• Journal of the Microelectronics and Packaging Society
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• v.16 no.4
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• pp.23-28
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• 2009

We investigated the wafer-level MEMS capping process for which cavity formation in Si wafer was not required. Ni caps were formed by electrodeposition on 4" Si wafer and Ni rims of the Ni caps were bonded to the Cu rims of bottom Si wafer by using epoxy. Then, top Si wafer was debonded from the Ni cap structures by using SnBi layer of low melting temperature. As-evaporated SnBi layer was composed of double layers of Bi and Sn due to the large difference in vapor pressures of Bi and Sn. With keeping the as-evaporated SnBi layer at $150^{\circ}C$ for more than 15 sec, SnBi alloy composed of eutectic phase and Bi-rich $\beta$ phase was formed by interdiffusion of Sn and Bi. Debonding between top Si wafer and Ni cap structures was accomplished by melting of the SnBi layer at $150^{\circ}C$.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.31-39
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• 2008

To develop the MEMS cap bonding process without cavity formation, we electroplated Cu/Sn rim structures and measured the bonding characteristics for the Cu/Sn rims of $25{\sim}400{\mu}m$ width. As the effective device-mounting area ratio decreased and the failure strength ratio increased for wider Cu/Sn rim, these two properties were estimated to be optimized for the Cu/Sn rim with 150 ${\mu}m$ width. Complete bonding was accomplished at the whole interfaces of the Cu/Sn packages with the rim widths of 25 ${\mu}m$ and 50 ${\mu}m$. However, voids were observed locally at the interfaces with the rim widths larger than 100 ${\mu}m$. Such voids were formed by local non-contact between the upper and lower rims due to the surface roughness of the electroplated Sn.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.9-15
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• 2008

Microstructure and contact resistance of the Au-Sn solder joints were characterized after flip-chip bonding of the Au/Sn bumps processed by successive electrodeposition of Au and Sn. Microstructure of the Au-Sn solder joints, formed by flip-chip bonding at $285^{\circ}C$ for 30 sec, was composed of the $Au_5Sn$+AuSn lamellar structure. The interlamellar spacing of the $Au_5Sn$+AuSn structure increased by reflowing at $310^{\circ}C$ for 3 min after flip-chip bonding. While the Au-Sn solder joints formed by flip-chip bonding at $285^{\circ}C$ for 30 sec exhibited an average contact resistance of 15.6 $m{\Omega}$/bump, the Au-Sn solder joints reflowed at $310^{\circ}C$ for 3 min after flip-chip bonding possessed an average contact resistance of 15.0 $m{\Omega}$/bump.

• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.21-25
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• 2016

When copper alloy is used in etching process for the production of lead frame, the high concentration of heavy metals, such as iron, nickel and zinc may be included in the etching waste. Those etching waste is classified as a specified one. Therefore a customized design was designed for the purification process of the lead frame etching waste liquid containing high concentrations of heavy metals for the production of an electroplating copper(II) oxide. Since the lead frame etching waste solution contains highly concentrated heavy metal species, an ion exchange method is difficult to remove all heavy metals. In this study, a copper(I) chloride was manufactured by using water solubility difference related to the reduction-oxidation method followed by the reunion of copper(II) chloride using sodium sulfate as an oxidant. The hydrazine was chosen as a reducing agent. The optimum added amount was 1.4 mol per 1.0 mol of copper. In the case of removal of heavy metals by using the combination of reduction-oxidation and ion exchange resin methods, 4.3 ppm of $Fe^{3+}$, 2.4 ppm of $Ni^{2+}$ and 0.78 ppm of $Zn^{2+}$ can be reused as raw materials for electroplating copper(II) oxide when repeated three times.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.672-678
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• 2011

In this work, carbon fibers were electrolessly Ni-plated in order to investigate the effect of metal plating on the electromagnetic shielding effectiveness (EMI-SE) of Ni-coated carbon fibers-reinforced epoxy matrix composites. The surfaces of carbon fibers were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Electric resistance of the composites was tested using a 4-point-probe electric resistivity tester. The EMI-SE of the composites was evaluated by means of the reflection and adsorption methods. From the results, it was found that the EMI-SE of the composites enhanced with increasing Ni plating time and content. In high frequency region, the EMI-SE didn't show further increasing with high Ni content (Ni-CF 10 min) compared to the Ni-CF 5 min sample. In conclusion, Ni content on the carbon fibers can be a key factor to determine the EMI-SE of the composites, but there can be an optimized metal content at a specific electromagnetic frequency region in this system.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.206-206
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• 2003

현재, 메탈의 내부식성 코팅막 제조에 사용되고 있는 크로메이트 기반 코팅제는 유독성 물질에 대한 환경 규제에 따라 조만간 사용이 금지 될 예정이다. 본 연구에서는 이러한 유독성 금속 내부식성 코팅제를 대체할 새로운 코팅 재료로 부식 억제제가 결합된 수용성 졸을 제조하고 그 특성을 보고하고자 한다 부식 억제제가 결합된 수용성 졸은 부분 가수 분해된 GPS((3-glycidoxypropyltriethoxysilane)에 Zirconiumoxychlorideoctahydrate 혹은 cerium nitrate를 일정 양 첨가하고 이온 교환수에 희석하여 제조하였다. 이 코팅 졸을 아연 도금 강판에 딥 코팅법으로 코팅한 후 상온에서 건조하고, 80~15$0^{\circ}C$에서 열처리하여 염수 분무 시험으로 백청 발생 정도를 관찰하여 내 부식성을 조사하였다. 코팅막의 두께는 수직으로 절단한 면을 전자 현미경으로 관찰하여 측정하였으며, 표면의 경도는 연필 경도계로 조사하였다. 또한 코팅막의 부식 전위는 전기화학적인 방법으로 분석되어 부식억제제의 종류에 따른 효과도 정량적으로 비교되었다.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1718-1723
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• 2007

The Probe Card is a test component which is to classify the good semiconductor chips before the packaging. The yield of semiconductor product can be better from analysis of probe test information. Recently the technology of the probe card needs narrow width and large amount of probe tip. In this research, the probe tip based on the MEMS(micro electro mechanical system) technology was designed and fabricated to improve the reliability of the test and to meet 2-dimensional Array of tip. The mechanical and electrical properties of proposed tip were evaluated and it has over 100,000 of repetition times in the condition of 5gf, $20{\mu}m$ Over Drive.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.118-121
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• 2003

The electrochemical behaviors of UBM nickel were investigated. Electrode potential has been changed with the surface composition. Zinc is dissolved into the solution immediately after immersion. Electrode potential has three distinct regions: Zinc dissolution region, transient region and nickel plating region. The effects additives on electrode potential and polarization curves were also investigated. The addition of suppressor lowered the current density which is related with deposition rate.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.46-46
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• 2011

각종산업의 건축자재, 전기기기 등의 분야에서 내식성 향상용 표면처리 도금재로 가장 많이 사용되고 있는 아연과 실용금속 중 가장 가벼우면서 비강도 및 치수 안정성이 뛰어난 Mg을 사용하여 Zn-Mg의 합금 박막을 제작하였다. 여기서는 Zn, Mg 단일 박막의 밀착성과 내식성의 한계점을 극복하기 위해서 모재와 코팅층 사이에 Al을 삽입하여 (Zn-Mg)/Al 합금 박막을 형성시켰다. 또한 박막의 증착과정 중 이들 막의 제어는 바이아스 전압을 일정하게 하고 진공도를 변수로 하였고, 진공도에 따라 달라지는 쳄버내의 가스 입자가 흡착 인히비터로 작용해서 박막의 몰포로지와 결정배향성의 구조에 중요한 영향을 준다는 것을 확인하였다. 그리고 이들 박막의 내식성과 밀착성에 미치는 몰포로지나 결정배향성과의 상관관계를 규명하여 최적의 코팅 프로세스를 결정하므로써 중간층 유무별 Zn계 합금박막의 기초적인 제작설계 지침을 제공하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.171-172
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• 2007

초고속용사법(HVOF)은 우수한 강도와 높은 경도를 가지는 치밀한 후막형성이 가능하고 피로특성 및 열충격에 대한 저항성이 양호하여 종래에 사용되어 오던 전기도금등을 통한 표면처리 방법을 대체시키고 있다. 항공기엔진의 주요부품, 초고속 air bearing spindle등의 내구성향상을 위한 WC계 분말을 이용한 표면처리의 공정을 다구찌실험계획법을 이용해 최적조건을 선정하였다.