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Research Papers

Crack Propagation in Glass by Laser Irradiation Along Laser Scribed Line

[+] Author and Article Information
Koji Yamamoto

 Mitsuboshi Diamond Industrial Co., Ltd., 1-4-37 Minami-kaneden, Suita, Osaka, 564-0044 Japankyamamoto@mitsuboshi-dia.co.jp

Noboru Hasaka, Hideki Morita

 Mitsuboshi Diamond Industrial Co., Ltd., 1-4-37 Minami-kaneden, Suita, Osaka, 564-0044 Japan

Etsuji Ohmura

Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871 Japan

J. Manuf. Sci. Eng 131(5), 051002 (Sep 04, 2009) (8 pages) doi:10.1115/1.3207739 History: Received September 19, 2008; Revised July 24, 2009; Published September 04, 2009

A mechanical breaking process after laser scribing is indispensable to complete the separation of glass substrate since the crack depth induced by the laser scribing is limited. Laser irradiation along the laser scribed line is introduced in this paper as a crack propagation method in depth direction after the laser scribing of a relatively thick glass in order to make the mechanical breaking easier. Since the separating load decreases by propagating the scribed crack deeply, it contributes to the inhibition of glass particle generation. The target of this research is to clarify the mechanism of crack propagation by the laser irradiation along the laser scribed line. Two-dimensional thermal elasticity analysis was conducted by a finite element method based on the experimental results in order to theoretically estimate the laser irradiation condition, which propagates crack. The following results were obtained. Compressive stress is generated on the glass surface and tensile stress is generated inside the glass by the laser irradiation along the laser scribed line. The tensile stress concentrates at the crack tip induced by the laser scribing, and the crack propagates into the depth direction. The condition of crack propagation can be estimated from the maximum surface temperature and the maximum tensile stress of the crack tip in practical processing velocity (200 mm/s or more mm/s).

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematics of (a) laser scribing and(b) laser overlapping irradiation along the laser scribed line

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Figure 2

Schematic of experimental setup for laser scribing and laser overlapping irradiation

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Figure 3

Positional relationship between heating area and cooling area for laser scribing

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Figure 4

Definitions and variables of geometry used for heating area of laser overlapping irradiation along the laser scribed line and analysis plane

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Figure 5

Photographs of separated surface by laser scribing (P1=14.7 W, v1=18 mm/s): (a) crack depth at center of substrate; (b) deep crack depth at end edge of substrate

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Figure 6

Domain of laser overlapping irradiation conditions obtained by combinations of laser power and scanning velocity. “×” marks on high-velocity side represent conditions that scribed crack was not able to propagate, and × marks on low-velocity side represent conditions that glass surface was damaged by laser heating.

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Figure 7

Photographs of separated surface of laser overlapping irradiation

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Figure 8

Relationship between crack depth Dc2 by laser overlapping irradiation and laser power P2. Deep crack depth side corresponds to the low-velocity condition in Fig. 6.

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Figure 9

Mesh geometry for FEM analysis

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Figure 10

Time variations in temperature on glass surface and at crack tip (P2=71.0 W, v2=200 mm/s)

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Figure 11

Temperature distributions at the time of Tsurfmax generating (P2=71.0 W, v2=200 mm/s): (a) temperature distribution along the z-axis and (b) temperature distribution on the x-z plane

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Figure 12

Time variations in stress σxx on glass surface and at crack tip corresponding to Fig. 1 (P2=71.0 W, v2=200 mm/s)

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Figure 13

Stress distributions of σxx at the time of σtipmax generating (P2=71.0 W, v2=200 mm/s). (i) Stress distribution of σxx along the z-axis and (ii) stress distribution of σxx on the x-z plane.

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Figure 14

The x-coordinate of nodal points at the time of σtipmax generating (P2=71.0 W, v2=200 mm/s)

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Figure 15

Schematic of propagation of laser scribed crack by laser overlapping irradiation

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Figure 16

Analysis results of maximum tensile stress σtipmax of crack tip and maximum surface temperature Tsurfmax at the laser scribed crack propagation conditions by laser overlapping irradiation. × marks on high-velocity side show the conditions that scribed crack was not able to propagate, and × marks on low-velocity show the conditions that glass surface was damaged by laser heating, corresponding to Fig. 6.

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Figure 17

Temperature distributions at the time of Tsurfmax generating (P2=30.4 W, v2=40 mm/s). (a) Temperature distribution along the z-axis and (b) temperature distribution on the x-z plane.

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