• 한국정밀공학회지
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• 제28권1호
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• pp.24-30
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• 2011

PC-TEMs (Polycarbonate Track-Etched membranes) were micro-drilled for biomedical applications by ultrafast pulsed laser. The ablation and damage characteristics were studied on PE-TEMs by assuming porous thin membranes. The experiments were conducted in the range of 2.02 $J/cm^2$ and 8.07$J/cm^2$. The ablation threshold and damage threshold were found to be 2.56$J/cm^2$ and 1.14$J/cm^2$, respectively. While a conical shaped drilled holes was made in lower fluence region, straight shaped holes were drilled in higher fluence region. Nanoholes made the membrane as porous material and ablation characteristics for both bulk and thin film membranes were compared.

• 한국기계가공학회지
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• 제12권6호
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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 $I_{ph}$.

• 반도체디스플레이기술학회지
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• 제8권4호
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• pp.31-36
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• 2009

In this paper, the laser cutting characteristics of the flexible PCB using high power Nd:YAG UV laser were investigated. A specific FPCB model was selected for the experiment. Test sheets were made, which had equal materials and layer structure to those of the outline (OL) region and the contact pad (CP) region in the FPCB. The experiment is made up of two stages. In the first stage of the experiment, the laser cutting fluence was found, which is the threshold fluence to cut the test sheets completely. The laser cutting fluence of the OL sheet is $1781.26{\sim}1970.16\;J/cm^2$ and that of the CP sheet is $2109.34{\sim}2134.34\;J/cm^2$. In the second stage, cutting performance and its qualities were analyzed by the experiment. The laser cutting performance remained almost unchanged for all laser and process parameter sets. The average cutting width (top side/bottom side) of the OL sheet was $40.45\;{\mu}m/11.52\;{\mu}m$ and that of the CP sheet was $22.14\;{\mu}m/10.93\;{\mu}m$. However, the laser cutting qualities were different according to the parameters. The adjacent region of the cutting line on the OL sheet was carbonized as the beam speed was low and the overlap coefficient was high. The surface quality around the cutting line of the CP sheet was about the same. Carbonization and debris occurred on the surface of the cutting line. As a result of the experiment, the cutting qualities were better as the overlap coefficient was made low and beam speed high. Therefore, the overlap coefficient 2 or 3 is proper for the FPCB laser cutting.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2003년도 somma/kms meeting
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• pp.150-150
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• 2003

• 한국광학회지
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• 제27권5호
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• pp.188-188
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• 2016

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 G
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• pp.3298-3300
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• 1999

In this paper, a $10{\times}10$ micro SLM array for phase and amplitude modulation of incident light is designed and fabricated using surface micromachining technology. Hidden spring structure is used in order to maximize the fill-factor and minimize diffraction effect at the support posts. Static and dynamic characteristics of designed micro SLM are simulated with ABAQUS and measured with optical measurement system using He-Ne laser and PSD(position sensitive devise).

• 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.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.620-623
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• 2003

The material processing by using ultrashort pulse laser, in recently, is actively applying into the micro machining and nano-machining technology since ultrashort pulse has so faster than the time which the electrons energy absorbing photon energy is transmitted to surrounding lattice-phonon that it has many advantages in point of machining. The micro machining of metallic thin film on the plain glass is widely used in the fields such as mask repairing for semiconductor, fabrication of photonic crystal, MEMS devices and data storage devices. Therefore, it is important to secure the machining technology of the sub-micron size. In this research, we set up the machining system by using ultrashort pulse laser and conduct on the Cr 200nm thin film ablation experiments of spot and line with the variables such as energy, pulse number, speed, and so on. And we observed the characteristics of surrounding heat-affected zone and by-products appeared in critical energy density and higher energy density through SEM, and also examined the machining features between in He gas atmosphere which make pulse change minimized by nonlinear effect and in the air. Finally, the pit size of 0.8${\mu}{\textrm}{m}$ diameter and the line width of 1${\mu}{\textrm}{m}$ could be obtained.

• 한국정밀공학회지
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• 제27권3호
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• pp.18-26
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• 2010

Diffraction gratings with precise spatial periods of 2 ${\mu}m$ and 5 ${\mu}m$ have been fabricated by using a femtosecond laser which does not have limits on materials of micromachining and small thermal effects due to high peak power. Diffraction angle and diffraction efficiency of those were measured. Simulation results of diffraction angle and diffraction efficiency of the diffraction grating calculated with the parameters such as line width, depth, and spatial period of the fabricated gratings were compared with experimental results measured with a He-Ne laser. Besides these, Fresnel Zone Plates (FZPs) with focal distances of 50 mm and 25 mm were fabricated and focal distances of fabricated FZP were measured. Those experimental results for diffraction gratings and FZPs match well with experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1759-1761
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• 1996

Md:YAG laser has been used in many applications such as micromachining, nonlinear optical experiments, holography, and rangefinding. These applications quite often require operation of the laser at the $TEM_{00}$ mode since this mode produces the smallest beam divergence, the highest power density, and, hence, the highest brightness. In this study, a pinhole is put between a rod and a half mirror to make the $TEM_{00}$ mode, and then we measured the intensity distribution of the output beam as reducing the diameter of the pinhole from 6mm to 1.5mm. As a result, the optimum size of the pinhole fixed in a resonator to make the $TEM_{00}$ mode was obtained, and we found out that the output beam of the pulsed Nd:YAG laser with a single elliptical cavity has a Gaussian distribution.