• Proceedings of the KWS Conference
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• 2010.05a
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• pp.32-38
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• 2010

Hybrid material(ceramic+metal) processes were developed for micro filter using ceramics coating at metal filter surface by thermal spray method, micro hole drilling at ceramic coated filter surface by femtosecond laser, and fiber laser direct welding of ceramic and metal (SUS304, SM45C) by capillary effect. Thermal spray process was used for ceramic powders and metal filters. The used ceramic powders were $Al_2O_3+40TiO_2$(Metco 131VF) powder of maximum particle size $5{\mu}m$ and ${Al_2O_3}99+$(Metco 54NS) power of maximum particle size 45m. Ceramic coated filters using thermal spray method had a great influence on powder material, particle size and coating thickness but had a fine performance as a micro filter. CW fiber laser was used to drill the top ceramic layer and melt the bottom metal layer for joining applications.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.6
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• pp.23-29
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• 2013

In this paper, pure $I_{ph}$ and hybrid carbon nanotube reinforced $I_{ph}$ were sintered using the SPS(spark plasma sintering) method for high densification. A nanosecond laser (${\lambda}=1063nm$, ${\tau}P=10ns$) and a femtosecond laser (${\lambda}=1027nm$, ${\tau}P=380fs$) were installed on an optical system for the micromachining test. The ablation characteristics of the pure $I_{ph}$ and CNT/$I_{ph}$ composites, such as thermal effect and ablation depth, were investigated using FE-SEM and a confocal microscope device. Laser machining results for the two mating materials showed improved performances: CNT/$I_{ph}$ composites showed good surface morphology of hole drilling without a melting zone due to the composites' high thermal properties; also, the ablated depth of CNT/$I_{ph}$ was higher than that of pure $I_{ph}$.

• 기계와재료
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• v.22 no.1
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• pp.22-29
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• 2010

최근 휴대폰 등 모방일 전자기기 산업에서 차세대 고부가 PCB(MLB, HDI, FPC, 등) 및 고기능 PCB(COF, MOF, SOF)의 급속한 적용 확대로 직경$20{\mu}m$급의 비아홀(viahole) 및 interconnection 홀 가공을 위한 초정밀/초고속 레이저 드릴링 공정 및 장비기술 개발에 대한 시장의 요구가 급증하고 있다. 이에 반해 기존의 CO2 레이저 드릴링은 기술적 한계에 도달하여 시장의 요구에 대응이 불가하며, 선진업체에서는 최근 UV 레이저 드릴링 장비에 대한 시장 점유율을 높여가고 있다. 특히 국내시장은 미국의 ESI사가 독점하고 있어 기술개발 투자를 통한 국산화가 절실한 상황이다. 이에 당사에서는 초고속/초정밀 UV laser 시스템을 이용한 FPC iva hole drilling을 연구과제로 개발을 진행하고 있으며 국산화를 넘어서 세계시장점유를 목표로 공정장비개발을 진행중이다.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.12
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• pp.1347-1352
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• 2011

Recently, as the aged population grows around the world, many medical instruments, devices, and their fabrication processes are developing. Among the devices, a drug delivery stent is a good example for precision machining. Conventional drug delivery stent has problem of the remaining polymer because the drug is coated on the surface with it. If the drug is impregnated into the micro hole array on the stent surface, the polymer can be perfectly eliminated. Micro sized holes are generally fabricated by laser machining however, the fabricated holes do not have an enough aspect ratio to contain the drug or a good surface finish to deliver the stend to blood vessel tissue. To overcome these problems, we propose a vibration-assisted machining mechanism with PZT (Piezoelectric Transducers) for abrication of micro sized holes better. The results indicated that the burr size can be significantly decreased with vibration assisted in nanosecond pulse laser drilling test.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.30-36
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• 2020

We demonstrated a successful fabrication of 4" Gallium Nitride (GaN)/Diamond High Electron Mobility Transistors (HEMTs) incorporated with Inner Slot Via Hole process. We made in manufacturing technology of 4" GaN/Diamond HEMT wafers in a compound semiconductor foundry since reported [1]. Wafer thickness uniformity and wafer flatness of starting GaN/Diamond wafers have improved greatly, which contributed to improved processing yield. By optimizing Laser drilling techniques, we successfully demonstrated a through-substrate-via process, which is last hurdle in GaN/Diamond manufacturing technology. To fully exploit Diamond's superior thermal property for GaN HEMT devices, we include Aluminum Nitride (AlN) barrier in epitaxial layer structure, in addition to conventional Aluminum Gallium Nitride (AlGaN) barrier layer. The current collapse revealed very stable up to Vds = 90 V. The trapping behaviors were measured Emission Microscope (EMMI). The traps are located in interface between Silicon Nitride (SiN) passivation layer and GaN cap layer.

• Current Photovoltaic Research
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• v.1 no.1
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• pp.17-26
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• 2013

In contrast to conventional crystalline cells, back-contact solar cells feature high efficiencies, simpler module assembly, and better aesthetics. The highest commercialized cell and module efficiency was recorded by n-type back-contact solar cells. However, the mainstream PV industry uses a p-type substrate instead of n-type due to the high costs and complexity of the manufacturing processes in the case of the latter. P-type back-contact solar cells such as metal wrap-through and emitter wrap-through, which are inexpensive and compatible with the current PV industry, have consequently been developed. In this paper the characteristics of EWT (emitter wrap-through) solar cells and their status and prospects for development are discussed.