• Title/Summary/Keyword: substrate effects

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Thermo-mechanical Behavior of WB-PBGA Packages Considering Viscoelastic Material Properties (점탄성 물성치를 고려한 WB-PBGA 패키지의 열-기계적 변형 거동)

  • Kim, Man-Ki;Joo, Jin-Won
    • Journal of the Microelectronics and Packaging Society
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    • v.19 no.2
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    • pp.17-28
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    • 2012
  • It is known that thermo-mechanical properties of solder material and molding compound in WB-PBGA packages are considerably affected by not only temperature but elapsed time. In this paper, finite element analysis (FEA) taking material nonlinearity into account was performed for more reliable prediction on deformation behavior of a lead-free WB-PBGA package, and the results were compared with experimental results from moire interferometry. Prior to FEA on the WB-PBGA package, it was carried out for two material layers consisting of molding compound and substrate in terms of temperature and time-dependent viscoelastic effects of molding compound. Reliable deformation analysis for temperature change was then accomplished using viscoplastic properties for solder ball and viscoelastic properties for molding compound, and the analysis was also verified with experimental results. The result showed that the deformation of WB-PBGA packages was strongly dependent on material model of molding compound; thus, temperature and time-dependent viscoelastic behavior must be considered for the molding compound analysis. In addition, viscoelastic properties of B-type molding compound having comparatively high glass transition temperature of $135^{\circ}C$ could be recommended for reliable prediction on deformation of SAC lead-free WB-PBGA packages.

Effects of Heat Treatment Conditions on the Interfacial Reactions and Crack Propagation Behaviors in Electroless Ni/electroplated Cr Coatings (열처리 조건에 따른 무전해 Ni/전해 Cr 이중도금의 계면반응 및 균열성장거동 분석)

  • Son, Kirak;Choi, Myung-Hee;Lee, Kyu Hawn;Byon, Eungsun;Rhee, Byong-Ho;Park, Young-Bae
    • Journal of the Microelectronics and Packaging Society
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    • v.23 no.3
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    • pp.69-75
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    • 2016
  • This study investigated the effect of heat treatment conditions not only on the Cr surface crack propagation behaviors but also on the Ni/Cr interfacial reaction characteristics in electroless Ni/electroplated Cr double coating layers on Cu substrate. Clear band layer of Ni-Cr solid solutions were developed at Ni/Cr interface after heat treatment at $750^{\circ}C$ for 6 h. Channeling cracks formed in Cr layer after 1 step heat treatment, that is, heat treatment after Ni/Cr plating, while little channeling cracks formed after 2 step heat treatment, that is, same heat treatments after Ni and Cr plating, respectively, due to residual stress relaxation due to crystallization of Ni layer before Cr plating.

Effects of Habitat Disturbance on Fish Community Structure in a Gravel-Bed Stream, Korea (자갈하천에서 서식처 교란이 어류 군집구조에 미치는 영향)

  • Kim, Seog Hyun;Lee, Wan-Ok;Cho, Kang-Hyun
    • Ecology and Resilient Infrastructure
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    • v.1 no.2
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    • pp.49-60
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    • 2014
  • Fish assemblages play an integral role in stream ecosystem and are influenced by stream environmental conditions and habitat disturbances. Fish community structures and habitat parameters of U.S. EPA rapid bio-assessment protocol were surveyed to investigate the effect of stream environment and habitat disturbance on fish communities at 13 study sites in the Gapyeong Stream, a typical gravel-bed stream. Principal component analysis (PCA) based on data from habitat assessment at each study site indicated that the study sites were differentiated by habitat parameters such as embeddedness, velocity/depth regime and sediment deposition, which were related with bed slope. A total of 46 species belonging to 12 families were collected in the Gapyeong Stream. A dominant species was Zacco koreanus, subdominant species was Z. platypus. Hierarchical cluster analysis based on species abundance classified fish communities into the three main groups along the stream longitudinal change. Non-metric multidimensional scaling (NMDS) portrayed that fish community structures were related to major habitat parameters, i.e., epifaunal substrate/available cover, embeddedness, velocity/depth regime, sediment deposition, channel alternation and frequency of riffles. These results suggested that fish community structures were primary affected by the longitudinal environmental changes, and those were modified by habitat disturbance in the Gapyeong Stream, a gravel-bed stream.

Preparation of Bismuth Telluride Thin Films using RF magnetron sputtering and Study on Their Thermoelectric Properties (RF 마그네트론 스퍼터링을 이용한 Bismuth Telluride 박막의 제조와 그 열전 특성 연구)

  • Kim, Dong-Ho;Lee, Gun-Hwan
    • Journal of the Korean Vacuum Society
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    • v.14 no.4
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    • pp.215-221
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    • 2005
  • Thermoelectric bismuth telluride thin films were prepared on $SiO_{2}$/Si substrate with co-sputtering of bismuth and tellurium targets. The effects of deposition temperature on surface morphology, crystallinity and electrical transport properties were investigated. Hexagonal crystallites were clearly visible at the surface of films deposited above $290 ^{\circ}C$. Change of dominant phase from rhombohedral $Bi_2Te_3$ to hexagonal BiTe was confirmed with X-ray diffraction analysis. The deviation from stoichiometric composition at high deposition temperature resulted in the change of structural and electrical characteristics. Seebeck coefficients of all samples have negative value, indicating the prepared $Bi_XTe_Y$ films are n-type thermoelectric. Optimum of Seebeck coefficient and power factor were obtained at the deposition temperature of $225 \^{circ}$C (about -55 $\mu$V/K and $3\times10^{-4}$ W/$k^{2}$m, respectively). Deterioration of thermoelectric properties at higher temperature.

Effect of Chemical Fertilizers and Organic Materials on Soil Actinomycetes Flora (화학비료(化學肥料) 및 유기물(有機物) 시용시(施用時) 방선균(放線菌) Flora의 구성변화(構成變化))

  • Hong, Sa-Hyun;Yang, Chang-Sool
    • Korean Journal of Soil Science and Fertilizer
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    • v.31 no.4
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    • pp.420-426
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    • 1998
  • This investigation was undertaken to clarify the effects of application of chemical fertilizers (Compound fertilizer and commercial compost) and organic matters (straw and clover) on changes of the composition of soil actinomycetes flora. Actinomycetes were isolated from chemical fertilizer and organic materials treated soils, and then grown on HV agar plate. The isolated strains were classified by Bergey's manual based on the morphological characteristics and color of substrate mycelium of actinomycetes. The number of actinomycetes increased 4 times in control, 36 times in clover, 20 times in straw, 5 times in chemical fertilizer and 4 times in commercial compost treated soil after 14th day of incubation. This result suggests that the application of straw or clover is more effective to increase the number of actinomycetes than compound fertilizer or commercial compost. It also showed that the application of chemical fertilizer or organic materials considerably changed the composition of soil actinomycetes flora. The proportion of streptomyces strains to the isolated total actinomycetes was 62% in control, 60% in clover, 68% in straw, 67% in chemical fertilizer and 64% in commercial compost treated soils at the 14th day.

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A topological metal at the surface of an ultrathin BiSb alloy film

  • Hirahara, T.;Sakamoto, Y.;Saisyu, Y.;Miyazaki, H.;Kimura, S.;Okuda, T.;Matsuda, I.;Murakami, S.;Hasegawa, S.
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.14-15
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    • 2010
  • Recently there has been growing interest in topological insulators or the quantum spin Hall (QSH) phase, which are insulating materials with bulk band gaps but have metallic edge states that are formed topologically and robust against any non-magnetic impurity [1]. In a three-dimensional material, the two-dimensional surface states correspond to the edge states (topological metal) and their intriguing nature in terms of electronic and spin structures have been experimentally observed in bulk Bi1-xSbx single crystals [2,3,4]. However, if we want to know the transport properties of these topological metals, high purity samples as well as very low temperature will be needed because of the contribution from bulk states or impurity effects. In a recent report, it was also shown that an intriguing coupling between the surface and bulk states will occur [5]. A simple solution to this bothersome problem is to prepare a topological metal on an ultrathin film, in which the surface-to-bulk ratio is drastically increased. Therefore in the present study, we have investigated if there is a method to make an ultrathin Bi1-xSbx film on a semiconductor substrate. From reflection high-energy electron diffraction observation, it was found that single crystal Bi1-xSbx films (0${\sim}30\;{\AA}A$ can be prepared on Si(111)-$7{\times}7$. The transport properties of such films were characterized by in situ monolithic micro four-point probes [6]. The temperature dependence of the resistivity for the x=0.1 samples was insulating when the film thickness was $240\;{\AA}A$. However, it became metallic as the thickness was reduced down to $30\;{\AA}A$, indicating surface-state dominant electrical conduction. Figure 1 shows the Fermi surface of $40\;{\AA}A$ thick Bi0.92Sb0.08 (a) and Bi0.84Sb0.16 (b) films mapped by angle-resolved photoemission spectroscopy. The basic features of the electronic structure of these surface states were shown to be the same as those found on bulk surfaces, meaning that topological metals can be prepared at the surface of an ultrathin film. The details will be given in the presentation.

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Proteome Profiling of Murine Macrophages Treated with the Anthrax Lethal Toxin (탄저 치사독소 처리에 의한 생쥐 대식세포의 단백질체 발현 양상 분석)

  • Jung Kyoung-Hwa;Seo Giw-Moon;Kim Sung-Joo;Kim Ji-Chon;Oh Seon-Mi;Oh Kwang-Geun;Chai Young-Gyu
    • Korean Journal of Microbiology
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    • v.41 no.4
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    • pp.262-268
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    • 2005
  • Intoxication of murine macrophages (RAW 264.7) with the anthrax lethal toxin (LeTx 100 ng/ml) results in profound alterations in the host cell gene expression. The role of LeTx in mediating these effects is unknown, largely due to the difficulty in identifying and assigning function to individual proteins. In this study, we have used two-dimensional polyacrylamide gel electrophoresis to analyze the protein profile of murine macrophages treated with the LeTx, and have coupled this to protein identification using MALDI-TOF mass spectrometry. Interpretation of the peptide mass fingerprint data has relied primarily on the ProFound database. Among the differentially expressed spots, cleaved mitogen-activated protein kinase kinase (Mek1) and glucose-6-phosphate dehydrogenase were increased in the LeTx treated macrophages. Mek1 acts as a negative element in the signal transduction pathway, and G6PD plays the role for the protection of the cells from the hyper-production of active oxygen. Our results suggest that this proteomic approach is a useful tool to study protein expression in intoxicated macrophages and will contribute to the identification of a putative substrate for LeTx.

Synthesis of YSZ Thin Films by PECVD (PECVD에 의한 YSZ(Yttria Stabilized Zirconia)박막 제조)

  • Kim, Gi-Dong;Sin, Dong-Geun;Jo, Yeong-A;Jeon, Jin-Seok;Choe, Dong-Su;Park, Jong-Jin
    • Korean Journal of Materials Research
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    • v.9 no.3
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    • pp.234-239
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    • 1999
  • A Abstract Yttria-stabilized zirconia(YSZ) thin films were synthesized by plasma enhanced chemical vapor deposition process. $Zr[TMHD]_4$ $Y[TMHD]_3$ precursors and oxygen were used with the deposition temperature of $425^{\circ}C$ and rf power ranging 0-100 watt. Effects of the deposition parameters were studied by X-ray diffraction and thickness anal­ysis. YSZ thin films have cubic crystal structure with (200) orientation. From the results of EDX analysis, the converte ed content of TEX>$Y_2O_3$ was determined to be 0-36%, and the film thickness was increased with bubbling temperature which is considered to be due to increasing TEX>$Y_2O_3$ flux. The depth profiles of Zr, Y and 0 appeared relatively $\infty$nstant through film thickness. Columnar grains of $1000~2000\AA$ grew vertical to the substrate surface for the case of Ar carri­er gas. In case of He carrier gas, the grain size was observed to be about $1000~2000\AA$. X-ray diffraction data showed the increase of lattice constant with TEX>$Y_2O_3$ content. It was that the presence of the cracks formed during film deposition, partially released the stress generated by the increase of lattice constant.

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The Effects of Electrode Distance on the Formation of $(ZnS)_{1-x}(SiO_2)_x$ Protective Films in Phase Change Optical Disk by R.F. Sputtering Method (R.F. Sputtering 방법에 의한 상변화형 광디스크의 $(ZnS)_{1-x}(SiO_2)_x$ 보호막 형성에 미치는 전극거리의 영향)

  • Lee, Jun-Ho;Kim, Do-Hun
    • Korean Journal of Materials Research
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    • v.9 no.12
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    • pp.1245-1251
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    • 1999
  • Phase-change optical disk very rapid recording, high densification of data, resulting in high feedback rate and good C/N(carrier to noise) ratio of a feedback signal. However, repetitive thermal energy may cause the deformation of a disk or the lowering of an eliminability and a cyclability of the recording. The lowering of the cyclability can be reduced by insertion of thin layer of ZnS-$SiO_2$ dielectric thin film in appropriate disk structure between the upper and lower part of the recording film. Using the Taguchi method, optimum conditions satisfying both the optimized quality characteristic values and the scattering values for film formation were found to be the target R.F. power of 200W, the substrate R.F. power of 20W, the Ar pressure of 6mTorr, and the electrode distance of 6cm. From the refractive index data, the existence of the strong interaction between the electrode distance and Ar pressure was confirmed, and so was the large effect of the electrode distance on transmittance. According to the analysis of TEM and XRD, the closer the electrode distance was, the finer was the grain size due to the high deposition rate. However, the closer electrode distance brought the negative effect on the morphology of the film and caused the reduction of transmittance. AFM and SEM analyses showed that the closer the electrode distance was, the worse was the morphology due to the high rate of the deposition. Under optimum condition, the deposited thin film showed a good morphology and dense microstructure with less defects.

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Variation of Characteristics of Nonstoichiometric Apatite Induced by Sodium Salt (나트륨염에 의한 비양론적 인회석의 특성 및 SaOS-2 세포반응에 미치는 영향에 관한 연구)

  • Jung, Jae-Young;Han, Juyun;Choi, Sun-Mi;Lee, Woo-Kul
    • Applied Chemistry for Engineering
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    • v.19 no.3
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    • pp.326-331
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    • 2008
  • The purpose of this work is to develope sodium-containing nonstoichiometric apatitic coatings on solid substrate. The apatitic coatings prepared at different concentrations of sodium salt indicated that the presence of sodium ions exerted significant effects on the physicochemical properties of the apatitic coating including surface morphology, chemical state, and Ca/P ratio. The variation of these properties was sustained up to 0.01 mM of sodium ion concentration. The ratio of calcium to phosphorus was varied from 2.18 to 2.03 which indicated the apatitic coating prepared in this study was calcium-rich nonstoichiometric apatite. The structure of all the samples appeared to be low crystalline. In the presence of sodium ion within the apaptitic coating, the adhesion of human osteoblast-like SaOS-2 cells was significantly promoted. On the other hand, the proliferation of the cells on the apatitic coatings was decreased with the increase of sodium ions. This reverse response of SaOS-2 cells indicates that the interaction between SaOS-2 and apatitic surface triggered considerable changes in intracellular mechanisms including cellular signal transductions.