• Journal of the Korean Society for Precision Engineering
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• v.22 no.7 s.172
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• pp.19-26
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• 2005

The objective of this study is to investigate the influence of process parameters, such as power of laser, cutting speed of laser and material thickness, on the practical cutting region and the kerfwidth fer the case of cutting of CSP IN sheet using high power Nd:YAC laser in continuous wave(CW) mode. In order to obtain the practical cutting region and the relationship between process parameters on the kerfwidth, several laser cutting experiments are carried out. The effective heat input is introduced to consider the influence of power and cutting speed of laser on the kerfwidth together. From the results of experiments, the allowable cutting region and the relationship between the effective heat input and kerfwidth fur the case of cutting of CSP 1N sheet using high power CW Nd:YAG laser have been obtained to improve the dimensionalaccuracyofthecutarea.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.25-26
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• 2009

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.32-35
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• 1989

A 150W industrial Nd:YAG laser was developed. The thermal lensing effect was examined and the radius and position of rear mirror were optimized for higher efficiency. The efficiency of 2.5% was achieved. Also, the performance of laser welding in fine thermocouples and between high-temperature-melting dissimilar metals were investigated.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.7
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• pp.463-468
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• 2017

For transdermal drug delivery, needless injection system is composed of laser and microjet injector. Main mechanism of microjet injector is the laser-induced bubble. Nd:YAG and Er:YAG laser are used as a power source. Laser parameters such as pulse duration and wavelength are considered, which are core parameters to control the bubble motion. The Nd:YAG laser, pulse duration is short than bubble life time making cavitation like bubble while in Er:YAG laser, long pulse duration and high absorption in water drive bubble as a boiling bubble. Detailed motion of bubble and microjet is captured by the high speed camera. So it is observed that microjet characteristics are determined by the bubble behavior. The performance of drug delivery system is evaluated by fluorescent staining of guinea pig skin.

• Korean Journal of Materials Research
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• v.10 no.2
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• pp.171-174
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• 2000

In this study, the laser patterning of sputter-deposited amorphous CoNbZr films has been tried usig Nd: YAG laser. However, the metal film was not removed because of its high reflectance of the alser on the metal surface. To solve this problem, authors tried to screen-print a block polymer on the metal film and then irradiate the laser on the polymer. This is a new method which was suggested by this study. Using this new method, the metal films were effectively removed with the laser power of 114W even though the metal films was not removed with the laser power of 332W using the conventional method. This result leads to the conclusion that the block polymer acts as a laser energy absorbing and transferring layer.

• Korean Journal of Optics and Photonics
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• v.9 no.4
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• pp.231-235
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• 1998

Passively Q-switched, laser diode(LD) end-pumped Nd:YAG laser was demonstrated by using $Cr^{4+}$:YAG as a saturable absorber. In addition , we could calculate an excitation efficiency, which is an important parameter to evaluate the pumping geometry, directly by measuring the absorbed power in Nd:YAG at threshold condition. We found that output parameters such as average power, pulse duration, and repetition rate strongly depended on the low intensity transmission of $Cr^{4+}$:YAG and driving current of lase diode. The maximum Q-switched output power of 1 W was obtained with 40 kHz repetition rate. The pulse duration was varied from 50 ns to 200 ns.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.6
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• pp.740-745
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• 2006

This study suggested the occurrence source of weld-defects and its solution methods in a welding of Electrolyte injection hole by pulsed Nd:YAG laser. In experiment, the ramp down was used in order that solidification crack was removed. Furthermore. shrinkage stress and heat input were reduced by changing of weld trajectory and defocused distance. As a results of a experiment, a sound weld bead shape and crack-free weld bead can be obtained. In conclusion this show that the welding stability is greatly affected by modulation of laser pulse shape for the same laser energy and welding parameters.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.5
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• pp.35-43
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• 2007

Laser welding of metals has been widely used to improve a wear resistance and a corrosion resistance of the industrial parts. The objective of this research works is to investigate the influence of the process parameters, such as the welding for metals with CW Nd:YAG lasers. The bead-on-plate welding tests are carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the butt welding, the welding quality of the cut section, stain-stress behavior and the hardness of the welded part are investigated. From the results of the investigation, it has been shown that the optimal welding condition without defects in the vicinity of the welded area and with a good welding quality is 1325W of the laser power, and 1.4m/min of laser welding speed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.5
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• pp.70-75
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• 2010

In this paper, laser marking systems dedicated to cylinderical parts was developed. We first develop the marking device which consists of Nd-Yag laser, galvano scanner and additional rotational axis, then develop algorithm for supporting the digital image with bmp data format. Additional rotational axis is so attached as to rotate the cylinderical parts for marking its whole surface. The image is separated into line by line and the separated line image is sent to galvano scanner while rotating the additional axis simultaneously. CxImage library, famous open source code, is employed for the image processing. The developed method was tested with various images and shows that it reduces marking time significantly without reducing marking quality.

• Laser Solutions
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• v.4 no.2
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• pp.39-45
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• 2001

This paper introduces a cleaning process for removing submicron-sized particles from NiP hard disk substrates by the liquid-assisted laser cleaning technique. Measurements of cleaning Performance and time-resolved optical diagnostics are Performed to analyze the physical mechanism of contaminant removal. The results reveal that nanosecond laser pulses are effective for removing the contaminants regardless of the wavelength and that a thermal mechanism involving explosive vaporization of liquid dominates the cleaning process.