Thermal Paste, Part 1

Thermal Interface Material, more commonly referred to as TIM or thermal paste/grease, is something that every enthusiast works with on a regular basis. It is undoubtedly one of the most controversial and heavily debated topics. Loyalty runs high as is the case with most brands in the enthusiast market and almost no one agrees with each other.

There are many things that factor in when talking about TIM, but for the sake of this blog we are going to talk about the basics at a bird’s eye view. In this and future blogs, we will discuss more in depth the various aspects of:

• Types
• Brands
• Application
• Cure Time
• Thermal Conductivity
• and more…

Types

There are 4 major types of TIM that are effective for use with CPU:

Thermal Grease: This is very basic stuff. You can usually find this included with low end heatsinks in some small plastic squeeze packaging. It will work, but it doesn’t really perform with a thermal conductivity of less than 1W/mK

Ceramic Thermal Compound: Ceramic thermal compound is a bit harder to work with and a little bit better than the basic grease. Its based on aluminum oxide and boron nitride. Performs at about 4W/mK.

Copper Thermal Compound: Not often used due to the relatively low cost of the silver stuff, but copper is next in line for top thermal conductors behind silver. It is very workable and performs at about 4.5W/mK.

Silver Thermal Compound: Easily the most commonly utilized paste amongst enthusiasts, itcontains particles of silver, zinc oxide, boron nitride, and aluminum oxide in an polysynthetic oil gel. It performs very nicely at around 8W/mK.

There are some advanced thermal solutions such as liquid metal, thermal pads, carbon nanotubes, and phase-change metals. There are various problems with these that make them unsuitable for CPU use. Thermal pads are usually used for DIMMs and other components with stick-on heat sinks. Liquid metal TIMs have a high electrical conductivity, carbon nanotube TIM is still under development and phase-change metal pads simply boils down to performance.

Brands

The thermal interface material market is very saturated with competition. I could type them all out, but it would take up several pages and ultimately there is a smaller list of more trusted brands.

Application

The wrong wayThis topic is so broad that we will actually have to cover the application of TIM in a future blog. For a brief overview, I can say that it truly does matter how you apply TIM. The purpose of TIM is to fill those small imperfections in the surface of the cooler and processor and only those imperfections. Too much TIM is a bad thing.

Engineering tells us that the difference between 1mm and 2mm is significant to nearly 1 degree Celsius per 100W. This is significant when you are comparing cooling solutions and the results are within a degree or two. Thus, it is important to make sure you have enough TIM, but not so much as to inhibit the thermal conductivity. Metal to metal conductivity is much higher than that of TIM. So it should be a nice thin layer between the cooler and the CPU as to only fill the microscopic imperfections in the surface of the metal.

The various methods of application include spreading, dot, line, double line, smiley face, and many more. Here at Asetek, we spread a thin layer of thermal paste. In a future blog we will measure the performance difference between all these methods.

Cure Time

Cure time is the time it takes for the product to set or reach its actual operating potential. Thermal paste commonly take a few hours of cure time which means that the performance will actually increase as the paste begins to set. After the cure time is complete, the thermal paste is operating at its best. One of the reasons we like using Shin Etsu is that it has a very low cure time. This means the paste gets to its peak performance very quickly. We’ll observe and test cure time in a future blog.

Who’s the best?

Honestly, as I said before, there are far too many out there to declare a single winner. There have been countless reviews on large roundups. One of my favorites is this 80-way shootout done by BenchmarkReviews.com. However, time after time, Shin Etsu finds its way into the top performer category. In fact, it is widely respected and trusted as enthusiast class thermal paste. This is the very thermal paste that comes pre-applied on all Asetek liquid coolers. We make products for the enthusiast and we don’t mess around when it comes to the details. You can trust that our thermal paste is no generic, but the real deal and top performer.

Until next time,
Stu