I believe there are many who only understand some traditional thermal conductivity materials, such as Ag, Cu, A1 and metal oxides such as A12O3 and other non-metallic materials such as graphite, carbon black, etc. They have relatively little understanding of thermally conductive silicone sheets. Let's take you to understand the thermal conductive silicone sheet.
Thermally conductive silicone sheet
With the development of industrial production and science and technology, people have put forward new requirements for thermally conductive materials, hoping that the materials have excellent comprehensive properties. For example, due to the rapid development of integration technology and assembly technology in the electrical and electronic fields, the volume of electronic components and logic circuits has shrunk thousands of times. Insulating materials with high thermal conductivity are required. In recent decades, the application fields of polymer materials have been continuously expanded. The use of synthetic polymer materials to replace various materials used in traditional industries, especially metal materials, has become one of the directions of scientific research efforts in the world.
1. What is thermal silica gel sheet
Thermally conductive silica gel sheet is a kind of thermally conductive media material synthesized by special process with silica gel as the base material and various auxiliary materials such as metal oxides. Thermally conductive silicone rubber is a polymer composite material that uses silicone resin as the bonding material and is filled with thermally conductive powder to achieve the purpose of heat conduction.
2. Commonly used thermally conductive silicone sheet base materials and fillers
Silicone resin (basic material)
1. Insulating and thermally conductive filler: aluminum oxide, magnesium oxide, boron nitride, aluminum nitride, beryllium oxide, quartz and other organic silicon plasticizers
2. Flame retardant: magnesium hydroxide, aluminum hydroxide
3. Inorganic colorants (color distinction)
4. Crosslinking agent (adhesive performance requirements)
5. Catalyst (requirements for process shaping)
Note: The thermal conductive silicone sheet plays a role in heat conduction, forming a good thermal path between the heating element and the heat sink, and forms a heat dissipation module together with the heat sink and structural fixing parts (fan).
Fillers include the following metals and inorganic fillers:
1. Metal powder filler: copper powder, aluminum powder, iron powder, tin powder, nickel powder, etc.;
2. Metal oxides: aluminum oxide, bismuth oxide, beryllium oxide, magnesium oxide, zinc oxide;
3. Metal nitride: aluminum nitride, boron nitride, silicon nitride;
4. Inorganic non-metals: graphite, silicon carbide, carbon fiber, carbon nanotube, graphene, beryllium carbide, etc.
Third, the classification of thermal silica gel
Thermally conductive silicone can be divided into: thermally conductive silicone gasket and non-silicone silicone gasket. The electrical insulation properties of most thermally conductive silica gels are ultimately determined by the insulation properties of the filler particles.
1. Thermally conductive silicone gasket
Thermally conductive silicone gaskets are divided into many sub-categories, each of which has its own different characteristics. Aochuan Technology mainly has 11 kinds of thermally conductive silicone gaskets.
2. 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.
Fourth, the thermal conductivity mechanism of thermal silica gel
The thermal conductivity of thermally conductive silica gel depends on the interaction between the polymer and the thermally conductive filler. Different types of fillers have different thermal conduction mechanisms.
1. The thermal conduction mechanism of metal fillers
The heat conduction of the metal filler is mainly conducted by the movement of electrons, and the process of the movement of electrons is accompanied by the transfer of heat.
2. The thermal conductivity mechanism of non-metallic fillers
The heat conduction of non-metallic fillers mainly depends on the heat conduction of phonons, and the diffusion rate of thermal energy mainly depends on the vibration of adjacent atoms or bonding groups. Including metal oxides, metal nitrides and carbides.
Sixth, how to choose thermal silica gel 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 heat sink or heat dissipation structure. Generally, the chip's 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 heat sources need to be heat-dissipating treatment, 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 the end customer is able to contact, 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.
Note: Heat flux density: defined as: the heat passing unit time (1 second) in a section of unit area (1 square meter). The junction temperature is usually higher than the case temperature and the surface temperature of the device. The junction temperature can be a measure of the time and thermal resistance required to dissipate heat from the semiconductor wafer to the packaged device housing.