|33-Way Thermal Interface Material Comparison|
|Reviews - Featured Reviews: Cooling|
|Written by Olin Coles|
|Tuesday, 04 March 2008|
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TIM Testing Methodology
In this comparison review article, it is the sole mission of Benchmark Reviews to test each product in a controlled environment in order to determine the maximum thermal conductivity which therefore translates into the best cooling performance. Almost all of these products have been collected over the past several months, so there will be no specific interest in one particular manufacturer. In our first series of tests, all thirty-three thermal interface materials were compared. Of those TIM's tested, only the top fourteen will move on to the second round of testing. In the third round of testing the top five will be compared.
One of the toughest parts of our benchmarking process was maintaining a temperature-controlled test environment. To establish a stable and consistent ambient room temperature, all of the testing hardware was partitioned off and the room was sealed. While we did our best to operate at exactly the same testing temperature for each product, there were very small fluctuations which resulted in fractional differences inside of one degree. As we progressed into the later stages of testing, the ambient temperatures were much tighter and more controlled.
Probably the most critical step in the testing process was the preparation. Thanks to the team at Arctic Silver, we were able to clean and prepare the surface of six brand-new stock Intel OEM heatsinks and Intel Core 2 Duo E6550 IHS (Integrated Heat Spreader) to a pristine state with their ArctiClean products. While these products are praised by product analysts like myself, they can be equally as useful for anyone who frequently separates the cooler from the CPU or frequently applies TIM material such as extreme overclockers and hardware enthusiasts.
Thixotropy is a term which is sometimes used to describe the property of pseudoplastic fluids to show a time-dependent change in viscosity; the longer the fluid undergoes shear stress the lower its viscosity. A thixotropic fluid is a fluid which takes a finite amount of time to attain equilibrium viscosity when introduced to a step change in shear rate.
As we see progression in the area of Thermal Interface Materials, there has become a substantial increase in the number of manufacturers who embrace thixotropic TIM's. Many of these products make up the newest names on the market, and can be compared to the revelation that the Heatpipe Direct Touch technology has seen in the CPU cooler industry.
Even though nearly all of our TIM products were new, some had been sitting on the test shelf for a many months. Before each test the TIM material was mixed and agitated to ensure proper consistency. Silicon-based TIM's are more susceptible to the breakdown because of dissimilar compound bonds, and should always be mixed prior to use regardless of product age. Newer carbon-enriched silicon compounds seldom exhibit breakdown because of their thixotropic consistency (see definition above). Regardless, all test samples were aggressively mixed prior to application onto the CPU cooler. Once the product was prepared, it was applied onto the surface in a very thin coating and spread evenly.
Benchmark Reviews used the following hardware parameters for all of our test equipment:
Do to the nature of our tests, no single Thermal Interface Material was allowed additional time to cure. Each test session would begin with a motherboard and idle temperature reading, followed by a system restart. Between the idle and load readings, only one thermal cycle was exposed, which would have no realized benefit to those materials requiring prolonged cure times.
Although only a couple of the items tested suggest it (on their website), we understand that certain interface products will exhibit improved thermal conductivity if they are allowed several temperate cycles to expand and contract the material. However, the best method to scientifically test each product was to either allow no cure time, or equal cure time to all test products. Because of the extremely long cure time one particular product recommends, this article would not have been possible if we allowed all test subjects the same benefit.
Arctic Silver II Application Instructions(48-hours minimum curing time recommended)
Arctic Silver 3 Application Instructions (up to 200-hours recommended curing time)
Arctic Silver 5 Application Instructions (up to 200-hours recommended curing time)
Arctic Silver Ceramique Application Instructions (25-hours minimum recommended curing time)
IC Seven Carat Diamond Application Instructions (10-minute evaporation time, 2-hour curing recommended)
In the final step of our testing, the test system utilized Lavalys EVEREST v4.20.1170 to stress all processor cores of the CPU to a point of maximum thermal output. After about four minutes, the processor would usually reach it's maximum heat output; however all of our test timelines last ten minutes in duration. The final maximum temperature is then recorded, and compared against the ambient room temperature for the differential temperature score.
EDITORS NOTE: Benchmark Reviews has published a new article since this one was released, titled Best Thermal Paste Application Methods. This article dicusses the various methods and patterns used on standard and Heat-pipe Direct Touch coolers.