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515nm 피코초 레이저를 이용한 구리 어블레이션 공정의 최대 가공율에 대한 이론적 분석
신동식,조용권,손현기,서정,Shin, Dongsig,Cho, Yongkwon,Sohn, Hyonkee,Suh, Jeong 한국레이저가공학회 2013 한국레이저가공학회지 Vol.16 No.2
Picosecond lasers are a very effective tool for micromachining metals, especially when high accuracy, high surface roughness and no heat affected zone are required. However, low productivity has been a limit to broadening the spectrum of their industrial applications. Recently it was reported that in the micromachining of copper with a 1064nm picosecond laser, there exist the optimal pulse energy and repetition rate to achieve the maximum volume ablation rate. In this paper, we used a 515nm picosecond laser, which is more efficient for micromachining copper in terms of laser energy absorption, to obtain its optimal pulse energy and repetition rate. Theoretical analysis based on the experimental data on copper ablation showed that using a 515nm picosecond laser instead of a 1064nm picosecond laser is more favorable in that the calculated threshold fluence is 75% lower and optical penetration depth is 50% deeper.
KrF Excimer Laser를 이용한 Polymer Ablation
신동식(Dongsig Shin),이제훈(Jaehoon Lee) 한국생산제조학회 2007 한국공작기계학회 춘계학술대회논문집 Vol.2007 No.-
The ablative decomposition mechanism of polymers with KrF excimer laser(λ: 248㎚, pulse duration: 5ns) is investigated. The UV/Vis spectrometer analysis showed that PMMA(polymethyl methacrylate) is a weak absorber and PET(polyethylene terephthalate) is a strong absorber at the wavelength of 248㎚. The results(surface debris, melt, etch depth, etching shape) from drilling and direct writing experiments imply that ablation mechanism of PMMA is dominated by photothermal process, while that of PET is dominated by photochemical process.
나노초 및 피코초 레이저를 이용한 FPCB의 절단특성 분석
신동식(Dongsig Shin),이제훈(Jaehoon Lee),손현기(Hyonkee Sohn),백병만(Byoungman Paik) 한국레이저가공학회 2008 한국레이저가공학회지 Vol.11 No.4
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 PL 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.
신동식(Dongsig Shin),이제훈(Jaehoon Lee),서정(Jeong Suh) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
In the last few years, lasers have found new applications in production engineering as tools for surface treatment, cutting, welding, drilling and marking. So far, the laser has mainly been used in special laser processing machines ('laser-only') directly integrated into a production line or serving as stand-alone stations in the workshop. By combining conventional metal cutting technologies with laser processes in one machine, complete processing of a workpiece with different technologies in one setting can be realized. The main advantages are a reduction of the material flow between the production machines, which leads to a reduction in processing time and logistics, and an enhancement of manufacturing quality due to the processing in one setting. In addition to this approach new processing technologies such as laser-assisted machining are possible.
UV Laser Cutting Process for FPCB
신동식(Dongsig Shin),이제훈(Jahoon Lee),정용운(Yongwoon Chung),손현기(Hyonkee Shon) 한국레이저가공학회 2007 한국레이저가공학회 학술대회 논문집 Vol.2007 No.-
The application of lasers in the area of microelectronics is growing and diversifying to innovative technologies to enable the increased sophistication of their products. Lasers are employed in manufacturing processes as varied as semiconductor lithography, wafer dicing, and micro-welding via drilling and FPCB cutting. In particular, the laser ablation process is required in sophisticated FPCB cutting as the prior punching process incurs shearing and scratching. 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 and adjusting variables such as the average/peak power, scanning speed, cycles, gas and materials. Using an alpha-stepper, it was possible to analyze the thermal effect, composition of the surface debris, and the ablation rate. 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. Finally, useful data will result for the cutting of elaborately designed FPCBs for portable devices such as laptops, PDAs and mobile phones.
피코초 레이저의 공정변수에 따른 TSV 드릴링 특성연구
신동식(Dongsig Shin),서정(Jeong Suh),김정오(Jengo Kim) 한국레이저가공학회 2010 한국레이저가공학회지 Vol.13 No.4
Today, the most common process for generating Through Silicon Vias (TSVs) for 3D ICs is Deep Reactive Ion Etching (DRIE), which allows for high aspect ratio blind holes with low surface roughness. However, the DRIE process requires a vacuum environment and the use of expensive masks. The advantage of using lasers for TSV drilling is the higher flexibility they allow during manufacturing, because neither vacuum nor lithography or masks are required and because lasers can be applied even to metal and to dielectric layers other than silicon. However, conventional nanosecond lasers have the disadvantage of causing heat affection around the target area. By contrast, the use of a picosecond laser enables the precise generation of TSVs with less heat affected zone. In this study, we conducted a comparison of thermalization effects around laser-drilled holes when using a picosecond laser set for a high pulse energy range and a low pulse energy range. Notably, the low pulse energy picosecond laser process reduced the experimentally recast layer, surface debris and melts around the hole better than the high pulse energy process.