Influence of Defocus Length on Hole Features in Laser Drilling of Ceramics

  • MORITA Noboru
    Department of Mechanical Engineering, Faculty of Engineering, Chiba University
  • KUWATA Takashi
    Department of Mechanical Engineering, Faculty of Engineering, Chiba University

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  • セラミックスのレーザ穴あけにおける焦点位置が加工穴形状に及ぼす影響
  • セラミックス ノ レーザ アナアケ ニ オケル ショウテン イチ ガ カコウ

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Abstract

Defocusing a laser beam is one of the most important factors to control the feature of drilling holes in ceramic materials. This suggests that laser beam energy is delivered and focused on the bottom of the drilling hole by multi-reflection from the internal wall surface of the hole. The deep hole drilling process of silicon nitride ceramics was simulated by the newly developed analysis model. The ray tracing method for a laser power intensity distribution analysis and difference method for thermal analysis was combined. The drilling hole is processed mainly by energy reflected from the internal wall surface of the hole. In this process laser beam intensity becomes higher in the center of the hole since the laser beam is focused by the wall-reflecting effect. The defocusing position from the material surface has direct effects upon the drilling process, which depends on reflection angle of a laser beam at the internal wall surface of the hole. The reflection angle controls the wall-focusing effect and determines the hole shape.

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