Discharge Erosion Mechanism And Experiment Of Monocrystalline Silicon

With the rapid development of science and technology, single crystal silicon, as the commonest semiconductor material, plays an irreplaceable role in frontier technology field. But for its brittleness, many manufacturing problems such as low productive efficiency, poor surface integrity, high processing costs and machining damage have caused during processing. Our team had tried to process Si by WEDM and had learned that its erosion mechanism was different from metal. In this paper, the erosion mechanism of single crystal silicon in EDM was proposed from the respect of simulation and testing, then the surface roughness and relative electrode wear of single crystal silicon in EDM had been studied based on this mechanism.Following are main research work:(1)Assumption of erosion mechanism of EDM on single crystal silicon was proposed from testing. It was considered that thermal stress played the leading role during the erosion process. Use ANSYS to simulation and tests to validate. Discharge model of single pulse was established on EDM, the temperature field and the thermal stress field of single-pulse discharge condition was analyzed based on finite element method. Theoretical amount of erosion of the silicon was calculated under the temperature field and thermal stress field, and was compared with the actual amount of erosion in tests. Results show that erosion process of the single crystal silicon EDM machining can be described by this assumption of erosion mechanism. The depth-diameter ratio of erosion pits and relative electrode wear were also studied by simulation.(2)Surface roughness is the key evaluation characteristic parameter of Processed surface quality. The change rule of erosion pits is coincident with surface roughness. In this paper, the surface roughness of single crystal silicon in EDM was studied by orthogonal experiment in WEDM Machine. Based on orthogonal experiment, on the one hand, the influence of each parameter on surface roughness was got, which well tallied with simulation after being compared; on the other hand, a set of optimum operating parameters was found, making minimum surface roughness of the workpiece.(3)In EDM process, tool wear is one of the primary factors that affect geometrical precision of workpiece. The EDM process rule of different doping types of silicon material with different process parameters was researched and compared with the machining process law of copper by copper electrode and silicon electrode. The relative electrode wear when machining silicon is far lower than copper, indicating that low electrode wear and even no electrode wear can be researched of silicon in EDM. The influence of voltage, pulse width, duty cycle, fluid flushing and other several factors on the electrode wear of silicon in EDM were also studied .