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Study on Process of Polishing Sapphire with Ultraviolet Laser

Author: SongYouQuan
Tutor: WeiZuo
School: Guangdong University of Technology
Course: Mechanical Manufacturing and Automation
Keywords: UV laser Etching Polishing Sapphire Photochemical action Thermal effect
CLC: TN249
Type: Master's thesis
Year: 2011
Downloads: 96
Quote: 0
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Abstract

Α-Al2O3 single crystal sapphire, good light transmission, thermal conductivity, insulation and mechanical mechanical; been widely used in industrial, medical, defense, aerospace and other fields. Laser polishing process has the traditional polishing unparalleled advantages, has broad prospects for development. In this paper, the mechanism of short wavelength UV laser polishing sapphire theoretical and experimental study of theoretical analysis on the basis of sum up of laser micromachining its mechanism laser etching sapphire thermal role and photochemical role; experimental study 355nm different process parameters the UV laser etched sapphire, as well as experimental studies of laser energy density, repetition rate, scan speed, scan mode, the laser incident UV laser polishing sapphire mechanism and its impact on surface roughness and orthogonal experiment various process parameters to optimize a theoretical analysis of 355nm UV laser etched sapphire damage threshold 16.23J/cm2, SSB model analysis of UV laser etched sapphire process both photochemical effects and thermal effects; combination of Gaussian The spot characteristics derived etching depth model of laser photochemical reaction and thermal effects. Drawn by UV laser the etched sapphire experimental research: 355nm UV laser etched sapphire destruction threshold 14.8J/cm2, close with the theory derived value. Etching experimental analysis proved the UV laser etched sapphire photochemical reactions and thermal effects exist mainly thermal effect. To study the impact of the laser energy density of sapphire etching mechanism: the laser energy density 18.7-40.3J/cm2, higher rates of photochemical role in etching, laser energy density 25.9-35.5J/cm2 photochemical role in etching the highest rate. Raman spectroscopy showed that the laser energy density is small, the thermal effect of the laser on the organizational structure of the sapphire surface destruction smaller laser photochemical action of sapphire etching the surface structure of the subtle changes in substrate of sapphire material damage; laser energy density high laser strong thermal action to destroy the structure of the sapphire surface tissue to generate amorphous thermal damage layer. The laser energy density increases, or etching of the number of pulses increases, the depth and diameter of the etch pits increases, the depth of the pit cross-sectional shape by the \the depth of the theoretical calculation. 3 drawn by the single factor polishing Experimental Study: With the laser energy density, repetition rate, scan speed, and the laser angle of incidence increases, the polishing surface roughness R. Reduced. When the laser energy density is 30.2-35J/cm2 photochemical effect polishing ratio, surface roughness R Minimum; when the repetition frequency of 25-30kHz, surface roughness R Lowest; in the scanning speed is 80-120mm / s, the surface roughness R. Minimum; at 20 ° -40 °, the surface roughness R Minimum. Scan mode is the more complex, the surface roughness Ra of the lower cross twice the scan angle of 60 °, the surface roughness Ra of the lowest. Multi-factor orthogonal optimization on experimental research: polishing scan speed the most significant impact on the polished surface roughness Ra of 355nm UV laser polishing sapphire lowest surface roughness optimal combination of process parameters: laser energy density 30.2J/cm2 is repetition frequency of 25kHz, a scanning speed of 120mm / s, the incident angle of 35 °, the scanning method twice to cross-scan and crossing angle of 75 °. Sapphire polished surface under conditions of optimal process parameters is relatively more flat tidy; thermal effect is relatively weak, less the microscopic surface groups flocculent broken; polished surface more uniform.

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