• Journal of Welding and Joining
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• 제20권5호
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• pp.106-112
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• 2002

In the present study, the wettability and interfacial tension between (bare Cu, electroless Ni/cu, immersion Au/Ni/Cu) substrates and indium solder were investigated as a function of soldering temperature, types of flux. The wettability of In solder increased with soldering temperature and solid content of flux. The wettability of In solder was affected by the substrate metal finish used, i.e., nickel, gold and copper. On the bare Cu substrate, In solder wet better than any of the substrate metal finishes tested. Intermetallic compound formation between liquid solder and substrate reduced the interfacial energy and improved wettability. For the identification of intermetallic compounds, X-Ray Diffraction(LRD) were employed. Experimental results showed that the intermetallic compounds, such as Cu11In9 and In27Ni10 are observed f3r different substrates respectively. The wetting kinetics is investigated by measuring wetting time with the wetting balance technique. The activation energy of wetting calculated for the In solder/cu substrate and In solder/electroless Au/Ni/Cu substrate are 36.13 and 27.36 kJ/mol, respectively.

• Journal of Welding and Joining
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• 제20권1호
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• pp.91-96
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• 2002

Three different kinds of substrate used in this study : bare Cu, electroless Ni/Cu substrate with a Nilayer thickness of $5\mu\textrm{m}$, immersion Au/electroless Ni/Cu substrate with the Au and Ni layer of $0.15\mu\textrm{m}$ and $5\mu\textrm{m}$ thickness, respectively. The wettability and interfacial tension between various substrate and Sn-3.5Ag solder were examined as a function of soldering temperature, types of flux. The wettability of Sn-3.5Ag solder increased with soldering temperature and solid content of flux. The wettability of Sn-3.5Ag solder was affected by the substrate metal finish used, i.e., nickel, gold and copper. Intermetallic compound formation between liquid solder and substrate reduced the interfacial energy and decreased wettability.

• 마이크로전자및패키징학회지
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• 제19권4호
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• pp.57-64
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• 2012

표면처리에 따른 Sn-1.2Ag-0.7Cu-0.4In 솔더범프의 접합 강도 평가를 위하여 전단 속도 및 열처리 시간에 따른 볼 전단강도 시험을 실시하였다. 전반적으로, 전단속도가 증가함에 따라 전단강도는 증가하였지만 인성은 감소하는 경향을 나타내었다. 파괴모드 관찰 결과, 전단 속도가 증가함에 따라 파괴모드의 경우, ENIG(electroless nickel immersion gold) 처리는 취성파괴가 대부분 지배적으로 존재하였고, OSP(organic solderability preservative) 처리는 pad open이 주로 발생하였다. 또한, 500 mm/s의 고속전단시험에서는 열처리 시간이 증가함에 따라 표면처리별 전단강도와 인성 값 모두 감소하는 경향을 보였다. ENIG 표면처리가 OSP 표면처리 보다 좋은 접합강도 특성을 보이는 것은 솔더범프 계면의 금속간화합물의 물성 및 두께와 밀접한 연관이 있는 것으로 판단된다.

• 전기화학회지
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• 제16권1호
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• pp.46-51
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• 2013

전극과 용액 사이 계면에서 일어나는 전기화학 반응 현상을 보다 정확하게 이해하기 위하여 전기화학 반응과정을 분광학적 방법으로 실시간으로 모니터링 할 수 있는 전극으로도 작동할 뿐만 아니라 표면증강라만산란(SERS) 활성도 강한 금 마이크로쉘을 제조하였다. 기존에 보고된 금 마이크로쉘에서 핵으로 사용한 폴리스티렌의 경우 균일성이 떨어지고 유기용매에 약하며 독성이 있다. 이에 본 연구에서는 폴리스티렌 보다 균일한 구조를 가지고, 유기 용매에서도 사용 가능하며 무독한 실리카 비드를 이용하여 금 마이크로쉘을 만들고 높은 SERS 신호를 낼 수 있도록 최적화시켰다. $2{\mu}m$ 실리카 비드 표면에 서로 다른 양의 3-aminopropyl triethoxysilane (APTES)를 반응시켜 얻은 금 마이크로쉘에서 SERS 신호가 가장 월등히 증폭되는 조건을 비교한 결과 1% (v/v) APTES 조건에서 SERS 신호의 증폭이 가장 컸다. 표면증강라만산란 스펙트럼 및 전계방출형 주사전자현미경(FE-SEM) 이미지를 통해 금 마이크로쉘을 분석하였다.

• 한국재료학회지
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• 제21권2호
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• pp.115-119
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• 2011

Si Nanowire (NW) field effect transistors (FETs) were fabricated on hard Si and flexible polyimide (PI) substrates, and their electrical characteristics were compared. Si NWs used as channels were synthesized by electroless etching method at low temperature, and these NWs were refined using a centrifugation method to get the NWs to have an optimal diameter and length for FETs. The gate insulator was poly(4-vinylphenol) (PVP), prepared using a spin-coating method on the PI substrate. Gold was used as electrodes whose gap was 8 ${\mu}m$. These gold electrodes were deposited using a thermal evaporator. Current-voltage (I-V) characteristics of the device were measured using a semiconductor analyzer, HP-4145B. The electrical properties of the device were characterized through hole mobility, $I_{on}/I_{off}$ ratio and threshold voltage. The results showed that the electrical properties of the TFTs on PVP were similar to those of TFTs on $SiO_2$. The bending durability of SiNWs TFTs on PI substrate was also studied with increasing bending times. The results showed that the electrical properties were maintained until the sample was folded about 500 times. But, after more than 1000 bending tests, drain current showed a rapid decrease due to the defects caused by the roughness of the surface of the Si NWs and mismatches of the Si NWs with electrodes.

• 한국재료학회지
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• 제24권3호
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• pp.166-173
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• 2014

The effects of printed circuit board electroless nickel immersion gold (ENIG) and organic solderability preservative (OSP) surface finishes on the electromigration reliability and shear strength of Sn-3.5Ag Pb-free solder bump were systematically investigated. In-situ annealing tests were performed in a scanning electron microscope chamber at 130, 150, and $170^{\circ}C$ in order to investigate the growth kinetics of intermetallic compound (IMC). Electromigration lifetime and failure modes were investigated at $150^{\circ}C$ and $1.5{\times}10^5A/cm^2$, while ball shear tests and failure mode analysis were conducted under the high-speed conditions from 10 mm/s to 3000 mm/s. The activation energy of ENIG and OSP surface finishes during annealing were evaluated as 0.84 eV and 0.94 eV, respectively. The solder bumps with ENIG surface finish showed longer electromigration lifetime than OSP surface finish. Shear strengths between ENIG and OSP were similar, and the shear energies decreased with increasing shear speed. Failure analysis showed that electrical and mechanical reliabilities were very closely related to the interfacial IMC stabilities.

• 마이크로전자및패키징학회지
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• 제16권1호
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• pp.7-11
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• 2009

본 연구에서는 electroless nickel / immersion gold (ENIG) 처리된 printed circuit board (PCB)를 무연 솔더인 Sn-3.5(wt%)Ag로 접합하였다. 리플로우 횟수를 1회부터 10회까지 다양하게 하여 리플로우 횟수가 증가함에 따른 솔더 접합부의 기계적, 전기적 특성의 변화에 대해 연구하였다. 접합부의 미세 조직 관찰을 위해 접합부 단면을 폴리싱 하여 금속간 화합물의 두께를 측정하고 종류를 분석하였다. 접합부의 기계적 특성을 평가하기 위해서 die 전단 시험을 하였는데, 리플로우 횟수가 4-5회일 때까지 전단 강도 값이 증가하다가 5회 이후로 감소하였다. 전기적 특성을 알아보기 위해 전기 저항 값을 측정하였는데, 리플로우 횟수가 증가할수록 접합부의 전기 저항 값은 점점 증가하였다.

• 마이크로전자및패키징학회지
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• 제10권1호
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• pp.7-11
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• 2003

반도체 칩이나 전자제품에 사용되는 부품들은 작동할 때 발열을 하게 되며 발생한 열이 적절히 제거되지 않을 경우 제품 오작동의 원인이 된다. 이러한 열을 제거하기 위해 히트싱크(heatsink)와 냉각 팬 (cooling fan)을 조합한 냉각 구조가 사용된다. 그러나 히트싱크와 냉각 팬의 조합 구조는 복잡한 형상을 취하기 때문에 전기 전자 제품의 소형화 추세에 부응하기에는 어려움이 따른다. 냉각 효율은 히트싱크의 표면적과 히트싱크 제조시 사용된 재료에 따라 달라진다. 일반적인 냉각 구조의 한계를 극복하기 위한 방안으로써, Trach-etched 멤브레인의 표면과 기공(pore)에 무전해 금도금과 구리 도금을 실행하여 크기는 작으면서 표면적을 증가시킨 마이크로 히트싱크를 제조하였다. 제조한 마이크로 히트싱크의 구조는 주사현미경(SEM)과 광학 현미경으로 관찰하였으며, 일반적인 구리보다 열효율이 우수함을 방열 특성 실험을 통해 관찰하였다.

• Current Photovoltaic Research
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• 제4권4호
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• pp.140-144
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• 2016

In this paper, core-shell structure of nickel/gold (Ni/Au) conductive layer on poly-methyl-methacrylate (PMMA) micro-ball was fabricated and its conduction property was investigated. Firstly, PMMA micro-ball was synthesized by using dispersion polymerization method. Size of the ball was $2.8{\mu}m$ within ${\pm}7%$ deviation, and appropriate elastic deformation of the PMMA micro-ball ranging from 31 to 39% was achieved under 3 kg pressure. Also, 200 nm thick Ni/Au conductive layer was fabricated on the PMMA micro-ball by uniformly depositing with electroless-plating. Adhesion of the conductive layer was optimized with help of surface pre-treatment, and the layer adhered without peeling-off despite of thermal expansion by collision with accelerated electrons. Composite paste containing core-shell structured particles well cured at low temperature of $130^{\circ}C$ while pressing the test chip onto the substrate to make electrical contact, and electrical resistance of the conductive layer showed stable behavior of about $6.0{\Omega}$. Thus, it was known that core-shell structured particle of the Ni/Au conductive layer on PMMA micro-ball was feasible to flexible electronics.

• E2M - 전기 전자와 첨단 소재
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• 제10권1호
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• pp.39-44
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• 1997

Bulk type radiation detector of Au/Cd$_{1-x}$ Zn$_{x}$Te(x=20%)/Au structure using Cd$_{1-x}$ Zn$_{x}$Te(x=20%) wafer(3x4xl mm$^{3}$) grown by high pressure Bridgman method has been developed. We etched wafer surfaces with 2% Br-methanol solution and coated gold thin film on the surfaces by electroless deposition method for 5 min. in 49/o HAuCI$_{3}$ 4H20 solution. Initial etch rates of Cd, Zn and Te were 46%, 12% and 42% respectively. After etched, the surface of wafer was slightly revealed to Te rich condition. The leakage current was increased with etch time, but it didn't exceed 3nA at 50volt. The thickness of Au film was about 100nm by Rutherford Backscattering Spectroscopy(RBS). The resolution were 6.7% for 22.1 keV photon from 109 $^{109}$ Cd and 8.2% for 59.5 keV photon from $^{241}$ Am. The radiation detector such as Au/Cd$_{1-x}$ Zn$_{x}$Te(x=20%)/Au structure was more effective to monitor the low energy gamma radiation.iation.