• Environmental Engineering Research
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• v.14 no.2
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• pp.134-139
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• 2009

In this study, oxidation of As (III) as well as removal of total arsenic by adsorbents coated with single oxides or multi-oxides (Fe (III), Mn (IV), Al (III)) was investigated. In addition, multi-functional properties of adsorbents coated with multi-oxides were evaluated. Finally, application of activated carbon impregnated with Fe or Mn-oxides on the treatment of As (III) or As (V) was studied. As (V) adsorption results with adsorbents containing Fe and Al shows that adsorbents containing Fe show a greater removal of As (V) at pH 4 than at pH 7. In contrast adsorbents containing Al shows a favorable removal of As (V) at pH 7 than at pH 4. In case of iron sand, it has a negligible adsorption capacity for As (V) although it contains 217.9 g-Fe/kg-adsorbent, Oxidation result shows that manganese coated sand (MCS) has the greatest As (III) oxidation capacity among all metal oxides at pH 4. Oxidation efficiency of As (III) by IMCS (iron and manganese coated sand) was less than that by MCS. However the total removed amount of arsenic by IMCS was greater than that by MCS.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.481-484
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• 2004

이 논문에서는 소포 배달 서비스를 위한 인텔리전트 모니터링 시스템(Intelligent Monitoring and Control System; IMCS)에 대해 기술한다. IMCS 는 GIS, GPS 그리고 무선 통신 기술을 이용하여 택배의 접수와 배달 업무를 효율적이고 효과적으로 개발하기 위한 시스템이다. IMCS는 모두 세개의 서브 시스템으로 구성되어 있는데 접수와 배달 계획을 수립하는 PDPS(Pick-up and Delivery Planning System)과 접수/배달 현황과 차량의 위치를 파악할 수 있는 PDMS(Pick-up and Delivery Monitoring System), 그리고 개인휴대단말기(PDA)을 이용한 실시간 업무 처리 시스템인 MOCS(Mobile Operations and Communication System)으로 구성되어 있다. PDPS는 GIS와 최적화 알고리즘을 이용하여 접수와 배달을 위한 방문 순서와 경로 그리고 고객에게 방문할 예정시간 등을 생성한다. MOCS에서는 GPS와 무선 통신을 이용하여 업무 중 발생한 접수/배달 결과와 위치 정보를 실시간으로 PDMS에 전송하고 바코드 스캐닝과 전자 서명 등의 업무를 지원한다. PDMS에서는 수신한 정보에 따라 소포의 접수/배달 현황과 차량의 위치를 전자지도 상에 표현하고 업무 차량의 이동 궤적을 표시하여 계획된 경로와 비교하여 모니터링하고 관제할 수 있다. 현재 IMCS는 국내 한 우체국에서 시범 운영되고 있다.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.6
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• pp.309-314
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• 2021

Due to the superior corrosion resistance and mechanical properties of TiAl alloy at high temperature, it has been utilized as a turbine wheel of a turbocharger. The dissimilar metallic bonding is usually applied to combine the TiAl turbine wheel with the SCM440 structural steel which is used as a driving shaft. In this study, the TiAl and SCM440 joint were fabricated by using a friction welding technique. During bonding process, to suppress the martensitic transformation and the formation of cracks, which might reduce a strength of the joints, Cu was used as an insert metal to relieve stress. As a result, the intermetallic compounds (IMCs) layer was observed at TiAl/Cu interface while no IMC formation was formed at SCM440/Cu interface. Since understanding of the IMCs effects on the mechanical performance of welded joint is also essential for ensuring the reliability and integrity of the turbocharger system, we estimated the nanohardness of welded joint region through nanoindentation. The relation between the microstructural feature and its mechanical property is discussed in detail.

• Proceedings of the KWS Conference
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• 2006.10a
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• pp.205-206
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• 2006

The microstructural evolutions and shear properties of the pure Sn solder bumps with Ni UBMs were investigated during multiple reflows and high temperature storage(HTS) tests. Only a $Ni_3Sn_4$ IMC was found at the bump/Ni UBM interface after 1 reflow. The layer thickness of these IMCs increased with increasing reflow number and testing time. The solder bumps showed a good reliability during multiple reflows and HTS tests.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.3
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• pp.49-56
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• 2012

Recently, by the trends of electronic package to be smaller, thinner and more integrative, fine bump is required. but It can result in the electrical short by reduced cross-section of UBM and diameter of bump. Especially, the formation of IMCs and KV can have a significant affects about electrical and mechanical properties. In this paper, we analyzed the thermal deformation of flip-chip bump by using FEM. Through Thermal Cycling Test (TCT) of flip-chip package, We analyzed the properties of the thermal deformation. and We confirmed that the thermal deformation of the bump can have a significant impact on the driving system. So we selected IMCs thickness and bump diameter as variable which is expected to have implications for characteristics of thermal deformation. and we performed analysis of temperature, thermal stress and thermal deformation. Then we investigated the cause of the IMC's effects.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.134-141
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• 2013

Reflow soldering process is essential in electronic package. Reflow process for a long time results from the decrease of reliability because IMC is formed excessively. Solder alloys of Sn-37Pb and Sn-Ag with different kinds of Cu contents (0, 0.5 and 1 wt.%) as compared with Ni and Cu plate joints are investigated according to varying reflow time. The interfaces of solder joints are observed to analyze IMC (intermetallic compound) growth rate by scanning electron microscope (SEM). Shear test is also performed by using SP (Share-Punch) tester. The test results are compared with the solder joints of two different plates (Ni and Cu plate). $Cu_6Sn_5$ IMCs are formed on Cu plate interfaces after reflows in all samples. Ni3Sn4 and $(Cu,Ni)_6Sn_5$ IMCs are also formed on Ni plate interfaces. The IMC layer forms are affected by reflow time and contents of solder alloy. These results show that mechanical strength of solder joints strongly depends on thickness and shape of IMC.

• 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.

• Korean Journal of Metals and Materials
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• v.50 no.1
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• pp.71-77
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• 2012

We studied the effect of heat treatment on the microstructures and mechanical strength of the solder joints in the Light Emitting Diode (LED) packages. The commercial LED packages were mounted on the a flame resistance-4 (FR4) Printed Circuit Board (PCB) in the reflow process, and then the joints were aged at $125^{\circ}C$ for 100, 200, 300, 500 and 1000 hours, respectively. After the heat treatment, we measured the shear strength of the solder joints between the PCB and the LED packages to evaluate their mechanical property. We used Pb-free Sn-3.0Ag-0.5Cu solder to bond between the LED packages and the PCBs using two different surface finishes, Electroless Nickel-Immersion Gold (ENIG) and Electroless Nickel-Electroless Palladium-Immersion Gold (ENEPIG). The microstructure of the solder joints was observed by a scanning electron microscope (SEM). (Cu,Ni)6Sn5 intermetallic compounds (IMCs) formed between the solder and the PCB, and the thickness of the IMCs was increased with increasing aging time. The shear strength for the ENIG finished LED package increased until aging for 300 h and then decreased with increasing aging time. On the other hand, in the case of an ENEPIG finished LED package, the shear strength decreased after aging for 500 h.

• Korean Journal of Metals and Materials
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• v.50 no.10
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• pp.775-783
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• 2012

The effect of thermal annealing on the in-situ growth characteristics of intermetallics (IMCs) and the mechanical strength of Cu pillar/Sn-3.5Ag microbumps are systematically investigated. The $Cu_6Sn_5$ phase formed at the Cu/solder interface right after bonding and grew with increased annealing time, while the $Cu_3Sn$ phase formed at the $Cu/Cu_6Sn_5$ interface and grew with increased annealing time. IMC growth followed a linear relationship with the square root of the annealing time due to a diffusion-controlled mechanism. The shear strength measured by the die shear test monotonically increased with annealing time. It then changed the slope with further annealing, which correlated with the change in fracture modes from ductile to brittle at a critical transition time. This is ascribed not only to the increasing thickness of brittle IMCs but also to the decreasing thickness of the solder, as there exists a critical annealing time for a fracture mode transition in our thin solder-capped Cu pillar microbump structures.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1820-1821
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• 2011

The equipment qualification test was accomplished before application to power generating stations because troubles in applying to real system could be prevented trough the test. That is, if a system was judged to be suitable in the equipment qualification test, the system was expected to be operated stable to the designed life.