What are the performance indicators of thermal conductive silicone grease

Thermal conductive silicone grease is a high thermal conductive insulating organic silicone material that rarely solidifies and can maintain its paste state when used for a long time at temperatures ranging from -50 ℃ to 200 ℃. It has excellent electrical insulation and thermal conductivity, as well as a low degree of ionization (approaching zero), and resistance to high and low temperatures, water, ozone, and climate aging.

The difference between silicone and silicone grease
Silicone and silicone grease are both materials that help with system heat dissipation. The difference is that silicone has good thermal conductivity and insulation properties, and will not lose its viscosity at higher temperatures. It is mainly used to stick heat sinks on the surface of equipment; Silicone grease, on the other hand, does not have viscosity and is an emulsion or paste. Its function is to fill the gap between the chip and the heat sink, improving thermal conductivity efficiency. Nowadays, many high-end fans have already been coated with thermal conductive silicone grease at the bottom, which is dry and different from the commonly used paste and emulsion liquid silicone grease.
 
But many people who have used thermal conductive silicone grease have discovered a phenomenon: why does the thermal conductive silicone grease purchased by others last so long without curing, while the one purchased by oneself solidifies and becomes powder after some time? What is the reason for it? Below, the editor will introduce several factors that affect the performance of thermal conductive silicone grease.

1. Working temperature
The working temperature of thermal conductive silicone grease is an important factor that leads to the curing and aging of thermal conductive silicone grease. The working temperature is an important parameter to ensure that the thermal conductive material is in a solid or liquid state. If the temperature exceeds the temperature borne by the thermal conductive silicone grease, the silicone grease will be converted into a liquid as a result. If the temperature is lower than the minimum temperature of silicone grease, it will transform into a solid due to the increase in viscosity. Both of these situations are not conducive to heat dissipation.
2. Thermal conductivity coefficient
The thermal conductivity coefficient of thermal conductive silicone grease is the same as that of a radiator, and its unit is W/m.K. The larger the thermal conductivity coefficient value, the faster the thermal conductivity speed of the material, and the better the thermal conductivity performance, which is a performance indicator.
3. Thermal resistance coefficient
The thermal resistance coefficient refers to the obstruction effect of an object on heat conduction, and the concept of thermal resistance is similar to that of resistance. The lower the thermal resistance, the lower the temperature of the heating object and the magnitude of thermal resistance is closely related to the material used for thermal conductive silicone grease.
4. Dielectric constant
Compared to some CPUs without metal top protection, the dielectric constant is a very important parameter, which is related to whether there is a short circuit problem inside the computer. The commonly used thermal conductive silicone grease uses materials with good insulation, but some special silicone greases, such as silver-containing silicone grease, have a certain degree of conductivity. But nowadays, CPUs are equipped with metal top covers for thermal conductivity and protection of the core, so there is no need to worry about short circuits caused by thermal silicone grease overflow.

5. Viscosity
Viscosity guides the viscosity of thermal silicone grease. Generally speaking, the viscosity of thermal silicone grease IDE needs to be around 68 to be within the normal range. Some thermal silicone greases on the market are exceptionally cheap due to their low viscosity and low thermal conductivity components.
6. Solid content
This coefficient in thermal conductive silicone grease refers to the mass percentage of the remaining part of the total amount after drying the silicone grease under specified conditions. It is more accurate to call it "nonvolatile content". The higher the solid content, the higher the viscosity of silicone grease, giving a harder feeling.
7. Oil content
Generally speaking, the lower the oil content of thermal conductive silicone grease, the better, because silicone grease with a higher oil content will separate some grease after a slightly longer storage time, which will to some extent hinder the conduction of heat. Therefore, when replacing thermal conductive silicone grease, we need to first remove the grease separated from the silicone grease to prevent the performance of the thermal conductive silicone grease from decreasing.