• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1295-1300
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• 2008

During the manufacturing and the service life of Au-Al wire bonded electronic packages, the ball bonds experience elevated temperatures and hence accelerated thermal diffusion reactions that promote the transformation of the Au-Al phases and the IMC growth. In this paper, the IC under high temperature storage (HTS) tests at $175^{\circ}C,\;200^{\circ}C$, and $250^{\circ}C$ are meticulously investigated. Thermal exposure resulted in the IMC growth, Kirkendall void and the crack of the Au-Al phases. The crack propagation occurs resulting in the failure of the Au-Al ball bonds. As the IC was exposed at the high temperature, decreased in the lifetime.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.831-836
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• 2001

In the case of axisymmetric thermal analysis of drum brakes, the distribution of frictional heat produced on the interface and temperature difference between mating frictional faces are very interesting problems to computational researchers. In this paper, heat conduction from the interface to the pad and the drum was modeled by using a thin interface element, so artificial division of the generated frictional heat between pad and drum is not necessary. Temperature difference between mating frictional faces is successfully modeled by using the interface element. The influence of some parameters on tile thermal stress was checked. The analysis was performed by ABAQUS/Standard code.

• 한국철도학회논문집
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• 제10권3호
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• pp.251-256
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• 2007

The research analyzed dynamo test results to evaluate compatibility between brake disk made of NCM-CV cast iron and various pads. The dynamo test was executed with one kind of resin pad and three kinds of sintered pads suitable for 200 km/h trains according to a program which refers to UIC 541-3. The thermocouples were established in specific location in order to measure the temperature of disk and pads. In addition, the thermal imaging camera was used for capturing the instantaneous thermal characteristic of disk. The research results may be utilized to use as basis data of pad development for NCM-CV brake disk hereafter.

• 마이크로전자및패키징학회지
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• 제17권3호
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• pp.27-32
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• 2010

Cu pillar 범프와 Sn 패드로 구성된 플립칩 접속부를 형성한 후, Sn 패드의 높이에 따른 Cu pillar 플립칩 접속부의 열 싸이클링 및 고온유지 신뢰성을 분석하였다. Cu pillar 플립칩 접속부를 구성하는 Sn 패드의 높이가 5 ${\mu}m$에서 30 ${\mu}m$로 증가함에 따라 접속저항이 31.7 $m{\Omega}$에서 13.8 $m{\Omega}$로 감소하였다. $-45^{\circ}C{\sim}125^{\circ}C$ 범위의 열 싸이클을 1000회 인가한 후에도 Cu pillar 플립칩 접속부의 접속저항의 증가가 12% 이하로 유지되었으며, 열 싸이클링 시험전과 거의 유사한 파괴 전단력을 나타내었다. $125^{\circ}C$에서 1000 시간 유지시에도 Cu pillar 플립칩 접속부의 접속저항의 증가가 20% 이하로 유지되었다.

• 마이크로전자및패키징학회지
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• 제22권3호
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• pp.51-56
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• 2015

솔더 조인트의 신뢰성 강화를 위해서 다양한 pad finish material이 사용되고 있으며, 최근에는 Electroless Ni Electroless Pd Immersion Gold (이하 ENEPIG) pad가 많이 사용되고 있다. 따라서, 본 연구는 상용화 되어 사용중인 Electrolytic Ni (soft Ni) pad와 최근 이슈가 되고 있는 ENEPIG pad에 대한 신뢰성 평가에 관한 것으로, 다양한 Cu 함량에 따른 거동을 관찰 하였다. Reflow 후 솔더와 pad간의 접합층은 $Cu_6Sn_5$에 Ni이 치환된 형태의 금속간 화합물로 구성되어 있었으며, ENEPIG pad의 경우, 접합층과 Ni layer 사이에 $Ni_3P$ (dark layer) layer가 관찰 되었다. 또한, Cu 함량에 따라 Dark layer의 두께를 제어할 수 있었다. 충격 낙하 시험 후, 파괴모드를 관찰한 결과 soft Ni pad와 ENEPIG pad에서 서로 다른 파괴모드가 관찰 되었으며, soft Ni의 경우, 1차 IMC와 2차 IMC 경계에서 파괴가 관찰 되었고, ENEPIG pad의 경우, dark layer에서 파괴가 관찰 되었다. IMC와 pad material, bulk 솔더와의 lattice mismatch에 의해 불안정한 계면이 존재하며, 이는 연속적인 외부 충격에 의해 가해진 열적, 물리적 스트레스를 IMC 계면으로 전송하기 때문에, 솔더의 신뢰성 향상을 위해서는 솔더 벌크의 제어와 IMC의 두께 및 형상의 제어는 필요하다.

• Tribology and Lubricants
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• 제27권5호
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• pp.269-274
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• 2011

The purpose of this paper is to study and analyze the improvement method for the failure examples including the vehicle brake system in actual field. It was verified that the indicator plate of pad wear scratched the brake disk because of wearing after displacement of non- identification parts pad. The caliper of other vehicle was installed with brake system verified the phenomenon produced groove in center point because of one side wear when the pad was not fully contacted with the rub disk by other action surface pressure and pad action condition. It verified that the crack phenomenon fatigue was produced by brake thermal deformation because of decreasing the thickness by grinding to modify the non-uniformed wear of brake disk. It verified that the friction sound was produced by the friction phenomenon because of non-uniformed contact of lining and an alien substance with inner of the drum and lining braking by crack phenomenon with brake drum surface.

• Journal of Welding and Joining
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• 제29권1호
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• pp.46-51
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• 2011

TSV technology raises several reliability concerns particularly caused by thermally induced stress. In traditional package, the thermo-mechanical failure mostly occurs as a result of the damage in the solder joint. In TSV technology, however, the driving failure may be TSV interconnects. In this study, the thermomechanical reliability of TSV technology is investigated using finite element method. Thermal stress and thermal fatigue phenomenon caused by repetitive temperature cycling are analyzed, and possible failure locations are discussed. In particular, the effects of via size, via pitch and bonding pad on thermo-mechanical reliability are investigated. The plastic strain generally increases with via size increases. Therefore, expected thermal fatigue life also increase as the via size decreases. However, the small via shows the higher von Mises stress. This means that smaller vias are not always safe despite their longer life expectancy. Therefore careful design consideration of via size and pitch is required for reliability improvement. Also the bonding pad design is important for enhancing the reliability of TSV structure.

• 한국생산제조학회지
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• 제19권2호
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• pp.211-215
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• 2010

Continuous contraction and expansion of disk brake can be due to friction and temperature difference at repeated sudden braking. As serious vibration at disk is produced, the braking force will be changed ununiformly and braking system can not be stabilized. Temperature and heat flux at disk brake are investigated by structural and thermal analysis in this study. The maximum equivalent stress and displacement are shown respectively at the ventilated hole and the lower part of disk plate. At thermal analysis of initial state, temperature on disk plate is distributed from $95.9^{\circ}C$ to $100^{\circ}C$. The maximum heat flux of $0.0168W/mm^2$ is shown at the inner friction part between disk plate and pad. At thermal analysis of transient state, temperature on disk plate is distributed from $95^{\circ}C$ to $96.5^{\circ}C$ after 100 second. The maximum heat flux of $0.0024W/mm^2$ is also shown at the inner friction part between disk plate and pad. By comparing with initial state, the temperature on disk plate is more uniformly distributed and heat flux is more decreased by 7 times at transient state.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년 추계학술발표대회 개요집
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• pp.181-183
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• 2006

This paper studies the mechanical behaviors of Sn-3.5Ag solder joint against substrate(such as Au/Ni/Cu, Au/cu, Ni/Cu and Cu pad) after induction heating, a new soldering method. It was found that the solder bump formation depends on the time and current of the induction heating system. Also the heating value of the solder bump were found to vary with respect to the thermal conductivity of the pads on the substrate. In case of Au/Ni/Cu pad and Au/Cu pad, solder bump's shear strength were high for the heating time of $1.5{\sim}2sec$. For Ni/Cu pad, solder bump's shear strength were found to increase with time increment.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.381-386
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• 2000

The brake force of drum brakes for commercial vehicles is applied by a s-cam. First of all the influence of the s-cam load angles and elastic modulus of the pad on the contact pressure distribution between pad and drum was checked by using 3 dimensional finite element model. In the second part, temperature and thermal stress analyses were carried out by an axisymmetric model with constant heat flux and pressure-proportional heat flux. In the case of temperature analysis the heat conduction from the interface to the pad and the drum was modeled using a thin soft film element, so artificial division of the generated heat flux between pad and drum is not necessary. The analysis was performed by ABAQUS/Standard code.