• Journal of Applied Reliability
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• v.7 no.1
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• pp.23-29
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• 2007

Probe card is a test component which is to classify the known good die with electrical contact before the packaging in the ATE (automatic testing equipment). Conventional probe tip was mostly needle type, it has been difficult to meet with conventional type, because of decreasing chip size, pad to pad pitch and pads size increasingly. For that reason, probe cards using MEMS (micro electro mechanical system) technology have been developed for various semiconductor chips. In this paper, Area Array type MEMS Probe tip was designed,, fabricated, and characterized its mechanical and electrical properties. The authors found that good electrical characteristics under $1{\Omega}$ were acquired with gold (Au) and aluminium (Al) pad contact test over 0.5gf and 4gf respectively. And, contact resistance variation under $0.1{\Omega}$ were achieved with 100,000 times of repetition test. And, insertion loss (IS) for high frequency operation was ascertained over 300MHz at -3dB loss.

• Korean Journal of Metals and Materials
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• v.47 no.9
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• pp.580-585
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• 2009

The effects of shear speed and tip height on the high speed shear test of Sn-3.0wt.%Ag-0.5wt.%Cu ball joints were investigated. Solder balls of $450{\mu}m$ in diameter were reflowed at $245^{\circ}C$ on a FR4 PCB (Printed Circuit Board) in order to obtain a sample for the high-speed shear test. The UBM was comprised of Cu/Ni/Au, and the shear speed and tip height varied from 0.5 to 3.0 m/s, and from 10 to $135{\mu}m$, respectively. According to the experimental results, faster shear speed enhanced the shear strength of the solder joints, regardless of the tip height. The fraction of ductile (solder) fracture decreased when the shearing speed was raised from 0.5 to 3.0 m/s. With an increasing tip height from 10 to 50 and $135{\mu}m$, the fracture mode changed from pad lift to mixed (ductile and brittle) and ductile fracture, respectively, while the shearing energy also increased in the same order. The shear energy had a proportional relationship with the fraction of the solder fracture.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.126-126
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• 2011

수직으로 정렬된 1차원 ZnO nanorod arrays (NRAs)는 효율적인 반사방지 특성의 기하학적 구조를 갖고 있어, 크기와 모양 그리고 정렬형태의 다양한 설계를 통해 빛의 흡수율과 광 추출효율을 증가시켜 광전소자 및 태양광 소자의 성능을 향상시킬 수 있으며, 최근 이러한 연구에 대한 관심이 집중되고 있다. 본 연구에서는 ZnO NRAs의 넓은 표면적과 불연속적인 독특한 표면을 활용하여 광학적 특성을 효과적으로 개선하였다. 실험을 위해, thermal evaporator를 사용하여 Au와 Ag 그리고 e-beam evaporator를 사용하여 $SiO_2$를 ZnO NRAs 표면에 여러 가지 조건으로 증착하여, 독특한 계층 나노구조의 형성과 광학적 특성을 관찰하였다. 표면 roughness가 큰 FTO/glass 위에 수열합성법을 통해 끝이 뾰족하고, 비스듬히 정렬된 ZnO nano-tip array에 Au를 증착할 경우 ZnO/Au core/shell 구조가 형성되며, Au의 광 흡수율이 매우 크게 증가함을 관찰할 수 있었다. 반면 flat한 표면위에 빽빽하게 수직으로 정렬된 ZnO NRAs를 성장시켜 그 위에 Ag를 증착할 경우, evaporated Ag flux가 ZnO nanorod의 사이에 scattered 되어 ZnO nanorod 기둥의 측면에 직경이 50 nm 이하인 nanoparticles이 decorated 되어 국소표면플라즈몬 현상이 관찰되었으며, 이러한 효과를 통해 입사되는 빛의 흡수율을 효과적으로 증가시킬 수 있었다. 또한, ZnO NRAs의 표면에 $SiO_2$를 e-beam evaporator를 이용하여 증착할 경우, 자연적으로 vapor flux와 ZnO nanorod 사이에 oblique angle이 $80^{\circ}$ 이상으로 증가하여 $SiO_2$ nanorods가 자발적으로 형성되어 ZnO/$SiO_2$ branch 계층형태의 나노구조를 제작할 수 있었다. 이러한 구조는 유효 graded refractive index profile로 인해 기존의 ZnO NRAs보다 개선된 반사방지 특성을 나타냈다. 이러한 계층 나노구조의 광학적 특성을 시뮬레이션을 통해 이론적으로 분석을 통해 광전자 소자의 성능의 개선에 대한 적용 가능성을 조사하였다.

• The Korean Journal of Nuclear Medicine Technology
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• v.13 no.3
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• pp.181-184
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• 2009

Purpose: Automated system that immunoassay examination are used widely. However, sample to sample carryover can cause that the next patient sample is false positive. Materials and Methods: We test HBs Ag, HBs Ab, HBc Ab(IgG) with Automated pipetting system (Tecan). It was placed with very high concentrations followed by saline solution. During this experiment, The fixed tip of Automated system wash With 0.25 moL/L NaOH. The Measurement results of saline solution confirm the occurrence of carryover. Results: Results of saline solution with 0.25 moL/L NaOH cleaning process was measured 100% negative, And results of patient serum with 0.25 moL/L NaOH cleaning process is similar reported results. Conclusion: As Results, 0.25 moL/L NaOH cleaning process was avoid carryover in experiment, And we know results of the hepatitis test did not affected by this solution we recommend 0.25 moL/L NaOH cleaning process as the Prevention of carryover in the automated system with fixed Tips.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.139-141
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• 2005

It is possble to study charge transfer property which is caused by height variation because we can see the organic materials barrier height and STM tip by organic materials energy band gap. Here, we investigated the negative differential resistance(NDR) and charge transfer property of self-assembled 4,4-Di(ethynylphenyl)-2'-nitro-1-(thioacetyl)benzene, which has been well known as a conducting molecule. Self-assembly monolayers(SAMs) were prepared on Au(111), which had been thermally deposited onto pre-treatment($H_{2}SO_{4}:H_{2}O_{2}$=3:1) Si. The Au substrate was exposed to a 1 mM/l solution of 1-dodecanethiol in ethanol for 24 hours to form a monolayer. After thorough rinsing the sample, it was exposed to a $0.1{\mu}M/1$ solution of 4,4-Di(ethynylphenyl)-2'-nitro-1-(thioacetyl)benzene in dimethylformamide(DMF) for 30 min and kept in the dark during immersion to avoid photo-oxidation. After the assembly, the samples were removed from the solutions, rinsed thoroughly with methanol, acetone, and $CH_{2}Cl_{2}$, and finally blown dry with $N_2$. Under these conditions, we measured electrical properties of self-assembly monolayers(SAMs) using ultra high vacuum scanning tunneling microscopy(UHV-STM). The applied voltages were from -1.50 V to -1.20 V with 298 K temperature. The vacuum condition is $6{\times}10^{-8}$ Torr. As a result, we found that NDR and charge transfer property by a little change of height when the voltage is applied between STM tip and electrode.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.40-44
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• 2002

The motivation of this work is to use SAM(Self-Assembled Monolayer) for developing a rapid and flexible non-photolithographic nano-structure fabrication technique which can be utilized in micro-machining of metals as well as silicon-based materials. The fabrication technique implemented in this work consists of a two-step process, namely, mechanical scribing followed by chemical etching. From the experimental results, it was found that thiol on copper surface could be removed even under a few nN normal load. The nano-tribological characteristics of thiol-SAM on various metals were largely dependent on the native oxide layer of metals. Based on these findings, nano-patterns with sub-micrometer width and depth on metal surfaces such as Cu, Au and Ag could be obtained using a diamond-coated tip.

• Journal of Microbiology and Biotechnology
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• v.14 no.5
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• pp.1038-1042
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• 2004

The photoelectric responses of a biodevice consisting of chlorophyll $\alpha$ Langmuir-Blodgett film were investigated. Chlorophyll $\alpha$ Langmuir-Blodgett films were deposited onto ITO and Au coated glass. To confirm film formation, surface analysis of chlorophyll $\alpha$ Langmuir-Blodgett film was carried out by measurement using atomic force microscopy. The metal/insulator/metal structured biodevice was constructed by depositing aluminum onto the chlorophyll $\alpha$ Langmuir-Blodgett film surface. To investigate the photoelectric response, the current-voltage characteristic was measured by the conducting metal tip. The photoswitching function and transient photovoltage characteristics of the proposed device were measured by irradiation with Ar ion laser and $N_2$ pulse laser, respectively. This research suggested that the proposed biodevice consisting of chlorophyll $\alpha$ could be applied to the molecular scale biosensor and/or bioelectronic device.

• Progress in Superconductivity
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• v.3 no.2
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• pp.146-150
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• 2002

We performed the point contact spectroscopy on newly discovered superconductor $MgB_2$ thin films with Au tip. In the point contact spectroscopy of the metallic Sharvin limit, the differential conductance below the gap is twice as that above the gap by virtue of Andreev Reflection. After some surface cleaning processes of sample preparation such as ion-milling and wet etching, the obtained dI/dV versus voltage curves are relatively well fitted to the Blonder-Tinkham-Klapwijk (BTK) formalism. Gaps determined by this technique were distributed in the range of 3meV~ 8meV with the BCS value of 5.9meV in the weak coupling limit. We attribute these discrepancies to the symmetry of the gap parameter and the degradation of the surface of the sample. We also present the temperature dependence of the conductance vs voltage curve and thereby the temperature dependence of the gap.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.2
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• pp.101-105
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• 2010

We fabricated FEDs(Filed emission devices) based on ZnO nanowires. The ZnO nanowires were synthesized on Au thin films by hydrothermal method at the temperature of 90[$^{\circ}C$] on hot plate. In order to form tips of the ZnO nanowire, SDS(Sodium Dodecyl Sulfate) was mixed in O.05-0.3[wt%] solution as capping material. After 2 hour growth, we obtained nanowires of chain form The high-purity nanowires showed sharp tip geometry with a wurtzite structure. The field emission properties of the ZnO nanowires were investigated in high vacuum chamber. The turn-on field for the ZnO nanowires was found to be about 4.1[V/${\mu}m$] at a current density of 0.1[${\mu}A/cm^2$].

• Journal of the Microelectronics and Packaging Society
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• v.15 no.2
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• pp.47-54
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• 2008

In this paper, we studied how and why did abnormal IMC growth at component affect on board level mechanical reliability. First, interfacial reactions between Sn2.5Ag0.5Cu solder and electrolytic Ni/Au UBM of component side were investigated with reflow times and thermal aging time. Also, to compare mechanical reliability of component level, shear energy was evaluated using the ball shear test conducted with variation of shear tip speed. Finally, to evaluate mechanical reliability of board level, we surface-mounted component fabricated with each condition on PCB side. After conducting of 3 point bending test and impact test, we confirmed solder joint crack mode using cross-sectioning and dye & pry penetration method.