What is the density and viscosity of thermal paste?

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Thermal paste is vital for cooling systems used to cool hardware such as GPU or CPU. This acts as an interface between the chip’s IHS and the heatsink, increasing conductivity. On the other hand, despite the fact that it is necessary, many people continue to consider it something unknown, just like some of its properties, such as density or viscosity, are an important thing when choosing the right putty.

What is the density of thermal paste?

Density, as you know, is a physical quantity that measures the amount (mass/volume) of a material present in a given area. For example, a block of lead (Pb) is denser than a material such as foam because lead is much denser than foam, so the density varies. In general, solids are denser than liquids and liquids are denser than gases.

This is not only important for flotation applications, but also for many other factors, such as choosing the right thermal paste.

What is the viscosity of thermal paste?

When you work with thermal paste, you will also see the viscosity of the paste specified. Some are more liquid than others, and this has its pros and cons. For example, thicker or denser thermal pastes may be more difficult to spread across the surface of the chip, while thinner or more viscous ones may be easier to apply but harder to prevent leakage and spreading.

The scientific unit of viscosity is Newton-seconds per square meter, usually expressed as Pascal-seconds (Pa-s) or milliPascal-seconds (mPa-s). 1 Pa-s = 1,000 mPa-s

You can find thermal pastes on the market with viscosities ranging from 300 units to 1500 units. As I said before, it is not good to be too low or too high. Ideally, look for pastes with medium viscosity. In other words, it spreads easily on the surface but does not dry quickly.

How do they affect your productivity?

To finish, we must see how these factors really affect thermal paste. For example:

  • When buying thermal paste, it is important that its density is between 3 g/cm³ and 4 g/cm³. This will prevent it from leaking into the environment or causing short circuits if it is a thermal paste with good electrical conductivity. If its density is high, it will remain more solid and prevent possible leaks.
  • Viscosity varies depending on density. That is, a denser dough will be more viscous, while a less dense dough will be less viscous. The most viscous ones behave like solids, being difficult to spread, but settling better than those with lower viscosity. Those with low viscosity behave more like liquids, as we said before. Therefore, it is necessary to look for a good balance, neither too viscous nor too little viscous.