Behavior Analysis And Control Research On Cut Surface Quality Of Laser-cut Ceramic

With the development of electronics industry, the demand for miniaturization andhigh processing precision drives the need for high quality cutting of thin electronicceramics. High cutting quality with recast layer of uniform microstructure andthickness, crack-free and striation-free cut surface was achieved by laser cutting.Compared to the traditional methods of ceramic cutting, laser cutting provides severaladvantages, such as high speed and efficiency, low cost and high processing quality.Besides, it’s especially suitable for cutting in free path such as curves and angles.1mm thickness96%alumina substrates were used in the experiment. The formationmechanisms of recast layer and striation were researched. The influence of cuttingparameters on profile and microstructure of laser-cut specimens was discussedthrough experiments and numerical simulation. By analyzing the heating and coolingcondition, parameter optimization was proceeded and specimen with high cuttingquality was obtained.The recast layer of laser-cut ceramic substrate is firmly attached to the basematerial which makes it hard to be removed. Therefore, it’s significant to achieve athin recast layer with uniform microstructure over the cut surface. By studying themicrostructure of recast layer and numerical simulation through ANSYS, the trend oftemperature gradient along the kerf and the velocity of assist gas were obtained. Theexperiment result showed that higher assist gas can reduce the thickness of recastlayer while cutting speed had a great influence on grain refinement. Combined withthe analysis of cooling condition for a good recast layer quality, optimal cuttingparameters of200W CO₂laser power in CW mode,1500mm/min cutting speed and8bar N2assist gas was employed for a thin and dense recast layer of uniformthickness and microstructure.On the other hand, two types of striation formed on the cut surface: upperstriation and lower striation. Conclusions were made by observation and analysis ofstriation formation that the upper striation was generated by the capillary force causedby the temperature difference around the cutting front, while the mismatch of cuttingspeed and melting speed resulted in the lower striation. The experiment and theoretical research indicated that a higher cutting speed can suppress the growth ofupper striation while the lower one can be eliminated by coordinating the laser powerand cutting speed. Fiber laser was employed for a much higher power density and theoptimal―ratio of velocity to power‖was determined as Xf≈21mm/（min·W） by aseries of experiment. Striation-free laser cutting was achieved with cutting parameterof1000W laser power,21000mm/min cutting speed and6bar assist gas pressure.In summary, two research results with significance were achieved:1) Highcutting quality ceramic specimen with uniform recast layer and striation-free cutsurface was obtained in free path laser cutting by experimental and theoreticalresearch.2) Fiber laser is more suitable for striation-free ceramic laser cutting. Thefeasibility of high precision fiber laser ceramic processing was proved by analyzingthe mechanism with Marangoni effect. The problem of low absorption rate withalumina can be overcome by temperature increase and phase change of the specimen.Research on laser cutting of thin electronic ceramic substrate was conductedthoroughly. The technique provides significant ground working for laser processing ofelectronic ceramic cutting and enriches the research content of non-metal materiallaser processing.