| There are many new micromachining methods developed for MEMS(Micro Electro Mechanical System) such as LIGA micromachining, micro-EDM and micro-ECM, etc. In Recent years, with the development of silicon-based microelectronic materials processing and sophisticated medical equipment manufacturing, water-jet guided laser micromachining develops quickly. It′s particular processing ability insures high machining precision, high machining speed, minimal machining force, minimal heat-affected zone, no remain stress and no crack. At present, SYNOVA Company in Sweden has mature products using this technology, but the price is quite high. Based on the situation above, this dissertation is aiming at doing research on the theories,simulation and experiments of water-jet guided laser micromachining. The simulation model was built up. The complete, steady and low cost water-jet guided laser micromachining system was designed and built up. The optimized machining parameters and high quality products were acquired from experiments.Firstly, on the bases of summing up the other researchers′work all over the world, the coupling mechanisms of water-jet guided laser micromachining were researched including the coupling alignments, the largest incidence angle of full reflection, multimode optical fiber transmission, the decay of laser energy in water and SRS(Stimulated Roman Scattering). The coupling status detecting and adjusting system was designed. This system was based on the coupling image acquired from the CCD camera machine vision. A self-developed image processing software was used. It can monitor the coupling status rapidly and accurately.The hydrokinetics principle of high speed water-jet was researched. The factors affecting the stability of water-jet, the contract flow principle and the cavitation principle were researched. The high-pressure water-jet hydraulic system was simulated by using FLUENT finite element analysis software. The reasonable parameters for creating ideal jet state were acquired. By using the simulation results high speed jet which was more than 100mm long at the speed of over 100m/s was formed in experiment. The interaction principle of laser, solid and liquid was researched. The temperature field of the machining process was simulated by using ANSYS finite element software. Meanwhile, material removal situation was simulated by using"elements killing technique". In the simulation, the laser energy distribution is not treated as Gaussian distribution. The cooling of high speed water-jet and the impact of shock on heat-affected zone distribution, temperature gradient and melt debris were focused on.Secondly, a set of water-jet guided laser micromachining system was designed and developed to realize the key techniques of water-jet guided laser micromachining. It composed of pulsed Nd: YAG laser system, high-pressure hydraulic system, coupling unit of laser and water-jet, CCD camera machine vision coupling status detecting system, computerized numerical control system and workbench, etc.The coupling unit of laser and water-jet is the key part. It′s structure affects the machining results much. The liquid cavity in the coupling unit is quite small. Liquid field in the cavity is steady and symmetrical. The thickness of the water layer which laser goes through is only 0.2mm. Sharp nozzle orifice edge guarantees the formation of the reflux contract water-jet. By adding telescope unit and beam expanding unit on pulse Nd: YAG laser system, the numerical aperture of focusing laser beam is reasonable, waist diameter is small and the focus depth is great, which is quite suitable for water-jet guided laser microprocessing.Finally, in order to master the processing principle, the experiments were carried out using the water-jet guided laser micromachining system. The experiments were done to find the influence of machining parameters on water-jet stability, focused laser spot diameter, the attenuation of laser energy and the processing efficiency of different materials. The processing parameters were optimized by using single factor method and orthogonal experimental method. At last, silicon-based chip and stainless steel 1Cr18Ni9Ti were machined by using optimized processing parameters. The experiments results proved the excellent micro-machining ability of water-jet guided laser micromachining and its wide practicality.
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