발간논문

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Recently, oxide dispersion strengthened(ODS) ferritic alloys have been considered for the critical component materials of ultra-super critical pressure power plants or nuclear power plants. The strength properties of ferritic 12%Cr ODS alloys with the addition of Ti and W were investigated in comparison with those of 17% Cr ODS and 12%Cr ODS alloys in the range of room temperature to 1323K. Nano-sized oxide dispersoids in the alloys suppressed the grain growth during annealing at a 1323K and resulted in a remarkable improvement of the strength. The fine particles in 12%Cr ODS alloys with the addition of Ti and W was identified to be a complex oxide type of Y-Ti-O. The Complex oxides containing Ti was the finest and showed the most uniform dispersion.

keyword : ODS, Ferritic alloys, Mechanical alloying, Nano-sized oxides, Strength properties, Tensile properties, Heat-resistant steel

Increased electronic packaging density requires thermal management materials with high thermal conductivities and low coefficients of thermal expansion (CTEs) matching those of ceramic substrates or semiconductors. Recently, metal matrix composites (MMCs) have been developed, which provide unique combination of properties that make them candidates for thermal management materials. Most of conventional processes to fabricate MMCs have complicated steps that reduce the cost effectiveness, such as the infiltration process requiring a preform preparation and long process time. Plasma spraying can be adopted to produce MMCs in a flexible and cost effective manner. In this study, SiC particles reinforced Al matrix composites were fabricated by atmospheric plasma spraying method. Al and SiC powders were blended and sprayed with plasma arc power. SiC were uniformly dispersed in the Al matrix with a volume fraction of up to 46%. There were also pores in the composite with a range of 1.8∼12 vol.%, which could be tailored by process parameters. The experimental CTEs showed 13.5∼17.6×10^-6/℃ for the Al-SiC composite containing about 40 vol.% SiC, which were matched well with the predicted ones.

keyword : Plasma spraying, Al-SiC, Composite, Electronic packaging, Coefficient of thermal expansion

The corrosion failure of electronic devices has been a major reliability concern lately. This failure is an ongoing concern because of miniaturization of integrated circuits(IC) and the increased use of polymers in electronic packaging. In this paper plasma-polymerized thiophene films were considered as a possible candidate for an interlayer dielectric for multilever metallization of ultra large scale integrated (ULSI) semiconductor devices. The protective ability of above films as a function RF power in an 3.5 wt.% NaCl solution was examined by electrochemical methods and contact angle measurement. The protective efficiency of the film increased with increasing RF power, which induced the higher degree of cross-linking and hydrophobicity of the films.

keyword : Corrosion, Plasma enhanced chemical vapor deposition, PECVD, Thiophene film

Transparent conducting indium tin oxide (ITO) films are deposited by rf-sputtering at a constant power of 400W in Ar atmosphere on the porous silicon (PS) layers anodized on p-type (100) Si wafers. At three successive stages of deposition for 10, 20 and 30 min. respectively, the growth of ITO on PS is thoroughly investigated by AFM, SEM and XRD techniques. The features of growth on other substrates like single crystal p-type (100) silicon, quartz and glass are also taken into consideration. The influence of ITO microstructure on the porous silicon interface is correlated with the electrical and luminescent behavior of the resulting heterojunction diode structure.

keyword : Porous silicon, Indium Tin Oxide, AFM, SEM, XRD

Mechanisms of misfit strain relaxation in epitaxially grown Bi_4-χLa_χTi_3O_12 (BLT) thin films deposited on SrTiO_3 (STO) and LaAlO_3(LAO) substrates have been investigated by means of transmission electron microscopy (TEM). The misfit strain of 20 nm thick BLT films grown on STO substrate was relaxed by forming misfit dislocations at the interface. However, cracks were observed in 100 nm thick BLT films grown on the same STO. It was confirmed that cracks were formed because of high misfit strain accumulated with increasing the thickness of BLT, which was not sufficiently relaxed by misfit dislocations. In the case of the BLT film grown on LAO substrate, the magnitude of lattice misfit between BLT and LAO was very small (∼1/10) in comparison with the case of the BLT grown on STO. The relatively small misfit strain formed in layered structure of the BLT films on LAO, therefore, was easily relaxed by distorting the film, rather than forming misfit dislocations or cracks, resulting in misorientation regions in the BLT film.

keyword : BLT, Epitaxial growth, Misfit strain, Transmission electron microscopy, TEM

The goal of this study was to determine the uniaxial flow curve for solder balls in a flip-chip from experimental-computational algorithms based on finite element modeling (FEM) of in-plane thermal displacement data measured by electronic speckle pattern interferometry (ESPI). In order to measure the deformation of such tiny components as the solder balls in the flip-chip, the spatial resolution of ESPI was increased to submicron scale by magnifying the areas studied. The flow curve for solder balls in the flip-chip was determined by the algorithm, which effectively matches the simulated solder deformation by FEM to the measured deformation by ESPI. The algorithms were applied to Sn-36Pb-2Ag flip-chip solder balls. The flow curve obtained for flip-chip solder was compared with those for bulk solder. The microstructure was also studied to clarify the flow curve results.

keyword : Flip-chip, Electronic speckle pattern interferometry, ESPI, Finite element modeling, FEM, Flow curve, Bulk solder, Reliability

In the world large amount of used printed circuit boards (PCBs) and spent autocatalysts which contain precious metals have been emitted. However, processes which can recover the precious metals simultaneously from them have not been developed yet. In this study a new process for recovering the precious metals contained in the used PCBs and spent autocatalyst by a pyrometallurgical process simultaneously was developed. The distinguish of that is to use copper, tin, and iron contained in the used PCBs as collector metals of the precious metals contained in the used PCBs and spent autocatalysts. Advantages of the process suggested are simply and economic compared with the previous processes which could recover the precious metals from the used PCBs and spent autocatalysts, respectively. Using the suggested process the precious metals such as Au, Pd, and Pt contained in the used PCBs and spent autocatalyst could be recovered up to 95 % in Cu alloy phase.

keyword : Precious metals, Printed circuit bords, PCBs, Autocatalysts, Recycling, Collector metals

The separation and recovery of cobalt and nickel from hydrochloric leaching solutions of manganese nodules were imitated by solvent extraction using Alamine336 in Xylene. The behavior of impurities such as iron, zinc, copper and manganese was also investigated. With the increase of chloride ion concentration, cobalt was selectively extracted from nickel owing to the difference of chlorocomplex in solution and the minimum chloride ion was 5.0M. But in this extraction step, the impurity metals such as copper, iron, manganese, zinc were also co extracted in the organic phase. However, co-extracted metals in the organic phase could be effectively separated in the scrubbing and stripping step. Manganese and nickel were effectively removed in the scrubbing step with 6.0M hydrochloric solutions but copper, iron and zinc were loaded in the organic phase with cobalt. Finally, the metal-bearing organic phase was contacted with the hydrochloric strip solution to recover the loaded cobalt. The impurity metals were effectively removed in this step with controlling the concentration of chloride ions in the strip solution. From the experiment, The behaviors of impurities on each of operation steps in extraction, scrubbing and stripping processes were investigated. Consequently the optimum condition for the separation of cobalt from hydrochloric solution were proposed.

keyword : Manganes nodule, Alamine336, Chloride, Cobalt, Nickel