What is thermal conductivity?

Since thermal conductivity is the mainstay of cooling in computing, it is essential for manufacturers of processors, heatsinks, graphics cards, and liquid cooling kits. We explain in depth scientifically what thermal conductivity is and all the details of this concept.

We are not physicists or chemists, but we have enough science and technical knowledge to understand the basics of component cooling. And meanwhile, it is necessary to explore the fundamentals of thermal performance, emphasizing the importance of said property in compounds. We will come across thermal paste and it is closely related to it.

What is thermal conductivity?

It is the physical property that determines the capacity of a material to transfer heat by direct contact. The unit of measurement is Watts per Kelvin (W/m K). This magnitude is equivalent to Joules, calculating J/m.s.K (meters per Kelvin).

It occurs through molecular agitation and contact. Heat progresses in a temperature gradient (from high to low). It starts from the high temperature and high molecular energy region. It reaches a colder region and lower molecular energy.

You can see that there is a constant and cyclical transfer where thermal equilibrium is attempted. Therefore, it is very important to have a good heat transfer rate. The aim is to transfer heat slowly.

For example, in overclocking the CPU, the processor is requested to be as cool as possible, and this is achieved by rapid heat transfer. But how do we ensure that heat is transferred quickly? It has high thermal conductivity thanks to high performance thermal paste.

What does the thermal conductivity of a material depend on?

When we talk about a material and its thermal conductivity, we have several factors that depend on it:

  • Temperature gradient
  • Material properties
  • Length of path taken by heat

However, it is important to know which materials are more and less conductive:

  • Thermal conductivity (W/m K)
  • Material
  • 5000
  • Graphene
  • 2000-2200
  • Diamond
  • 429
  • Silver
  • 385
  • Copper
  • 314
  • Gold
  • 205
  • Aluminum
  • 109
  • Brass
  • 79.5
  • Iron
  • 50.2
  • Steel
  • 0.8
  • Glass
  • 0.8
  • Concrete
  • 0.12-0.04
  • Wood
Scroll left for the entire table.

Of these materials, graphene or diamond will almost never be used to dissipate heat in everyday life, with copper and aluminum being more common for this purpose. So what do we do with materials with low thermal conductivity? You can use them for homes, offices, etc. We can use it to isolate.

For insulation, not only the material used is important, but also the type of enclosure we use. On the contrary, materials that are heat conductors are used in kitchen utensils, refrigerator cooling, powerful equipment, etc. is used.

How to understand whether the thermal conductivity of the thermal paste is high?

Basically, its application in computing concerns thermal pastes or thermal pads. The first is a compound that results from a mixture of conductive materials applied over the CPU’s IHS that serves to transfer heat from the heatsink to the CPU.

When does a paste have high thermal conductivity? We can say that there is a high conductivity in thermal pastes above 8 W/m K, a value that is not easy to obtain in all thermal pastes. To save you from searching one by one to check their conductivity, we can say that there are 3 types of thermal paste:

  • Ceramic. They are the ones with the lowest conductivity, acting between 3 and 6 W/m K, characterized by not conducting electricity and being safer than others. It is easy to distinguish by their whitish color.
  • Metallic. In its mixture there are metals with silicon, which has a much higher conductivity: they can reach 13 W/mK.
  • Liquid metal. This product is not sold, but thanks to the components used, they achieve a record conductivity of 80 W/m K.

Of all the aforementioned, the most dangerous is the liquid metal, because when heated it becomes very liquid and is also an electrical conductor. Therefore, it is not sold at retail as it is not very simple to apply and maintain and must be handled by professionals.

Finally, we have the Thermal pad alternative, which surprises many with its thermal conductivity of up to 35 W/m K. Not all heating pads have this conductivity, but those that achieve these values ​​are made of graphite. For those who don’t know, graphite is such a conductive material that it was used in nuclear reactors (although the Chernobyl accident was related to a graphite-related design flaw).

In general, metallic thermal pastes contain zinc oxide in most cases. You have to distinguish between being electrically capacitive and being electrically conductive.

While there are many electrically capacitive metallic thermal pastes, a few models are electrically conductive. When in doubt, it is always better to look for information about the thermal paste that interests you before buying.