• Journal of the Microelectronics and Packaging Society
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• v.10 no.3
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• pp.37-42
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• 2003

In soldering of electronic packaging, the research on substituting lead-free solder materials for Pb-Sn alloys has become active due to environmental and health concerns over the use of lead. The reliability of the solder joint is very important in the development of solder materials and it is known that it is related to wettability of the solder over the substrate and microstructural evolution during soldering. It is also highly affected by type and extent of the interfacial reaction between solder and substrate and therefore, it is necessary to understand the interfacial reaction between solder and substrate completely. In order to predict the intermetallic compound (IMC) phase which forms first at the substrate/solder interface during the soldering process, a thermodynamic methodology has been suggested. The activation energy for the nucleation of each IMC phases is represented by a function of the interfacial energy and the driving force for phase formation. From this, it is predicted that the IMC phase with the smallest activation energy forms first. The grain morphology of the IMC at the solder joint is also explained by the calculations which use the energy. The Jackson parameter of the IMC grain with a rough surface is smaller than 2 but it is larger than 2 in the case of faceted grains.

• Journal of Korea Foundry Society
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• v.11 no.6
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• pp.491-497
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• 1991

Vanadium은 비중이 6.09로써 비교적 무거운 금속에 속하나 Al을 30wt% 이내로 첨가하여 $Ni_3Al$ 및 TiAl와 유사한 비강도가 크며 내열성을 지니는 V-Al합금을 얻을 가능성을 지니고 있다. 본 연구에서는 V-Al합금에 Si, Y, Ti, B등 제3원소를 첨가함에 따르는 미세 응고조직의 거동과 기계적 성질을 조사하였다. 알곤 분위기에서 제조된 V-30%Al합금은 상온에서 고용체와 취성이 큰 금속간 화합물인 $VAl_3$등 2상으로 존재하므로 용체화 처리 과정이 요구되며 24시간 이상 장시간 열처리에 의하여 단일 고용상을 이룰 수 있었다. 규소의 첨가는 금속간 화합물의 형성과 아울러 합금의 경도를 크게 증가시키는 경향을 나타내며 B을 0.3%정도가지 첨가할 때 경도가 낮아지는 현상이 관찰되었다. �c칭된 V-30%Al 합금은 입계면을 따라 decohesive rupture 현상을 나타내며 입자간 파괴 현상도 일부 관찰되었다.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.1
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• pp.35-41
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• 2022

In the era of Fifth-Generation (5G), technology requirements such as Artificial Intelligence (AI), Cloud computing, automatic vehicles, and smart manufacturing are increasing. For high efficiency of electronic devices, research on high-intensity circuits and packaging for miniaturized electronic components is important. A solder paste which consists of small solder powders is one of common solder for high density packaging, whereas an electroplated solder has limitation of uniformity of bump composition. Researches are underway to improve wettability through the addition of nanoparticles into a solder paste or the surface finish of a substrate, and to suppress the formation of IMC growth at the metal pad interface. This paper describes the principles of improving the wettability of solder paste and suppressing interfacial IMC growth by addition of nanoparticles.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1146-1154
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• 2000

Fatigue strength of NiAl and Ni$_3$Al particulate reinforced aluminum alloy composites fabricated by the diecasting method was examined at room and elevated temperatures. The results were compared wit h that of SiC particulate reinforced one. The particulate reinforced composites showed some improvement in the static and fatigue strength at elevated temperatures when compared with that of Al alloy. The composites reinforced by intermetallic compound particles showed good fatigue strengths at elevated temperatures especially $Ni_3AI_{p}/Al$ alloy composite showed good fatigue limit up to high temperature of 30$0^{\circ}C$. Adopting intermetallic compound particle as a reinforcement phase, it will be possible to develop MMC representing better fatigue property at elevated temperature.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1988.06a
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• pp.31-38
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• 1988

최근, 유체윤활영역에 있어서 될수 있는 한 점성저항을 감소시키기 위해서 윤활유의 저점도화가 진행되고 있는 실정이다. 그러나 윤활유의 저점도화로 인한 문제점으로써 금속-금속간 접식부가 증가하게 된다. 금속간 접식이 증가함에 따라 마찰저항이 커지게 되며, 이와 같은 마찰저항의 증대를 방지하기 위하여 마찰조정제(FM)가 자동차 엔진유를 비롯한 각종 윤활유에 첨가되어지고 있다. 또한 윤활유의 사용조건이 가곡(고온, 고가중) 해짐에 따라 첨가제의 다기능성이 요구되고 있는 가운데, 이와 같은 요구를 만족시켜 주기 위한 연구가 진행되고 있다. 최근에 와서 유용성 유기모리브덴계 화합물이 마찰,마모 및 산화방지제로서 주목받고 있다. 마찰, 마모을 감소시키기 위한 목적으로 널리 사용되고 있는 $MoS_2$는 고체윤활제로서 각광을 받고 있지만, 실제사용상의 문제로서 입자의 크기, 분산상의 문제 및 분산제와의 반응으로 인하여 마찰, 마모를 증대시키므로 역효과를 가져 오기도 한다. $MoS_2$와 같은 고체윤활제의 분상상의 무제점을 보완한 유용성 모리브덴계 화합물은 마찰, 마모 및 산화방지제로서 자동차 엔진유를 비롯하여 각종 윤활유에 첨가되고는 있지만 메카니즘에 대해서는 거의 해명되고 있지 않는 현실정이다. 본 연구는 유용성 유기모리브덴계 화합물중의 Molybdenum dialkyl dithiophosphate (MoDTP)의 마찰감소작용을 해명하기 위해서, MoDTP 첨가제의 마찰시험 및 마찰표면의 분석을 통하여 MoDTP의 마찰감소작용의 메카니즘을 명확하게 함을 자적으로 하고 있다.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1997.10a
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• pp.19-19
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• 1997

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.2
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• pp.112-120
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• 1998

A nondestructive evaluation technique was developed for the quantitative determination of the reinforcement volume fractions in particulate reinforced metal matrix composites. The proposed technique employed a composite micromechanics which accounts for the microstructure of the composite medium together with the measurement of anisotropic electrical conductivity. When the measured conductivity was coupled with the theoretically predicted conductivity, the unknown reinforcement volume fraction was calculated. An analytical model based on the Mori-Tanaka method was described which relates the NDE signatures to the composite microstructure. The volume fractions were calculated using eddy current measurements made on a wide range of silicon carbide particulate ($SiC_p$) reinforced aluminum (Al) matrix composites. The calculated $SiC_p$ volume fractions were in good agreement with the measured volume fractions in the range of 0-30%. The technique was also found to be effective in estimating the total volume percentage of reinforcement and intermetallic compound formed during the processing stage.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.4
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• pp.27-36
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• 2007

In this study, we investigated the interfacial reactions between various Sn-Ag-Cu(SAC) solder alloys and ENIG(Electroless Ni Immersion Gold) and Cu-OSP(Organic Solderability Preservative) pad finish. In the case of the interfacial reaction between Sb added SAC solder and ENlf thinner P-rich Ni layer was formed at the interface. In the case of the interfacial reaction between Ni added SAC solder and Cu-OSP, the uniform $Cu_6Sn_5$, intermetallic compounds(IMCs) were formed and $Cu_6Sn_5$ grain did not grow after multiple reflows. Thinner $Cu_3Sn$ IMCs were farmed at the interface between $Cu_6Sn_5$ and Cu-OSP after $150^{\circ}C$ thermal aging.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.4
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• pp.61-68
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• 2023

In this study, Sn-3.5Ag-15.0Fe composite solder was manufactured and applied to TLP bonding to change the entire joint into a Sn-Fe IMC(intermetallic compound), thereby applying it as a high-temperature solder. The FeSn₂ IMC formed during the bonding process has a high melting point of 513℃, so it can be stably applied to power modules for power semiconductors where the temperature rises up to 280℃ during use. As a result of applying ENIG surface treatment to both the chip and substrate, a multi-layer IMC structure of Ni₃Sn₄/FeSn₂/Ni₃Sn₄ was formed at the joint. During the shear test, the fracture path showed that cracks developed at the Ni₃Sn₄/FeSn₂ interface and then propagated into FeSn₂. After 2hours of the TLP joining process, a shear strength of over 30 MPa was obtained, and in particular, there was no decrease in strength at all even in a shear test at 200℃. The results of this study can be expected to lead to materials and processes that can be applied to power modules for electric vehicles, which are being actively researched recently.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.2
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• pp.103-111
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• 1998

A nondestructive ultrasonic technique is presented for estimating the reinforcement volume fractions of particulate composites. The proposed technique employs a theoretical model which accounts for composite microstructures, together with a measurement of ultrasonic velocity to determine the reinforcement volume fractions. The approach is used for a wide range of SiC particulate reinforced Al matrix ($SiC_p/Al$) composites. The method is considered to be reliable in determining the reinforcement volume fractions. The technique could be adopted in a production unit for the quality assessment of the metal matrix particulate composite extrusions.