Parameters to be noted for choose thermal conductive adhesive
There are a total of seven key points, including heat transfer coefficient, thermal conductivity coefficient, thermal resistance coefficient, viscosity, operating temperature range, dielectric constant, and oil viscosity.
1. Heat transfer coefficient
The heat transfer coefficient refers to the temperature difference between the fluids on both sides of the enclosure structure under stable heat transfer conditions, which is 1 ℃ (or 1K), and the amount of heat reported over an area of 1 square meter within 1 hour. The unit is W/m2. K (or W/m2. C). ·The heat transfer coefficient and thermal conductivity coefficient are two different viewpoints. In thermal conductive adhesives, thermal conductivity coefficient is more commonly used and is rarely used as an indicator.
2. Thermal conductivity coefficient

The unit of thermal conductivity is W/m.K, which represents the thermal conductivity power of a cylinder with a cross-sectional area of 1 square meter and a temperature difference of 1 Kelvin (K=C+273.15) at intervals of 1 meter along the axial direction. The larger the value, the faster the thermal reporting rate of the data and the better the thermal conductivity.

The significant difference in thermal conductivity is mainly due to the different thermal conductivity mechanisms of different materials. Normally, metals have the highest thermal conductivity, followed by non metals and liquids, while gases have the lowest thermal conductivity. ·The thermal conductivity of silver is 420, copper is 383, aluminum is 204, and the thermal conductivity of water is 0.58. Nowadays, the thermal conductivity of mainstream thermal conductive silicone is greater than 1W/m. K, and excellent ones can reach 6W/m.K or more, but
3. Thermal resistance coefficient
·The thermal resistance coefficient represents the obstruction effect of an object on heat conduction, measured in ℃/W, that is, when the continuous heat transfer power of the object is 1W, the temperature difference between the two thermal conduction paths is true.
·The lower the thermal resistance, the better, because in the same situation of temperature and thermal conductivity, the lower the thermal resistance, the lower the temperature of the feverish object. The size of thermal resistance is closely related to the data used for thermal conductive adhesive.
4. Viscosity
·Viscosity is a measure of the viscosity of a fluid, which refers to the resistance of the fluid to external activity. It is expressed as the ratio of shear stress to shear rate of the fluid. There are many ways to measure viscosity, such as the unit of energy viscosity being poise or pascals.
5. Dielectric constant
·The dielectric constant is used to balance the ability of an insulator to store electrical energy, referring to the ratio of the capacitance between two metal plates with insulating material as the medium to the capacitance between the same two plates with atmosphere or vacuum as the medium. ·The dielectric constant represents the polarization level of the dielectric, which is the ability to constrain charge. The larger the dielectric constant, the stronger the constraint on charge.
6. Working temperature range
·Due to the characteristics of thermal conductive adhesive itself, its task temperature scale is very wide. The working temperature is a major parameter to ensure that the thermal conductive silicone is in a solid or liquid state. If the temperature is too high, the volume of the thermal conductive silicone grease fluid will expand, the intermolecular spacing will widen, the mutual influence will weaken, and the viscosity will decrease; The temperature drops, the fluid volume shrinks, the intermolecular spacing shrinks, the mutual influence increases, and the viscosity rises, both of which are unfavorable for heat dissipation.
·However, Han Si thermal conductive adhesive is heat cured, which has a wider range of high and low temperature resistance compared to thermal conductive silicone.
7. Oil viscosity
Oil separation degree refers to the amount of silicone oil precipitation after a product is maintained at 200 ℃ for 24 hours, and is an indicator for evaluating the heat resistance and stability of the product.