Study On Femtosecond Laser Microstructural Processing Technology Of Single Crystal Diamond

As the most hard material in nature,single crystal diamond has the characteristics of high thermal conductivity,high carrier mobility,high breakdown electric field and low dielectric constant.Therefore,it is widely used in the key fields of micro cutting tools and micro electromechanical system components.However,because of the high hardness,anisotropy,small size and complex shape of the micro structure devices,the traditional machining methods are faced with the problems of high wear rate,high processing stress and less freedom.In this paper,the mechanism and technology of the multi microstructure of single crystal diamond are studied by using a more flexible non-contact femtosecond laser as the processing method to solve the key problems in the manufacture of the micro structured diamond devices.The single pulse and multi pulse ablation threshold of green and infrared laser processing single crystal diamond are calculated by the threshold test of femtosecond laser processing.The single pulse ablation threshold of green light is 2.86 j/cm~2,and that of infrared light is 2.49 j/cm~2.The results of research on multi pulse threshold show that the ablation threshold changes with the number of pulses,the saturation threshold of green light is close to 1.4 j/cm~2,and the saturation threshold of infrared light is close to 1 j/cm~2.The effects of laser wavelength,average power,pulse number,scanning speed,defocusing distance and different processing methods on the morphology and size of micro holes and micro grooves and the surface quality of the machined surface were studied.It is found that the material removal rate is positively correlated with the average power of laser and the scanning speed is negative.The material removal efficiency and surface quality of single crystal diamond processed by infrared light is higher than that of green light.In addition,the best surface roughness Sa=0.076μm can be obtained by parallel machining method through the combination of the best technological parameters.The method of scanning galvanometer-assisted femtosecond laser milling is proposed,and the comparative experiments show that this method can significantly improve the material removal efficiency compared with the traditional processing method.The advantages of scanning galvanometer assisted femtosecond laser processing micro pillar microstructure are further proved by numerical simulation.The 5×5 micro pillar micro structure array with average pillar top diameter of 6.9μm,height 225.6μm and aspect ratio of 32.7 was successfully prepared by the best combination of process parameters.The results show that the main removal forms of the materials are graphitization and the sublimation of graphitization carbon by Raman spectroscopy.Based on the research of technological parameters,the suitable processing parameters are selected,and three kinds of micro milling tools are designed.Only femtosecond laser is used to prepare three kinds of micro milling tools with different structures.The three kinds of micro milling main cutting edge are tested,and the blunt radius of the three kinds of micro milling tools is 10.21μm,4.83μm and 5.66μm respectively.The milling performance of three micro milling cutters is tested by milling test,and the wear forms of the three kinds of cutters are analyzed by Raman spectroscopy.