Installing a temperature sensor. Gripcott NF High Temperature Assembly Paste Thermal Conductivity and Thermal Resistance

Nowadays, when almost every house has a computer, and overclocking is no longer something outlandish for many users, real enthusiasts are fighting for every degree - they arm themselves with super-powerful cooling systems, select successful cold copies of processors, organize powerful blowing of their cases, etc. .P. Do not forget about one of the most important components in cooling systems - thermal paste. This material is devoted to testing twelve modern thermal interfaces widely available on the Ukrainian market.

But first, let's dwell a little on theory.

Thermal paste - what it is and what it is used for

Thermally conductive paste is a substance with high thermal conductivity and plasticity used to improve thermal contact between two contacting surfaces.

The lid of any processor and the sole of any radiator has roughness. Even if visually the surface looks well polished and absolutely smooth, it still has irregularities. Yes, on a well-processed surface they can reach only a couple of microns, but this is already enough for air gaps to appear between the processor cover and the heatsink sole. And, as you know, air conducts heat very poorly, that is, the transfer of heat from the processor to the cooler is difficult. In order to improve thermal contact, thermal pastes are used (heat-conducting paste, thermal interface). The point of use is to fill air gaps, since any normal thermal paste conducts heat much better than air.

About applying thermal paste

There is an opinion among some users that the thicker the layer of thermal paste, the better the cooling will be. This opinion is fundamentally wrong! The thermal conductivity of the paste is significantly higher than the thermal conductivity of air, but significantly lower than the thermal conductivity of any metal. For comparison, copper has a thermal conductivity of 390 W / (m K), and the popular domestic thermal grease KTP-8 - only 0.65-1 W / (m K). This means that applying an excessive layer of thermal interface will only worsen the thermal contact between the processor and the cooler. Therefore, you need to apply as thin, even layer as possible.

Thermal conductivity and thermal resistance

Thermal interface manufacturers often indicate thermal conductivity and thermal resistance on the packaging of their products. What do these indicators mean?

Thermal conductivity, as you know, is the transfer of heat by particles (molecules, atoms, electrons) of a substance from more heated to less heated areas of the body. This process takes place until equilibrium is established - until both parts of the substance have the same temperature.

Numerically, thermal conductivity is equal to the amount of heat passing through a material with a thickness of 1 m and an area of \u200b\u200b1 sq. M. per hour with a temperature difference on two opposite surfaces of 1 K. From here, the dimension of the value of thermal conductivity is taken - Watt / (meter · Kelvin).

There is also thermal resistance of a substance, which is the ability to inhibit the transfer of heat. In fact, this value is the reciprocal of the thermal conductivity.

If we talk about the choice of a thermal interface, then the lower the thermal resistance and the higher the thermal conductivity, the better it is. But how reliable the values \u200b\u200bof these indicators indicated on packages with thermal pastes are is another question.

After a short introduction, let's move on to our subjects.
Packaging and description of properties of thermal interfaces

Perhaps the most popular product among thermal interfaces on our market. KPT-8 is produced in accordance with the requirements of GOST 19783-74 and is a thick white mass. Produced on the basis of polydimethylsiloxane liquid and zinc oxide powder. Recently, KPT-8 in such a package "spoiled" - the consistency is excessively thick, grains are often found. The declared thermal conductivity is not less than 0.65 W / (m · K) at +100 degrees Celsius. Working temperature from -60 to +180 degrees Celsius. It is produced by the Moscow LLC "Soldering and Montage". Due to its high viscosity, it is applied and removed with some effort.

An analogue of the previous paste. The manufacturer and the declared characteristics are the same. However, plastic packaging has an obvious plus - thermal paste is much less viscous. This allows it to be applied in a thinner and more even layer. There are also no hard grains. Perhaps it's not about the packaging, but about a specific batch, but three metal tubes from different batches turned out to be equally viscous. Therefore, it was decided to single out KPT-8 in a plastic tube as a separate contestant. This paste is applied and removed quite simply and effortlessly. Allows to apply a thin, even layer.

Supplied in a 2-gram syringe. It is a rather liquid substance of yellowish-gray color. The manufacturer claims a thermal conductivity of at least 2.4 W / (m · K) and an operating temperature range of -50 to +240 degrees Celsius. Very easy to apply and remove.

Produced by the Swiss company Arctic Cooling. Supplied in a transparent plastic bag with a black insert inside. The syringe contains 4 g of the substance. The consistency is very thick, viscous and sticky. It is applied with some effort, but it is possible to distribute in a thin and even layer if you try hard. It is removed from the surface with some difficulty, but the use of a solvent (for example, alcohol) greatly facilitates this process. Thermal conductivity of Arctic MX-2 is not specified in the specifications.

Supplied in a transparent blister package with a silvery cardboard insert, which describes all the key features and shows testing of pastes with a confident victory of MX-4 (who would doubt it). The validity of such testing remains to be seen.

In general, in terms of physical properties, this thermal grease repeats its predecessor MX-2. The color is the same - gray. The declared thermal conductivity is 8.5 W / (m · K), the syringe contains 4 g of paste.

This paste was kindly provided for testing by the well-known Ukrainian bencher MaJ0r - alas, we could not find it on the free market. Arctic Silver Ceramique is the favorite thermal paste of many overclockers using nitrogen for overclocking due to its ability to maintain its thermal conductivity at ultra-low temperatures. Supplied in a 2-gram syringe. There are no specifications on the packaging. White colour. The consistency is quite thick, viscous and sticky. The paste is plastic and well applied to the cooled surface, but due to its stickiness it is relatively difficult to remove.

Thermal grease NT-H1 is a proprietary development of scientists at the Austrian University "Heat Transfer and Fan". It not only comes with the new Noctua coolers, but is also offered as a separate product.

Noctua NT-H1 is packed in a plastic shell with a cardboard insert. Thermal paste is extremely thick, but at the same time quite plastic. Very good application and distribution over the surface of the heat spreader. Removal is just as easy. Temperature range for continuous operation - from 40 degrees below zero to plus 90 degrees Celsius. There is no thermal conductivity data on the packaging.

This sample ended up in our test lab complete with a Megahalems cooler. Sold as a separate product in a blue cardboard box. The syringe contains 4 g of thermal interface. No data on thermal conductivity and other indicators are given on the syringe. The color is gray. The consistency is moderately thick and viscous. Very flexible. The paste is perfectly applied and can be easily removed from any surface.

Supplied in a 2-gram syringe. The color is gray. Dry and not very plastic thermal interface, which is rather difficult to apply to the surface of the heat spreader. When applying thermal paste, it has to be stretched, as it were, over the surface. It is very difficult to apply this paste in a thin, even layer. But, what is nice, the paste is not sticky, so it is still more convenient to apply it, for example, with your finger than MX-2 and MX-4. There is no data on the characteristics on the packaging.

We got a 2-gram syringe for testing from the Thermalright Archon cooler. Chill Factor III specifications - thermal conductivity according to the manufacturer's statement is not less than 3.5 W / (m · K), and thermal resistance is equal to 0.032 K · cm² / W. The color is gray. The consistency is thick and viscous, but very pliable. The paste is absolutely not sticky. It is very easy to apply, and the layer is thin and even. Unlike the first and second versions, this thermal interface is sold as a separate product in 4-gram syringes.

Supplied in a blister pack with a colorful insert showing product characteristics. The declared thermal conductivity is 1.5 W / (m · K), and the operating temperature range is from -40 to +150 degrees Celsius. Gray paste. The consistency is quite runny, but still thicker than the AK-455. It spreads very easily over the surface. Can be easily applied in a thin and even layer. It can be removed just as well.

Zalman ZM-STG2 thermal paste is not only supplied with new coolers, but is also offered as a separate product. The syringe contains 3.5 grams of gray matter. The declared thermal conductivity of Zalman ZM-STG2 is 4.1 W / (m · K), which is 3.5 times higher than the thermal conductivity of its predecessor - ZM-STG1. Thermal resistance - 0.080 K · cm² / W. Operating temperature - from minus 45 to plus 150 degrees Celsius. Thermal paste is thick, viscous and quite plastic, a little sticky. Its properties resemble MX-2 and MX-4, but it is applied even more difficult than the latter. It rolls down quite hard, so it is very, very difficult to apply it in a thin, even layer.

The next section will already be devoted to testing the considered thermal interfaces.
Testing methodology and test bench configuration

Thermal grease testing is a more difficult task than testing coolers. The fact is that the difference between thermal interfaces is not as great as the difference between cooling systems. In addition, the application process itself plays a role - if you apply a higher-quality thermal paste with a thick and uneven layer, then it will lose to a weaker competitor, applied correctly. It is important to create such conditions in which thermal paste will be a bottleneck in the heat exchange between the processor and the cooler. This requires a very hot processor and very powerful cooling. There are no problems with hot processors - an overclocked Intel Core i7-920 will do just fine. But the situation with cooling is ambiguous. On the one hand, it is better to use a water cooling system, as it is more efficient, on the other hand, most of the readers use air coolers. Therefore, testing will be carried out with both air cooling and SVO. In addition, it is necessary to achieve high repeatability of the results in order for testing to be of practical use - for this you need to apply the pastes in the same layer and take several measurements, followed by averaging the results.

Test bench configuration:

• motherboard: ASUS Rampage III Formula (Intel X58 Express);
• central processor: Intel Core i7-920 (2, [email protected], 095 GHz, HT on, VCore 1.36 V);
• cPU cooling system 1: Thermalright Archon (2 x TY-140 at 1300 rpm);
• cPU cooling system 2: CBO based on XSPC Delva v3 processor water block, Laing D5 Vario pump (MCP655), Black Ice GTS240 radiator, four Zalman 1000 rpm fans and Magicool reservoir;
• rAM: OCZ Gold DDR3 3x2 GB;
• video card: GeForce 8600GT;
• hard drive: Western Digital WD6401AALS;
• power supply: Zalman ZM1000-HP (1000 W).

Testing was carried out on an open bench at an ambient temperature of 23 degrees Celsius. The processor was warmed up in the Windows 7 Ultimate Edition x32 operating system using the LinX 0.6.4 program (test cycle of 10 Linpack passes in each cycle with 1792 MB of RAM used). The CoreTemp utility and Everest Ultimate Edition were used for temperature monitoring.

All thermal pastes were applied to the processor cover in the thinnest and most even layer possible. For each tested thermal interface, the application was carried out three times with intermediate cleaning with alcohol of both surfaces.

Test results

For ease of viewing, the test results have been grouped into two graphs depending on the cooling system used. The pastes are ranked from worst to best.

So, analysis of the results. Six products immediately stood out in the group of high-performance thermal pastes: Zalman ZM-STG2, Thermalright Chill Factor III, Arctic Cooling MX-4, Noctua NT-H1, Arctic Cooling MX-2 and Prolimatech PK-1. Next came the mid-range Thermalright Chill Factor 2 and Arctic Silver Ceramique. Ineffective solutions close the circle - Thermaltake TG-2, Akasa AK-455 and KPT-8 (plastic).

KPT-8 (metal) turned out to be an absolute outsider. We generally do not recommend using such thermal paste. The lag behind the leader by more than 15 degrees is not even compensated by the cheapness of the product.

conclusions

So, we have tested twelve thermal interfaces. As it turned out, not all of them are equally effective. The difference between the best and the worst of the contestants was over fifteen degrees Celsius. This is quite a lot even for non-overclocking users, let alone extreme overclockers.

Be sure to pay attention to the fact that the declared characteristics of the products are very different from the real ones. The test results clearly demonstrate how the MX-4 thermal paste with a declared thermal conductivity of more than 8 W / mK loses, albeit slightly, to the cheaper Zalman ZM-STG2. The passport thermal conductivity of the latter is in the region of 4 W / m · K. Therefore, you should not blindly trust what is written on the packaging. If you want to choose the really best thermal interface and get a few more cherished degrees, then it is better to read the reviews and see the test results.

Also, products from different manufacturers differ significantly in the application process. If you assemble your computer once for long-term use, then you can suffer with a viscous and sticky thermal interface. But if you have to change the cooling often, then it is better not to waste extra time and pay attention to thermal pastes, which are easier to apply. Of the products we tested, Noctua NT-H1 and Thermalright Chill Factor III meet these requirements - one of the high-quality thermal interfaces.

The most effective paste was Zalman ZM-STG2. With an average cost in Ukraine of $ 5, this product demonstrates excellent thermal conductivity, and it can be safely called the best buy!

Testing equipment was provided by the following companies:

• 1-Incom - Prolimatech PK-1 thermal paste;
• Arctic Cooling - Arctic Cooling MX-4 Thermal Paste
• ASUS - ASUS Rampage III Formula motherboard;
• Eletek - Zalman ZM-STG2 thermal grease
• Noctua - Noctua NT-H1 thermal paste;
• Thermalright - Thermalright Chill Factor III thermal paste and Thermalright Archon cooler.

Sometimes questions arise about the time-tested thermal paste KPT-8 - To what temperature can it be used? You can answer this question by trying KPT-8 thermal paste at different temperatures.

To check the temperature resistance of the thermal paste, you will need:

Heat-resistant and heat-conducting dishes;

Two-channel temperature meter with heat-resistant sensors on the wires;

We use a tin can as thermal dishes. Let's put it on the tile. We stick the temperature sensors into the paste, but not completely. Thermal paste must transfer heat through itself. As soon as it stops transferring heat, we will register a drop in temperature, for no apparent reason, and at this temperature, we can say that the thermal paste no longer works like thermal paste. We turn on the tile.

18 gr. Celsius everything is fine.

100 degrees. The temperature rises quickly enough. With thermal paste, no changes are even planned.

200 degrees. No changes are visible. The paste is shiny - this is a good sign. Both tube and syringe thermal pastes look equally good.

270 degrees. A barely noticeable light smoke appeared, the thermal paste has no changes. Unfortunately, the haze is not visible in the picture. This indicates that the changes are extremely insignificant.

350 degrees. There is a steady stream of smoke, the thermal paste loses its plasticity in places. But it continues to transmit heat. She works!

400 degrees. Thermal grease continues to smoke ... and work!

At a temperature of 270, a light smoke reminded us that the silicone base says goodbye to us and the thermal paste gradually ceases to be a paste. Its further fate will be clear at high temperatures. Indeed, at a temperature of 350 degrees Celsius, the smoke becomes quite noticeable and this suggests that at this temperature the life of the thermal paste is very limited.

In the end, after a long smoke release, KPT-8 thermal paste only partially lost its plasticity. No sharp drop in temperature expected due to the deterioration in thermal conductivity was found. This means that the thermal paste retained its heat-conducting properties, partially losing its plasticity.

It is absolutely safe to use thermal paste at temperatures up to 200 degrees with short jumps up to 300. Thermal paste that has been operated at temperatures from 200 to 300 degrees cannot be reused.

Where thermal grease is applied at high temperatures.

In electronics, the most common task today for transferring heat using thermal paste is computers. There are two main heat sources in computers that require cooling: the processor and the video card. They constantly compete to generate heat. In desktop, gaming computers, the video card wins. In office computers and laptops, the processor wins. The maximum temperature of modern video cards is 105 degrees. This data is for NVIDEO GeForce video cards. And then only one card - the bulk, models of this company, no more than 90 degrees.

The same picture is with processors. I know of only one processor with a maximum temperature of 110 degrees Celsius - the Athlon Mobil. Modern Intel i7 2600 heats up to a maximum of 72 degrees. The tendency is that processor transistors do less, and they consume less currents, and therefore they heat up less, and the number of transistors in the crystal is constantly increasing and the total heat generated by them, respectively, grows. These two processes, plus little power-saving tweaks, balance each other out in processor temperatures. We can say that with the development of technologies, the temperature of processors does not change much anymore.

However, it should be noted that due to the active proliferation of laptops and other mobile devices, there is a trend towards lowering temperatures. Today it is issued by manufacturers as a sign of the modernity of the processor. Thus, to sum up, the maximum temperature in computers is 110 degrees, and most likely, in the future it will only decrease.

Another consumer of thermal pastes is transistors and diodes. To control high power, a semiconductor element base is created for operation at high power. These semiconductor devices dissipate a lot of excess energy and are therefore subject to a lot of heat. For them, the task is to transmit controlled power through the same device. Therefore, they are taken in the area of \u200b\u200bhigher temperatures. Modern crystals, some transistors, can heat up to 500 degrees Celsius, and common ones up to 175-200 degrees. But here you need to understand that the area of \u200b\u200bthe crystal is small, but it lies on a metal substrate 100 times larger and the temperature on the substrate is 2-5 times lower than on the crystal. Thus, the real temperatures at which the paste will work will not exceed 200 degrees Celsius. This temperature will be only if the transistor operates at a temperature of more than 200 degrees Celsius. I asked the suppliers of transistors about the 500 degree transistors and got the question: "Why?" Here's what I was told: "What developer would set himself the task of designing a circuit with such a low efficiency?" In other words, no one simply orders such transistors, due to the lack of a market for them. We can say that a temperature of 150-170 is most likely all that thermal paste will have to deal with in semiconductor devices.

The new fashion of anti-icing has created another niche for the use of thermal paste - thermal cords. The thermal cord is such a heating cable. Most often it is used for floor heating, but we are more interested in heating pipes and barrels. For this, thermal cords are used that can heat up to temperatures of 90 degrees. In order to heat not the air but the pipe, the contact is coated with thermal paste.

Basically, these are all the main areas of application of thermal paste. From this we can conclude that, in general, the use of thermal pastes is in the zone up to 110 degrees and sometimes reaches 170 degrees.