• Title/Summary/Keyword: 이소성

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Development of Polymer Elastic Bump Formation Process and Bump Deformation Behavior Analysis for Flexible Semiconductor Package Assembly (유연 반도체 패키지 접속을 위한 폴리머 탄성범프 범핑 공정 개발 및 범프 변형 거동 분석)

  • Lee, Jae Hak;Song, Jun-Yeob;Kim, Seung Man;Kim, Yong Jin;Park, Ah-Young
    • Journal of the Microelectronics and Packaging Society
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    • v.26 no.2
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    • pp.31-43
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    • 2019
  • In this study, polymer elastic bumps were fabricated for the flexible electronic package flip chip bonding and the viscoelastic and viscoplastic behavior of the polymer elastic bumps according to the temperature and load were analyzed using FEM and experiments. The polymer elastic bump is easy to deform by the bonding load, and it is confirmed that the bump height flatness problem is easily compensated and the stress concentration on thin chip is reduced remarkably. We also develop a spiral cap type and spoke cap type polymer elastic bump of $200{\mu}m$ diameter to complement Au metal cap crack phenomenon caused by excessive deformation of polymer elastic bump. The proposed polymer elastic bumps could reduce stress of metal wiring during bump deformation compared to metal cap bump, which is completely covered with metal wiring because the metal wiring on these bumps is partially patterned and easily deformable pattern. The spoke cap bump shows the lowest stress concentration in the metal wiring while maintaining the low contact resistance because the contact area between bump and pad was wider than that of the spiral cap bump.

Examination of Allowable Displacement by Structural Analysis of IPM Bridge (토압분리형 교량의 구조해석을 통한 허용 변위량 검토)

  • Kim, Hong-Bae;Han, Heui-Soo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.4
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    • pp.534-544
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    • 2019
  • Because the pile-bent of IPM Bridge is projected from the soil surface, excessive displacement of abutment can be induced. According to design guide of IPM Bridge, the shape of the bridges used in this study was applied to the maximum applicable 120.0m span, 30-degree for skew angle, and 10.0m for the protruded pile-bent height. The maximum displacement by the maximum span application condition of the IPM Bridge was calculated using this bridge model, and the safety of a horizontal displacement of the IPM Bridge was investigated based on the allowable displacement presented by Bozozuk. The maximum horizontal displacement of the IPM Bridge was calculated to be larger in the winter shrinkage condition than in the summer expansion condition, the horizontal displacements were more affected by the length of a bridge than by the skew angle. And the vertical displacement was not affected by the skew angle and length. As the span increases, the horizontal displacement increases significantly, the horizontal displacement at 120.0m span length was found to exceed the allowable displacement proposed by Bozozuk. However, the moment generated in the pile-bent did not exceed the plastic moment.

Fabrication and Evaluation of Heat Transfer Property of 50 Watts Rated LED Array Module Using Chip-on-board Type Ceramic-metal Hybrid Substrate (Chip-on-board 형 세라믹-메탈 하이브리드 기판을 적용한 50와트급 LED 어레이 모듈의 제조 및 방열특성 평가)

  • Heo, Yu Jin;Kim, Hyo Tae
    • Journal of the Microelectronics and Packaging Society
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    • v.25 no.4
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    • pp.149-154
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    • 2018
  • This paper describes the fabrication and heat transfer property of 50 watts rated LED array module where multiple chips are mounted on chip-on-board type ceramic-metal hybrid substrate with high heat dissipation property for high power street and anti-explosive lighting system. The high heat transfer ceramic-metal hybrid substrate was fabricated by conformal coating of thick film glass-ceramic and silver pastes to form insulation and conductor layers, using thick film screen printing method on top of the high thermal conductivity aluminum alloy heat-spreading panel, then co-fired at $515^{\circ}C$. A comparative LED array module with the same configuration using epoxy resin based FR-4 PCB with thermalvia type was also fabricated, then the thermal properties were measured with multichannel temperature sensors and thermal resistance measuring system. As a result, the thermal resistance of the ceramic-metal hybrid substrate in the $4{\times}9$ type LEDs array module exhibited about one third to the value as that of FR-4 substrate, implying that at least triple performance of heat transfer property as that of FR-4 substrate was realized.

Population Ecology of Acheilognathus chankaensis (Pisces: Acheilognathinae) in the Churyeongcheon (Stream), Korea (추령천에 서식하는 가시납지리, Acheilognathus chankaensis (Pisces: Acheilognathinae)의 개체군 생태)

  • Kim, Hyeongsu;Kim, Suhwan
    • Korean Journal of Environment and Ecology
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    • v.35 no.2
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    • pp.115-125
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    • 2021
  • This study surveyed the population ecology of Acheilognathus chankaensis (Pisces: Acheilognathinae) in the vicinity of the Churyeongcheon (Stream) and Seomjingang (River) in Jeonbuk, Korea, from February 2006 to May 2007. The survey found the habits mainly in the slow-flowing waters having sand, mud, and gravel bottoms. Age groups estimated by the standard length-frequency distribution of the population indicated that the one-year-olds were 30-46 mm long, the two-year-olds were 47-58 mm long, the three-year-olds were 59-68 mm long, and the four-year-olds were longer than 69 mm. The gonadosomatic index (GSI) and the ratio of ovipositor length/standard length were the highest in March (♀: 12.9%, ♂: 5.0%) and in April (46.3%), respectively. The ratio of mature egg diameters that were 1.6 mm was highest in May (13.2%). The comprehensive analysis of spawning characteristics showed that the spawning season was from March to June with water temperatures in 11.5-22.5℃, and the sex ratio of female:male was 1:1.13. The fecundity in the ovaries and the number of mature eggs were 318±174.5 (50~583) and 220±139.2 (50~406), respectively. The size of the mature eggs was 2.04±0.110 mm on the long axis and 1.55±0.100 mm on the short axis for the study period. Gut contents of A. chankaensis were mainly phytoplankton such as the genera Fragilaria, Synedra, Navicular, Cymbella (Bacillariophyceae), and Cosmarium (Chlorophyceae).

A Study on Lateral Displacement of Caisson Constructed on Improved Ground (개량 지반에 설치된 케이슨의 측방변위에 대한 연구)

  • Kim, Myunghak;Lee, Sangwook;Yoon, Minseung;Han, Byungwon
    • Journal of the Korean GEO-environmental Society
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    • v.12 no.4
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    • pp.33-41
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    • 2011
  • In case of building up port facilities on soft ground, unsymmetrical surcharge of embankment, which make the excess pore water pressure to increase, causes to occur lateral displacement due to plasticity of soil. A study on lateral displacement and settlement of the caisson, which is installed on improved ground, was accomplished. The field measurement data and calculated values obtained from FEM program of Plaxis were compared and analyzed. For numerical analysis, the properties of soils, constructions stage and time were considered. Lateral displacement was measured at the point of inclinometers installed in front of caisson. Settlement was measured at the center of extra embankment behind of caisson. Comparison of measured and calculated for lateral displacement showed that the calculated value was greater than the measured, and increasing trend was different. The calculated value showed step increasing as step extra embankment applied, whereas the measured gradually was increased. For settlement of embankment, the amount of both measured and calculated were similar, but the trend was different like that of lateral movement.

Investigation on the Preparation Method of TiO2-mayenite for NOx Removal (질소산화물 제거를 위한 TiO2-mayenite 제조 방법에 관한 연구)

  • Park, Ji Hye;Park, Jung Jun;Park, Hee Ju;Yi, Kwang Bok
    • Clean Technology
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    • v.26 no.4
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    • pp.304-310
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    • 2020
  • In order to apply a photocatalyst (TiO2) to various building materials, TiO2-mayenite was prepared in this study. The TiO2 was synthesized using the sol-gel method by fixing titanium isopropoxide (TTIP) and urea at a ratio of 1 : 1. Later, they were calcined in a temperature range of 400-700 ℃ to analyze the properties according to temperature. BET, TGA, and XRD were used to analyze the physical and chemical properties of TiO2. The nitrogen oxide removal test was confirmed by measuring the change in the concentration of NO for 1 h according to KS L ISO 22197-1. The prepared TiO2 samples exhibited an anatase crystal structure below 600 ℃, and TiO2 (urea)-400 showed the highest nitrogen oxide removal rate at 2.35 µmol h-1. TiO2-mayenite was prepared using two methods: spraying TiO2 dispersion solution (s/s) and sol-gel solution (g/s). Through BET and XRD analysis, it was found that 5-TiO2 (g/s) prepared by spraying a sol-gel solution has maintained its crystallinity even after heat treatment. Also, 5-TiO2 (g/s)-500 showed the highest removal rate of 0.55 µmol h-1 in the nitrogen oxide removal test. To prepare TiO2-mayenite, it was confirmed that mayenite should be blended with TiO2 in a sol-gel state to maintain the crystal structure and exhibit a high nitrogen oxide removal rate.

The Evaluation of Durability Performance in Mortar Curbs Containing Activated Hwangtoh (활성 황토를 혼입한 모르타르 기반 경계석의 내구성능 평가)

  • Kwon, Seung-Jun;Kim, Hyeok-Jung;Yoon, Yong-Sik
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.8 no.4
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    • pp.520-527
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    • 2020
  • Hwangtoh is the rich resource that accounts for about 15.0% of the domestic soil, and can be used as the admixture of concrete with Pozzolan characteristics if activated by rapidly freezing after burning with high temperature. In this study, the mortar curbs containing active hwangtoh were produced, based on the mixture for the mortar curbs sold on the market. The substitution rate of active hwangtoh were considered 10.0% and 25.0%, and the test items were selected to compressive and flexural strength tests, freezing/thawing resistance tests, accelerated carbonation tests, and accelerated chloride diffusion tests. In the results of the mechanical performance, it was showed that the highest strength was evaluated in OPC mixture, and the increase in strength was small by the increase of age, which was believed to be due to the fact that most of the strength in each mixture was created in three days of steam curing. The results of the freezing/thawing tests for 28 aged days showed the reduction rate of compressive strength was 85.0% or higher for all specimen, meeting the criteria presented. The accelerated carbonation tests were carried out on the specimen at 28 days of age, and the results showed that the mortar with active hwangtoh had lower carbonation resistance performance than mortar with OPC. The passed charge of each mixture was assessed in accordance with ASTM C 1202 on 28 and 91 aged days. The OPC mixture had "Low" rate and the mortar with active hwangtoh had "Moderate" rate. So it was thought that the mortar with active hwangtoh had appropriate resistance performance for chloride attack.

Immobilization of As and Pb in Contaminated Soil Using Bead Type Amendment Prepared by Iron NanoparticlesImpregnated Biochar (철 나노 입자가 담지된 바이오차 기반 비드 형태 안정화제를 이용한 비소 및 납 오염토양의 안정화)

  • Choi, Yu-Lim;Kim, Dong-Su;Kang, Tae-Jun;Yang, Jae-Kyu;Chang, Yoon-Young
    • Journal of Environmental Impact Assessment
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    • v.30 no.4
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    • pp.247-257
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    • 2021
  • In this work, Iron Nano-Particles Impregnated BioChar/bead (INPBC/bead) soil amendment was developed to increase biochar's reactivity to As in soil and preventing possible wind loss. Prior to preparation of INPBC/bead, INPBC was produced utilizing lignocellulosic biomass and Fe(III) solution in a hydrothermal method, followed by a calcination process. Then, the bead type amendment, INPBC/bead was produced by cross-linking reaction of alginate with INPBC. FT-IR, XRD, BET, and SEM-EDS analyses were utilized to characterize the as-synthesised materials. The particle size range of INPBC/bead was 1-4 mm, and different oxygen-containing functional groups and Fe3O4 crystalline phase were produced on the surface of INPBC/bead, according to the characterization results. The soil cultivation test was carried out in order to assess the stabilization performance of INPBC/bead utilizing As and Pb-contaminated soil obtained from an abandoned mining location in South Korea. After 4 weeks of culture, TCLP and SPLP extraction tests were performed to assess the stabilization efficacy of the amendment. The TCLP and SPLP findings revealed that raising the application ratio improved stabilizing efficiency. The As stabilization efficiency was determined to be 81.56 % based on SPLP test findings for a 5% in (w/w) INPBC/bead treatment, and the content of Pb in extracts was reduced to the limit of detection. According to the findings of this study, INPBC/bead that can maintain pH of origin soil and minimize wind loss might be a potential amendment for soil polluted with As and heavy metals.

Numerical Simulation of 72m-Long Ultra High Performance Concrete Pre-Stressed Box Girder (72m 초고강도 콘크리트 프리스트레스트 박스 거더의 수치 해석)

  • Mai, Viet-Chinh;Han, Sang Mook
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.35 no.2
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    • pp.73-82
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    • 2022
  • The study presents a three-dimensional approach to simulate the nonlinear behavior of a 72 m long Ultra High Performance Fiber Reinforced Concrete (UHPFRC) pre-stressed box girder for a pedestrian bridge in Busan, South Korea. The concrete damage plasticity (CDP) model is adopted to model the non-linear behavior of the UHPFRC material, in which the material properties are obtained from uniaxial compressive and tensile tests. The simulation model based on the proposed stress-strain curve is validated by the results of four-point bending model tests of a 50 m UHPFRC pre-stressed box girder. The results from the simulation models agree with the experimental observations and predict the flexural behavior of the 50 m UHPFRC pre-stressed box girder accurately. Afterward, the validated model is utilized to investigate the flexural behavior of the 72 m UHPFRC pre-stressed box girder. Here, the load-deflection curve, stress status of the girder at various load levels, and connection details is analyzed. The load-deflection curve is also compared with design load to demonstrate the great benefit of the slender UHPFRC box girder. The obtained results demonstrate the applicability of the nonlinear finite element method as an appropriate option to analyze the flexural behavior of pre-stressed long-span girders.

Application of Damage Index for Limit State Evaluation of a Steel Pipe Tee (강재 배관 Tee의 한계상태 평가를 위한 손상지수의 적용)

  • Kim, Sung-Wan;Yun, Da-Woon;Jeon, Bub-Gyu;Kim, Seong-Do
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.26 no.4
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    • pp.30-39
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    • 2022
  • Maintaining structural integrity of major apparatuses in a nuclear power plant, including piping system, is recognized as a critical safety issue. The integrity of piping system is also a critical matter related to the safety of a nuclear power plant. The actual failure mode of a piping system due to a seismic load is the leakage due to a fatigue crack, and the structural damage mechanism is the low-cycle fatigue due to large relative displacement that may cause plastic deformation. In this study, in-plane cyclic loading tests were conducted under various constant amplitudes using specimens composed of steel straight pipes and a steel pipe tee in the piping system of a nuclear power plant. The loading amplitude was increased to consider the relative displacement generated in the piping system under seismic loads, and the test was conducted until leakage, which is the limit state of the steel pipe tee, occurred due to fatigue cracks. The limit state of the steel pipe tee was expressed using a damage model based on the damage index that used the force-displacement relationship. As a result, it was confirmed that the limit state of the steel pipe tee can be quantitatively expressed using the damage index.