• 마이크로전자및패키징학회지
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• 제8권4호
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• pp.1-10
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• 2001

유리 기판상에 증착된 패드(pad)의 접합부 가열에 의한 면배열(area array) 형태 선자 패키지의 chip-on-glass(COG) 마운팅 공정이 시도되었다. 패드는 접합층(즉, Cr 또는 Ti)과 상부 코팅층(즉, Ni 또는 Cu)으로 구성되었으며, 이 중 접합층이 유리 기판을 투과하는 UV레이저에 의해 가열되었다. 접합층에 흡수된 레이저 에너지는 열전노 과정을 통하여 패드와 물리적으로 접촉되어 있는 솔더볼의 온도를 상승시켰으며, 리플로우 과정을 통하여 솔더 범프를 형성하였다. 레이저 가열 동안 솔더볼의 온도 이력(profile)을 측정함으로써 레이저 리플로우 솔더링시 접합층 및 상부 코팅층의 영향이 조사되었다. 그 결과들은 접합층의 반사율 측정 견과에 기초하여 논의되었다. 아울러 솔더 범프의 미세구조와 기계적 특성이 조사되었다.

• 한국진공학회지
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• 제6권2호
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• pp.114-121
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• 1997

투명전도성 산화주석 박막이 펄스레이저증착에 의하여 파이렉스유리 기판상에 제조 되었다. 진공, $O_2$, 및 $Sn(CH_3)_4$분위기에서 Nd-YAG레이저 빛살이 다결정 $SnO_2$ 타겟을 융제 하여 실온에서 기판상에 박막을 증착시키고, 증착된 막을 230, 420, 및 $610^{\circ}C$에서 각각 2시 간 동안 공기중에서 열처리하였다. 박막의 특성이 UV-VIS-NIR 분광법과 X-선 회절법에 의하여 조사되고, 전기적 성질이 촉심식법으로 구해진 막의 두께와 함께 사점탐침법에 의하 여 측정되었다. $Sn(CH_3)_4$이 존재할 때 $SnO_2$상들이 실온에서조차 성장되는 것이 관찰되었다. 이는 레이저 융제 동안 발생된 마이크로플라즈마가 전구물질분자의 분해에 중요한 역할을 함을 시사한다.

• Applied Science and Convergence Technology
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• 제26권4호
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• pp.79-85
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• 2017

The crack-free AlGaN template has been successfully grown by using selective area growth with triangular GaN facet. The triangular GaN stripe structure was obtained by vertical growth rate enhanced mode with low growth temperature of $950^{\circ}C$ and high growth pressure of 500 torr. The lateral growth rate enhanced mode of AlGaN for crack-free and flat surface was also investigated. Low pressure of 30 torr and high V/III ratio of 4400 were favorable for lateral growth of AlGaN. It was confirmed that the $4{\mu}m$ -thick $Al_{0.2}Ga_{0.8}N$ was crack-free over entire 2-inch wafer. The dislocation density of $Al_{0.2}Ga_{0.8}N$ was as low as ${\sim}7.6{\times}10^8/cm^2$ measured by cathodoluminescence. Based on the high quality AlGaN with low dislocation density, the ultraviolet laser diode epitaxy with cladding, waveguide and GaN/AlGaN multiple quantum well (MQW) was grown by metalorganic chemical vapor deposition. The stimulated emission at 349 nm with full width at half maximum of 1.8 nm from the MQW was observed through optical pumping experiment with 193 nm KrF laser. We also have fabricated the deep ridge type ultraviolet laser diode (UV-LD) with $5{\mu}m-wide$ and $700{\mu}m-long$ cavity for electrical properties. The turn on voltage was below 5 V and the resistance was ${\sim}55{\Omega}$ at applied voltage of 10 V. The amplified spontaneous emission spectrum of UV-LD was also observed from pulsed current injection.

• 한국정밀공학회지
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• 제17권8호
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• pp.134-139
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• 2000

In order to understand the removal mechanism and seek the optimal conditions. KrF excimer laser ablation of Cr films on glass substrates is investigated. The surface morphology of the laser-irradiated spot is examined by SEM. The measured single-shot ablation rate is found to be about two times the result of numerical analysis based on a surface vaporization model and heat conduction theory. Surface morphology examination indicates that the Cr film is removed by the sequence of melting-surface vaporization-,melt expulsion by plasma recoil and that the outmost ripple of the diffraction pattern gives a strong effect on the morphology of molten Cr during the melting and vaporization processes. To seek the optimal process parameters for micro patterning morphological investigation is carried out experimentally on samples having different chromium film thicknesses. Optimal processing conditions are determined to enhance the accuracy and quality of thin film removal for micro patterning.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.143-146
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• 2009

One of the most important issues of crystalline silicon solar cell is minimizing reflectance at the surface. Laser texturing is an isotropic process that will sculpt the surface of a silicon wafer, regardless of its crystallographic orientation. We investigated surface texturing process using Nd-YAG laser ($\lambda$=1064 nm) on multi-crystalline silicon wafer. Removal of slag formed after the laser process was performed using acid solution (HF : $HNO_3$ : $CH_3COOH$ : DI water). The reflectance and carrier lifetime of the samples were measured and analyzed using UV-Vis spectrophotometer and carrier lifetime tester. It was found that the minimum reflectance of the samples was 16.39% and maximum carrier life time was $21.8\;{\mu}s$.

• 한국정밀공학회지
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• 제27권10호
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• pp.14-22
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• 2010

The most costly and time-consuming process in the fabrication of today's multi-layer circuit board is drilling interconnection holes between adjacent layers and via holes within a layer. Decreasing size of via holes being demanded and growing number of via holes per panel increase drilling costs. Component density and electronic functionality of today's multi-layer circuit boards can be improved with the introduction of cost-effective, variable depth laser drilled blind micro via holes, and interconnection holes. Laser technology is being quickly adopted into the circuit board industry but can be accelerated with the introduction of a true production laser drilling system. In order to get optimized condition for drilling to FPCB (Flexible Printed Circuit Board), we use various drill pattern as drill step. For productivity, we investigate drill path optimization method. And for the precise drilling the thermal drift of scanner and temperature change of scan system are tested.

• 한국산업융합학회 논문집
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• 제23권4_2호
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• pp.693-699
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• 2020

355nm UV pulse laser is irradiated on the surface of polyimide (PI) by LDW (Laser Direct Writing) method to produce a high sensitivity flexible humidity sensor using a simple one-step process. The LDW method continuously investigates 2-D CAD data using a galvano scanner and an F-lens. This method is non-contact, so it minimizes physical strain on the PI. Laser-induced graphene (LIG) produced by lasers has a high surface area due to its high flexibility and numerous pores and oxidizers compared to conductors. For this reason, it is highly useful as a flexible humidity sensor. The humidity sensor produced in this study was attached to the inside of a mask filter, which has become a hot topic recently, and its applicability was confirmed.The measurement of humidity measured the sensitivity, reactivity, stability and recovery behavior of the sensor by measuring changes in capacitance and resistance.

• 한국세라믹학회지
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• 제43권3호
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• pp.185-192
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• 2006

The effects of annealing on structural and electrical properties of ITO/PES (Indium Tin Oxide/Polyethersulfone) films was investigated. Amorphous ITO thin films were grown on plastic substrates, PES using low temperature DC magnetron sputtering. Various post annealing techniques were attempted to research variations of microstructure and electrical properties: i) conventional thermal annealing, ii) excimer laser annealing, iii) UV irradiation. The electrical properties were obtained using Hall effect measurements and DC 4-point resistance measurement. The microstructural features were characterized by FESEM, XRD, Raman spectroscopy in terms of morphology and crystallinity. Optimized UV treatment exhibits the enhanced conductivity and crystallinity, compared to those of conventional thermal annealing.

• 한국레이저가공학회지
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• 제11권4호
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• pp.29-34
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• 2008

Ultraviolet laser micromachining has increasingly been applied to the electronics industry where precision machining of high-density, multi-layer, and multi material components is in a strong demand. Due to the ever-decreasing size of electronic products such as cellular phones, MP3 players, digital cameras, etc., flexible printed circuit board (FPCB), multi-layered with polymers and metals, tends to be thicker. In present, multi-layered FPCBs are being mechanically cut with a punching die. The mechanical cutting of FPCBs causes such defects as burr on layer edges, cracks in terminals, delamination and chipping of layers. In this study, the laser cutting mechanism of FPCB was examined to solve problems related to surface debris and short-circuiting that can be caused by the photo-thermal effect. The laser cutting of PI and FCCL, which are base materials of FPCB, was carried out using a pico-second laser(355nm, 532nm) and nano-second UV laser with adjusting variables such as the average/peak power, scanning speed, cycles, gas and materials. Points which special attention should be paid are that a fast scanning speed, low repetition rate and high peak power are required for precision machining.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2000년도 춘계총회,특별강연,심포지움,연구발표회
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• pp.79.2-79.2
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• 2000