Preparation And Properties Of Epoxy Electronic Encapsulating Materials With High Thermal Conductivity And Low Thermal Expansion Coefficient

With the rapid development of electronic information technology,multifunctional and high-performance encapsulating materials are required.Especially with the progress of microelectronics industry,heat-producing capability of electronic component increases greatly,leading to the need of electronic packaging materials with high thermal properties.Current encapsulating materials fail to meet the electronic industry requirement because of two main limitations:low thermal conductivity and high thermal expansion coefficient.The large coefficient mismatch of thermal expansion between the substrate and silicon chip would result in too much distortions during the thermal cycling.So it is one of the most important projects for electronic encapsulating materials to improve its thermal conductivity and reduce its thermal expansion coefficient.The usage of plastic package in electronic packaging materials accounts for above 95%because of its excellent performances,such as low density,low price,easy molding technology,excellent shock resistance and so on.Among the plastic packaging materials, modem epoxy electronic encapsulating materials have developed rapidly and reached about 90%of the total application in the past few years.Herein,ZrW₂O₈ powders with negative thermal expansion properties prepared via solid-state reaction method,together with high-thermal-conducting nano-A1N powders were used as inorganic fillers and mixed into o-cresol formaldehyde epoxy resin to improve the thermal performance of the resulting composites.Results indicated that the thermal expansion coefficient of the composites was greatly reduced by adding ZrW₂O₈ fillers,and the thermal conductivity was greatly improved with the adding of A1N fillers.The adding of 50% micrometer-ZrW₂O₈ and 50%nano-A1N fillers reduced the thermal expansion coefficient to 0.87×10^-5/K,12%of the composites without fillers,and improved the thermal conductivity to 3.885 W·m^-1·K^-1,16.8 times higher than the non-fillers composites.After the comparison of the effects of the fillers sizes and content on the properties of the composites,the author found that the thermal properties of the composites could be adjusted by changing the contents and mixture ratio of the fillers, and the epoxy electronic encapsulating material mixed with 50%ZrW208 and 20% nano-A1N had the most excellent properties(its thermal conductivity is 2.083 W·m^-1·K^-1, thermal expansion coefficient is 1.25x10-5/K,and bending strength is 168.5 MPa).In this material,the thermal conductivity was greatly improved and the thermal expansion coefficient was greatly reduced,while the electrical and mechanical properties were maintained.