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論文 |
論文
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山田, 啓司 ; 西岡, 真吾 ; 細川, 晃 ; 上田, 隆司
概要:
Laser cleaving process is a prospective technique to divide a thin plate of brittle materials into small pieces, because of its high yield ratio and controllability. In addition, the process is carried out without coolant which
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causes the environmental pollution and the contamination of the electrical devices etched on the wafer. In this paper, laser cleaving of silicon wafer is conducted with pulsed Nd: YAG laser. The temperature of laser spot is measured by means of the two-color pyrometer with optical fiber and the acoustic emission caused by crack propagation is also observed. When the laser spot is scanned at the appropriate interval and velocity, the crack propagates in sequence by the corresponding laser irradiation. As a result, both high linearity of cleaved edge and fine fractured surface roughness are obtained. The thermal stress distribution induced by laser irradiation is analysed with FEM model, in which the stress intensity factor is calculated at the vicinity of the crack tip in order to clarify the criterion of crack propagation. The analysis and experiments reveal that the maximum tensile stress at the crack tip increases with temperature and the crack propagates when the stress intensity factor reaches the fracture toughness of the material.
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論文 |
論文
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辺見, 慎吾 ; 古本, 達明 ; 細川, 晃 ; 小谷野, 智広 ; 上田, 隆司
概要:
Many methods for dental treatment using heat produced by laser irradiation have been developed. It is necessary to deter
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mine the surface temperature of the laser-irradiated area to elucidate the mechanism of enamel removal by laser irradiation. In this study, the surface temperature of human enamel during CO2 laser irradiation was measured by two-color pyrometry. In addition, acoustic emission occurring inside the tooth during laser irradiation was also measured. The results indicated that the surface temperature increased with increasing laser energy. In addition, acoustic emission occurred when the enamel surface was removed, and the removal volume increased with increasing number of acoustic emission signals. 歯科医療の分野では，主にレーザ照射に起因して生じる熱を利用して歯質除去などの治療が行われる．そのため，レーザ照射による歯質の除去メカ二ズムを解明する上で，照射部の温度は重要な要素である．本研究では，ファイバ導光型赤外線輻射温度計を用いて，CO2レーザ照射中のエナメル質表面温度を測定した．また，エナメル質内部に発生するAE波を同時に測定し，温度と併せてエナメル質の除去機構を検討した．その結果，エナメル質表面の温度はレーザエネルギの増加にともない上昇した．また，エナメル質の除去に対応してAE波が発生し，AE波の発生回数が増えると除去体積が線形的に増加することがわかった．
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