• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.329-332
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• 2001

In this paper, it's shown that the saturable absorber Nd:LSB has a capability as a saturable absorber in Q-switching system. In the passively Q-switched 1.3${\mu}{\textrm}{m}$ Nd:YAG laser with saturable absorber, we theoretically investigated the optimized output mirror, peak power, output power, pulse width and output efficiency. The passively Q-switched Nd:YAG laser with saturable absorber Nd:LSB gives peak power of 30MW and pulse width of 6.23 ps at 30cm resonator length and output mirror reflectivity 98%. Consequently the output energies are 143, 200 and 209 $\mu$J at loss of 2.2%, 2.1% and 1.5%, respectively.

• KIEE International Transactions on Electrophysics and Applications
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• v.2C no.6
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• pp.309-313
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• 2002

In this paper, we have studied minimization of the kerf-width and surface burning, which occurred after the conventional singulation process of the multi-layer BGA board with copper, polyethylene and epoxy glass fiber. The high thermal energy of a pulsed Nd:YAG laser is used to cut the multi-layer board. The most considerable matter in the laser cutting of the multi-layer BGA boards is their different absorption coefficient to the laser beam and their different heat conductivity. The cut mechanism of a multi-layer BGA board using a 2$^{nd}$ harmonic Nd:YAG laser is the thermal vaporization by high temperature rise based on the Gaussian profile and copper melting point. In this experiment, we found that the sacrifice layer and Na blowing are effective in minimizing the surface burning by the reaction between oxygen in the air and the laser beam. In addition, N2 blowing reduces laser energy loss by debris and suppresses surface oxidation. Also, the beam incidence on the epoxy layer compared to polyimide was much more suitable to reduce damage to polyimide with copper wire for the multi layer BGA singulation. When the polyester double-sided tape is used as a sacrifice layer, surface carbonization becomes less. The SEM, non-contact 3D inspector and high-resolution microscope are used to measure cut line-width and surface morphology.

• The Journal of the Korean dental association
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• v.54 no.11
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• pp.865-873
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• 2016

Background/Purpose: The purpose of this study was to evaluate the effect of Nd:YAG irradiation on adherence of retrograde filling materials (mineral trioxide aggregate [MTA] and Super-EBA) by micro-computed tomography (CT) measurement and to observe the dentinal surface after irradiation by scanning electron microscopy (SEM). Materials and methods: Forty retrofilling models using extracted human teeth were divided into four groups according to the material and method used: ProRoot MTA (MTA group), Super-EBA (EBA group), MTA with Nd:YAG laser irradiation (LMTA group), and Super-EBA with Nd:YAG laser irradiation (LEBA group). All specimens were stored in 100% humidity for 24 hours until micro-CT was performed. The gap volume of the tooth/material interface was measured using the CTAn program. In six samples, the laser-irradiated dentin surface was observed using SEM. Results: The mean percent difference in gap volume was not statistically significant between the Nd:YAG laser-irradiated groups and non-irradiated in both materials(P > 0.05). The gap volume in the MTA group was significantly lower than that in the EBA group (P < 0.05). Examination of the non-irradiated specimens by SEM showed patent dentinal tubules. In contrast, alterations in the texture of the dentin surface and obliteration of the dentinal tubules were evident in the Nd:YAG laser-irradiated specimens. Conclusion: In this study, changes in the dentinal surface after Nd:YAG irradiation did not affect adherence between the apical filling material and the dentin wall.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.626-631
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• 2002

This paper describes the weldability and mechanical behavior of JIS S45C medium carbon steel (corresponding to KS SM45C and SAE 1045) for machine structures in CW Nd:YAG laser welding. ill general, medium carbon steels have a limited application to the industrial fields in spite of good mechanical characteristics. This is due to welding difficulty because of the high carbon contents and impurities in this material. Therefore, in this study the laser weldability of medium carbon steel with adjusted contents of S and P has been investigated in order to extend the application to medium carbon steels. Several experiments and numerical simulations have been conducted to determine the characteristics of mechanical behavior in CW Nd:YAG laser welds. The results of the simulations concur with the experiment results. From the result of this study, the application possibility of CW Nd:YAG laser welding to medium carbon steel has been confirmed. Also, the appropriateness of mechanical behavior simulation has been verified to analyze and predict the welding phenomena.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1703-1705
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• 2001

The pulsed Nd:YAG laser is used widely for materials processing and medical instrument etc. It is important to control the laser energy in those fields using a pulsed Nd:YAG laser. In this paper, constant-frequency current resonant half-bridge inverter and Cockcroft-Walton circuit are used to charge the energy storage capacitor variably. This laser power supply is designed and fabricated which has no high-voltage transformer, less switching losses, compact size and capability in varying the laser output power. Also, the output characteristics of this Nd:YAG laser system are investigated. The tested results are described.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.6
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• pp.720-728
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• 2011

Lap joint welding conducts low carbon steel plates using a 2.0kW continuous wave Nd:YAG laser beam. The specimen is composed of thin plate of 20 sheets. Process Variables contain two controlled parameters of the laser power and the welding speed. In order to quantitatively examine the characteristics of the lap welding, the welding quality of the cut section, stain-stress behavior, and the hardness of the welded part are investigated. The weld width difference between the top and the bottom because the welding speed is increased. The reason, cooling rate is decreased because of fast welding speed. When the heat input is higher, larger volume of the base metal will melt and the welding heat has longer time to conduct into the bottom from the top. The microstructure and tensile properties of the joints are investigated in order to analyze the effects of heat input on the quality of laser welded specimen. From the results of the investigation, We observe that welding quality is good for the laser power of 1800W, and laser welding speed from 1.8m/min to 2.2m/min.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.5
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• pp.629-635
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• 2006

Manufacture of motor by laser has been studying realization that was demands on market for lightening and miniaturization. Moreover. early in the 1980s. manufacture of parts for automobiles by laser welding was already successfully introduced. The purpose of this study was to develop production technology of the high quality laminated stator core for motor by pulsed Nd:YAG laser heat source. In the event of adjusting defocus and voltage to control humping in laser welding of the laminated core. sound bead could be obtained. but deep penetration was not. Therefore. explosive evaporating plasma was controlled by adjustment of peak power on pulse width. Particularly, because explosive evaporating plasma induced high peak power, made molten metal in keyhole scatter. a suitable adjustment of peak power was required to obtain sound bead. As a results of experiment. sound bead and deep penetration could be obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.437-438
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.425-426
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.405-406
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• 2008