• Journal of the Microelectronics and Packaging Society
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• v.25 no.1
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• pp.41-45
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• 2018

As the size of semiconductor chip shrinks, the electronic industry has been paying close attention to fan-out wafer level packaging (FO-WLP) as an emerging solution to accommodate high input and output density. FO-WLP also has several advantages, such as thin thickness and good thermal resistance, compared to conventional packaging technologies. However, one major challenge in current FO-WLP manufacturing process is to control wafer warpage, caused by the difference of coefficient of thermal expansion and Young's modulus among the materials. Wafer warpage induces misalignment of chips and interconnects, which eventually reduces product quality and reliability in high volume manufacturing. In order to control wafer warpage, it is necessary to understand the effect of material properties and design parameters, such as chip size, chip to mold ratio, and carrier thickness, during packaging processes. This paper focuses on the effects of thickness of chip and molding compound on 12" wafer warpage after PMC of EMC using finite element analysis. As a result, the largest warpage was observed at specific thickness ratio of chip and EMC.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.813-816
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• 2008

In this research we present a method to reconstruct the casting flow simulation result as a 3D model and visualize it on a VR display. First, numerical analysis of heat flow is performed using an existing commercial CAE simulation software. In this process the shape of the original design model is approximated to a regular rectangular grid. The filling ratio and temperature of each voxel are recorded iteratively by predefined number of steps starting from pouring the melted metal into a mold until it is entirely filled. Next we reconstruct the casting by voxels using the simulation result as an input. The color of voxel is determined by mapping the colors to temperature and filling ratio at each step as the flow proceeds. The reconstructed model is visualized on the Projection Table which is one of horizontal-type VR display. It provides active stereoscopic images.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.3
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• pp.130-134
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• 2016

Due to the need for advanced technologies in the automotive industry, the demand for lighter and safer vehicles has increased. Even though various nonferrous metals, like Aluminum, Magnesium and also Carbon Fiber Reinforced Plastic (CFRP), have been implemented in the automotive industry, a lot of technical research and development is still focused on ferrous metals. In particular, the market volume of High Strength Steel (HSS) parts and Ultra High Strength Steel (UHSS) by hot press forming parts has expanded significantly in all countries' automotive industries. A new tool steel, High Thermal-Conductivity Tool Steel (HTCS), for stamping punches and dies has been developed and introduced by Rovalma Company (Spain), and it is able to support better productivity and quality during hot press forming. The HTCS punches and dies could help to reduce cycle time due to their high thermal conductivity, one of the major factors in hot press forming operation. In this study, test dies were manufactured in order to verify the high thermal conductivity of HTCS material compared to SKD6. In addition, thermal deformation was inspected after the heating and cooling process of hot press forming. After heating and cooling, the test dies were measured by a 3D scanner and compared with the original geometry. The results showed that the thermal deformation and distortion were very small even though the cooling time was reduced by 2 seconds.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.4
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• pp.433-440
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• 2004

Since the numerical analysis was adopted in the mold design, lots of computational methods have been proposed for the simulations of casting processes for the various shaped molds. Today, it is possible to simulate the filling and solidification processes of most casts using the VOF technique. Though the three-dimensional numerical model based on the Cartesian coordinate system can be applied to any shape of cast, it becomes very inefficient when the three-dimensional model is applied to the cast of axi-symmetrical shape since the control volume includes at least 11 of the physical model. In addition, the more meshes should be distributed along the circumferential boundaries of curved shape in the Cartesian coordinate system fur the better results, while such curved circumferential boundary does not need to be considered in the two-dimensional cylindrical coordinate system. This motivates the present study i.e. developing a two-dimensional numerical model for the axi-symmetrically shaped casts. The SIMPLER algorithm, the VOF method, and the equivalent specific heat method have been adopted in the combined algorithm for the flow calculation, the free surface tracking, and the phase change heat transfer, respectively. The numerical model has been applied to the casting process of a pulley, and it was proven that the mesh and time effective calculation was accomplished comparing to the calculation using three-dimensional model.

• Journal of the Korea Convergence Society
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• v.11 no.8
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• pp.159-163
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• 2020

In this study, the flow analyses around according to the existence or non- existence of the trailer's deflector and the shapes were carried out. In the absence of a deflector, the kinetic energy of the turbulence behind the container also generates higher kinetic energy in a wider area than in the presence of a deflector, which adversely affects the vehicle's driving performance. As a trailer's wind deflector-free model has unstable flow rates around the trailer and high kinetic energy of turbulence than a model with a deflector, it can be thought that the increase of fuel economy can be expected by installing a deflector in the trailer. By applying the study result on flow analysis near trailer due to shape of wind deflector, this study is seen to be suitable for the aesthetic convergence.

• Journal of the Korea Convergence Society
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• v.11 no.8
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• pp.153-158
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• 2020

In this study, the thermal and stress analyses were performed by applying a temperature condition of 100℃ at CPU cooler model. The value of heat flux value is shown to be the most at the lower rod area. The upper part becomes, the smaller the heat flow rate. The highest temperature is shown at the bottom of the CPU cooler model. Overall, the upper part becomes, the smaller the temperature becomes. Based on the temperature analysis, the thermal deformation caused by expansion, the deformation becomes smaller as the upper part of the overlapping plates. The great deformation happens at the bent area of the small rod as the lower part of model and the least deformation is shown at the lowest floor of model. In addition, the maximum thermal stress of 570.63 MPa happens at the floor below model. The stress is shown to decrease as the upper part of the overlapping plates becomes. But the stress is shown to increase somewhat at the middle part of model. By applying the study result on the thermal and stress analyses of CPU cooler, this study is seen to be suitable for the aesthetic convergence.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.116.1-116.1
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• 2011

Materials with a combination of high electrical conductivity and optical transparency are important components of many electronic and optoelectronic devices such as liquid crystal displays, solar cells, and light emitting diodes. In this study, to fabricate a low-resistance and high optical transparent electrode film for organic photovoltaic, the following steps were performed: the design and manufacture of an electroforming stamp mold, the fabrication of thermal roll imprinted (TRI) poly-carbonate (PC) patterned films, the manufacture of high-conductivity and low-resistance Ag paste which was filled into patterned PC film using a doctor blade process and then coated with a thin film layer of conductive polymer by a spin coating process. As a result of these imprinting processes the PC films obtained a line width of $10{\pm}0.5{\mu}m$, a channel length of $500{\pm}2{\mu}m$, and a pattern depth of $7.34{\pm}0.5{\mu}m$. After the Ag paste was used to fill part of the patterned film with conductive polymer coating, the following parameters were obtained: a sheet resistance of $9.65{\Omega}$/sq, optical transparency values were 83.69 % at a wavelength of 550 nm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.8
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• pp.3625-3630
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• 2013

The modularization accomplished a big contribution in cost down and assembly-time shortening and the quality increase. But few improvements were made to this design largely due to the inflexibility of steel. In recent years, door modules made of PP-LFT material is manufactured using injection molding method. As a result, the plastic door modules allow more flexibility of door shape and become lighter. Warpage is generally large in the molded plastic door carrier plate due to the limitation of gate location and the fiber orientation. So after a few test injection the mold compensation processing for the improvement of an assembly characteristic. This research was performed to determine the factors that contribute to warpage for a injection-molded door carrier plate and presented differences in three mesh types of meshing method and its results. as a result we can improve process of tooling modification can reduce process of trial and error.

• Journal of Korea Foundry Society
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• v.3 no.1
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• pp.13-21
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• 1983

In order to determine the feeding distance of aluminiun alloys (Alsi7Mg and AlCu4Ti) bar castings in the sand mold, the distance of the sound castings has been observed by radiograph for various risers, melt treatment, and casting design. Variation of porosity and hardness with the distance from the riser were also measured in order to determine the casting soundness. The results obained were as follows; 1) The modulus of riser should be 1.4 times of the casting`s 2) The maximum distance which can be made sound is greatly dependent on chemical composition and ingate location, and follows the rules given by the formula; a) When the melt flows into the casting first, and the riser afterward, D = 37.7 ${\sqrt{T}}$ for AlSi7Mg D = 31.2 ${\sqrt{T}}$ for pure aluminium D ${\ge}$ 54.8 ${\sqrt{T}}$ for AlCu4Ti Where T = casting thickness in mm Of this maximum distance, $aa{\sqrt{T}}$ for AlSi7Mg and 7.5 ${\sqrt{T}}$ for pure aluminium is made sound by the chilling effect of the casting edge. b) When the melt flows into the casting passing through the riser, $30{\times}30{\times}600mm$ bars can be made sound in all cases 3) Percentage of porosity is higer in AlCu4Ti than AlSi7Mg. And it is increased gradually by moving closer to the riser in case of $30{\times}30{\times}600mm$ bars, but for the $30{\times}30{\times}600mm$ bars it is increased gradually by moving closer to the center of bars. 4) Hardness variation is similar to the tendency of porosity. And it decreased gradually with approaching to the center in case of $30{\times}30{\times}600mm$ bars.

• Journal of Environmental Science International
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• v.24 no.11
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• pp.1363-1370
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• 2015

This study was aimed to determine effects of soil organic amendment as plant growing media component on restoration of planting ground. The changes of soil physical and chemical properties and germination and growth of kentucky bluegrass (Poa pratensis L.) were investigated. For treatments, soil was excavated at depth of 0-50 cm (referred as $S_1$) and at depth of 50-100 cm (referred as $S_2$). Then the half amount of $S_1$ soil was mixed with the soil organic amendment (coir dust 40% (v/v), bottom ash 25%, leaf mold 25%, vermiculite 5%, carbonized rice hull 5%) at a rate of 6% (v/v) (referred as $S_1CC$) and also the half amount of $S_2$ soil was mixed with the soil organic amendment at a rate of 6% (v/v) (referred as $S_2CC$) on pot in a 16 cm diameter and 14 cm height. The experiment was replicated 3 times with 3 pots per replication in randomized block design, and 100 seeds were planted per pot. In results, there was no significant difference in soil pH among the treatments with a slight decrease in soil hydraulic conductivity. However, in the $S_1CC$ treatment, positive increases in soil chemical properties, including electrical conductivity, organic matter, phosphoric acid, total nitrogen, exchangeable cation, and cation exchange capacity. Also, the germination rate, plant height, and number of leaves were higher in the $S_1CC$ treatment than those in other treatments. These results suggest that the addition of organic amendment to the soil at depth of 0-50 cm might be proper for restoring planting ground.