Study On Microgroove Feature Model And Processing Parameter Optimization Of Monocrystalline Silicon By Laser Assisted Waterjet

The traditional laser ablation, as a non-contact machining technology with no cutting force and pollution, is an effective technology to process brittle and hard material. However, the thermal damages, such as the heat affected zone, thermal stress, thermal crack and recast layer caused during the material melting and vaporization associated with the traditional laser machining process, are inevitable produced along the groove. In order to minimize the thermal damages, this study applies a laser with lower power intensity to heat and soften the target material, and the mechanical properties of the target decrease significantly with an increase in the heating temperature, and during the whole process, the temperature of material would be below its melting point. Therefore, the material remains solid, no melting and vaporization. Waterjet is applied off-axially to expel the softened elemental material by laser radiation and cool the material for low damage micromachining.The microgroove feature and the effect of processing parameters on the microgroove feature was researched experimentally in the process of laser-assisted waterjet microgrooving monocrystalline silicon. It was shown that the microgroove depth was increased with an increase in the focal plane position and the laser pulse energy, and was firstly increased and then reduced with an increase in the waterjet offset distance, and also was reduced with an increase in the water pressure and impact angle. The influence on the microgroove depth was decreased in the order of the water pressure>the laser pulse energy>the focal plane position>the waterjet offset distance >the laser pulse overlapping ratio> the impact angle. It was also shown that the microgroove width was almost an constant with the change of the focal plane position, was increased with an increase in the laser pulse energy and the impact angle, and was reduced with an increase in the waterjet offset distance and the water pressure. And the influence on the microgroove width was decreased in the order of the water pressure> the laser pulse energy>the waterjet offset distance>the laser pulse overlapping ratio > the impact angle> the focal plane position. The influence of the processing parameters on HAZ width was studied. It was shown that the HAZ width was reduced with an increase in the the waterjet offset distance and the water pressure, and was changed slightly with the focal plane position, the impact angle, the laser pulse energy and the laser pulse overlapping ratio. The influence on the HAZ width was decreased in the order of the waterjet offset distance> the water pressure> the laser pulse overlapping ratio> the laser pulse energy> the impact angle.The models of microgroove depth, width and HAZ width were established by using dimensional analysis. Then the models were verified through the orthogonal experiment. The results showed that the average relative error between the theoretical values and the experimental values could be controlled within 15%.The models were of good consistency. Thus, the models can be used to predict the cutting quality in the process of laser assisted waterjet microgrooving on monocrystalline silicon surface.Taking the largest microgroove depth, and the smallest microgroove width and the HAZ width as the optimization target, the preliminary optimum combination of the experimental samples was selected by comparing the number of Grey relational grades, and then the estimated Grey relational grade for optimum levels of machining parameters was solved. The estimated optimum level was proved to realize the optimization goal of the maximum microgroove aspest ratio. Meanwhile the HAZ width could be controlled within 20 μm. It was concluded experimentally that the microgroove aspect ratio is 1.398, which is better than the original result of 1.376.