Take you to understand the knowledge of thermal conductive silica gel sheet

I believe that many people only understand some traditional thermal conductive materials, such as Ag, Cu, A1 and metal oxides such as A12O3 and other non-metallic materials, such as graphite, carbon black, etc., and have a relatively small understanding of thermal conductive silicone sheets. Today, HFC Small series will take you to understand the thermal conductive silicone sheets.
　　With the development of industrial production and science and technology, people have put forward new requirements for thermal conductivity materials, hoping that the materials have excellent comprehensive properties. For example, due to the rapid development of integration technology and assembly technology in the field of electrical and electronics, the volume of electronic components and logic circuits has been reduced tens of thousands of times, and high thermal conductivity insulation materials are required. In recent decades, the application field of polymer materials has been expanding, and replacing various materials used in traditional industry with synthetic polymer materials, especially metal materials, has become one of the directions of scientific research efforts in the world.
　　First, what is thermal silicone sheet
　　Thermal conductive silica gel sheet is a kind of thermal conductive medium material synthesized by special process with silica gel as the base material and various auxiliary materials such as metal oxide. Thermal conductive silicone rubber is a polymer composite material with silicone resin as bonding material and filled with thermal conductive powder to achieve thermal conductivity.
　　Second, commonly used thermal conductive silicone sheet matrix materials and fillers
　　Silicone resin (base material)
　　1, insulation and thermal filler: alumina, magnesium oxide, boron nitride, aluminum nitride, beryllium oxide, quartz and other organosilicon plasticizers
　　2, flame retardant: magnesium hydroxide, aluminum hydroxide
　　3, inorganic colorant (color separation)
　　4, crosslinking agent (adhesive performance requirements)
　　5, catalyst (process molding requirements)
　　Note: Thermal conductive silicone sheet plays a role in heat conduction, forming a good heat conduction path between the heating body and the heat dissipation device, and the heat dissipation fin, structural fasteners (fans) together to form a heat dissipation module.
　　Fillers include the following metallic and inorganic fillers:

1, metal powder filler: copper powder, aluminum powder, iron powder, tin powder, nickel powder, etc.;
　　2, metal oxides: alumina, bismuth oxide, beryllium oxide, magnesium oxide, zinc oxide;
　　3, metal nitride: aluminum nitride, boron nitride, silicon nitride;
　　4, inorganic non-metal: graphite, silicon carbide, carbon fiber, carbon nanotubes, graphene, beryllium carbide, etc.
　　Third, the classification of thermal silica gel
　　Thermal conductive silicone can be divided into: thermal conductive silicone gasket and non-silicon silicone gasket. The electrical insulation properties of most thermal conductive silica gel are ultimately determined by the insulation properties of filler particles.
　　1, thermal silicone gasket
　　Thermal conductive silicone gaskets are divided into many small categories, none of which have their own different characteristics. Aokuan technology mainly has 11 kinds of thermal silicone gaskets.
　　2, non-silicon silicone gasket
　　Non-silicon silicone gasket is a material with high thermal conductivity, self-adhesive on both sides, and exhibits low thermal resistance and good electrical insulation characteristics under low compression force when assembling electronic components. It can work stably at -40℃~150℃. Meet the flame retardant grade requirements of UL94V0.
　　Fourth, the heat conduction mechanism of thermal silica gel
　　The thermal conductivity of thermal silica gel depends on the interaction between polymer and thermal conductive filler. Different kinds of fillers have different thermal conductivity mechanisms.
　　1. Thermal conductivity mechanism of metal packing
　　The heat conduction of metal packing is mainly carried out by the movement of electrons, and the process of electronic movement is accompanied by the transfer of heat.
　　2, non-metallic filler heat conduction mechanism
　　The heat conduction of non-metallic packing mainly depends on the phonon heat conduction, and the heat diffusion rate mainly depends on the vibration of neighboring atoms or binding groups. Including metal oxides, metal nitrides and carbides.
　　Six, how to choose thermal silicone sheet
　　Thermal conductivity selection
　　The selection 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. The general chip temperature specification parameters are relatively low, or more sensitive to temperature, or the heat flux is relatively large (generally greater than 0.6w/cm3 need to do heat dissipation treatment, the general surface is less than 0.04w/cm2 only need natural convection treatment) These chips or heat sources need to be heat dissipation treatment, and try to choose the high thermal conductivity of the thermal silicone sheet. The consumer electronics industry generally does not allow the chip junction temperature to be higher than 85 degrees, and it is also recommended that the control chip surface be less than 75 degrees during the high temperature test, and the components of the entire board are basically commercial-grade components, so the internal temperature of the system is recommended not to exceed 50 degrees at normal temperature. The recommended temperature of a surface, or surface accessible to the end customer, shall be less than 45 degrees at room temperature. The selection of thermal conductive silica gel sheet with high thermal conductivity can meet the design requirements and retain some design margin.
　　Note: Heat flux: defined as: the amount of heat passed per unit time (1 second) in a section per unit area (1 square meter). Junction temperature It is usually higher than the enclosure temperature and device surface temperature. Junction temperature is a measure of the time required to dissipate heat from the semiconductor wafer to the package device housing, as well as the thermal resistance.