| With the rapid development of integrated microelectronic and electronic packaging technology, the size of smart and wearalbe electronics continues to be shrinked and their power density continues to be increased, which results in the increasing temperature of electronic components. As known, the life of electronic components are closely related with their temperature. Therefore, the thermal management of smart and wearable electronic is challengable. In this paper, graphite films are used to prepare laminated composite with high thermal conductivity and low density, in the purpose of meeting the demands of thermal management of electronics with high power density.First of all, we presented an effective approach to fabricate Cu-graphite-Cu laminated composites with high thermal conductivity by electroplating Cu on HG(High thermal conductive) graphite sheets. To enhance the adhesion between the copper and the graphite film,micropores with the diameter of 50-100μm were prepared on the HG graphite sheets, which really improved the binding between Cu layers and graphite sheets by the fastening of microholes. We demonstrate experimentally that the obtained Cu–G–Cu heat spreaders with higher thermal conductance(526–626 W/(m·K)) and thermal diffusivity(319–442 mm2/s) and lower density(2.36–3.17 g/cm~3) present outstanding ability of heat dissipation on electronic cooling as compared with Cu substrates. The temperature of chip attached on as-prepared 35 mm Cu–G–Cu sandwich was ~8℃ lower than that on 50μm Cu foil with the chip power of 1.4W. Moreover, Ansys simulation illustrates that the temperature of the chip attached on the Cu–G–Cu sandwich with Sn solder as the thermal interface material(TIM) can be further reduced by 22.06±9.88oC(3.0W) compared with that with polymer adhesive as a TIM, due to its good weldability with Sn solder and lower contact thermal resistance, revealing the huge benefits of the obtained Cu–G–Cu sandwich heat spreaders.Secondly, the LG(Low thermal conductive) graphite films and HG graphite sheets were mixed with epoxy to fabricate graphite films/epoxy laminated composites with high thermal conductivity by hot-pressing curing. Under pressure, the epoxy infiltrated into graphite films and cur ed in graphite films, resulting in the enhanced interfacial adhesion between graphite films and epoxy. In addition, the influence of curing pressure on the mechanical and thermal properties of the composites was disclosed. With the increased curing pressure from 1 to 80 KPa, the tensile strength of composites was gradually decrease from 25.83 to 6.53 MPa, and the thermal conductivity was gradually increased from 120 to 240 W/m·K. Moreover,the thermal conductivity of LG graphite films/epoxy laminated composites can be up to 240 W/(m·K) at room temperature, and theirthe cooling effect is similar with that of aluminum, but they have lower density of 1.678 g/cm~3. The thermal conductivity of HG graphite sheets/epoxy laminated composites can be up to 1050 W/(m·K) at room temperature, which are 2.69 times higher than copper, and they have lower density of 1.65g/cm~3.At last, the printed circuit boards(PCB) and the back cover of smart phonewith excellent heat-dissipation ability are fabricated by the laminate processing using graphite films. In cooling experiments, the temperature of chip attached on the HG graphite sheets filled PCB with the density of 1.4g/cm~3 is lower 30-50 oC than that on common PCB, and is 7.4-16 oC higher than that on aluminum board, in the power density of 1.15-2.07 W/cm2. And the temperature of as-prepared LG graphite films/polycarbonate back cover is 98.4oC lower than that of polycarbonate back cover. Ansys simulation illustrates that the temperature of the chip attached on as-prepared LG graphite films/polycarbonate back cover is only 3oC lower than that on aluminium alloy back cover with the power density of 1.14 W/cm~2. |
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