The continuous improvement of the functionality, integration and power density of advanced electronic devices of the third generation of semiconductor materials will inevitably lead to a high concentration of waste heat generated during device operation. Electronic packaging materials are the key to the thermal management of electronic devices. The thermal conductivity of currently used epoxy resin electronic packaging materials can no longer meet the development needs of advanced semiconductor materials. Since its discovery, graphene has attracted much attention due to its many excellent physical properties. The ultra-high thermal conductivity (up to 5300W / mK) and large specific surface area of ​​graphene make it easy to build effective thermal conduction paths, and it is a reinforced polymer. Ideal filler for thermal conductivity of matrix materials. The preparation of three-dimensional graphene structure is an effective method to improve the thermal conductivity of composite materials. Currently commonly used methods include chemical vapor deposition method and ice template method, etc., but the preparation cost of these methods is relatively high and it is difficult to obtain higher graphene content, so there is still a challenge to greatly improve the thermal conductivity of the resin matrix.
Based on the above problems, the functional carbon material team of the Surface Division of the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences used low-cost commercial polyurethane foam as a template, coated graphene nanosheets on its surface and used rapid heating to remove the polyurethane template. Three-dimensional graphene foam with complete structure. As shown in Figure 1, when the graphene content is 6.8wt%, the thermal conductivity of the epoxy composite material reaches 8.04W / mK, which is 44 times higher than the pure epoxy resin. The epoxy composite material also maintains good mechanics performance. Related work has been published in the Nanoscale journal Nanoscale (2019,11, 17600-17606) and was selected as the cover article.
In addition, the study also found that the introduction of micron-scale spherical alumina particles during the graphene suction filtration process can change the orientation of the graphene sheet from the horizontal direction to the longitudinal direction, resulting in a structure similar to "pea pod". This kind of binary graphene-alumina filler imitating the "pea pod" structure can effectively enhance the thermal conductivity of polymer materials. The thermal conductivity of the epoxy composite prepared by this method can reach 13.3W / mK and 33.4 in the vertical and horizontal directions, respectively. W / mK (as shown in Figure 2), related work will be published in the chemical field journal Chem. Eng. J. (2020, 381, 122690), the development of high thermal conductivity epoxy composite materials is expected to replace traditional polymer materials to solve the current The heat dissipation problem of highly integrated electronic equipment.
The above work was supported by the National Natural Science Foundation of China (51573201), Zhejiang Provincial Public Welfare Technology Applied Research Program (2016C31026) and the 3315 Innovation Team.
Figure 1 (a) Relationship between the thermal conductivity of epoxy composites and the content of graphene; (b) The thermal conductivity enhancement ratio of epoxy composites with pure epoxy resins and composites prepared by traditional blending methods; (c) The cover of the paper
Figure 2 The "pea pod" binary graphene-alumina structure enhances the thermal conductivity of epoxy resin
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