Research On Mechanism And Process Of SiC Single Crystal Cut With Wire Saw Excited By Ultrasonic

Silicon carbide(SiC)single crystal has been an ideal material for high performance optoelectronic devices in many complex environments and harsh conditions due to its high temperature resistance,high thermal conductivity,high electron saturation drift rate,low dielectric constant,impact resistance and high hardness.In cutting high-hard and brittle SiC wafer required for large-diameter and ultra-thin,the problems has occurred for conventional cutting method,such as low processing efficiency and difficulty in achieving wafer accuracy.Based on the technology of diamond wire saw cutting,SiC single crystal is cut by applying ultrasonic excitation to moving wire saw.The cutting mechanism and the optimization of processing parameters were analyzed by theoretical deduction,finite element simulation and experimental research.The dynamic model of moving wire saw cutting section is established and the vibration displacement equation at cutting point is solved.The modal analysis model of wire saw is established by using finite element software.The influence of processing parameters on the vibration characteristics of wire saw is analyzed,which is consistent with the theoretical analysis.The kinematics equation of wire saw under ultrasonic excitation and the kinematics equation of ordinary wire saw were established,and two different kinematics characteristics were analyzed.The trajectory of abrasive particles changed fundamentally.The theoretical value of sawing force under ultrasonic excitation is significantly lower than that of conventional cutting.The cutting arc length of wire saw increases within the effective processing time ?t,which effectively improves the material removal rate.The finite element simulation model of single diamond abrasive cutting SiC single crystal was established.The influence of processing parameters on sawing force,surface morphology of SiC single crystal cut with abrasive excited by ultrasonic and ordinary diamond abrasive cutting was analyzed.The sawing force of diamond abrasive excited by ultrasonic is much less than that of ordinary diamond abrasive cutting and the surface morphology is fairly flat.The cutting depth of abrasive has a significant influence on the sawing force and wafer surface,which is consistent with the theoretical analysis of cutting mechanism.The rationality of the theoretical analysis and simulation analysis of the cutting mechanism is verified by the experiments of SiC single crystal cutting under the conditions of ultrasonic excitation and common wire saw.Orthogonal experimental design was used to study the affecting relationships of the comprehensive influence on the sawing force and surface roughness of SiC single crystal cut with wire saw excited by ultrasonic.The order of influence factors is: workpiece lateral movement speed,amplitude,wire saw cutting speed and workpiece rotation speed.The surface roughness Ra of SiC single crystal was predicted by the fruit fly optimization algorithm of grey neural network model.The results show that the average relative error between the predicted value of the surface roughness and the experimental value is 2.09%.It can better predict the surface roughness of SiC single crystal.