The seven key parameters affecting the performance of thermal grease

Since the introduction of thermal grease to the market, it has been quite popular due to its ability to better address heat dissipation issues for some electronic components. As a chemical substance, thermal grease also has certain performance parameters that reflect its characteristics. Understanding the meaning of these parameters can generally help buyers and users to judge the performance level of a thermal grease product.Below, Anpin introduces the seven key parameters that affect the performance of thermal grease products:

(1) Thermal Conductivity

Thermal conductivity refers to the amount of heat transferred through a square meter of material with a thickness of 1 meter, with a temperature difference of 1 degree (K, ℃) between the two sides, within 1 second, with the unit being W/m K (here K can be replaced by ℃).

(2) Thermal Conductance

The thermal conductance coefficient was formerly known as the total heat transfer coefficient. The current national standard has standardized the name to the heat transfer coefficient. The K value of the heat transfer coefficient refers to the amount of heat transferred through 1 square meter of area within 1 second, with a temperature difference of 1 degree (K, ℃) between the two sides of the enclosure structure, with the unit being W/㎡ K (here K can be replaced by ℃).

(3) Thermal Resistance

The thermal resistance coefficient represents the resistance effect of an object to heat conduction. The concept of thermal resistance is very similar to that of electrical resistance, and the unit is also similar (℃/W), which means the temperature difference between the two ends of the heat conduction path when the heat transfer power is sustained at 1W. The lower the thermal resistance, the better, because under the same environmental temperature and heat transfer power, the lower the thermal resistance, the lower the temperature of the heated object. The size of the thermal resistance is largely related to the material used for the thermal grease.

(4) Dielectric Constant

For some CPUs without a metal cover, the dielectric constant is a very important parameter, which relates to whether there is a short circuit inside the computer. Ordinary thermal greases use materials with good insulation properties, but some special pastes (such as silver-containing pastes, etc.) may have a certain degree of electrical conductivity. Now many CPUs are equipped with metal covers for heat dissipation and protection, so there is no need to worry about short circuits caused by the overflow of thermal grease.

(5) Viscosity

Viscosity is the resistance to flow when two plates with an area of 1m² are immersed in a liquid, with a distance of 1 meter between the two plates. If a shear stress of 1N is applied, causing the relative speed between the two plates to be 1m/s, then the viscosity of this liquid is 1Pa.s. Viewing the flowing liquid as many parallel layers moving relative to each other, each layer has a different speed, forming a velocity gradient (dv/dx), which is the basic characteristic of flow. Due to the existence of the velocity gradient, the slower-moving liquid layer hinders the flow of the faster layer, thus generating resistance to motion. To maintain a certain velocity gradient movement, a force opposite to the resistance must be applied to the liquid layer.

(6) Operating Temperature

The operating temperature is an important parameter to ensure that the thermal material is in a solid or liquid state. If the temperature is too high, the thermal material will melt into a liquid; if the temperature is too low, it will become solid due to increased viscosity, neither of which is conducive to heat dissipation. The operating temperature of thermal grease is generally between -50℃ and 230℃. We don't have to worry about the operating temperature of thermal grease, as it is difficult to exceed this range with conventional means.

(7) Oil Separation

Oil separation refers to the amount of silicone oil that separates out after the product is maintained at 200℃ for 24 hours, and is an indicator for evaluating the heat resistance and stability of the product. When the paste is applied to white paper, oil separation can be observed, with a high oil separation, the oil separation phenomenon is obvious; or when opening a container that has been stored with paste for a long time, a significant oil separation phenomenon can be seen on the surface of the paste or around the container.

The above seven parameters basically cover the performance description of thermal grease and are also the main reference for judging the quality of thermal grease. Therefore, when using it, we had better understand these parameters clearly to better grasp the operational performance of the product.

Shenzhen Anpin Silicone Material Co., Ltd. is a high-tech enterprise dedicated to the research and development, production, and management of new materials such as thermal grease, electronic adhesives, thermal encapsulants, thermal soft film, and water-based paint emulsions. 

Source: http://www.apsi.cn/