• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년 추계학술발표대회 개요집
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• pp.205-206
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• 2006

The microstructural evolutions and shear properties of the pure Sn solder bumps with Ni UBMs were investigated during multiple reflows and high temperature storage(HTS) tests. Only a $Ni_3Sn_4$ IMC was found at the bump/Ni UBM interface after 1 reflow. The layer thickness of these IMCs increased with increasing reflow number and testing time. The solder bumps showed a good reliability during multiple reflows and HTS tests.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.485-488
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• 2000

In this study, the fatigue characteristic of spot weld specimen was studied by using the various specimen. The specimen types were tensile shear specimen welded one spot and two spot, and cross tension. The tensile tests and fatigue tests were executed to know the mechanical properties under static and fatigue load condition. In addition, the relationship was illustrated by finite element method.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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• pp.71-75
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• 1998

This study deals with the friction weldability of A7075-T6 having high specific strength. The friction welding conditions used are rotation speed 2000rpm, friction pressure 40MPa, friction time 1.5sec, upset pressure 40~100MPa, upset time 5sec. First, upset length was measured by displacement transducer. The plastic flow in 7075-T6 weld generates convex lens shaped resion by friction and concave lens shaped resion by axial force. Under the condition of upset pressure 85MPa, the friction welds have tensile strength of 552MPa and shear strength of 262MPa.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 춘계 학술발표대회 개요집
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• pp.51-53
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• 2004

An analytical method is developed which focused on the end effects for determining the thermal stress distribution in an laminated beam bonded with adhesive layer. This method gives the stress distribution which satisfy the stress-free boundary condition at edge completely. Numerical example, in which an Al-Cu beam bonded with solder(Pb-Sn) is treated, shows that the shear and peeling stresses at the interfaces are significant near the edge and become negligible in the interior region.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.573-578
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• 2000

Recently, Tailor Welded Blanks(TWB) is widely used in automotive industry since the transformation characteristics of its material can be changed. However, clearance between welding surface becomes the important factor which affect the quality of the laser weld, causing difficulties in preparing the sheet. The objective of this paper is to systematically evaluate the effects of previously presented fracture criterion and shearing condition on precise mechanical shearing simulation result. Also predict the optimum shearing condition, effect of shearing condition such as clearance and punch radius on the shear plane shape was evaluated.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.247-249
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• 2005

Evaluation and prediction of fatigue crack initiation life in EZNCEN(Galvanized steel sheet) and HS40R(High strength steel sheet) tensile-shear spot weldment were studied by using DCPDM(DC Potential Drop Method)

• 마이크로전자및패키징학회지
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• 제24권1호
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• pp.83-90
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• 2017

본 연구에서는 미세피치 패키지 적용을 위한 기초 실험으로 thin ENEPIG(Electroless Nickel Electroless Palladium Immersion Gold) 도금층을 형성하여 솔더링 특성을 평가하였다. 먼저, Sn-3.0Ag-0.5Cu (SAC305) 솔더합금에 대한 thin ENEPIG 도금층의 젖음 특성이 평가되었으며, 순차적인 솔더와의 반응에 대한 계면반응 및 솔더볼 접합 후 고속 전단 시험을 통한 접합부 기계적 신뢰성이 평가되었다. 젖음성 시험에서 침지 시간이 증가함에 따라 최대 젖음력은 증가하였으며, 5초의 침지 시간 이후에는 최대 젖음력이 일정하게 유지되었다. 초기 계면 반응 동안에는 $(Cu,Ni)_6Sn_5$ 금속간화합물과 P-rich Ni 층이 SAC305/ENEPIG 계면에서 관찰되었다. 연장된 계면반응 후에는 P-rich Ni 층이 파괴 되었으며, 파괴된 P-rich Ni 층 아래에는 $(Cu,Ni)_3Sn$ 금속간화합물이 생성되었다. 고속 전단 시험의 경우, 전단속도가 증가함에 따라 취성 파괴율이 증가하였다.

• 한국자동차공학회논문집
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• 제6권5호
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• pp.20-27
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• 1998

According as the member of the automobile body structure have been thinned their thickness and have become high strength, each part of the body structure has been put more severe stress condition. And, because fatigue strength of the spot welded lap joint is influenced by its geometrical and mechanical factors, welding condition and etc., there needs a quantitative and systematic evaluation method for them. In this study, by considering nugget edge of the spot weld part of the IB-type spot welded lap joint under tension-shear load to the ligament crack. fatigue strength of various IB-type spot welded lap joints was estimated with the stress intensity factor(S.I.F.) KIII which is fracture mechanical parameter. We could find that fatigue strength evaluation of the IB-type spot welded lap joints by KIII is more effective than the maximum principal stress ($\sigma$1max) at edge of the spot weld obtained from FEM analysis.

• 한국강구조학회 논문집
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• 제28권5호
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• pp.303-312
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• 2016

최근에 스테인리스강의 우수한 연성과 내식성 등의 재료적 특성으로 건축물의 구조용 강재로 적용하기 위한 많은 연구들이 수행되어 오고 있다. 특히, 니켈을 거의 함유하고 있지 않은 페라이트계 스테인리스강은 재료비 측면에서 니켈을 함유하고 있는 오스테나이트계 스테인리스강에 비해 저렴하고 탄소강에 비해서는 월등한 내식성능과 구조성능을 제공하기 때문에 그 사용성이 증대되고 있다. 본 연구에서는 페라이트계 스테인리스강 용접접합부에 있어 용착금속이 아닌 모재 블록전단파단의 구조적 거동을 조사하기 위해 용접길이와 용접방법(아크, 티그)을 변수로 하여 단순인장 실험을 실시하였다. 용접접합부의 블록전단 거동은 용접에 의한 삼축응력효과 때문에 볼트접합부의 블록전단 거동과 상이하며, 현행설계기준식은 이러한 특성을 반영하지 못하고 있다. 티그용접 접합부의 변형능력과 최대내력이 아크용접 접합부보다 높게 나타났고, 현행기준식과 기존연구자에 의해 제시된 내력식에 의한 예측내력과 실험결과 최대내력을 비교 검토하였다.

• 한국재료학회지
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• 제22권9호
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• pp.454-458
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• 2012

Various adhesive materials are used in flip chip packaging for electrical interconnection and structural reinforcement. In cases of COF(chip on film) packages, low temperature bonding adhesive is currently needed for the utilization of low thermal resistance substrate films, such as PEN(polyethylene naphthalate) and PET(polyethylene terephthalate). In this study, the effects of anhydride and dihydrazide hardeners on the low-temperature snap cure behavior of epoxy based non-conductive pastes(NCPs) were investigated to reduce flip chip bonding temperature. Dynamic DSC(differential scanning calorimetry) and isothermal DEA(dielectric analysis) results showed that the curing rate of MHHPA(hexahydro-4-methylphthalic anhydride) at $160^{\circ}C$ was faster than that of ADH(adipic dihydrazide) when considering the onset and peak curing temperatures. In a die shear test performed after flip chip bonding, however, ADH-containing formulations indicated faster trends in reaching saturated bond strength values due to the post curing effect. More enhanced HAST(highly accelerated stress test) reliability could be achieved in an assembly having a higher initial bond strength and, thus, MHHPA is considered to be a more effective hardener than ADH for low temperature snap cure NCPs.