Research On High Thermal Conductivity Epoxy Casting Compound

In recent years, the increasing power and integrated level of motors and electronic products raised advanced requirement on the heat conduction property of insulation material. Rapid heat extraction of the products will ensure safety and increase service life. Study on high thermal conductivity products become a hot issue.This thesis is focused on developing a kind of high thermal conductivity epoxy casting compound with good durability and reliability and can be easily cast and widely used in different environment. The main work of this thesis includes: study on basic resin, the influence of different kinds and dosage of powder to casting compound property, the influence of coupling treatment to casting compound property. Then screen out casting compound with good performance through its viscosity, heat conductivity, impact strength, bending strength, distortion temperature, coefficient of linear expansion, glass transition temperature, volume resistivity and electrical strength. The conclusion is following:First, according to the study on four epoxy hybrid resin, which mixed by ERL-4221 and MHR-070, matching with 90phr anhydride will get a system with low viscosity, and can easily adding powder and casting. The cured epoxy resin has nice mechanical property and moderate distortion temperature, additional 6% toughening agent and 1% accelerating agent will improve its mechanical property and got an appropriate gel time.Then, according to the study on three powder of BN, Al₂O₃, silica micro powder, different filling dosage of powder caused significant change of property of casting compound. When the casting compound is filled by 65 weight percent 325 and 800 mesh Al₂O₃, its viscosity is 3375cp, coefficient of heat conductivity is 0.853W/m·k, impact strength is 15.3kJ/m², bending strength is 101.8MPa, distortion temperature is 126.8℃, volume resistivity is 1.8×10¹⁴Ω·m, electric strength is 24.8MV/m. After the filled 325 and 800 mesh Al₂O₃ is coupling treated, property of the casting compound is changed. When coupling agent accounts for 3 weight percent of inorganic powder, its glass transition temperature rises to 148.7℃, viscosity reduces to 2100cp, impact strength ascends to 17kJ/m². When coupling agent accounts for 5 weight percent of inorganic powder, its coefficient of linear expansion reduces to the minimum value of 19.5×10^-6/K and bending strength ascents to the maximum value of 117.8 MPa. When coupling agent accounts for 7 weight percent of inorganic powder, its coefficient of heat conductivity ascents to the maximum value of 0.919W/m·k.Finally, through compare with STYCAST2850 high thermal conductivity casting compound, the product of this paper has better electrical property. Meanwhile, the product of this paper also has relatively higher distortion temperature and glass transition temperature, and lower coefficient of linear expansion. The mechanical property and thermal conductivity of the product of this paper is relatively lower, however, it can still meet the service conditions.