• 한국주조공학회지
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• 제31권4호
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• pp.205-211
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• 2011

Al-Si alloys have been steadily used as a potential material for the achievement of an efficient weight reduction in the automobile and aerospace industries due to its excellent castability and high strength-to-weight ratio. In this study, riser effect and mechanical properties were investigated according to the size of the sleeve. In addition, the effects of riser size on mechanical properties of castings were investigated. On the other hand flow and solidification process were simulated with a hybrid FDM/FEM package named ZCast. As a result, results of simulation and experiments were comparable regarding to the yield strength, tensile strength, elongation and hardness of casting. It proves the reliability of the simulation. It is expected that the proper size of riser can improve the recycling rate of metallic materials and reduce the cost of casting.

• 한국기계가공학회지
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• 제21권7호
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• pp.71-76
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• 2022

This study describes an evaluation of the vibration-level reduction effect of natural rubber inserted between two aluminum blocks, in which the modal parameters are predicted using two different damping systems. A numerical model with two degrees of freedom was established for both the cases. One was an eigenvalue problem analysis using a state space method and general viscous damping, whereas the other was a method using hysteretic damping. The modal parameters obtained from these two approaches were compared with those obtained from the finite element method using a commercial package. As a result, the natural frequencies observed in the complex frequency response curve were consistently less than the average of four percents. The damping ratios also showed good agreement within a reasonable range. However, the hysteretic damping system showed a relatively larger difference for all modal parameters. This suggests that the analysis procedure makes it easier to predict the vibration transmission characteristics of the shape and configuration of any cushioning layer.

• Structural Engineering and Mechanics
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• 제85권6호
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• pp.755-764
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• 2023

The article examines the impact response of the sandwich beam furnished by a novel bilayer core as inspired by the woodpecker's head architecture under different repeatedly exerted low-velocity impact loadings by employing the finite element package, ABAQUS. The sandwich beam forms four essential parts comprising bottom and top carbon fiber reinforced polymer laminates encasing bilayer core made of laterally arched solid hot melt adhesive material and aluminum honeycomb. Impact loadings are implemented repeatedly with a steel hemisphere impactor for various impact energies, 7.28 J, 9.74 J, and 12.63 J. Essentially, the commonly concentrated stresses at the impact region are regulated away by the arched core in all considered cases thus reducing the threat of failure. The sandwich beam can resist up to 5 continual impacts at 7.28 J and 9.74 J but only up to 3 times repeated loads at 12.63 J before visible failure is noticed. In the examination of several key impact performance indicators under numerous loading cases, the proposed beam demonstrates favorably up to 1.3-11.2 higher impact resistance efficacies compared to existing designs, therefore displaying an improvement in repeated impact resistance of the new design.

• Steel and Composite Structures
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• 제50권2호
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• pp.159-181
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• 2024

In the present study, the effect of geometrical parameters of two different types of aluminum thin-walled structures on energy absorption under three-bending impact loading has been investigated experimentally and numerically. To evaluate the effect of parameters on the specific energy absorption (SEA), initial peak crushing force (IPCF), and the maximum crushing distance (δ), a design of experiment technique (DOE) with response surface method (RSM) was applied. Four different thin-walled structures have been tested under the low-velocity impact, and then they have simulated by ABAQUS software. An acceptable consistency between the numerical and experimental results was obtained. In this study, statistical analysis has been performed on various parameters of three different types of tubes. In the first and the second statistical analysis, the dimensional parameters of the cross-section, the number of holes, and the dimensional parameter of holes were considered as the design variables. The diameter reduction rate and the number of sections with different diameters are related to the third statistical analysis. All design points of the statistical method have been simulated by the finite element package, ABAQUS/Explicit. The final result shows that the height and thickness of tubes were more effective than other geometrical parameters, and despite the fact that the deformations of the cylindrical tubes were around forty percent greater than the rectangular tubes, the top desirability was relevant to the cylindrical tubes with reduced cross-sections.

• 한국산학기술학회논문지
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• 제15권6호
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• pp.3442-3447
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• 2014

본 논문에서는 간단한 플라스틱전자패키지의 폴리머 흡습특성 평가 방법을 제시하였다. 흡습팽창에 의한 변형을 측정하고 유한요소법으로 해석하였다. 흡습특성 평가를 위해 시편제작을 제작하고, 흡습시간에 따라 폴리머에 내재된 수분질량을 측정하여, 수치해석 결과와 비교분석하였다. 흡습확산 방정식은 열전달 방정식과 유사한 형태를 가지고 있기 때문에 열전달 해석 절차에 따라 상용 유한요소코드를 적용하여 흡습압력비를 구하고, 자체코드로 흡습질량을 계산하였다. 비전도성 폴리머는 동일 제품이라도 생산시기에 따라 흡습특성에 변화가 있었다. 여러 가지 흡습특성에 대해 흡습질량을 수치해석으로부터 계산하고 측정치에 가장 근접한 흡습질량 변화의 그래프를 선택하여 최적의 확산계수와 용해도를 구하였다. 제시된 방법은 빠른 대응을 요구하는 생산현장에서 반도체 패키지 폴리머의 흡습특성을 신속하게 평가하는 데 적용될 수 있을 것이다. 또한 흡습팽창을 모아레 간섭계로 측정하고 수치해석으로 비교하였다. 결과적으로 흡습질량의 측정값과 수치해석 결과를 비교하여 용해도와 확산계수는 0.0320 [g/mm/N]과 0.243 [$mm^2/{\mu}s$]으로 결정하였고, ANSYS 구조해석에 의한 변형은 모아레 간섭에 의한 측정결과와 매우 유사하였다.

• 마이크로전자및패키징학회지
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• 제25권3호
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• pp.31-36
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• 2018

본 연구에서는 DRAM 소자의 Pressure Cooker Test (PCT) 신뢰성 평가 후 발생한 불량 원인에 대한 연구를 진행하였다. 불량 시료의 물리적 관측 결과 변색, Al의 부식 및 손실, 그리고 금속 간 중간 절연막 박리 등이 관측되었다. 추가 물리적 화학적 분석 결과 비정상적인 물질인 $Al_XO_Y$ 층을 발견하였다. 불량 원인을 파악 하기 위해 package ball 크기 실험 및 보호막 pin hole 등의 연관성 실험을 진행하였으나 원인으로 판명되지 않았다. 또한 EMC 물질에 포함되어 있는 Cl에 의한 Al 할로겐화 평가를 진행하였다. 진행 결과 약간의 개선 효과를 보였지만 완벽한 문제 해결을 이루어 내지 못했다. Galvanic corrosion 가능성 가설을 세웠고, 면밀한 분석 결과 pad open 지역에서 Ti 잔존물을 발견할 수 있었다. 검증 실험으로 repair 식각 분리 실험을 진행하여 개선 효과를 보았다. 개선 된 조건에서 PCT 신뢰성 기준치를 만족 하는 결과를 얻었다. 금번 PCT 불량 메카니즘은 다음과 같이 설명할 수 있다. 공정 repair etch시 Ti 잔류물이 남아 Galvanic 메커니즘에 의해 Al이 이온화 된다. 이온화 된 Al이 후속 PCT 신뢰성 측정 시 $H_2O$와 반응하여 비 정상 물질인 $Al_XO_Y$를 생성하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.431-432
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• 2012

In the era of 20 nm scaled semiconductor volume manufacturing, Microelectronics Manufacturing Engineering Education is presented in this paper. The purpose of microelectronic engineering education is to educate engineers to work in the semiconductor industry; it is therefore should be considered even before than technology development. Three Microelectronics Manufacturing Engineering related courses are introduced, and how undergraduate students acquired hands-on experience on Microelectronics fabrication and manufacturing. Conventionally employed wire bonding was recognized as not only an additional parasitic source in high-frequency mobile applications due to the increased inductance caused from the wiring loop, but also a huddle for minimizing IC packaging footprint. To alleviate the concerns, chip bumping technologies such as flip chip bumping and pillar bumping have been suggested as promising chip assembly methods to provide high-density interconnects and lower signal propagation delay [1,2]. Aluminum as metal interconnecting material over the decades in integrated circuits (ICs) manufacturing has been rapidly replaced with copper in majority IC products. A single copper metal layer with various test patterns of lines and vias and $400{\mu}m$ by $400{\mu}m$ interconnected pads are formed. Mask M1 allows metal interconnection patterns on 4" wafers with AZ1512 positive tone photoresist, and Cu/TiN/Ti layers are wet etched in two steps. We employed WPR, a thick patternable negative photoresist, manufactured by JSR Corp., which is specifically developed as dielectric material for multi- chip packaging (MCP) and package-on-package (PoP). Spin-coating at 1,000 rpm, i-line UV exposure, and 1 hour curing at $110^{\circ}C$ allows about $25{\mu}m$ thick passivation layer before performing wafer level soldering. Conventional Si3N4 passivation between Cu and WPR layer using plasma CVD can be an optional. To practice the board level flip chip assembly, individual students draw their own fan-outs of 40 rectangle pads using Eagle CAD, a free PCB artwork EDA. Individuals then transfer the test circuitry on a blank CCFL board followed by Cu etching and solder mask processes. Negative dry film resist (DFR), Accimage$^{(R)}$, manufactured by Kolon Industries, Inc., was used for solder resist for ball grid array (BGA). We demonstrated how Microelectronics Manufacturing Engineering education has been performed by presenting brief intermediate by-product from undergraduate and graduate students. Microelectronics Manufacturing Engineering, once again, is to educating engineers to actively work in the area of semiconductor manufacturing. Through one semester senior level hands-on laboratory course, participating students will have clearer understanding on microelectronics manufacturing and realized the importance of manufacturing yield in practice.

• 동아시아식생활학회지
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• 제23권4호
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• pp.461-469
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• 2013

This research is performed to investigate the changes in the physicochemical properties and microbial growths of seasoned anchovies with various packaging materials (PET/CPP : polyethylene terephthalate/cast polypropylene, PET/EVOH : polyethylene terephthalate/ethylene-vinyl alcohol, PET/AL/LDPE: polyethylene terephthalate/aluminum/low density polyethylene), which are stored at various temperatures (25, 35, $45^{\circ}C$) for 60 days. Generally, it is being observed that changes in physicochemical properties (i.e., moisture content, color, brown intensity, TBA value, TMA, VBN etc) of seasoned anchovies are significant when stored at higher temperatures. Particularly, the packaging materials are found to influence substantially on the physicochemical properties of seasoned anchovies. With packaging materials of high oxygen transmission rates and moisture vapor transmission rates (i.e., PET/CPP), the changes in physicochemical properties of seasoned anchovies are significant, while being low with low oxygen transmission rates and low moisture vapor transmission rates (i.e., PET/EVOH). In addition, results of microbial growths in seasoned anchovies show that significant increases in total aerobic bacteria counts (about 100-fold after 60 day of storage) are observed in samples with packaging materials of high oxygen transmission rates and moisture vapor transmission rates (i.e, PET/CPP), while with only small increases for samples of low oxygen transmission rates and low moisture vapor transmission rates (i.e., PET/EVOH). Based on the changes in the physicochemical properties and results of microbial growths, it is being concluded that PET/EVOH film is suitable for the packaging of seasoned anchovies.

• 소성∙가공
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• 제6권3호
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• pp.239-249
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• 1997

The behaviour of alloys in the semi-solid state strongly depends on the imposed stress state and on the morphology of the phase which can vary from dendritic to globular. To optimal net shape forging of semi-solid materials, it is important to investigate for filling phenomena in forging process of arbitrarily shaped dies. To produce a automotive part which has good mechanical property, the filling pattern according to die velocity and solid fraction distribution has to be estimated for arbitrarily shaped dies. Therefore, the estimation of filling characteristic in the forging simulation with arbitrarily shaped dies of semi-solid materials are calculated by finite element method with proposed algorithm. The proposed theoretical model and a various boundary conditions for arbitrarily shaped dies is investigated with the coupling calculation between the liquid phase flow and the solid phase deformation. The simulation process with arbitrarily shaped dies is performed to the isothermal conditions of two dimensional problems. To analysis of forging process by using semi-solid materials, a new stress-strain relationship is described, and forging analysis is performed by viscoelastic model for the solid phase and the Darcy's law for the liquid flow. The calculated results for forging force and filling limitations will be compared to experimental data. The filling simulation of simple products performed with the uniform billet temperature(584$^{\circ}C$) from the induction heating by the commercial package MAGMAsoft. The initial step of computation is the touching of semi-solid material with the end of die gate and the initial concept of proposed system just fit with the capability of MAGMAsoft.

• 대한전자공학회논문지SD
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• 제39권9호
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• pp.19-27
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• 2002

실리콘 기판가 교차하는 금속 선의 밑층 기하구조를 고려한 연결선로의 특성이 정교하게 고안된 패턴을 가지고 실험적으로 분석되었다. 이 작업에서, 여러 종류의 밑층 기하구조에 따른 전송선로을 위한 테스트 패턴들을 고안하였고, 신호 특성과 반응은 S-parameter 와 TDR을 통해 측정되었다. 사용된 패턴은 두 개의 알루미늄 선과 한 개의 텅스텐 선을 가지는 deep-submicron CMOS DRAM 기술을 가지고 설계되고 제작되었다. 패턴위에서 측정되 결과 분석으로부터, 라인 파라메터들 (특히 라인 커패시턴스와 저항) 과 그것들에 의한 신호 왜곡에 대한 밑층 구조에 의한 효과는 무시 할수 없음을 발견하였다. 그러한 결과는 고속 클럭과 데이터 라인 같은 글로벌 신호 선이나 패키지 리드의 스큐 발렌스의 심도있고 유용한 이해에 도움이 된다.