• Title/Summary/Keyword: DPSS laser

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Measurement of Thermal Diffusivity and the Optical Properties of a Carbon Nanotube Dispersion by Using the Thermal Lens Effect (열렌즈 효과를 이용한 탄소 나노 튜브 분산액의 열확산도와 광학적 특성 측정)

  • Park, Hyunwoo;Kim, Hyunki;Kim, Sok Won;Lee, Joohyun
    • New Physics: Sae Mulli
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    • v.68 no.11
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    • pp.1167-1172
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    • 2018
  • Carbon nanotubes (CNTs) are structures of carbon atoms bonded together in hexagonal honeycomb shapes, with multi-walled CNTs having a very high thermal conductivity of $3000W/m{\cdot}K$ and single-walled CNTs having a conductivity of $6000W/m{\cdot}K$. In this work, the transmittance and the thermal diffusivity of a multi-walled carbon nanotube dispersion with a concentration of 1.5 M were measured using a single beam method, a dual beam method, and the thermal lens effect. The nonlinear optical coefficients were obtained by using the z-scan method, which moved the sample in the direction of propagation of the single laser beam, propagation and the thermal diffusivity was measured using a double laser beam. As a pump beam, a diode-pumped solid state (DPSS) laser with a wavelength of 532 nm and an intensity of 100 mW was used. As the probe beam, a He-Ne laser having a wavelength of 633 nm and an intensity of 5 mW was used. The experimental result shows that when the concentrations of the sample were 9.99, 11.10, 16.65, and 19.98 mM, the nonlinear absorption coefficients were 0.046, 0.051, 0.136 and 0.169 m/W, respectively. Also, the nonlinear refractive indices were 0.20, 0.51, 1.25 and $1.32{\times}10^{-11}m^2/W$, respectively, and the average thermal diffusivity was $1.33{\times}10^{-6}m^2/s$.

Study on Auto Focusing System of Laser Beam by Using Fiber Confocal Method (파이버 공초점법을 이용한 레이저 빔 자동 초점 제어 장치에 관한 연구)

  • Moon, Seong-Wook;Kim, Jong-Bae;King, Sun-Hum;Bae, Han-Seong;Nam, Gi-Jung
    • Laser Solutions
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    • v.9 no.3
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    • pp.7-13
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    • 2006
  • Auto focusing system to find optimized focal position of laser beam used for material process has been investigated by using fiber confocal method. Wavelength of laser diode (LD) and diameter of single-mode fiber are 780nm and $5.3{\mu}m$, respectively. Intensity distributions of beam reflected from the surface of mirror and silicon bare wafer have been observed in a gaussian form. Experimental results show that focal position obtained by LD is shifted from one observed from surface scribed by laser about $80{\mu}m$. It is due to the difference of wavelength and each divergence of between LD and laser used for material process. It is confirmed that auto focusing control system through position calibration has operated steadily.

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Three-dimensional micro photomachining of polymer using DPSSL (Diode Pumped Solid State Laser) with 355 nm wavelength (355nm 파장의 DPSSL을 이용한 폴리머의 3차원 미세 형상 광가공기술)

  • 장원석;신보성;김재구;황경현
    • Korean Journal of Optics and Photonics
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    • v.14 no.3
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    • pp.312-320
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    • 2003
  • The basic mechanistic aspects of the interaction and practical considerations related to polymer ablation were briefly reviewed. Photochemical and photothermal effects, which highly depend on laser wavelength have close correlation with each other. In this study, multi-scanning laser ablation processing of polymer with a DPSS (Diode Pumped Solid State) 3rd harmonic Nd:YVO$_4$ laser (355 nm) was developed to fabricate a three-dimensional micro shape. Polymer fabrication using DPSSL has some advantages compared with the conventional polymer ablation process using KrF and ArF laser with 248 nm and 193 nm wavelength. These advantages include pumping efficiency and low maintenance cost. And this method also makes it possible to fabricate 2D patterns or 3D shapes rapidly and cheaply because CAD/CAM software and precision stages are used without complex projection mask techniques. Photomachinability of polymer is highly influenced by laser wavelength and by the polymer's own chemical structure. So the optical characteristics of polymers for a 355 nm laser source is investigated experimentally and theoretically. The photophysical and photochemical parameters such as laser fluence, focusing position, and ambient gas were considered to reduce the plume effect which re-deposits debris on the surface of substrate. These phenomena affect the surface roughness and even induce delamination around the ablation site. Thus, the process parameters were tuned to optimize for gaining precision surface shape and quality. This maskless direct photomachining technology using DPSSL could be expected to manufacture tile prototype of micro devices and molds for the laser-LIGA process.

An analysis of Cutting Characteristic of Multilayer FPCB using Nd:YAG UV Laser System (Nd:YAG UV 레이저를 이용한 연성회로 다층기판 절단특성에 대한 연구)

  • Choi, Kyung-Jin;Lee, Young-Hyun
    • Journal of the Korean Society for Precision Engineering
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    • v.27 no.3
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    • pp.9-17
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    • 2010
  • The FPCB is used for electronic products such as LCD display. The process of manufacturing FPCB includes a cutting process, in which each single FPCB is cut and separated from the panel where a series of FPCBs are arrayed. The most-widely used cutting method is the mechanical punching, which has the problem of creating burrs and cracks. In this paper, the cutting characteristics of the FPCB have been experimented using Nd:YAG DPSS UV laser as a way of solving this problem. To maximize the industrial application of this laser cutting process, test samples of the multilayered FPCB have been chosen as it is actually needed in industry. The cutting area of the FPCB has four different types of layer structure. First, to cut the test sample, the threshold laser cut-off fluence has been found. Various combinations of laser and process parameters have been made to supply the acquired laser cut-off fluence. The cutting characteristics in terms of the variation of the parameters are analyzed. The laser and process parameters are optimized, in order to maximize the cutting speed and to reach the best quality of the cutting area. The laser system for the process automation has been also developed.

Direct UV laser projection ablation to engrave 6㎛-wide patterns in a buildup film (빌드업 필름의 선폭 6㎛급 패턴 가공을 위한 직접식 UV 레이저 프로젝션 애블레이션)

  • Sohn, Hyonkee;Park, Jong-Sig;Jeong, Jeong-Su;Shin, Dong-Sig;Choi, Jiyeon
    • Laser Solutions
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    • v.17 no.3
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    • pp.19-23
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    • 2014
  • To directly engrave circuit-line patterns as wide as $6{\mu}m$ in a buildup film to be used as an IC substrate, we applied a projection ablation technique in which an 8 inch dielectric ($ZrO_2/SiO_2$) mask, a DPSS 355nm laser instead of an excimer laser, a ${\pi}$-shaper and a galvo scanner are used. With the ${\pi}$-shaper and a square aperture, the Gaussian beam from the laser is shaped into a square flap-top beam. The galvo scanner before the $f-{\theta}$ lens moves the flat-top beam ($115{\mu}m{\times}105{\mu}m$) across the 8 inch dielectric mask whose patterned area is $120mm{\times}120mm$. Based on the results of the previous research by the authors, the projection ratio was set at 3:1. Experiments showed that the average width and depth of the engraved patterns are $5.41{\mu}m$ and $7.30{\mu}m$, respectively.

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A Study on UV Laser Ablation for Micromachining of PCB Type Substrate (다층 PCB 기판의 미세 가공을 위한 UV레이저 어블레이션에 관한 연구)

  • 장원석;김재구;윤경구;신보성;최두선
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.10a
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    • pp.887-890
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    • 1997
  • Recently micromachining using DPSSL(Diode Pumped Solid State Laser) with 3rd harmonic wavelength is actively studied in laser machining area. Micromachining using DPSSL have outstanding advantages as UV source comparing with excimer laser in various aspect such a maintenance cost, maskless machining, high repetition rate and so on. In this study micro-drilling of PCB type substrate which consists of Cu-PI-Cu layer was performed using DPSS Nd:YAG laser(355nm, wavelength) in vector scanning method. Experimental and numerical method(Matlab simulation, FEM) are used to optimize process parameter and control machining depth. The man mechanism of this process is laser ablation. It is known that there is large gap between energy threshold of copper and that of PI. Matlab simulation considering energy threshold of material is performed to effect of duplication of pulse and FEM thermal analysis is used to predict the ablation depth of copper. This study could be widely used in various laser micromachining including via hole microdrilling of PCB, and micromachining of semiconductor components, medical parts and printer nozzle and so on.

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Study on High Speed Laser Cutting of Rigid Flexible Printed Circuit Board by using UV Laser with Nano-second Pulse Width (자외선 나노초 펄스 레이저를 이용한 경연성(Rigid Flexible) 인쇄전자회로기판(Printed Circuit Board) 고속 절단에 관한 연구)

  • Bae, Han-Sung;Park, Hee-Chun;Ryu, Kwang-Hyun;Nam, Gi-Jung
    • Journal of the Korean Society for Precision Engineering
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    • v.27 no.2
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    • pp.20-24
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    • 2010
  • High speed cutting processes of rigid flexible printed circuit board by making use of high power UV laser with nano-second pulse width have been proposed and investigated experimentally. Also robust laser cutting system has been designed and developed in order to obtain a good cutting quality of rigid and flexible PCB with multi-layers (2-6 layers). Power controller module developed for ourselves is adapted to control the laser output power in the range less than 1%. The systems show the good performance of cutting speed, cutting width and cutting accuracy, respectively. Especially we have confirmed that the short circuit problem due to the carbonized contamination occurred in cross section of multi-layers by thermal effect of high power laser has been improved largely by using multi-pass cutting process with low power and high speed.

Study on auto focusing system of laser beam by using fiber confocal method (파이버 공초점법을 이용한 레이저 빔 자동 초점 제어 장치에 관한 연구)

  • Moon, Seong-Wook;King, Sun-Hum;Kim, Jong-Bae;Bae, Han-Seong;Nam, Gi-Jung
    • Proceedings of the Korean Society of Laser Processing Conference
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    • 2006.11a
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    • pp.41-45
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    • 2006
  • Auto focusing system to find optimized focal position of laser beam used for material process has been investigated by using fiber confocal method. Wavelength of laser diode (LD) and diameter of single-mode fiber we 780nm and $5.3{\mu}m$, respectively. Intensity distributions of beam reflected from the surface of mirror and silicon bare wafer have been observed in a gaussian form. Experimental results show that focal position obtained by LD is shifted from one observed from surface scribed by laser about $80{\mu}m$. It is due to the difference of wavelength and each divergence of between LD and laser used for material process. It is confirmed that auto focusing control system through position calibration has operated steadily.

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High-speed angular-scan pulse-echo ultrasonic propagation imager for in situ non-destructive evaluation

  • Abbas, Syed H.;Lee, Jung-Ryul
    • Smart Structures and Systems
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    • v.22 no.2
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    • pp.223-230
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    • 2018
  • This study examines a non-contact laser scanning-based ultrasound system, called an angular scan pulse-echo ultrasonic propagation imager (A-PE-UPI), that uses coincided laser beams for ultrasonic sensing and generation. A laser Doppler vibrometer is used for sensing, while a diode pumped solid state (DPSS) Q-switched laser is used for generation of thermoelastic waves. A high-speed raster scanning of up to 10-kHz is achieved using a galvano-motorized mirror scanner that allows for coincided sensing and for the generation beam to perform two-dimensional scanning without causing any harm to the surface under inspection. This process allows for the visualization of longitudinal wave propagation through-the-thickness. A pulse-echo ultrasonic wave propagation imaging algorithm (PE-UWPI) is used for on-the-fly damage visualization of the structure. The presented system is very effective for high-speed, localized, non-contact, and non-destructive inspection of aerospace structures. The system is tested on an aluminum honeycomb sandwich with disbonds and a carbon fiber-reinforced plastic (CFRP) honeycomb sandwich with a layer overlap. Inspection is performed at a 10-kHz scanning speed that takes 16 seconds to scan a $100{\times}100mm^2$ area with a scan interval of 0.25 mm. Finally, a comparison is presented between angular-scanning and a linear-scanning-based pulse-echo UPI system. The results show that the proposed system can successfully visualize defects in the inspected specimens.

Study of Laser Trimming and Cutting of Printed Circuit Board by using UV Laser with Nanosecond Pulse Width (나노초 펄스폭을 갖는 자외선 레이저를 이용한 전자회로기판의 저항체 트리밍과 절단공정 특성에 관한 연구)

  • Ryu, Kwang-Hyun;Shin, Suk-Hoon;Park, Hyeong-Chan;Nam, Gi-Jung;Kwon, Nam-Ic
    • Journal of the Korean Society for Precision Engineering
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    • v.27 no.10
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    • pp.23-28
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    • 2010
  • Resistance trimming and cutting processes of printed circuit board by making use of high power UV laser with nano-second pulse width have been proposed and investigated experimentally. Also laser-based application system with high flexibility and complex has been designed and adopted power controller, auto beam size control, auto-focusing and control program developed for ourselves. The function of each module shows that they can be reliable for industrial equipments. Resistance trimming method used a plunge and double cut process with $20{\mu}m$ spot size beam. Results show that double cut process is more effective to control resistance trimming in precision than plunge cut process.