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Written by Olin Coles   
Monday, 21 April 2008
Table of Contents: Page Index
Best Thermal Paste Application Methods
Mounting Pressure and Finish
Thermally Conductive Element Reference
Application on Round-base Coolers
Application on Square-base Coolers
Application on HDT Coolers

Thermal Paste Application

Over the past several months, I have read an unreasonable number of discussion forum posts which offer inaccurate and often times incorrect information. It's not really all that surprising to read poorly conceived information on the Internet, which seems to be an anonymous means of passing off opinion for fact. As a general rule we don't let too many things go untested, and the advice of wanna-be experts is not doing the hardware enthusiast and overclocker community any good. In this article, Benchmark Reviews dispels myth and establishes fact on the topic of proper application of Thermal Interface Material.

These days, Intel and AMD are producing very efficient central processing units that put out far less heat than prior generations. The CPU powering my primary workstation uses the Intel E8200 processor, which is rated for 65 watts using the 45 nm fabrication process. The constant production refinement has allowed the new 2.66 GHz E8200 to operate at the roughly the same Thermal Design Power (TDP) of an old P4 HT 2.66 GHz, but at the same time offer multiples more performance power. The trend of power efficient central processors is slowly making its way into graphics processors, too. The lesson we are learning in 2008 is that size matters, except that instead of skyscraper sized CPU coolers we are trying to reduce the footprint and shrink the area consumed by our systems.


After discussing this topic with real industry experts who are much more informed of the process, they offered some specific advice that didn't appear to be a "one size fits all" answer:

  1. CPU Cooling products which operate below the ambient room temperature (some Peltier and Thermo-electric coolers for example) should not use silicon-based materials because condensation may occur and accelerate compound separation.
  2. All "white" style TIM's exhibit compound breakdown over time due to their thin viscosity and ceramic base (usually beryllium oxide, aluminium nitride and oxide, zinc oxide, and silicon dioxide). These interface materials should not be used from older "stale" stock without first mixing the material very well.
  3. Thicker carbon and metal-based TIM's may benefit from several thermal cycles to establish a "cure" period which allows expanding and contracting surfaces to smooth out any inconsistencies and further level the material.

The more we researched this subject, the more we discovered that because there are so many different cooling solutions on the market it becomes impossible to give generalized advice to specific situations. Despite this, there is one single principal that holds true in every condition: Under perfect conditions the contact surfaces between the processor and cooler would be perfectly flat and not contain any microscopic pits, which would allow direct contact without the need for Thermal Interface Material. But since we don't have perfectly flat surfaces, Thermal Material must fill the tiny imperfections. This is where our testing comes into play.

In the next few pages, which we plan to adjust and refine as necessary to meet with industry product changes, Benchmark Reviews will test several different methods of applying Thermal Interface Material to cooling equipment. The object here is simple: define the best methods to apply thermal paste, primary to central processing units. This guide will also be the first of its kind to test the proper application of material on a Heat-pipe Direct Touch (HDT) cooler, which requires a little more attention.



# ChampMark 2010-08-12 22:20
Thanks for this mate. It's made installing HDT coolers much easier for me.
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# RE: Best Thermal Paste Application MethodsJay 2010-09-30 06:09
Thanks Benchmarkreviews for this is a very informative article.
This kind of quality reviews makes it a lot easier for enthusiasts, like me, which do not have much resources for us to try such tests.
Thanks again... and i hope for more quality reviews from you guys..
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# Thanks for your work!Wilson 2010-10-31 12:09
Thank you for researching and publishing your work on applying thermal paste. I don't have a HDT heat sink, but the design is exactly the same as the Cooler Master Hyper 212 Plus Direct (blah blah the name is sooooo long).

Thanks Again!
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# Excellent Article!Twisted 2010-11-02 20:15
Thank you for a well written and presented article. I recently purchased a Xigmatek 'Red Scorpion' cooler to replace my stock Intel LGA775 cooler. Now I know how to best apply the paste! Also, my Red Scorpion was supplied with the white thermal paste, thanks again for explaining what these compounds are made from. I will throw out the white paste and get some that has a high silver content.
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# ExcellentMohammad 2010-12-01 20:15
Very well done. Just today I took apart a 212+ and noticed the truly pathetic contact I'd achieved using the Arctic Silver-recommended 'single line' method.

Definitely going this route next time.
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# Heatpipe Directional OrientationJim 2010-12-28 20:13
Olin, under the section "Heatpipe Directional Orientation" are you stating that it is better for the CPU cooling fan to point toward the top of the case, rather than front to back? I would think this would be true for PC cases that have the PSU mounted on the bottom of the case, and have a fan at the top, blowing outward. The new Lian Li PC-A04 case is a perfect example of this. Can you comment? (Thanks!) Perhaps a picture would be helpful here.
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# CorrectionJim 2010-12-28 20:28
In further reading, I realize that I didn't catch what you were explaning. I do understand what you are saying now. But my additional point/question is still relevant. If you take a look at the Lian Li PC-A04 case, wouldn't it make sense to re-orient the CPU cooler towards the top of the case? (They actually do not include a rear fan.) I would think that a vertical orientation of the heat pipes, along with a bottom to top fan direction would be optimal, considering that hot air rises.
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# CorrectionJim 2010-12-30 10:45
Correction: I would think that a horizontal orientation of the heat pipes, along with a bottom to top fan direction would be optimal, considering that hot air rises.
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# RE: CorrectionOlin Coles 2011-01-01 10:05
As you've stated, heat rises. Additionally, despite capillary action gravity still affects the heat-pipe fluid. It's best to orientate the heatsink so that heat-pipes are either level or collecting fluid at the base.
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# EarthwormJimEarthworm Jim 2011-03-29 15:15
Assuming that "BB" size is equal to 4,57 mm and "BBB" to 4,83, and as "LGA775" is 37,5 x 37,5 millimetres, and on the picture with the peas the pea is approximately 1/3rd of the diameter which results in 12,5 mm. which is 1,25 cm I do arrive to the conclusion that in you country agronomy is really advanced. In my country peas are generally around half a centimetre, which make them BBB size and almost BB size. So, in conclusion, the community
is still as keen as it thought, or in other words, it is not mistaken - your peas are mistaken ( they are really f***** up ;) ). I do hope this is cleared out, and I do hope that somebody confirms the size of the peas on the picture, based on my assumptions!
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# RE: EarthwormJimOlin Coles 2011-03-29 15:31
These were frozen peas, and they are slightly larger than a pencil eraser. In the photo, that bit of thermal paste was roughly half the mass of a BB, and it covered the entire contact base on an old LGA775 cooler.
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# Peas and such...StressLess 2011-08-13 16:52
The peas being referred to by the term "the size of a pea" (and in the fable "The Princess and the Pea") are the peas you make pea soup out of, which are dried peas. Dried peas are much smaller than frozen peas, about the size of the TIM you used in the now infamous frozen peas picture. But instead of peas, I had heard the amount to place was the size of a rice grain which also works and is less confusing.

On a different subject, I would liked to have seen the results of mounting the square cooler that you did a thin, even spread of TIM on. How did it look when removed?

Also I would like to see heat readings from all these different application methods. While you may want one or the other spreads visually, how does that translate into actual practice? Could less coverage translate into a thinner layer that increases metal to metal contact, yielding better results than 100% CPU coverage but thicker layer? Inquiring minds want to know!!
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# RE: Best Thermal Paste Application MethodsEarthworm Jim 2011-03-29 15:16
Still, thanks for the knowledge!
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# Hyper 212#3 2011-04-13 17:38
When using the line method with the thermal 212+ would I need two lines or three (since it has 4 copper pipes?
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# RE: Hyper 212Olin Coles 2011-04-13 17:43
Three. The number shall be three.
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# Meaning of the following statementMohan 2011-07-28 00:22
"it is important to fill the channels level with thermal compound so that the the additional material may spread somewhat unrestricted to the edges"

now what is 'channels level' we are talking about here?
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# RE: Best Thermal Paste Application MethodsMoto Psycho 2011-07-28 07:09
^Where you have pipes on the heatsink base, there are tiny dips as the surfaces meet, the base is not 100% flat, therefore it is vital that you ensure these channels are filled with paste to properly conduct the heat away from the processor
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# hands claplacky 2011-08-14 20:39
thanks for that. great job.
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# Deep HDT pipes?Traveller 2011-09-04 11:15
Hi Olin. I found your article to be extremely informative, thanks. I was wondering if you could shed some further light on whether or not failure to sand down an HDT cooler would make any significant difference for a pc that is never going to be overclocked at all. I would particularly appreciate your views on the Coolermaster Hyper TX3 cooler, which looks as if the the pipes are set too deep into the mounting base. See links below. x3/8.jpg

After having read your article, I have concluded that the two drops on the two centre partitions of the mounting base would be the best option for the Hyper TX3 cooler (to be used with an AMD Phenom II x6 1100T CPU), however, if sanding is not carried out, how would one deal with the space between the deeply set pipes and the CPU surface? Also, I have read that even merely touching the metal with a finger can cause grease and all kinds of particles to become stuck to it, so if sanding were to be carried out, how could one possible ensure that the cooler is thoroughly cleaned of all the residue from sanding? Thank you for any advice.
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# RE: Deep HDT pipes?Olin Coles 2011-09-04 12:00
Why would you ever sand/lap the surface of a CPU/heatsink that isn't going to be heavily overclocked? Almost any aftermarket cooler can handle stock voltage loads.
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# RE: Deep HDT pipes?Traveller 2011-09-05 06:54
Ok Olin, thank you for clearing that up. I'm new to all of this and didn't know if the sanding was recommended for 'normal' use or not.
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# RE: RE: Deep HDT pipes?Olin Coles 2011-09-05 10:31
Just use a thin amount of thermal paste over the CPU, and make sure to mount the heatsink as firmly as possible. This alone will give you more cooling performance than required.
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# RE: Deep HDT pipes?Traveller 2011-09-05 11:24
Is that in addition to the two drops on the two centre partitions of the cooler or only on the CPU? In either case, shouldn't I still be filling the channels on the cooler base? Thanks.
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# RE: RE: Deep HDT pipes?Olin Coles 2011-09-05 11:44
You can apply two drops, or you can use a clean finger to spread a very light film over the top of the CPU. I prefer to apply a thin film.
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# RE: Deep HDT pipes?Traveller 2011-09-06 06:47
Ok thanks for the advice, Olin.
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