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With the progress of national defense science and technology, the thermal effect of components in aerospace technology has greatly hindered the operation of devices. In order to solve the problem of high interface thermal resistance between materials, a new method of femtosecond processing combined with thermal interface materials was proposed to reduce interface thermal resistance. By using the high-efficiency positioning response method and the non-material selectivity and low thermal effect of femtosecond laser, the micro-structure with low roughness is precisely machined on the surface of copper based on the laser five-axis machining system, and the internal structural roughness, depth and width of the micro-structure are characterized. Then the surface is covered with thermal interface materials to achieve the purpose of reducing the interface thermal resistance between materials. At the same time, the effect of microstructure on interface thermal resistance is simulated with simulation software. A uniform array structure was obtained on the surface of copper substrate with a roughness less than 0.3μm, and the measured linear roughness of the microstructure was 0.23μm, which was consistent with the surface roughness of copper. Firstly, in order to verify that the surface heat conduction efficiency of the material with a microstructure surface is higher, the heat transfer time of the composite substrate with a microstructure is 0.0073s after simulation, which is faster than that of the composite substrate without a microstructure. Then, the thermal conductivity of the composite substrate with low roughness is 355 W·m-1 ·K-1, while that of the composite substrate with high roughness is 325 W·m-1 ·K-1 . Through the ultrafine processing, the heat transfer efficiency of the prepared composite substrate is increased by 17%, and the heat transfer efficiency is higher with lower roughness, which provides a research basis for high energy consumption devices.
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