• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.6
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• pp.575-579
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• 2004

Package reliability test was conducted to investigate the effect of solder paste composition at BGA Package. It was found that the shape and size of the phase form are affected by the processing parameters. The material have used to fill in the via was Sn/36Pb/2Ag and Sn/0.75Cu type solder paste. Sn/36Pb/2Ag and Sn/0.75Cu paste were fabricated on Tape-BGA substrates by screen printing process, and via ball mount data were characterized with variations of dwell time of 85 seconds at reflow peak temperature at 22$0^{\circ}C$ or 24$0^{\circ}C$. The test condition was MRT 30 $^{\circ}C$/60 %RH/96 HR. Failures formed of a ball-off in solder paste process were observed by using a Optical Microscope and SEM(Scanning Electron Microscope). It was concluded that intermetallic layer growth played important roles in increasing solder fatigue strength for addition of Ag composition. The degradation of shear strength of solder composition is discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.431-432
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• 2007

In this study, we used screen printing on the rear glass with silver electrodes, phosphor and a dielectric which is on the silver electrodes, and carried out firing in the temperature of $550^{\circ}C$, $570^{\circ}C$, $450^{\circ}C$ each. To seal the rear and top glass together, we used crystalline frit paste as a sealing material with dispenser and carried out firing up to $450^{\circ}C$. As using this panel, we focused on optimizing the condition which influences characteristics of discharging by the distance between electrodes, electrode structure, type and pressure of gases for FFL.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.4
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• pp.100-106
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• 2022

Topology optimization is applied for the optimal design of various products to ensure weight reduction and productivity improvement. Reducing the weight of the mold while maintaining its rigidity can ensure shortening of the production cycle, stabilization of the mold temperature, and reduction of mold material costs. In this study, a topology optimization technique was applied to the optimal design of the injection mold, and a topology-optimized model of the mold was obtained. First, the injection mold for the square specimens was modeled. Subsequently, a structural analysis was performed by implementing a load condition generated during the injection molding process. Topology optimization was performed based on the structural analysis results, and the models of the initial and topology-optimized designs were manufactured at 1/4 magnification using a 3D printer. Consequently, compared with the existing model, the weight of the topology-optimized model decreased by 9.8%, and the manufacturing time decreased by 7.61%.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.5
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• pp.937-943
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• 2023

In this study, the mast cover of submarine was reverse engineered and structural analysis was performed. In order to print with the 3D printer, the modeling was reduced to 1/5 size by applying geometric similarity. From the structural analysis results, it was found that the maximum value of equivalent stress generated in the mast cover was 180.9 MPa. This stress value occurs on the inner surface in the major axis. As a result of applying the load condition at a diving depth of 600 m, the mast cover is in a completely elastic state. The 1/5 size model printed on FDM 3D printer with PLA filament was the same as the reverse engineered modeling and it was printed in a perfect shape with no apparent defects. The 1/5 size model printed on PBF 3D printer with SUS316L powder was perfectly manufactured with no apparent defects.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.5
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• pp.91-97
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• 2015

Papermakers wish to increase the filler content of printing and writing grades because it allows saving in production cost through fiber replacement and improving the formation, and optical and printing properties of the paper. However, high filler loading in the base paper has negative side effects. It reduces the mechanical properties of paper and induces cracking at the fold after coating process. Fold cracking is one of the most frequent quality complaints for magazines, high quality books, etc. Two approaches were examined as methods to reduce fold cracking. One approach was to use preflocculated fillers, which was expected to reduce the fold cracking because it would decrease the interfiber bonding. The other approach was to use a new coating binder that gives greater binding power and thereby provides an opportunity of reducing the fold cracking of coated paper. When filler preflocculation was employed in producing the base paper, fold cracking becomes more severe than conventional filler loading condition. On the other hand, use of nano sized binder in coating improved the tensile properties of the coating layer and thereby decreased the crack area. It was shown that tensile properties of coating layer played an important role in fold cracking of coating.

• Journal of Conservation Science
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• v.7 no.2
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• pp.80-85
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• 1998

The structure, dimensions, condition and other characteristics of the Koryo Buddhist Canon (the Koreana Tripitaka) Printing Wood Blocks stored at the Haein-sa Monastery were surveyed to obtain basic data needed for the conservation of the Wood Blocks. The dimensions of the Wood Blocks Were measured and we could figured out the blueprint designed at the time of the carving the Wood Blocks. The dimensions of the wooden board were as follows: width, 8'chi'('cun' in Chinese, 24 cm);thickness, 1 'chi' (3 cm); length, 2'cha' ('chi' in Chinese) and 3 'chi' (68 cm) or 2 'cha' and 6 'chi' (78 cm). The dimensions of the end pieces were as follows: width, 1 'chi' and 5 'fun' (4.5 cm; thickness, 1 'chi' and 4 'fun' (4 cm); length, 8 'chi' and 2-4 'fun' (24.6-25.2 cm). There were 6 types of metal strips and the length of the nails employed was 1 'chl' (3 cm). Investigation on the differences in the length of the wood Blocks and the shapes of the metal strips will be of interest. Since we surveyed only small portion of the Wood Blocks. the result may be different if entire Wood Blocks were examined. The data acquisition of the entire Wood Blocks will be the basis to the conservation of the Wood Blocks.

• Journal of Institute of Convergence Technology
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• v.8 no.1
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• pp.33-39
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• 2018

The screen printing method for forming the electrode by applying the existing pressure is difficult to apply to thin wafers, and since expensive Ag paste is used, it is difficult to solve the problem of cost reduction. This can solve both of the problems by forming the front electrode using a plating method applicable to a thin wafer. In this paper, the process conditions of electrode formation are optimized by using LIEP (Light-Induced Electrode Plating). Experiments were conducted by varying the Ni plating bath temperature $40{\sim}70^{\circ}C$, the applied current 5 ~ 15 mA, and the plating process time 5 ~ 20 min. As a result of the experiment, it was confirmed that the optimal condition of the structural characteristics was obtained at the plating bath temperature of $60^{\circ}C$, 15 mA, and the process time of 20 min. The Cu LIEP process conditions, experiments were conducted with Cu plating bath temperature $40{\sim}70^{\circ}C$, applied voltage 5 ~ 15 V, plating process time 2 ~ 15 min. As a result of the experiment, it was confirmed that the optimum conditions were obtained as a result of electrical and structural characteristics at the plating bath temperature of $60^{\circ}C$ and applied current of 15 V and process time of 15 min. In order to form Ni silicide, the firing process time was fixed to 2 min and the temperature was changed to $310^{\circ}C$, $330^{\circ}C$, $350^{\circ}C$, and post contact annealing was performed. As a result, the lowest contact resistance value of $2.76{\Omega}$ was obtained at the firing temperature of $310^{\circ}C$. The contact resistivity of $1.07m{\Omega}cm^2$ can be calculated from the conditionally optimized sample. With the plating method using Ni / Cu, the efficiency of the solar cell can be expected to increase due to the increase of the electric conductivity and the decrease of the resistance component in the production of the solar cell, and the application to the thin wafer can be expected.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.923-928
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• 2012

Optimizing a water-phase suspending system is very important to manufacture high-quality suspension polymerized toners. Therefore, in this study, the effects of the molar ratio of calcium hydroxide ($CaOH_2$)/phosphoric acid ($H_3PO_4$)(Ca/P), which were used as inorganic suspending agents, and pH of the water-phase on the characteristics of styrene-based suspension polymerized toners were mainly investigated. At first, the water-phase was fixed to neutral condition (pH=7.5) and Ca/P molar ratio was changed from 1.5:1 to 1.76:1. As a result, an ideal calcium phosphate (hydroxyapatite) was prepared at the Ca/P molar ratio of 1.73:1 and polymerized toners prepared at this condition showed good particle size distribution, circularity and charging characteristic. Based on this result, Ca/P molar ratio was fixed to 1.73:1 and pH of the water-phase was changed to weak acidic (pH=5.5) and weak basic (pH=9.5) conditions. As a result, polymerized toners prepared under the weak acidic condition showed very good particle size distribution, circularity and charging characteristic along with excellent printing quality. High-quality suspension polymerized toners could be prepared via optimizing Ca/P molar ratio and pH of the water-phase.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.8
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• pp.461-465
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• 2016

n-type silicon shows the better tolerance towards metal impurities with a higher minority carrier lifetime compared to p-type silicon substrate. Due to better lifetime stability as compared to p-type during illumination made the photovoltaic community to switch toward n-type wafers for high efficiency silicon solar cells. We fabricated the front electrode of the n-type solar cell with AgAl paste. The electrodes characteristics of the AgAl paste depend on the contact junction depth that is closely related to the firing temperature. Metal contact depth with p+ emitter, with optimized depth is important as it influence the resistance. In this study, we optimize the firing condition for the effective formation of the metal depth by varying the firing condition. The firing was carried out at temperatures below $670^{\circ}C$ with low contact depth and high contact resistance. It was noted that the contact resistance was reduced with the increase of firing temperature. The contact resistance of $5.99m{\Omega}cm^2$ was shown for the optimum firing temperature of $865^{\circ}C$. Over $900^{\circ}C$, contact junction is bonded to the Si through the emitter, resulting the contact resistance to shunt. we obtained photovoltaic parameter such as fill factor of 76.68%, short-circuit current of $40.2mA/cm^2$, open-circuit voltage of 620 mV and convert efficiency of 19.11%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.618-626
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• 2019

Stem cell therapy is not expected to bestow any therapeutic benefit because of the low engraftment rates after transplantation.Various cell-carrying scaffolds have been developed in order to overcome this problem. When the scaffold is formed by 3-dimensional (3D) printing, it is possible to create various shapes of scaffolds for specific regions of injury. At the same time, scaffolds provide stem cells as therapeutic-agents and mechanically support an injured region. PCL is not only cost effective, but it is also a widely used material for 3D printing. Therefore, rapid and economical technology development can be achieved when PCL is printed and used as a cell carrier. Yet PCL materials do not perform well as cell carriers, and only a few cells survive on the PCL surface. In this study, we tried to determine the conditions that maximize the cell-loading capacity on the PCL surface to overcome this issue. By applying a plasma treated condition and then collagen coating known to improve the cell loading capacity, it was confirmed that the 3% collagen coating after plasma treatment showed the best cell engraftment capacity during 72 hours after cell loading. By applying the spheroid cell culture method and scaffold structure change, which can affect the cell loading ability, the spheroid cell culture methods vastly improved cell engraftment, and the scaffold structure did not affect the cell engraftment properties. We will conduct further experiments using PCL material as a cell carrier and as based the excellent results of this study.