• Proceedings of the KWS Conference
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• 2010.05a
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• pp.82-82
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• 2010

표면실장 공법을 통해 CSP 패키지를 보드에 실장 하는데 있어 무연솔더 접합부의 신뢰성에 영향을 미치는 인자 중 가장 중요한 것은 접합부에 형성되는 IMC (Intermetallic compound, 금속간화합물)인 것으로 알려져 있다. 접합부의 칩 부분에는 솔더와 칩의 UBM (Under bump metalization)이 접합하여 IMC가 형성되나, 보드 부분에는 솔더와 보드의 UBM 뿐만 아니라 그 사이에 솔더 페이스트가 함께 접합되어 IMC가 형성된다. 본 연구에서는 패키지의 신뢰성 연구를 위해 솔더 페이스트의 유무 및 두께에 따른 무연 솔더 접합부의 미세조직의 변화를 분석하였다. 본 실험에서는 Sn-3.0(Wt.%)Ag-0.5Cu 조성과 본 연구진에 의해 개발된 Sn-Ag-Cu-In 조성의 직경 $450{\mu}m$ 솔더 볼을 사용하였으며, 솔더 페이스트는 상용 Sn-3.0Ag-0.5Cu (ALPHA OM-325)를 사용하였다. 칩은 ENIG (Electroless nickel immersion gold) finish pad가 형성된 CSP (Chip scale package)를, 보드는 OSP (Organic solderability preservative)/Cu finish pad가 형성된 것을 사용하였다. 실험 방법은 보드를 솔더 페이스트 없이 플라즈마 처리 한 것, 솔더 페이스트를 $30{\mu}m$ 두께로 인쇄한 것, $120{\mu}m$의 두께로 인쇄한 것, 이렇게 3가지 조건으로 준비한 후, 솔더 볼이 bumping된 칩을 mounting하여, $242^{\circ}C$의 peak 온도 조건의 oven(1809UL, Heller)에서 reflow를 실시하여 패키지를 형성하였다. 이후 시편은 정밀 연마한 후, OM(Optical Microscopic)과 SEM(scanning electron microscope) 및 EDS(energy dispersive spectroscope)를 사용하여 솔더 접합부 IMC의 미세조직을 관찰, 분석하였다.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.43-48
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• 2004

Electromigration of Sn-3.5Ag-0.5Cu solder bumps was investigated with current densities of $3{\~}4{\times}10^4 A/cm^2$ at temperatures of $130{\~}160^{\circ}C$ using flip chip specimens which consisted of upper Si chip and lower Si substrate. Electromigration failure of the Sn-3.5Ag-0.5Cu solder bump occurred with complete consumption of Cu UBM and void formation at cathode side of the solder bump. The activation energies for electromigration of the Sn-3.5Ag-0.5Cu solder bump were measured as 0.61 eV at current density of $3{\times}10^4 A/cm^2$, 0.63 eV at $3.5{\times}10^4 A/cm^2$, and 0.77 eV at $4{\times}10^4 A/cm^2$, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.1-7
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• 2008

We studied a growth behavior of Intermetallic compounds(IMCs) during solder bumping with two reflow methods. Ti(50 nm), Cu($1{\mu}m$), Au(50 nm) and Ti(50 nm) thin films were deposited on $SiO_2$/Si wafer using the DC magnetron sputtering system as the under bump metallization(UBM). And the $5{\mu}m$ thick Cu bumps and $20{\mu}m$ thick Sn bumps were fabricated on UBM by electroplating. Sn bumps were reflowed in RTA(Rapid Thermal Annealing) system and convection reflow oven. When RTA system was used, reflow was possible without using flux and IMC thickness formed in the solder interface was thinner than that of a convectional method.

• Korean Journal of Materials Research
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• v.9 no.11
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• pp.1095-1101
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• 1999

Electroless Ni plating is applied to form bumps and UBM layer for flip chip interconnection. Characteristics of electroless Ni are also investigated. Zincate pretreatment is analyzed and plated layer characteristics are investigated according to variables like temperature, pH and heat treatment. Based on these observations, characteristics dependence to each variables and optimum electroless Ni plating conditions for flip-chip interconnection are suggested. Electroless Ni has 10wt% P, $60\mu\Omega$-cm resistivity, 500HV hardness and amorphous structure. It changes crystallized structure and hardness increases after heat treatment After interconnection of electroless Ni bumps by ACF flip chip method, we show their advantages and possibility in microelectronic package applications.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.3
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• pp.1-10
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• 2023

Recently, as the demand for high-performance computers and mobile products increases, semiconductor packages are becoming high-integration and high-density. Therefore, in order to transmit a large amount of data at once, micro bumps such as flip-chip and Cu pillar that can reduce bump size and pitch and increase I/O density are used. However, when the size of the bumps is smaller than 70 ㎛, the brittleness increases and electrical properties decrease due to the rapid increase of the IMC volume fraction in the solder joint, which deteriorates the reliability of the solder joint. Therefore, in order to improve these issues, a layer that serves to prevent diffusion is inserted between the UBM (Under Bump Metallization) or pillar and the solder cap. In this review paper, various studies to improve bonding properties by suppressing excessive IMC growth of micro-bumps through additional layer insertion were compared and analyzed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.9
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• pp.1491-1497
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• 1997

The purpose of this research is to improve the surface roughness of cast-iron pipe porduced by the centrifugal casting. A twin-fluid atomizer of mold-wash slurry is designed for this project. New atomizer is equipped with the existing manufacturing facility to produce pipes. Cast-iron pipes (.cent.125*L3000mm) are produced and the surface roughnesses of those are analysed by UBM. The average surface roughness of new products is 6.7.mu.m while the old products of sand-resin coating method have 17.0.mu.m of average surface roughness. The surface roughness of cast-iron pipe is improved very much than before.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.155-156
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• 2013

소셜 TV 사용 시, 사용자들은 TV를 시청하면서 타 사용자와의 소통을 위해 리모컨을 이용해서 텍스트를 작성해야하는 불편함을 가지고 있다. 본 논문에서는 소셜 TV의 이러한 불편함을 해결하기 위해 사용자 반응 사운드를 자동으로 인식하여 상대방에게 이모티콘을 전달하기 위한 시스템을 제안하며, 사용자 반응 사운드 인식에 사용되는 분류방식들을 비교한다. 사용자 반응 사운드 인식을 위해 사용되는 분류 방식들 중에서, Gaussian Mixture Model(GMM), Gaussian Mixture Model - Universal Background Model(GMM-UBM), Hidden Markov Model(HMM), Support Vector Machine(SVM)의 성능을 비교하였다. 각 분류기의 성능을 비교하기 위하여 MFCC 특징값을 각 분류기에 적용하여 사용자 반응 사운드 인식에 가장 최적화된 분류기를 선택하였다.

• ETRI Journal
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• v.28 no.6
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• pp.811-814
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• 2006

In this letter, we introduce confusion-based confidence measures for detecting an impostor in speaker recognition, which does not require an alternative hypothesis. Most traditional speaker verification methods are based on a hypothesis test, and their performance depends on the robustness of an alternative hypothesis. Compared with the conventional Gaussian mixture model-universal background model (GMM-UBM) scheme, our confusion-based measures show better performance in noise-corrupted speech. The additional computational requirements for our methods are negligible when used to detect or reject impostors.

• Journal of Welding and Joining
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• v.20 no.4
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• pp.498-504
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• 2002

Fluxless flip chip bonding process using plasma treatment instead of flux was investigated. The effect of plasma process parameters on tin-oxide etching characteristics were estimated with Auger depth profile analysis. The die shear test was performed to evaluate the adhesion strength of the flip chip bonded after plasma treatment. The thickness of oxide layer on tin surface was reduced after Ar+H2 plasma treatment. The addition of H2 improved the oxide etching characteristics by plasma. The die shear strength of the plasma-treated Sn-Pb solder flip chip was higher than that of non-treated one but lower than that of fluxed one. The difference of the strength between plasma-treated specimen and non-treated one increased with increase in bonding temperature. The plasma-treated flip chip fractured at solder/TSM interface at low bonding temperature while the fracture occurred at solder/UBM interface at higher bonding temperature.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.94-98
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• 2003

The microstructure of Sn1.8Bi0.8Cu0.6In alloys was evaluated at various aging time. The bumps of Sn1.8Bi0.8Cu0.6In alloys after reflowed at $250^{\circ}C$ were well-formed and had 260um height. The craters on the bumps, however, were observed. Intermetallic compounds formed on the interface between so]der and Cu/Ni UBM were consist of $(Cu,Ni)_6Sn_5$. As aging goes on up to 1000hours, the composition of Ni changed from $6.63\%$ at initial stage(as-reflowed) to $13.47\%$ at final stage(1000hours aging ). In addition, after 500hours aging, the floating of IMC to the solder was observed.