• Journal of the Korean institute of surface engineering
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• v.45 no.4
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• pp.143-150
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• 2012

Laser cleaning have been found to be a useful cleaning tool to remove contaminants without inducing damage to the substrate and making secondary pollutant. In this study, the effect of Nd:YAG laser cleaning system, emitting at 1064 nm and 532 nm, on acrylic resin applied onto copper coupons and pieces of bronze was investigated. The samples after laser cleaning tests were examined using microscopy, FT-IR, SEM-EDS. As a result, the acrylic resin could be removed from most of the samples at low laser energy density. Laser wavelength 532 nm was more effective than 1064 nm because of using lower laser energy density, which could reduce heat damage to substrates. Although the acrylic resin was easily removed, it revealed melted surfaces and removed bronze patina which must remain. The problems should be solved by future studies using different laser system or laser wavelengths.

• Electrical & Electronic Materials
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• v.9 no.6
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• pp.593-599
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• 1996

Laser scribing of silicon plays an important role in metallization including the grid pattern and the front surface geometry which means aspect ratio of metal contacts. To make a front metal electrode of buried contact solar cell, we used ND:YAG lasers that deliver average 3-4W at TEM$\_$00/ mode power to sample stage. The Q-switched Nd:YAG laser of 1.064 gm wavelength was used for silicon scribing with 20-40.mu.m width and 20-200.mu.m depth capabilities. After silicon slag etching, the groove width and depth for buried contact solar cell are -20.mu.m and 30-50.mu.m respectively. Using MEL 40 Nd:YAG laser system, we can scribe the silicon surface with 18-23.mu.m width and 20-200.mu.m depth controlled by krypton arc lamp power, scan speed, pulse frequency and beam focusing. We fabricated a buried contact Silicon Solar Cell which had an energy conversion efficiency of 18.8 %. In this case, the groove width and depth are 20.mu.m and 50.mu.m respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.119-120
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• 2008

• Proceedings of the KWS Conference
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• 2008.05a
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• pp.47-47
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• 2008

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.93-94
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• 2006

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.19-20
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• 2007

• Journal of Welding and Joining
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• v.20 no.3
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• pp.109-115
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• 2002

In this study high power Nd:YAG laser welding of structural steel was investigated. For the test steel blocks of $50{\times}50{\times}200mm$ were cut and machined, and bead-on-plate weld was made on the machined surface. Argon, nitrogen, helium, dry air or mixed gases were used to find the effect of shielding conditions on the bead formation. Results demonstrated that there were Fe I rich region and Fe II rich region in the laser induced plasma column based on the spectral analysis with S-2000 field spectrometer The Fe I region was located at the root of the column near keyhole opening. On the other hand, Fe II region was found at the middle of the plasma column. In the Nd:YAG laser welding, Fe I region emitted continuum which had peak value at wave length of around 710nm, and Fe II region had the peak at 580nm. In the welding of steel by $CO_2$ laser, however, no continuum was observed. There showed two groups of strong spikes in the $CO_2$ laser welding; the first group was displayed at the wave band of 450-560nm. This spike group emitted stronger intensity of light and sharper peaks than those group at 680-800nm.

• Korean Journal of Optics and Photonics
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• v.9 no.3
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• pp.186-190
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• 1998

We fabricated a diode-side pumped high power Nd:YAG laser with a gold coated flow tube(diameter of 10mm) and three sets of 140W diode bar. The diameter of Nd:YAG rod was 6mm and its length was 130mm. We obtained 130W cw power from a linear resonator with an 11% output coupler, which corresponds to the slope efficiency of 43% and the optical efficiency of 31%. The measured beam quality factor(M$^2$) reached about 85 which is fairly large due to the large size of the rod. Thermal lensing of the rod was measured to be 5.3-7.4D/$kW_{pump}$ when the laser was operating.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.989-992
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• 1997

The objective of this study is to develop stencil cutting process and determine optimal conditions which make good-quality stencil by using a Nd:YAG laser. The effects of process parameters such as laser power, type of mask, gas pressure, cutting speed and pulse width on the cut edge quality were investigated. In order to analyze the cut surface characteristics(roughness, kerf width, dross) optical microscopy, SEM photography and roughness test were used. A a results, the optimal conditions of process parameters were determined, and the practical feasibility of the proposed system is also examined by using a commercial gerber file for PCB stencil manufacturing.

• Journal of Welding and Joining
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• v.19 no.3
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• pp.317-324
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• 2001

This study deals with high power Nd:YAG laser welding of thin steels for small pressure vessels. Full penetration welding at the overlap joint was performed so as to assure sufficient weld strength. Results showed that mid-depth weld size reduced drastically with increasing the travel speed. Position of focus had little effect on the bead formation even though short focal system was used. However, the shape factor and the bead width had closely related with the position of focus. Based on the microstructural inspection, acceptable weld was obtained when the overlap clearance was controlled up to 20% of the base metal thickness. In the case that the joint contained more clearance than the critical value, both the tensile shear strength and the tear strength were reduced. Results also demonstrated that shielding gases were proved to play a key role as far as the bead formation characteristics was taken into consideration. Blowing dry air through 5mm in diameter nozzle produced narrower bead cross-section than that of argon or nitrogen shielding.