil. Once we add the diamonds, we improve the performance of the silicone oil but not by that much. Perhaps if I added more diamonds, the performance would increase, but the mixture was already pretty viscous and dry. When we added diamonds to the Dow Thermal Fluid, it improved its performance. It was actually the best performing out of all of them. The catch is that it did not improve it by all that much. As you can see, there isn't much room for performance anyways. The temperature difference between the heatsink and the steel plate for the best performing TIM's was in the 5-6 F range.




Conclusion:

The adding of diamonds did improve the performance of the of both the silicone oil and DC Thermal Fluid, but it did not improve them by that much. A few things might be effecting this. The mixtures might not be mixed well enough leaving clumps of diamonds. The problem with increased mixing is that it introduces more sub mm and um sized bubble. And since we cannot remove the smallest of these bubbles, increased mixing might lead to worse performance. Also, the amount of diamonds may have been too small. The problem with adding more is the viscosity of the slurry increases. Since slurries behave like solids and liquids, this may effect the mixtures ability to thin once the heatsink is added. Playing with juts these two variables adds two orders of magnitude to the complexity of the problem and that is why I did not explore them further. However, it is safe to conclude that you will not stumble upon the optimal mixture as inventgeek seems to suggest they did.

The best performing TIM turned out to be the DC Thermal Fluid with diamonds. It preformed slightly better than AS5. One may wonder why I didn't add diamonds to AS5. That is because I'm not made of money. It may have also decreased performance if I added too much or if the mixing added too many bubbles. But in the end, performance could not be improved by that much anyways.

If we take the temperature difference between the the plate and heatsink to be the average temperature across both interfaces, then the overall performance of the best performing TIM's are 4700-5700 Watts/F*m^2. Even if you were to drastically improve that, since the temperature of the heatsink is fixed by its own performance, you'd only be able to get 4-5 F improvement at the very extreme.

These results are for ~30 Watt output but they can easily be scaled up. For 60 watts, the temperature difference for the heatsink to ambient would roughly double, 6.5F --> 13F. The same would happen for the temperature difference between the steel plate and the heat sink 5F --> 10F. So with the same ambient temperature of 71F, doubling the heat output with take the heatsink equilibrium temperature from 83F to 94F. Reducing the area, will have a similar effect.

When you look at this as cost vs performance, the Dow Corning Thermal Fluid wins hands down. They sent me 1 kg of it for free. It works better than Ceramique and will be good enough for 99% of applications.

As you can see the diamonds did not perform any sort of miracle as reported by inventgeek, nor can it. All of the inconsistencies in their procedure and advice (don't add the diamonds to a zinc oxide grease as I did for the best results), combined with their insane results which are non reproducible makes me conclude that this was all a big joke played by them.

Lastly, here are some images of my setup and experimenting. Also, I've attached the data from all of my experiments. Thank you and good night.

Materials
Vacuum chamber
I didn't have a picture of the fire extinguisher before I cut it. So I included an artists rendering of what it looked like before.
Test rig front Test rig side
Finally, here is the Dow Thermal Fluid with diamonds that beat AS5. I might try this later on an actually cpu and post results but I'm done for now.
Edited by freddyman - 9/5/09 at 2:40pm

+rep

Nice experiment that proves the fairly obvious: the results of the inventgeek article are completely absurd.

The problem with TIMs, and a major reason why adding super conductive materials to them doesn't help as much as some people think it should, is that the thermal conductivity of the liquid is far more important than that of the material suspended in it.

This is also why the thicker pastes tend to do better, they use very high concentrations of extremely fine solids. Inventgeek only used something liek 30-40% diamond by weight. Professional TIMs are usually 70-95% filler, with just enough silicone or synthetic oil to displace the air between particles and hold the stuff together as a fluid.

Anyway, a kilogram of the Dow TIM for free is great. Should last you quite a while.

Tried mineral oil?
Edited by Blameless - 9/5/09 at 12:57pm

I am actually using the inventgeek thermal compound on my Intel Quad Core right now with very good results. i haven’t testes the other compounds but it is worth mentioning this is the first DIY Thermal compound ever. and while the results of testing may be flawed with his methodology, he as inspired alot of people to experiment and opened this up as world to experiment in!

I again highly doubt your results are correct. Freddyman systematical and reproducibly proved that the inventgeek mix sucks.

You think this was the first DIY thermal compound? People have been playing with making their own TIMs for over a decade.

One thing to you all need to take into account is that article is 3 years old! Why hackaday even published something so old is besides me… When he did it there was no and I repeat “NO†Diamond based thermal compound to compare it to. The author was truly in uncharted territory. He exclusively compared it to arctic silver in his testing. In this new comparative test even the dow compounds are more modern than when this test was done. And Grammar and spelling aside I applaud the author for testing, experimenting and being the first to do anything real with diamond based thermal compounds in a how to article.

One more thing… your results are just as flawed as his are. I know of only one truly scientific study that used the appropriate scientific equipment to determine actual results. Overclockers.com conclusively showed the power of diamond based cooling a year before the InventGeek article. InventGeek even reference it. The article has been ironically removed but is available on the way back machine. So before you go throwing the first stone… remember your testing methods are equally flawed though well thought out. In the words of the original article, “a specially designed and built calorimeter was used. This is a precise instrument that cost about $75,000 to build.â€. Secondly I would never test with or use in construction for test equipment wood. It is a tremendous insulator and with each test you change the thermal characteristics of the material with repeated attaching and seating of your heat sink and smearing of thermal compounds absorbed by the wood. Finally you didn’t even test and compare the actual test they did using arctic silver, so you’re testing is far from conclusive. Unless you reproduce his exact environment you are not proving anything. Though kudos for the efforts!

Archived article referenced
http://web.archive.org/web/200802071.../articles1389/

Original article link
http://www.overclockers.com/articles1389/

I've read that article, and it is completely valid. They are measuring the true thermal conductivity of the TIM's by fixing the gap between the heater and the heatsink. The problem is that in practice, you can't set the gap height between your cpu and your heatsink. You use the clamp provided and hope for the best. If you read one of the first posts I made in this thread, I talk about how different amounts of pressure from your heat sink will cause different results. This test used approximately the same force on all of the thermal greases. If one thinned more than the other and cooled better, then obviously you'd want to use that one as opposed to the grease that is 99% silver and doesn't flatten under your heatsink.

One last note I forgot to mention was that with the inventgeek batch I only mixed by hand just like they suggested in the article. The huge (mm size) clumps in that batch made me realize that I need to mix my own batches more thoroughly.

I actually believe it. The 16 degree drop brings the CPU down to reasonable temps. If it were 30 C idle before and 16 C idle after, then I'd say it is BS. But the grease brought the load temps down from 54 to 38. Sounds believable to me.