• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.616-619
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• 2003

Photochemical and photothermal effects have correlation with each other and depend on laser wavelength. Multi-scanning laser ablation process of polymer with DPSS(Diode Pumped Solid State) 3rd harmonic Nd:YVO$_4$ laser with wavelength of 355nm is applied to fabricate three-dimensional micro shape. The DPSSL photomachining system can rapidly and cheaply fabricate 2D pattern or 3D shape with high efficiency because we only use CAD/CAM software and precision stages instead of complex projection mask. Photomachinability of polymer is highly influenced by laser wavelength and its own chemical structure. So the optical characteristics of polymers for 355nm laser source is investigated by experimentally and theoretically.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.612-615
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• 2003

Maskless laser patterning process is developed using 3rd harmonic Diode Pumped Solid State Laser with near visible wavelength of 355 nm. Photo-sensitive curable polymer is irradiated by UV laser and developed using polymer solvent to obtain quasi-3D patterns. We performed basic experiments for the various process conditions such as laser power, writing speed, laser focus, and polymer optical property to gain the optimal conditions. Experimentally, the patterns of trapezoidal shape were manufactured into dimension of 8${\mu}{\textrm}{m}$ width and 5.4${\mu}{\textrm}{m}$ height. This process could be applied to fabricate a single mode waveguide without expensive mask projection method.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.1
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• pp.120-125
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• 2008

A flip-chip bonding system using DPSS(Diode Pumped Solid State) Nd:YAG laser(wavelength : 1064nm) which shows a good quality in fine pitch bonding is developed. This laser bonder can transfer beam energy to the solder directly and melt it without any physical contact by scanning a bare chip. By using a laser source to heat up the solder balls directly, it can reduce heat loss and any defects such as bridge with adjacent solder, overheating problems, and chip breakage. Comparing to conventional flip-chip bonders, the bonding time can be shortened drastically. This laser precision micro bonder can be applied to flip-chip bonding with many advantage in comparison with conventional ones.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.231-233
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• 2005

Laser have been utilized as a heat source for the soldering of electronic components for the their capability of localized heating and faster heating rate. Laser soldering process, especially the diode laser soldering of BGA solderball was investigated. In this study, an attempt was made to investigate the possibility of laser soldering using Sn-37Pb and Sn-3Ag-0.5Cu solderball. The laser energy absorbed on the pad raised the temperature of the solderball forming a reflowed solder bump. The result were discussed based on the measurement of pull and shear strength of the bond.

• Laser Solutions
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• v.18 no.4
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• pp.6-11
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• 2015

Specially designed and 3D printed samples were prepared and joined by a diode laser source. To increase the strength of joining and reliability of samples, the surface was patterned by using a 3D printer. The joining surface was prepared as hemispherical shape with no-patterns, 0.5mm pitch, 0.75mm pitch and 1mm pitch. The optical properties of samples were measured by using an integrated sphere where classical Kubelka-Munk theory and modified Richard-Mudgetts theory for the analysis applied. Scanning speed was set at 500mm/min and laser power was varied between 9 and 10watts for the preliminary joining characteristic analysis.

• International Journal of Korean Welding Society
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• v.3 no.1
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• pp.45-50
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• 2003

Welding using lasers can be mass-produced in high speed. In the laser welding, performing real-time monitoring system of the welding quality is very important in enhancing the efficiency of welding. In this study, the plasma and molten metal which are generated during laser welding were measured using the UV sensor and IR sensors. The results of laser welding were classified into five categories such as optimal heat input, little low heat input, low heat input, partial joining due to gap mismatch, and nozzle deviation. Also, a system was formulated which uses the measured signals with a fuzzy pattern recognition method which is used to perform real-time evaluation of the welding quality and the defects which can occur in laser welding.

• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.340-341
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• 2005

• Proceedings of the Optical Society of Korea Conference
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• 1998.08a
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• pp.86-87
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• 1998

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.123-124
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• 2007

• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.364.1-364
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• 2001