Changing Thermal Compounds to Arctic Silver 5

Changing CPU Thermal Compound to Arctic Silver 5

Scope
This article is not intended as a definitive article on how to apply thermal compound. It is a write up of three experiments conducted on a new build, top end 4 core computer.

Preamble
There are several ‘correct’ ways of applying thermal compound depending on what you read and who tells you. Some of the instructions from the manufacturers of CPUs, thermal compounds and heatsinks conflict with each other. It is left to the reader to decide which method they should adopt according to the prevailing conditions.

If you do have conflicting instructions or in any doubt as to which set of instructions to follow, let common sense prevail and bear in mind the following needs of efficient thermal transfer:
* Both mating surfaces must be spotlessly clean, almost clinically so.
* Sufficient compound must be employed to cover the whole of the area of the mating surfaces.
* No air pockets, occlusions or contaminants such as dust, hairs, skin flakes etc be trapped between the surfaces.

Unfortunately, it is very rare for the two mating surfaces to be perfectly flat. CPUs cases are pressed metal and unless specially ground and polished are usually very slightly off being perfectly flat. Heatsinks themselves are not always perfectly flat. This means that if mated ‘dry’, there will be areas of the heat spreader (the surface of the CPU) that will not be in physical contact with the heatsink. There will be minute airs spaces or occlusions between the two surfaces. Not good! (Never mate the surfaces dry. Always use a thermal compound - mention of a 'dry' assembly was to get the reader to appreciate that there are very real, though minute, gaps where the two surfaces are not touching.)

Thermal compound has two primary tasks:
1) To fill and eliminate all airspaces and give 100% cover of the heatspreader and heatsink mating surfaces.
2) To have a low thermal resistance and create a heat conduction layer that will give maximum transfer from the CPU to the heatsink.
Note: Not all thermal compounds are equal.

The New Build.
When assembling a new build machine based on Intel’s Extreme QX6800 quad core processor, a Zalman CNPS9500 heat sink & fan assembly was incorporated as the processor cooling system.
http://www.zalman.co.kr/ENG/product/...ad.asp?Idx=277


Fig 1 - the Zalman CNPS9500 heat sink & fan. It was assembled using the Zalman CSL850 thermal grease that came with the unit.

On completing the build, it was noticed that the core temperatures where a little high. At that time, no specific temperatures were recorded. It was decided to replace the stock thermal grease with Arctic Silver 5 thermal compound.

It was noted that there are conflicting instructions on the methodology of applying thermal grease between Zalman and Arctic Silver Inc. Zalman state putting thermal grease on both the CPU and the heat sink, spreading it thinly across the surfaces before mating the two components together. See the Zalman website. (Link below)

On the other hand Arctic Silver Inc. state that the thermal compound should be applied in a specific manner which will vary depending on the make and technology of processor in question. With the Intel Quad Core such as the QX6800, thermal compound should be applied as a thin bead across the ‘heatspreader’ as per Fig 15.

When the original, Zalman thermal grease was applied, it was done in the same manner as described in Method 1 below.

The Experiments:
To quantify the differences achieved, a record of temperatures 'before & after' were kept. 'Core Temp' programme was used to record and log the various results. The graphs below were generated from the Core Temp log in MS Excel.

Four sets of temperature readings were made:
a) before changing old thermal paste - Graph 1;
b) after applying of Arctic Silver 5 thermal compound as per Zalman instructions - Graph 2;
c) after applying Arctic Silver 5 according to the manufacturer’s instructions - Graph 3;
d) after applying an extra dose of Arctic Silver 5 - Graph 4.

It was also necessary to devise a repeatable process that put a steady stress on the processor but did not push the QX6800 to 100%.

The repeatable stress procedure:
Using Adobe Photoshop CS2, a 3504 x 2336 pixel image was manipulated with the 'liquefy' tool, rotating it in a Twirl . In each test, the same portion of an image was processed and for the same timing. That involves a great deal of processing and vamped up the temperatures on each of the 4 cores nicely.

The timing of the test:
Once the image was loaded into the ‘liquefy’ filter of Photoshop, a pause for a few seconds for temperature to settle. The timing consisted of:
a) activating Core Temp Logging and allow it to log the idle temperatures for 30 seconds, then
b) running the twirl process for 30 seconds
c) waiting a further 30 seconds idle time before stopping the logging.


Fig 2 - Start Image



Fig 3 - Image after 30 seconds of 'twirl'

The process of replacing Thermal Grease:


Fig 4 - The Jeantech case drops down for easy access to the ‘works’.


Fig 5 - Anti-static wrist strap

When working inside the computer ALWAYS use an anti-static strap. The human body can have a static charge of 50,000 volts or more! (Yes, fifty thousand volts) - More than enough to fry the £650 processor or even a single semi-conductor! A strap like the one above can be obtained in any good computer or electronics hobby shop costing about £5. (In the UK: PC World, Maplins. USA: Radio Shack. Australia & NZ: Dick Smiths etc)


Fig 6 - a small container for screws etc.

Without exception, always use a container to put screws and other bits in. Screws etc just lying about on the bench can & will get lost. They can also cause a short circuit if they get loose inside your computer.


Fig 7 - The heat sink removed.

This image shows the old thermal grease. It shows excess compound extruded from the mating surfaces – a bit messy, but it is far better to apply a little too much compound than not enough! Also notice the fluff. This shows that the inside of a computer is a dusty environment. It is essential to take anti-dust/foreign matter precautions while preparing to apply thermal compound. The surface of the heat sink is highly polished. It was later discovered that the surface was very slightly concave. See below.


Fig 8 - The top surface of the QX6800 quad core processor.

This shows the corresponding pattern of old thermal grease. It has to be very carefully removed. Be sure to wear the anti-static strap at all times.


Fig 9 - Cleaning off the old thermal grease

To clean off the old thermal grease, a single drip of turpentine (Turps substitute) on a cotton bud was used to wipe off the old grease. It took several buds to remove it all. These buds can leave behind particles of matter such as cotton hairs. Buds should only be used as a course cleaning method. Extreme care must be taken not to ‘flood’ the surface, only just enough on the ‘bud’ to soften the old paste. It must be noted that whilst turpentine does a good job of shifting the old grease, it should be looked upon as a contaminant and all traces of the turpentine residue must be cleaned off. It is essential that no liquids are allowed to find their way off the top surface of the processor.

Arctic Silver Inc. give warnings about contaminants:
"NEVER use any oil or petroleum based cleaners (WD-40, citrus oil based cleaners and many automotive degreasers) on the base of a heat sink. The oil, which is engineered to not evaporate, will fill in the microscopic valleys in the metal and significantly reduce the effectiveness of any subsequently applied thermal compound."

Although Isopropyl alcohol is recommended for cleaning, ethyl alcohol 90% was used which was at hand. Several cleanings with alcohol were done to ensure a spotless surface.

The heat sink surface was cleaned in a similar manner.


Fig 10 - the cleaned processor

After cleaning, do not touch the surface of either the processor or the heat sink. Make sure that they are kept absolutely clear of dust or other fine debris like hairs or skin flakes etc.
Just prior to applying thermal compound, the surfaces were blasted from an aerosol can of compressed air to ensure no foreign matter being trapped.

Application of Arctic Silver 5 thermal compound:


Fig 11 - Arctic Silver 5 Thermal Compound
Arctic Silver 5 with its unique high-density filling of micronized silver and enhanced thermally conductive ceramic particles provides performance and stability. Arctic Silver 5 is optimised for use between modern high-power CPUs and high performance heat sinks or water-cooling solutions. It contains 99.9% pure silver together with other thermally-enhanced ceramic particles improve the compound's performance and long-term stability.

For full details and specifications, see:
http://www.arcticsilver.com/as5.htm

When in storage, it should be stored in an upright position with the black nozzle protector at the bottom. Preferably in a dark cool place.

Method 1: Zalman way. Arctic Silver 5 thermal compound spread very thinly over both surfaces.


Fig 13 - Arctic Silver 5 spread thinly (as per Zalman instructions)

The instructions that accompany the Zalman heat sink state: “Clean off particles and residue from the top of the CPU. Then spread the included thermal grease thinly on the top of the CPU.”

During the spreading process, much surplus material was removed ensuring just a thin layer making this a wasteful process.

The Zalman instructions are are variance with the instructions dictated by the manufacturer of Arctic Silver 5. The tube of Arctic Silver 5 compound as supplied by the a UK retailer did not contain any instructions.


Fig 14 - The heat sink mating surface.
The instructions on the Zalman website also shows thermal grease being also applied to the heat sink surface also. Again Arctic Silver 5 compound was liberally applied and excess removed during the spreading process thus ensuring only a thin layer as per Fig 13.

When mating the two surfaces together, a gentle downward pressure was applied and at the same time twisting the heat sink slightly to bed it well down and into physical contact with each other. The Zalman Mounting sprung arm applies a constant force once all parts are reassembled.

Temperature measurements were then taken for comparison. See Graph 2

Method 2 - the Arctic Silver Inc. way:

To make ready for this experiment, all trace of the Arctic Silver 5 compound were removed and the processor & heat sink surfaces were cleaned down as per above.

Arctic Silver Inc. instructions on application of the compound:
Different processors and technologies require different methods of applying the Arctic Silver 5 compound. See:
http://www.arcticsilver.com/arctic_s...structions.htm


Fig 15 shows the recommended position of a strip of Arctic Silver 5 compound on an Intel 4 core unit.

Mechanical layout of the Intel 4 core processor such as the QX6800

For the QX6800 processor, a thin strip across the centre as per fig 15 was called for. Cleaning of the CPU and heat sink surfaces was done again.


Fig 16 - A thin strip of Arctic Silver 5 applied in accordance with Arctic Silver Inc. instructions.
"Carefully apply Arctic Silver 5 directly to your quad core heatspreader. Only apply thermal compound to the top of the actual CPU heatspreader and not the heat sink."

On completion of this new application, the stress test was performed. Graph 3 indicated higher temperatures than Arctic Silver 5, method 1.

The assembly was taken apart once more to investigate. It was found that the Arctic Silver 5 compound was not covering the whole of the surface. It was also noticed vertical abrasions in the highly polished surface. These were cause by contact with the CPU an indicated an irregularity of even contact between the two surfaces.


Fig 17 - abrasions & poor spread of the Arctic Silver 5
Arrows indicate abrasions caused by contact of the CPU. Those abrasions coupled with the fact that the Arctic Silver 5 compound had not spread across the whole surface confirmed that the heat sink was quite concave. This indicates how important it is to fill the void with enough compound.



Fig 18 - Zalman heat sink showing the concave surface.

This shows that the surface of the heat sink is very slightly concave. The straight edge is an engineer’s precision steel ruler. This photo demonstrates the importance of using thermal paste to fill any voids between the processor and the heat sink!

Method 3 - slight modification to Method 2

The surface of the heat sink was cleaned down but not the processor. An additional thin strip of Arctic Silver 5 compound was applied to the processor heat spreader.


Fig 19 – Although not really recommended to do it this way, a second bead of Arctic Silver 5 compound applied.

This photograph also shows the points of contact with the heat sink (between the arrows). Basically the vast majority of the processor heat spreader is not in contact with the heat sink! It is only the thermal compound that conducts the heat from the processor to the heat sink. This really does demonstrate the importance of the use of thermal compounds.

The heat sink was reassembled and the stress test was again performed. See Graph 4

Because of the heat sink being slightly concave it is intended to lap the surfaces of both the processor an the heat sink to render the mating surfaces absolutely flat. this will be the subject of another related article.

Graphs:
Each of the temperature graphs below represents a 90 second time period. 30 seconds idle time, 30 seconds ‘twirl’ stressing, followed by 30 seconds idle time. The temperature scale is in degrees Celsius.


Fig 20


Fig 21


Fig 22


Fig 23


Summary:
The instructions for applying thermal grease supplied with the Zalman Unit was at variance with those recommended by Arctic Silver Inc for their Arctic Silver 5 compound. The notes & measurements contained herein were compiled using both methods.

At the end of the day, it must be remembered that the prime objective of any thermal grease or compound is to aid in the transfer of heat away from the processor case to the heat sink.

It is highly likely that the top surface of the processor is not perfectly flat. It is a metal pressing and not a precision ground or machined surface. Likewise, it is likely that the surface of most heat sinks is also not perfectly flat. As a result, when these two surfaces are bought together, there will be a small void or space where the surfaces are not in physical contact with each other. This void, though very small will not conduct heat by transmission. It will introduce a thermal resistance. If this void is not filled with some form of thermal transfer material it will cause a heat build up beyond the safe working of the device.

It is the task of the thermal compound to fill this void or space. The material must be made up with particles small enough to find its way into the smallest of gaps and yet have the ability to efficiently transfer heat from one surface to another.

Note:
During the CPU's initial use, Arctic Silver 5 compound thins out to enhance the filling of the microscopic valleys and ensure the best physical contact between the heatsink and the CPU core. Then the compound thickens slightly over the next 50 to 200 hours of use to its final consistency designed for long-term stability.

On systems measuring actual internal core temperatures via the CPU's internal diode, the measured temperature will often drop 2C to 5C over this "break-in" period

Website references:
A detailed installation manual for the CNPS9500 heat sink in PDF format is available for download at:
http://www.zalman.co.kr/ENG/product/...ad.asp?Idx=277

Arctic Silver 5, the product:
http://www.arcticsilver.com/as5.htm

The detailed instructions for applying Arctic Silver 5 to an Intel Quad Core processor in a pdf form at:
http://www.arcticsilver.com/pdf/appi..._quad_wcap.pdf

Arctic Silver Instructions: http://www.arcticsilver.com/arctic_s...structions.htm

Zalman CNPS9500 product specifications:
http://www.zalman.co.kr/ENG/product/...ad.asp?Idx=277
A detailed installation manual in PDF format is available for download on that web page.
Zalman Instructions (small Flash movie) on their website:
http://www.zalman.co.kr/ENG/product/...up.asp?Idx=164

Core Temp:
"Core Temp" is a neat free utility written by Arthur Liberman. Core Temp can be downloaded at:
http://www.alcpu.com/CoreTemp/

© 2008 DonaldG &  www.techsupportforum.com