Page 1:Introduction & Overview
Page 2:Interaction Of The Heat Spreader & Heat Sink
Page 3:Thermal Paste: How It Works & How You Should Apply It
Page 4:Special Case: Cooling Your Graphics Card
Page 5:Special Case: Thermal Pads & Backplate Cooling
Page 6:Liquid Metal & Its Limits
Page 7:Test Setup & Measurement Methods
Page 8:Results: Closed-Loop Liquid Cooler; High Mounting Pressure
Page 9:Results: Air Cooler; High Mounting Pressure
Page 10:Results: CPU Air Cooler; Low Mounting Pressure
Page 11:Results: Air-Cooled GPU; Medium Mounting Pressure
Page 12:Results: Viscosity
Page 13:Results: Usability
Page 14:Summary & Conclusion
Special Case: Cooling Your Graphics Card
If you want to know more about improving your graphics card's thermal performance, check out How To: Optimizing Your Graphics Card's Cooling.
Lose The Goop! Start With A Proper Cleaning
Various methods are used to apply thermal paste to graphics cards. Often, paste is applied directly to the heat sink by the cooler manufacturer (via screen printing, pad printing, or using soft pads off a transfer film), or a certain portion of liquid paste is applied later during the marriage of the heat sink to the board. However, almost all manufacturers overdo it with thermal paste, and in the case of our test subject, the result is messy.
Apparently, thermal paste was applied in such abundance that even half of the package was filled as well. While this makes no sense as far as temperatures are concerned, at least it isn't dangerous. Simple silicone-based pastes are generally non-conductive, and thus there is no chance of causing a short-circuit.
Nevertheless, a thorough clean-up is advisable. As a first step, we recommend using a soft cloth to remove all residue that can easily be wiped off without additional (chemical) aid. When cleaning the heat sink, pay attention to the grating, as remnants of the old thermal paste are easily left behind in the various grooves. This is also true for the surface of flattened heat pipes.
It is important to ensure that those surfaces are thoroughly cleaned because mixing different pastes can be extremely counterproductive. Specialized shops sell cleaning kits for this purpose, but even isopropyl alcohol (2-propanol) will do the trick. It's available on Amazon and at various pharmacies, and usually sold for about two or three dollars per sixteen ounces. It is advisable not to use methylated spirits. And totally unsuitable for the task at hand are acetone cleaners, nitro-cellulose thinners, and nail polish remover. While the latter may also be based on 2-propanol, it often contains other unfavorable additives as well.
Be careful when you're cleaning the GPU package. Avoid scraping or scratching. Even forceful rubbing with a soft cloth can damage the fragile hardware if a certain amount of pressure is exceeded. Whatever remnants are unwilling to part freely are better left alone. Only the GPU itself needs to be polished to a high gloss.
Perfect Application Of The Correct Thermal Paste
What makes a paste "correct," anyway? The Internet is full of dubious tests, many of which contradict each other. In fact, any benchmark that ignores the change in fan speeds after modification, or doesn't look at the temperatures of other on-board components are more or less useless.
Except for water cooling, which doesn't need a fan, control mechanisms like AMD's PowerTune and Nvidia's GPU Boost ensure that the GPU's thermal behavior significantly affects fan speed, voltage regulation, and of course clock rate. So, even if the measured temperatures appear the same, the card may suddenly be holding a higher boost frequency for a significantly longer time, the fans may rotate slower, or both. Furthermore, a lower GPU temperature, and thus a reduction of fan activity, can result in a higher thermal load on other components.
The minimum burn-in time necessary for a new application of paste to reach its peak performance is another issue that is rarely taken into account. We have thus allowed all our thermal pastes to "burn in" over a total operating time of 24 hours each. Of course, this prolongs our measurement window, but the extra effort is worthwhile.
Since we generally prefer the "blob" method, and like to tighten the GPU heat sink's four screws crosswise, the choice of an appropriate paste actually is the most important task. To recap, a lentil-sized blob is more than enough, and it is absolutely okay if a little bit of paste leaks at the sides once the screws are tightened. It's better to be generous than to create empty spaces with no paste at all. Once your burn-in period is completed, it might be a good idea to check whether the four screws need to be re-tightened.
In addition to the paste's basic properties, such as high thermal conductivity (low thermal resistance), its consistency also plays an important role. In the hands of a professional, thermal pastes with high viscosity (like diamond pastes) can be a perfect weapon to battle excess heat. However, for less experienced modders, they're often unpredictable and difficult to handle. To achieve the perfect result with a highly viscous paste, you have to preheat the paste, warm up the heat sink to somewhere between 60 and 70°C, apply the right amount of paste to the sink, and then screw it all back together before the product cools down.
These two images show that the above pictured blob was sufficient, and hardly any of the product got spilled. Furthermore, the image shows a thin and uninterrupted layer of thermal paste across the GPU, which goes to show there's no reason to fumble with a spatula.
Now it's time to talk money. Not everything that is expensive and/or boldly advertised is suitable for the job. When testing under similar conditions, and by taking fan activity into account, the results reveal relatively small differences. This disqualifies many products due to an unfavorable cost-benefit ratio.
MORE: Best CPU Cooling
MORE: All Cooling Content
- Introduction & Overview
- Interaction Of The Heat Spreader & Heat Sink
- Thermal Paste: How It Works & How You Should Apply It
- Special Case: Cooling Your Graphics Card
- Special Case: Thermal Pads & Backplate Cooling
- Liquid Metal & Its Limits
- Test Setup & Measurement Methods
- Results: Closed-Loop Liquid Cooler; High Mounting Pressure
- Results: Air Cooler; High Mounting Pressure
- Results: CPU Air Cooler; Low Mounting Pressure
- Results: Air-Cooled GPU; Medium Mounting Pressure
- Results: Viscosity
- Results: Usability
- Summary & Conclusion