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  With the development of industrial production and science& technology， people constantly put forward new requirements for materials. In the field of electronic appliances, as the rapid development of integrated and assembly technology, electronic components、logic circuit develop into light、thin、small direction, thermal power increase accordingly, there for high thermal insulation materials are required to remove the heat generated by the electronic device effectively, this is related to the reliability of life and quality of the product.

  The traditional method of solving the heat dissipation of electronic equipment is to put a layer of insulation between the heat body and the body pad insulation as a thermal conduction material such as mica, PTFE and beryllia ceramics etc, this method has some effectiveness, but there are issues such as poor thermal conductivity, low mechanical properties and high price. At present, the solution of the heat dissipation of electronic equipment is solved by various forms of radiator, but most must be resolved through thermal conduction materials, thermal conduction silicone rubber material is the most important one in heat conduction materials, this paper mainly introduces the kinds of thermal conduction silicone rubber material, and raises some application solutions which need thermal conduction products. 

  1. Mechanism of thermal conduction of silicone rubber materials

     Thermal conduction silicone rubber material is a typical polymer composite material, thermal conduction performance is determined by the kinds of heat conduction fillers and the distribution of heat conduction fillers in silicone rubber matrix. Metal fillers (such as Ag, Al, etc.) have a high thermal conductivity, but most of the heat conduction is also electric conduction; The thermal conductivity of inorganic nonmetal materials (such as SiC, AlN, etc.) is also high, but the price is quite expensive; At present, the main metal oxides (such as Al2O3, ZnO, etc.) as heat conduction fillers, such as thermal conductivity of some heat conduction fillers in table 1. The heat conduction mechanism of various filler materials are different, heat conduction of metal materials mainly depend on the electron movement, the metal thermal conductivity decreases with the increase of temperature, the thermal diffusion rate of the nonmetal depends mainly on the vibration of the neighboring atoms and the binding group, In the materials strongly covalent bonding, the thermal conduction in ordered crystal lattices is more efficient. So when using non-metallic materials as heat conduction fillers, how to improve the thermal conduction pile degree of the system is the main method to improve the thermal conductivity of the system.

  2.Type and application of silicone rubber materials

  2.1Thermal grease& thermal pad

    Thermal grease is a cream mixture of silicone oil and thermal conductive fillers, with the characteristics of stereotypes at any time, high thermal conductivity, non - curing, no corrosion of interface materials. In electronic equipments, there are many contact surfaces and assembly surfaces between the various electronic components, there is space between them to make the heat radiation retardant, to solve the problem, we usually coating the thermal grease between the contact surface, using the flow of thermal grease to remove the air from the interface to reduce or even eliminate thermal resistance. Thermal pad is a sheet thermal conductive and insulation material which is processed by special production technology, with natural viscosity on surface、high thermal conductivity、high compression resistance、high buffer etc, they are mainly used between the heating device and the heat sink & shell of the gap filling material, as the material is soft and the elastic variable under low pressure, making the close contact on the device surface or rough surface, reduce air thermal impedance, the weakness such as the silicone oil leakage after high temperature and dust on the surface is solved perfectly.

  2.2Thermal flame retardant silicone rubber materials

     In recent years, silicone rubber materials is widely used in the electronic and electrical appliances industry, but as it is polymer material, flammability& smoked, sometimes it is the direct cause of the fire; Therefore, the flame retardant silicone rubber has been gradually become the main force of electronic industry of silicon rubber material. The company develops a flame retardant reached UL94V-0 grade& thermal conductivity of over 1.0 W/m·K ( tested and certified by the authority)named SKF323 flame retardant& thermal conductivity of silicone sealants for products with heat conduction fillers after surface treatment &homemade flame retardant, which is now widely used in automotive modules, circuit modules and PCB board and all that electronic and electrical appliances(standard of thermal and flame retardant are high).

  2.3Thermal embedment silicone rubber materials

     Potting is divided into local and overall potting. Local potting is only used on high power devices, which connect the conductive silicone rubber material and the body together, generated heat can quickly spread to the heat sink. The overall potting is potting all components on printed circuit board, the heat produced can spread quickly and distribute directly to the environment. Such products are generally two-component, the two kinds of components mixed bubble when using and pour on the circuit board& vulcanized elastic body, Such products not only have heat dissipation insulation function but also the effect of shock absorption & three proofing, now widely used in LED lamp potting& adhesive and other circuits, home appliances insulation seal.

  2.4High thermal silicone rubber adhesive

     High thermal conductive adhesive is widely used in insulation occasions, because in the development of electronic and electrical appliances industry, electrical and electrical devices material field need heat conduction insulation material, especially for the occasion of high power dissipation, such as the bonding of semiconductor and heat sink、the protection of the pipe heart、pipe shell seal、electronic rectifier、thermal insulation of thermisistor、the thermal insulation of the multi plate in the micro package, such as the thermal insulation of the laminates, requires the thermal insulation of the different technological properties.

2.5Thermal high temperature silicone rubber

Heat conduction and high temperature silicone rubber are mainly used in the bonding and sealing of low pressure and high current transformers; Thermal conduction insulation of magnetic field coil for radar; all kinds assembly of high temperature power tube& radiator& printed plate；Micro packaging technology、electric appliances and military electric appliance of high temperature heat dissipation body.

  3.Summarize

    The RD of thermal conductive silicone rubber material in foreign countries is more mature, such as Dow Corning, GE Toshiba etc developed a variety of conductive silicone rubber products, while the domestic is still in the development stage, if the consistent of overall performance and process performance can be solved, heat conduction silicone rubber will have a very good development prospects. In short, the thermal conductivity of silicone rubber not only has good thermal conductivity, but also has performance which many other materials do not have, such as weather resistance, adhesion and so on, so its development prospect is considerable, the application will be more and more widely.