Thermally conductive silica gel sheet

Classification of thermal silica gel

Thermally conductive silicone can be divided into thermally conductive silicone gaskets and non-silicone silicone gaskets.
The electrical insulation properties of most thermally conductive silica gels are ultimately determined by the insulation properties of the filler particles.

Thermally conductive silicone gasket

Thermally conductive silicone gaskets are divided into many sub-categories, each with its own different characteristics.

Non-silicone silicone gasket

Non-silicone silicone gasket is a material with high thermal conductivity. It is self-adhesive on both sides.
When used in the assembly of electronic components, it exhibits lower thermal resistance and better electrical insulation characteristics under low compression force. It can work stably at -40℃~150℃. Meet the flame retardant grade requirements of UL94V0.

The difference between thermal conductive silicone gasket adhesive and non-adhesive.

Thermal conductive silicone gasket double-sided adhesive.

The double-sided adhesive is mainly because the product has no fixing device or is inconvenient to fix.
The double-sided adhesive can be used to fix the radiator, stick the IC and the heat sink, and there is no need to design a fixing structure.

Benefits: It can be used to fix the radiator, without the need to design a fixed structure.

Impact: The thermal conductivity will be worse, and the derivative coefficient will be much lower.

Single-sided adhesive for thermal conductive silicone gasket

The single-sided adhesive is mainly to facilitate the installation and bonding of thermal silica.
For example, a backlight source uses thermal silica with a size of 400*6, which is not easy to install.
Therefore, the single-sided adhesive should be used, and the thermal silica is glued. One side is attached to the PCB board, and the other side is attached to the housing.

Benefit: It can stick to the surface of the heater on one side.
When the radiator or the shell slides relatively during the assembly process, the thermally conductive silicone gasket will not cause a position shift.

Impact: The thermal conductivity will be lower, but the effect is better than double-sided adhesive.

To sum up, whether it is a double-sided adhesive or a single-sided adhesive for thermally conductive silicone gaskets will result in lower thermal conductivity, but it is conducive to structural design and installation.

How to choose thermal conductive silicone sheet

Thermal conductivity selection. The choice of thermal conductivity mainly depends on the power consumption of the heat source and the heat dissipation capacity of the radiator or heat dissipation structure.

Generally, the chip temperature specifications are relatively low, or sensitive to temperature, or heat flux density is relatively large (generally greater than 0.6w/cm3 requires heat dissipation treatment, generally when the surface is less than 0.04w/cm2, only natural convection treatment is required) these chips Or the heat source needs to be heat-dissipated, and try to choose a thermally conductive silicone sheet with high thermal conductivity.

The consumer electronics industry generally does not allow the junction temperature of the chip to be higher than 85 degrees, and it is also recommended to control the chip surface to be less than 75 degrees during the high-temperature test. The components of the entire board are basically commercial-grade components, so the internal temperature of the system is recommended at room temperature.No more than 50 degrees.

It is recommended that the temperature of the first appearance surface, or the surface that can be contacted by the end customer, be lower than 45 degrees at room temperature. Choosing a thermally conductive silicone sheet with higher thermal conductivity can meet the design requirements and retain some design margins.

Factors Affecting the thermal conductivity of thermal silica gel

• Types and characteristics of polymer matrix materials. The thermal conductivity of the matrix material is super high, the better the dispersion of the filler in the matrix and the better the degree of bonding between the matrix and the filler, the better the thermal conductivity of the thermally conductive composite material.
• Types of fillers.The higher the thermal conductivity of the filler, the better the thermal conductivity of the thermally conductive composite material.
• The shape of the filler. Generally speaking, the order of easy formation of heat conduction path is whisker> fibrous> flake> granular. The easier the filler is to form the heat conduction path, the better the heat conduction performance.
• Filler content. The distribution of the filler in the polymer determines the thermal conductivity of the composite material. When the filler content is small, the heat conduction effect is not obvious; when the filler is too much, the mechanical properties of the composite material will be greatly affected. When the filler content increases to a certain value, the interaction between the fillers forms a network-like or chain-like heat-conducting network chain in the system. When the direction of the heat-conducting network chain is consistent with the direction of heat flow, the thermal conductivity is the best. Therefore, there is a certain critical value for the amount of thermally conductive filler.
• The bonding characteristics of the interface between the filler and the matrix material.The higher the degree of bonding between the filler and the matrix, the better the thermal conductivity. Choose a suitable coupling agent for surface treatment of the filler, and the thermal conductivity can be increased by 10%-20%.