• Journal of Applied Reliability
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• v.5 no.3
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• pp.327-342
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• 2005

전자 패키지가 열을 받을 때 회로기판과 칩의 열팽창계수 차이에 의해 발생되는 응력은 솔더 조인트의 파손에 영향을 미친다. 본 연구에서는 이 영향을 정량적으로 규명하기 위하여 열충격시험기를 이용해 얻어진 솔더 조인트의 전기저항 변화와 수명과의 상관관계를 규명하였고, BGA솔더 조인트의 수명을 정량적으로 도출하였다. 또한 Sn-3.5Ag-0.5Cu 무연 솔더와 63Sn-37Pb 유연 솔더를 위의 실험에 동시에 적용시켜 건전성을 FORM(first-order reliability method)과 Weibull Function Model을 이용해 비교하였다.

• Proceedings of the Korean Reliability Society Conference
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• 2005.06a
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• pp.287-294
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• 2005

전자 패키지가 열을 받을 때 회로기판과 칩의 열팽창계수 차이에 의해 발생되는 응력은 솔더 조인트의 파손에 영향을 미친다. 본 연구에서는 이 영향을 정량적으로 규명하기 위하여 열충격시험기를 이용해 얻어진 솔더조인트의 전기저항 변화와 수명과의 상관관계를 규명하였고, BGA 솔더조인트의 수명을 정량적으로 도출하였다. 또한 Sn-3.5Ag-0.5Cu 무연솔더와 63Sn-37Pb 유연솔더를 위의 실험에 동시에 적용시켜 건전성을 FORM(first-order reliability method)과 Weibull Function Model을 이용해 비교하였다.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.1
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• pp.17-22
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• 2018

In this paper, the effects of solder joint aging on the reliability of embedded package solder joints were investigated using numerical analysis by finite element method. Solder joints were SAC305 with aging time 0, 60, 180 days. For reliability analysis, warpage of package and equivalent creep strain (ECS) and total strain energy density (TSED) of solder joint were analyzed. The analysis results show that the package warpage is decreased in the case of the embedded package compared to the non embedded package, and the reliability life of the solder joint is predicted to be high. Also, it was interpreted that the longer the aging time, the less the warpage of the embedded package, but the reliability life of the solder joint would be shortened.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.55-60
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• 2010

The honeycomb composite joint structure designed for application to a tilting KTX railroad car body is subjected to bending loads of a cantilever type. Honeycomb sandwich composite panel-joint attached in the real tilting car body was fabricated and sectioned as several beam-joint specimens for the bending test. The fracture behaviors of these specimens under static loads were different from those under cyclic loads. Static bending loads caused shear deformation and fracture in the honeycomb core region, while fatigue cyclic bend loading caused delamination along the interface between the composite skin and the honeycomb core, and/or caused a fracture in the welded part jointed with the steel under-frame. These fracture behaviors could occur in other industrial honeycomb composite joints with similar sub-structures, and be used for improving design parameters of a honeycomb composite joint structure.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06d
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• pp.278-282
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• 2010

모바일 애드혹 네트워크에서의 멀티패스 라우팅 프로토콜은 기존의 단일패스 라우팅 프로토콜에 비하여 대역폭을 효율적으로 사용할 수 있고 혼잡을 완화시킬 수 있으며, 데이터 전달의 신뢰성을 제공할 수 있다. 하지만 멀티패스 라우팅 프로토콜에서의 경로 탐색 과정은 오버헤드가 크고 계산의 복잡도 또한 높다. 본 논문에서는 무선 애드혹 네트워크에서의 멀티패스 라우팅을 위한 효율적인 노드디스조인트 경로 탐색 알고리즘을 제안한다. 제안하는 알고리즘은 지연된 RREP(Route Reply) 패킷을 사용하여 최적의 노드 디스조인트 경로를 탐색하고 그중 간섭 및 충돌의 영향이 적은 경로 집합을 선택한다. 이를 통해 빠르게 트래픽을 분산시킬 수 있고 충돌로 인한 오류의 발생을 낮추어 신뢰성을 높일 수 있다. 실험을 통하여 제안하는 경로 탐색 알고리즘이 최적의 멀티패스를 선택함을 확인하였다.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.1 s.38
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• pp.63-72
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• 2006

Mobile products, such as cellular phones, PDA and notebook, are subjected to many different mechanical loads, which include bending, twisting, impact shock and vibration. In this study, a cyclic bending test of the BGA package was performed to evaluate the fatigue life. Special bending tester, which was suitable for electronic package, was developed using an electromagnetic actuator. A nonlinear finite element model was used to simulate the mechanical bending deformation of solder joint in BGA packages. The fatigue life of lead-free (95.5Sn4.0Ag0.5Cu) solder joints was compared with that of lead-contained (63Sn37Pb). When the applied load to the specimen is small, the lead-free solder has longer fatigue life than lead-contained solder. The fatigue crack is initialized at the exterior solder joints and is propagated into the inner solder joints.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.315-321
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• 2010

Co-cured single lap joints under cyclic tensile loads fail initially at the tip of the interface corner between the two adherents. The failure mechanism is complex because it is related to corrosion fatigue. Corrosion behavior at the interface affects the failure of the joints because corrosion deteriorates fatigue resistance. In this study, we clarified the cause of interfacial corrosion in co-cured single lap joints under cyclic tensile loads. The failure mechanism was also analyzed by observing the failed surfaces of specimens and the stress distribution along the interface. The surface roughness at the interface and the stacking sequence of the composite adherent were examined to investigate their effects on failure of the joint.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.298-303
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• 2016

Owing to the advantages of reduced weight and wind effect, the space-framed towers that consist of vertical and horizontal members of circular hollow tubular sections have been adopted widely for various purposes. It is critical to guarantee the strengths of tubular joints where vertical and horizontal members are connected structurally to make the entire space-framed system behave as a single tower structure. In this study, a strength evaluation was conducted for T-type tubular joints subjected to the concurrent action of compression and bending. Three of the available design codes, i.e., AISC, Eurocode 3, ISO 19902 were investigated and a design equation was suggested for an ultimate strength interaction between the axial force and bending moment based on nonlinear finite element analyses by selecting the slenderness ratios at the joints as major parameters.

• Journal of Biomedical Engineering Research
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• v.11 no.1
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• pp.1-4
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• 1990

An implementation scheme of the magnetic nerve stimulator using a switching mode power supply is proposed. By using a switching mode power supply rather than a conventional linear power supply for charging high voltage capacitors, the weight and size of the magnetic nerve stimulator can be considerably reduced. Maximum output voltage of the developed magnetic nerve stimulator using the switching mode power supply is 3,000 volts and switching time is about 100 msec. Experimental results or human nerve stimulations using the developed stimulator are presented.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2017.11a
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• pp.145-146
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• 2017

최근 세계적으로 많은 지진이 발생하고 있으며 기상이변으로 인한 자연재해로 인해 주요 시설물들의 안전성에 관한 관심이 증가하고 있는 추세이다. 특히 비구조 요소의 경우 구조 요소보다 건설 초기 투자비용이 높아 지진이 발생하였을 때 많은 피해가 발생할 가능성이 있으며 비구조 요소의 파괴는 심각한 2차피해로 발전 될 수 있으므로 내진안전성 평가는 반드시 이루어져야 한다고 볼 수 있다. 따라서 본 연구에서는 압착식 조인트의 접촉을 고려한 수계소화설비 파이프라인의 내진성능 평가를 위한 비선형 유한요소 모델을 구축하였다.