摘要
切削刀具和微电子散热器件对金刚石微槽结构的质量有较高要求。结合数值仿真和实验结果,研究了紫外皮秒激光工艺参数对化学气相沉积(CVD)金刚石微槽刻蚀质量的影响规律。首先,构建了温度场仿真模型,进行了网格无关性验证,分析了单脉冲激光作用下温度的分布特征。其次,建立了CVD金刚石激光切割质量评价指标,分析了工艺参数对CVD金刚石微槽表面质量的影响。结果表明,当网格尺寸小于光斑半径的1/50时,单脉冲作用下的温度不再随网格尺寸的变化而剧烈波动。等离子体会影响微槽表面颗粒的分布,并在金刚石表面以下诱导微裂纹缺陷;在同一能量密度下热影响区(HAZ)内的裂纹垂直于扫描方向的长度和改性区的宽度是相同的。主效应分析结果表明,激光功率对微槽宽度的影响最大,扫描速度对HAZ宽度的影响最大,当激光功率为8 W、扫描速度为10 mm·s^(-1)时,HAZ范围最小,获得的微槽质量较好。
Objective Diamond possesses high hardness,excellent thermal conductivity,and extremely high electron mobility.Cutting tools and microelectronic heat dissipation devices have high requirements for the quality of diamond microgroove structures.Therefore,achieving mass production,lowcost,and highprecision microstructure processing is a focus of current research.Compared with traditional diamond processing methods,ultrafast lasers cause the target material to detach from the ablation area in a gaseous or plasma state,which offers significant advantages,such as noncontact,good controllability,and a small heataffected zone.However,owing to the extremely short pulse width of ultrafast lasers,the interaction mechanism between the laser and material is difficult to observe,and the physical phenomena in the laserirradiated area are complex,which makes it challenging to ensure the resolution and controllability of diamond microgrooves.Therefore,studying the processing mechanism of ultrafast laser irradiation on chemical vapor deposition(CVD)diamond,analyzing the surface morphology of microgroove processing,and optimizing process parameters are of great significance.Methods This study reveals the interaction mechanism between ultrafast lasers and diamonds by establishing a finite element simulation model.Using an ultraviolet picosecond laser with a pulse width of 10 ps,laser wavelength of 355 nm,and maximum power of 10 W,microgrooves were etched on the surface of the sample.The dimension of the singlecrystal CVD diamond sample was 7 mm×7 mm×1 mm.A shape measurement optical microscope system was used to observe the surface morphology and particle distribution of the microgrooves,whereas a confocal microscope was employed to observe the sample dimensions and defect characteristics.Based on the surface morphology characteristics of the diamond after laser processing,quality evaluation criteria were established for the picosecond laser processing of CVD diamond.A factor effect analysis was applied to the established evaluation criteria to determine the contributions of different process parameters,thereby ensuring the resolution and controllability of the diamond microgrooves.Results and Discussions In this study,a transient temperature field model is established to analyze the temperature field distribution under a single pulse.Grid independence verification shows that the grid is gradually refined when the grid size is smaller than 1/50 of the spot radius.Moreover,the maximum and minimum temperatures eventually stabilize(Fig.3).In addition,under the action of 10 pulses,a repetition rate of 1000 kHz causes thermal accumulation more easily(Fig.6).The results of a morphological analysis using a shape measurement optical microscope system reveal that the highpressure airflow formed inside the microgrooves drives particles out of the irradiated area.The further the distance from the ablation area,the lower the airflow pressure is,and this causes particles to deposit outward,along the microgroove edges.At higher scanning speeds,hightemperature,highpressure plasma formed on the diamond surface,causes ablation particles to fly out at high speeds,which results in a particlefree deposition area near the processing region(Fig.7).The established quality evaluation criteria for CVD diamond laser cutting indicate that the size of the heataffected zone(HAZ)is fixed under the same energy density(Fig.10).The maximum outward extension distances of different types of defects within the HAZ are identical.When various defects appear in the microgrooves,the defects on one side of the microgroove are more significant than are those on the other side.This may be because of the offset angle generated between the center of the processing area and the center of the galvanometer during scanning leading to different thermal stresses at the microgroove edges.The results of a factor effect analysis of the process parameters show that when using the microgroove width as the evaluation criterion,laser power has a greater impact on the microgroove width than does the scanning speed(Table 3).When the laser power is 6 W and the scanning speed is 10 mm/s,the interaction between the two factors reaches a minimum(Fig.12).When using the HAZ width as the evaluation criterion,the scanning speed has a greater impact on the HAZ width than does the laser power(Table 4).When the laser power is 8 W and the scanning speed is 10 mm/s,the interaction between the two factors reaches a minimum(Fig.14).The scanning number has a weaker effect on both the microgroove and HAZ widths(Fig.13 and Fig.15).Conclusions This study primarily presents simulation and experimental research on the picosecond pulse laser processing of CVD diamonds.The main conclusions are as follows.1)When the grid size is smaller than 1/50 of the spot radius,the maximum and minimum temperatures no longer fluctuate significantly with a varying grid refinement.2)Hightemperature,highpressure plasma affects surface particle deposition in different states and causes microcracks to form beneath the diamond surface.3)The establishment of microgroove quality evaluation criteria shows that the HAZ size is fixed under the same energy density and that the maximum outward extension distances of different types of defects within the HAZ are the same.4)When using the microgroove width as the evaluation criterion,the laser power has a greater impact on the microgroove width than does the scanning speed.When the laser power is 6 W and the scanning speed is 10 mm/s,the interaction between the two factors reaches its minimum.When using the microgroove HAZ width as the evaluation criterion,the scanning speed has a greater impact on the HAZ width than does the laser power.When the laser power is 8 W and the scanning speed is 10 mm/s,the interaction between the two factors reaches its minimum.The scanning number has a weaker effect on both the microgroove and HAZ widths.
作者
曹龙超
胡文星
王俊涛
李维鸿
郭文涛
蔡旺
吴从义
Cao Longchao;Hu Wenxing;Wang Juntao;Li Weihong;Guo Wentao;Cai Wang;Wu Congyi(Hubei Key Laboratory of Digital Textile Equipment,School of Mechanical Engineering&Automation,Wuhan Textile University,Wuhan 430073,Hubei,China;School of Mechanical Science and Engineering,Huazhong University of Science and Technology,Wuhan 430074,Hubei,China;State Key Laboratory of Intelligent Manufacturing Equipment and Technology,Huazhong University of Science and Technology,Wuhan 430074,Hubei,China)
出处
《中国激光》
北大核心
2025年第8期272-285,共14页
Chinese Journal of Lasers
基金
国家自然科学基金(52105446)
智能制造装备与技术国家重点实验室开放项目(IMCTKF2023011)
湖北省自然科学基金(2023AFB878、2024AFB259)
武汉-曙光计划知识创新项目(2022010801020252)。
关键词
皮秒激光
化学气相沉积
金刚石
微槽
温度场
加工质量
picosecond laser
chemical vapor deposition
diamond
microgroove
temperature field
processing quality
