• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.652-655
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• 2001

In this paper, I have studied minimization of the kerf-width and surface burning which are occurred after the singulation process of multi layer $\mu$-BGA( thickness 1.1 mm, 0.9 mm) with a pulsed Nd:YAG( = 532 nm, repetition rate = 10 Hz) laser. The thermal energy of a pulsed Nd:YAG laser is used to cut the copper layer. I have studied are minimization of the surface burning and kerf-width using a photo resist, $N_2$blowing and polyester double sided tape as a cutting parameter. The $N_2$blowing reduces a laser energy loss by debris and suppresses a surface carbonization. Also, I have studied characters of cutting with a choice of side of laser beam incidence. The SEM(Scanning Electron Microscope), non-contact 3D inspector and high-resolution microscope are used to measure kerf width and surface state. The optimum value of 1.1 mm $\mu$-BGA singulation is 524 $\mu$m that is reduced kerf width of 60 % with $N_2$blowing. And I obtained reduction of carbonization of 68 % with a polyester double side tape in 0.9 mm $\mu$-BGA. I used laser intensity of 1.91$\times$10$^{6}$ / $\textrm{cm}^2$ in this study.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.4
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• pp.10-15
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• 2007

Taguchi methods have been used for a long time to improve the product quality and process performance of a manufacturing system, Few researchers have applied this methodology in laser beam cutting (LBC) of sheet metals and found the considerable improvement in cut qualities. In all experimental investigations of LBC so far, the objective was to optimize the single quality characteristic at a time. In this paper the simultaneous optimization of multiple quality characteristics such as Kerf width and material removal rate (MRR) during pulsed Nd:YAG LBC of thin sheet of magnetic material (high Silicon-steel) has been presented using Taguchi's quality loss function. The results show the considerable improvement in multiple S/N ratio as compared to initial cutting condition. Also, the comparison of results from single and multi-objective optimization have been presented and it was found that the loss in quality is always possible shifting from single quality to multiple quality optimization.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.334.1-334.1
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• 2016

다른 재료에 비해 에너지 변환 효율의 관점에서 높은 경쟁력을 가진 결정질 실리콘은 지난 수십 년 동안 그 특성이 태양전지 분야에 널리 이용되어 왔다. 하지만 결정질 실리콘 웨이퍼는 일반적으로 제조 단계에서 많은 양의 에너지를 소비하고 절단 단계에서 절단 손실(Kerf-loss)이 발생된다. Epoxy Resin을 이용한 Kerf-less Wafering은 초박형 실리콘 웨이퍼 제조 기술 중 하나로, 비교적 간단한 장비와 공정을 통하여 절단 손실 없이 $50{\mu}m$이하의 초박형 실리콘 웨이퍼를 얻을 수 있는 기술이다. 실리콘과 Epoxy Resin 간의 열팽창 계수 차이를 이용하여 초박형 실리콘을 박리 시키는 기술로, 실리콘 기판 위에 Epoxy Resin으로 stress inducing layer를 올려 공정을 진행한다. stress inducing layer를 경화시키는 열처리가 끝나고 급냉되는 과정에서 stress inducing layer에 의해 실리콘 기판에 큰 응력이 가해지게 되고 실리콘 기판에 crack이 발생된다. 공정이 계속 됨에 따라 발생된 crack은 실리콘 표면과 평행한 방향으로 전파 되고 초박형 실리콘 layer가 실리콘 기판에서 박리 된다. 본 실험에서 중요한 공정 변수로는 stress inducing layer의 구성성분 및 두께, 열처리 온도 및 시간, cooling rate 등이 있다. 이러한 공정 변수들을 조절 하여 Epoxy Resin을 이용하여 $100{\mu}m$ 이하의 박리된 wafer를 얻을 수 있었다. 박리된 wafer의 단면과 두께를 Scanning Electron Microscopy(SEM)을 통해 관찰 하였고, 이를 통해 초박형 실리콘 박리 공정에 대한 연구를 진행하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.255-256
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• 2013

• Journal of Veterinary Science
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• v.25 no.2
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• pp.26.1-26.6
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• 2024

Bone loss from the kerf of the sawblade may influence the final outcomes when employing three-dimensional-printed surgical guides. However, no studies have systematically addressed saw blade-induced bone loss. This study aims to quantify bone loss and propose a reduction guide to minimize the fracture gap. The postoperative gap tended to decrease as the amount of gap compensation increased. Osteotomy gaps can be attributed to the thickness of the saw blade, and the proposed methodology addresses this surgical error. Surgeons can proactively plan and design reduction guides with applied compensation using the method described in this study.

• KIEE International Transactions on Electrophysics and Applications
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• v.2C no.6
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• pp.309-313
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• 2002

In this paper, we have studied minimization of the kerf-width and surface burning, which occurred after the conventional singulation process of the multi-layer BGA board with copper, polyethylene and epoxy glass fiber. The high thermal energy of a pulsed Nd:YAG laser is used to cut the multi-layer board. The most considerable matter in the laser cutting of the multi-layer BGA boards is their different absorption coefficient to the laser beam and their different heat conductivity. The cut mechanism of a multi-layer BGA board using a 2$^{nd}$ harmonic Nd:YAG laser is the thermal vaporization by high temperature rise based on the Gaussian profile and copper melting point. In this experiment, we found that the sacrifice layer and Na blowing are effective in minimizing the surface burning by the reaction between oxygen in the air and the laser beam. In addition, N2 blowing reduces laser energy loss by debris and suppresses surface oxidation. Also, the beam incidence on the epoxy layer compared to polyimide was much more suitable to reduce damage to polyimide with copper wire for the multi layer BGA singulation. When the polyester double-sided tape is used as a sacrifice layer, surface carbonization becomes less. The SEM, non-contact 3D inspector and high-resolution microscope are used to measure cut line-width and surface morphology.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.5
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• pp.301-306
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• 2017

Wire electrical discharge machining (WEDM) process was evaluated to slice Silicon (Si) for various applications. Specifically, various Si workpieces with various resistances, such as single and multi crystalline Si bricks and wafers were used. As conventional slicing processes, such as slurry-on or diamond-on wire slicing, are based on mechanical abrasions between Si and abrasive, there is a limitation to decrease the wafer thickness as well as kerf-loss. Especially, when the wafer thickness is less than $150{\mu}m$, wafer breakage increases dramatically during the slicing process. Single crystalline P-type Si bricks and wafers were successively sliced with considerable slicing speed regardless of its growth direction. Also, typical defects, such as microcracks, craters, microholes, and debris, were introduced when Si was sliced by electrical discharge. Also, it was found that defect type is also dependent on resistance of Si. Consequently, this study confirmed the feasibility of slicing single crystalline Si by WEDM.