| With the trend of chip products towards small and multifunctional integration and the rapid spread of 5G communication technology,there is a higher performance demand for multifunctional chip packaging materials.Epoxy resin is considered as the first choice of chip packaging material due to its excellent mechanical properties,easy preparation and low cost.However,with the rapid development of chip technology,the electromagnetic interference between chips is becoming more and more serious,which seriously affects the performance stability of chips.Therefore,how to enhance the electromagnetic interference(EMI)capability of epoxy resin composites has become a bottleneck to restrict the development of chips in the direction of high power.There are a lot of reports on the EMI shielding performance(EMI SET)of epoxy resin-based chip packaging materials,which can be divided into the study of the intrinsic EMI shielding performance of epoxy resin and the study of filled epoxy resin EMI shielding composites.Meanwhile,the intrinsic low thermal conductivity of epoxy resin(about 0.22 W/(m·K))in high power chip packaging makes it difficult to diffuse the heat generated by the chip in time,which has a serious impact on the chip performance and service life.Therefore,how to enhance the thermal conductivity of epoxy resins to reduce the negative impact of heat generated by chips has inevitably become a focus of research.Giving epoxy resin-based chip packaging materials excellent electromagnetic shielding performance and thermal conductivity to meet both the electromagnetic interference problems of chips and the needs of chip heat dissipation is a popular research trend and development of chip packaging materials in the future.In this paper,a series of filler-filled epoxy resin composites were prepared from the perspective of heterogeneous complex microstructure design between fillers of different dimensions and the orientation construction of fillers,and the relationship between the electromagnetic shielding performance,thermal conductivity and mechanical properties of epoxy resin composites and heterogeneous complex microstructure were systematically studied as follows:(1)Magnetically responsive T-Fe3O4@CNTs were prepared by electrostatic adsorption between alkylation-modified iron tetroxide(Fe3O4)nanoparticles and carboxylated carbon nanotubes(CNTs),and then epoxy resin composites with filleraligned structures in the vertical direction were prepared by magnetic force in a latentcuring epoxy resin system.The unique heterogeneous complex interface between magnetic nanoparticles and conductive nanowires promotes the loss of electromagnetic waves by interfacial polarization,wave absorption and dipole polarization,resulting in an EMI SET of 45.86 dB in the X-band(thickness of 2 mm ± 0.1 mm)of the material,which significantly exceeds that of other epoxy-based shielding materials.Due to the introduction of the latent curing agent,the epoxy resin mixture can maintain a low viscosity state at room temperature for 40 days without curing,which facilitates the construction of a well-aligned structure with a magnetically responsive filler under the action of magnetic force.The aligned structure in the vertical direction facilitates the phonon transport in the composite,exhibiting a thermal conductivity of up to 1.59 W/(m·K)in the out-of-plane direction.In addition,the composites still have excellent thermal stability.(2)Epoxy/Zn@Ti3C2Tx MXene/CNF composites were prepared by self-assembly between Zn2+ and Ti3C2Tx MXene,introduction of nanocellulose(CNF),vacuumassisted filtration,hot pressing and spin coating.The unique heterogeneous complexation between Zn@Ti3C2Tx MXene nanosheets and CNF nanowires promoted the loss of interfacial polarization,and the composite reached 60.3 dB and 5025 dB/mm in X-band total electromagnetic shielding value(EMI SET)and shielding efficiency per unit thickness(SE/d)at a thickness of 12 μm ± 2 μm,which significantly exceeded other epoxy resin-based shielding materials.In addition,the absorption coefficient gradually increases with the increase of CNF content.In addition,the composites showed excellent oxidation resistance(stable performance after 30 days)under the synergistic effect of Zn2+,which greatly exceeded the previous test cycle.The mechanical properties and flexibility of the film layers were greatly enhanced(tensile strength at 60 MPa and stable properties after 100 bending tests)due to the CNF and hot pressing processes.Meanwhile,the epoxy resin and composite film compound prepared in this chapter have a thermal conductivity of up to 2.3 W/m-K in the thinplane in-plane direction,providing an efficient thermal conductivity pathway for the diffusion of heat generated in the chip package.(3)The GO@MXene aerogel was prepared by improving the preparation method of freeze orientation with specific temperature difference in both directions simultaneously,and then the rGO@MXene aerogel was obtained by thermal reduction at high temperature,and finally the Epoxy/rGO@MXene composite with ultra-low filler content was further prepared by vacuum impregnation of epoxy resin and curing process.Due to the large amount of gas generated in the high-temperature thermal reduction,the aerogel exhibits a loose and porous oriented structure.At the same time,the good interconnection structure between the fillers effectively reduces the interfacial thermal resistance inside the composites,and the thermal conductivity of the composites increases to 1.65 W/(m·K)in the out-of-plane direction under the ultra-low filler loading.The thermal conductivity is enhanced by 650%compared with that of pure epoxy resin.(4)Through a simple hot pressing method,utilizing the fluidity of liquid metals,and through the heterogeneous combination between carbon nanotubes and liquid metals,a composite material with efficient filler networks in both the vertical and horizontal directions was prepared,with an EMI performance of up to 52.4 dB and an isotropic thermal conductivity of 1.21 W/(m·K). |
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