UVレーザによる高アスペクト比小径穴あけ加工 (第2報):—集光条件の影響— High-aspect-ratio Microdrilling with UV Laser Ablation II:—Influence of Beam Parameters on Hole Profile—
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High-aspect-ratio microdrilling of borosilicate glass has been demonstrated by the forth harmonic of nanosecond Nd : YVO<sub>4</sub> laser. In this paper, we investigated about the influence of the beam profile on the hole profile. Beam profile was changed by using focal lens with the focal length of 10 mm, 20 mm, 30 mm, 50 mm and 100 mm. As a result the glass was drilled deeper than 2200 μm using the focusing lenses with the focal length of 20 mm, 30 mm and 50 mm. On the other hand, the depths of the holes were less than 800 μm using the focusing lenses with the focal length of 10 mm and 100 mm. The profiles of the holes drilled with the focusing lens with the focal length of 20 mm, 30 mm and 50 mm were almost same. The diameters of the holes were smaller than 15 μm in the range deeper than 500 μm, therefore the aspect ratio was higher than 110. Drilled depths and profiles were measured with changing focus positions. No clear were difference were observed when the defocus distances were less than ∼70 % of Rayleigh range. Transmitted laser energy passing through the holes were measured by using the glass plates with different thickness and compared with calculated energy supposing the laser beam propagates as Gaussian beam and no reflection on the inner surface of the drilled hole. As a result the energy of the transmitted light was almost same as that of the calculated energy when the plate was thinner than 1 mm. On contrast, when the plate thickness was 2 mm, the transmitted light was larger than that of the calculated energy. This result conducts the laser beam was reflected and the reflected laser was dominant when the hole was deeper than 1mm.
- Journal of the Japan Society for Precision Engineering
Journal of the Japan Society for Precision Engineering 76(11), 1266-1270, 2010
The Japan Society for Precision Engineering