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Optimization of Elastic Modulus and Cure Characteristics of Composition for Die Attach Film (다이접착필름용 조성물의 탄성 계수 및 경화 특성 최적화)

  • Sung, Choonghyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.4
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    • pp.503-509
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    • 2019
  • The demand for smaller, faster, and multi-functional mobile devices in increasing at a rapidly increasing rate. In response to these trends, Stacked Chip Scale Package (SCSP) is used widely in the assembly industry. A film type adhesive called die attach film (DAF) is used widely for bonding chips in SCSP. The DAF requires high flowability at high die attachment temperatures for bonding chips on organic substrates, where the DAF needs to feel the gap depth, or for bonding the same sized dies, where the DAF needs to penetrate bonding wires. In this study, the mixture design of experiment (DOE) was performed for three raw materials to obtain the optimized DAF recipe for low elastic modulus at high temperature. Three components are acrylic polymer (SG-P3) and two solid epoxy resins (YD011 and YDCN500-1P) with different softening points. According to the DOE results, the elastic modulus at high temperature was influenced greatly by SG-P3. The elastic modulus at 100C decreased from 1.0 MPa to 0.2 MPa as the amount of SG-P3 was decreased by 20%. In contrast, the elastic modulus at room temperature was dominated by YD011, an epoxy with a higher softening point. The optimized DAF recipe showed approximately 98.4% pickup performance when a UV dicing tape was used. A DAF crack that occurred in curing was effectively suppressed through optimization of the cure accelerator amount and two-step cure schedule. The imizadole type accelerator showed better performance than the amine type accelerator.

Modern transformation phrase of (<공무도하가>의 현대적 변용 양상)

  • Ha, Gyoung Sook
    • (The)Study of the Eastern Classic
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    • no.43
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    • pp.93-123
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    • 2011
  • is a work of art that was composed through fluid and laminating by being passed down orally for a long time like other ancient songs. As well as, it is given a history of literature's value in the point that it is a Korea's first poetry work, it is considered it casts a long shadow to establishing traditionality of our country's poetry. Even today, has been transformed and recreated into a variety of genres because its literary subject carry the universal emotions and win the sympathy. This manuscript examines modern poetry, modern novel and modern songs that consist of changed ancient song and looks modern writers' perspective about through characteristic that each of works has and then aims checking special situation and meaning that is implicit and recognizing the value of the original. As the has been recreated as modern poetry, it shows the current chaotic situation specifically by embodying it and actively seeks expressing human character, agony and longing, etc, by excluding factor of the original mythical interpretation. Also it rouses situation of reality as detained and repressed. , recreated as modern novel, expands narrative structure and shows portrait of various characters and speaks diverse human condition about reality and suggests plan for dealing with that. Basic emotions of the original is strongly passed to modern popular song . It makes us know that universal emotions which human has across generations can touch people transcending time and space and it is a fresh discovery and possibility that reaffirms the emotion of our people. Ancient song has been studied with emphasis on resignation and grief by focusing on the subject, simply parting and death. But recently, through transformation between a wide range of genres. it carries the spirit of the times that author toward, showing realistic and specific situations. Flexibility of ancient song is expected to continue its vitality transcending generations. Ancient song is assured that it can lead various aspects through active groping in era of change with a various possibility, that the original has, through communication between genres.

A Study on the Analysis of the Trend of installations Using 3D Printing Technique (3D프린팅 조형설치물 경향분석에 관한 연구)

  • Kim, Ji Min;Lee, Tae Hee
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.22 no.1
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    • pp.52-60
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    • 2021
  • The aim of this study was to derive a new trend by analyzing installations using 3D printing that are out of the limits of size and design according to the trends of developing 3D printing technology. This paper classified the types of installations using 3D printing and analyzed them with two trends: the trend of design and the trend of output. The trends of installations using 3D printing derived from this study are as follows. First, as the implementation of design through an algorithm is accomplished, the transformation appears with the atypical design that is prominent in complex expression. Second, Robotics and FDM 3D Printing is fused, which is changing the existing paradigm. Therefore, the production and utilization of installations using 3D printing proceeded at a faster pace through the interaction between the algorithm design method and freeform 3D printing technology. This study was conducted on installations using 3D printing around the world and played a basic role in the research on the production of installations using 3D printing along with domestic 3D printing technology to be developed in the future. Follow-up studies in various aspects, such as materials and combination methods, will be needed.

A Study on Simplifying Flow Analysis of VaRI Process (VaRI 공정 유동해석 간소화 방법에 대한 연구)

  • Kim, Yeongmin;Lee, Jungwan;Kim, Jungsoo;Ahn, Sehoon;Oh, Youngseok;Yi, Jin Woo;Kim, Wiedae;Um, Moon-kwang
    • Composites Research
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    • v.34 no.4
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    • pp.233-240
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    • 2021
  • VaRI(Vacuum assisted Resin Infusion) process, which is cost effective and suitable for manufacturing large-sized composites, is an OoA(Out-of Autoclave) process. For rapid resin infusion in the VaRI process, a DM(distribution media) is placed on top of the fabric. The resin is rapidly supplied in plane direction of the fiber along the DM, and then the supplied resin is impregnated in the out-of-plane direction of fiber. It is difficult to predict the flow of resin because the flow of in-plane direction and the out-of-plane direction occur together, and a 3D numerical analysis program is used to simulate the resin infusion process. However, in order to analyze in 3D, many elements are required in the out-of-plane direction of fabric. And the product size is larger, the longer the analysis time needs. Therefore, in this study, a method was suggested to reduce the time required for flow analysis by simplifying the 3D flow analysis to 2D flow analysis. The usefulness was verified by comparing the 3D flow analysis with the simplified 2D flow analysis at the same conditions. The filling time error was about 7% and the reduction of flow analysis time was about 95%. In addition, by utilizing the constant difference in the flow front between the top, middle, and bottom of the fabric of the 3D analysis, the flow front of the top, middle, and bottom of the fabric can be also predicted in the 2D flow analysis.

Thermal Stress Induced Spalling of Metal Pad on Silicon Interposer (열응력에 의한 실리콘 인터포저 위 금속 패드의 박락 현상)

  • Kim, Junmo;Kim, Boyeon;Jung, Cheong-Ha;Kim, Gu-sung;Kim, Taek-Soo
    • Journal of the Microelectronics and Packaging Society
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    • v.29 no.3
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    • pp.25-29
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    • 2022
  • Recently, the importance of electronic packaging technology has been attracting attention, and heterogeneous integration technology in which chips are stacked out-of-plane direction is being applied to the electronic packaging field. The 2.5D integration circuit is a technology for stacking chips using an interposer including TSV, and is widely used already. Therefore, it is necessary to make the interposer mechanically reliable in the packaging process that undergoes various thermal processes and mechanical loadings. Considering the structural characteristics of the interposer on which several thin films are deposited, thermal stress due to the difference in thermal expansion coefficients of materials can have a great effect on reliability. In this study, the mechanical reliability of the metal pad for wire bonding on the silicon interposer against thermal stress was evaluated. After heating the interposer to the solder reflow temperature, the delamination of the metal pad that occurred during cooling was observed and the mechanism was investigated. In addition, it was confirmed that the high cooling rate and the defect caused by handling promote delamination of the metal pads.

Load-Displacement Relationship of Passive Vibration Units Composed with a Spring and Vibration-Proof Rubbers (스프링과 방진고무가 융합된 제진장치의 하중-변위 관계)

  • Mun, Ju-Hyun;Im, Chae-Rim;Wang, Hye-Rin;Yang, Keun-Hyeok
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.6
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    • pp.226-234
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    • 2021
  • The objective of this study is to establish the fundamental design data for axial load-displacement relationship under axial monotonic or cyclic responses of seismic damping·isolation (SDI) units developed for ceiling structures. The main parameters include the installation of a spring, the number of rubber layer, prestress stress of bolts for connector between the spring and rubbers, and loading type. Test results showed that SDI units with a spring in the core and higher prestress stress of bolts tended to be higher stiffness at the ascending branch and more ductile behavior at the descending branch. This trends more notable for the specimens under monotonic load rather than cyclic loads. Consequently, the energy dissipation of SDI unit can be optimally designed with the following conditions: installation of a spring within 3-layer rubbers and prestress applied to the bolts at 10% of their yielding strength . When compared with the experimental tension capacity of the developed SDI units, the predictions by JIS B 2704-1 and KDS 31 00 are conservative under monotonic loading but higher by approximately 10% under cyclic loading.

Multi-scale Progressive Fatigue Damage Model for Unidirectional Laminates with the Effect of Interfacial Debonding (경계면 손상을 고려한 적층복합재료에 대한 멀티스케일 피로 손상 모델)

  • Dongwon Ha;Jeong Hwan Kim;Taeri Kim;Young Sik Joo;Gun Jin Yun
    • Composites Research
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    • v.36 no.1
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    • pp.16-24
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    • 2023
  • This paper presents a multi-scale progressive fatigue damage model incorporating the model for interfacial debonding between fibers and matrix. The micromechanics model for the progressive interface debonding was adopted, which defined the four different interface phases: (1) perfectly bonded fibers; (2) mild imperfect interface; (3) severe imperfect interface; and (4) completely debonded fibers. As the number of cycles increases, the progressive transition from the perfectly bonded state to the completely debonded fiber state occurs. Eshelby's tensor for each imperfect state is calculated by the linear spring model for a damaged interface, and effective elastic properties are obtained using the multi-phase homogenization method. The fatigue damage evolution formulas for fiber, matrix and interface were proposed to demonstrate the fatigue behavior of CFRP laminates under cyclic loading. The material parameters for the fiber/matrix fatigue damage were characterized using the chaotic firefly algorithm. The model was implemented into the UMAT subroutine of ABAQUS, and successfully validated with flat-bar UD laminate specimens ([0]8,[90]8, [30]16) of AS4/3501-6 graphite/epoxy composite.

Enhancement of Buckling Characteristics for Composite Square Tube by Load Type Analysis (하중유형 분석을 통한 좌굴에 강한 복합재료 사각관 설계에 관한 연구)

  • Seokwoo Ham;Seungmin Ji;Seong S. Cheon
    • Composites Research
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    • v.36 no.1
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    • pp.53-58
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    • 2023
  • The PIC design method is assigning different stacking sequences for each shell element through the preliminary FE analysis. In previous study, machine learning was applied to the PIC design method in order to assign the region efficiently, and the training data is labeled by dividing each region into tension, compression, and shear through the preliminary FE analysis results value. However, since buckling is not considered, when buckling occurs, it can't be divided into appropriate loading type. In the present study, it was proposed PIC-NTL (PIC design using novel technique for analyzing load type) which is method for applying a novel technique for analyzing load type considering buckling to the conventional PIC design. The stress triaxiality for each ply were analyzed for buckling analysis, and the representative loading type was designated through the determined loading type within decision area divided into two regions of the same size in the thickness direction of the elements. The input value of the training data and label consisted in coordination of element and representative loading type of each decision area, respectively. A machine learning model was trained through the training data, and the hyperparameters that affect the performance of the machine learning model were tuned to optimal values through Bayesian algorithm. Among the tuned machine learning models, the SVM model showed the highest performance. Most effective stacking sequence were mapped into PIC tube based on trained SVM model. FE analysis results show the design method proposed in this study has superior external loading resistance and energy absorption compared to previous study.

Electrochemical Characteristics of CFX Based Lithium Primary Batteries Produced by Carbon Fiber Reinforced Plastic -Derived Waste Carbon Fibers (탄소섬유강화플라스틱 유래 폐 탄소섬유로 제조된 불화탄소 기반 리튬일차전지의 전기화학적 특성)

  • Naeun Ha;Chaehun Lim;Seongmin Ha;Seongjae Myeong;Young-Seak Lee
    • Applied Chemistry for Engineering
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    • v.34 no.5
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    • pp.515-521
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    • 2023
  • In this study, waste carbon fiber obtained by pyrolysis of carbon fiber reinforced plastic (CFRP) was used to produce carbon fluoride through vapor phase fluorination and recycled as a reducing electrode material for lithium primary batteries. First, the physicochemical properties of the waste carbon fiber obtained by pyrolysis were determined, and the structural and chemical properties of carbon fluoride were analyzed to evaluate the effect of vapor phase fluorination on the waste carbon fiber. XRD analysis confirmed that the hexagonal network carbon laminated structure (002 peak) of the waste carbon fiber was gradually converted into a carbon fluoride structure (CFX, 001 peak) as the temperature of gas phase fluorination increased. The discharge capacity of the lithium primary battery produced using this carbon fluoride was up to 862 mAh/g. This was compared to the discharge capacity of carbon fluoride-based Li-ion batteries made of other carbon materials. These results suggest that carbon fluoride made from waste CFRP-based carbon fibers can be used as a reducing electrode material for Li-ion batteries.

Manufacture and Qualification of Composite Main Reflector of High Stable Deployable Antenna for Satellite (위성용 전개형 고안정 반사판 안테나 주반사판 제작 및 검증)

  • Dong-Geon Kim;Hyun-Guk Kim;Dong-Yeon Kim;Kyung-Rae Koo;Ji-min An;O-young Choi
    • Composites Research
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    • v.37 no.3
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    • pp.219-225
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    • 2024
  • It is essential to develop a light-weight, high-performance structure for the deployable reflector antenna, which is the payload of a reconnaissance satellite, considering launch and orbital operation performance. Among them, the composite main reflector is a key component that constitutes a deployable reflector antenna. In particular, the development of a high-performance main reflector is required to acquire high-quality satellite images after agile attitude control maneuvers during satellite missions. To develop main reflector, the initial design of the main reflector was confirmed considering the structural performance according to the laminate stacking design and material properties of the composite main reflector that constitutes the deployable reflector antenna. Based on the initial design, four types of composite main reflectors were manufactured with the variable for manufacturing process. As variables for manufacturing process, the curing process of the composite structure, the application of adhesive film between the carbon fiber composite sheet and the honeycomb core, and the venting path inside the sandwich composite were selected. After manufacture main reflector, weight measurement, non-destructive testing(NDT), surface error measurement, and modal test were performed on the four types of main reflectors produced. By selecting a manufacturing process that does not apply adhesive film and includes venting path, for a composite main reflector with light weight and structural performance, we developed and verified a main reflector that can be applied to the SAR(Synthetic Aperture Rader) satellite.