• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.28-28
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• 2009

Fabrications of antireflection structures on solar cell were investigated to trap the light and to improve quantum efficiency. Introductions of patterned substrate or textured layer for Si solar cell were performed to prevent reflectance and to increase the path length of incoming light. However, it is difficult to deposit conformally flat electrode on perpendicular plane. ZnO is II-VI compound semiconductor and well-known wide band-gap material. It has similar electrical and optical properties as ITO, but it is nontoxic and stable. In this study, Al-doped ZnO thin films are deposited as transparent electrode by atomic layer deposition method to coat on Si substrate with micro-scale structures. The deposited AZO layer is flatted on horizontal plane as well as perpendicular one with conformal 200 nm thickness. The carrier concentration, mobility and resistivity of deposited AZO thin film on glass substrate were measured $1.4\times10^{20}cm^{-3}$, $93.3cm^2/Vs$, $4.732\times10^{-4}{\Omega}cm$ with high transmittance over 80%. The AZO films were coated with polyimide and performed selective polyimide stripping on head of column by reactive ion etching to measure resistance along columns surface. Current between the micro-columns flows onto the perpendicular plane of deposited AZO film with low resistance.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.12
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• pp.1101-1106
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• 2014

Hybrid manufacturing technology has been advanced to overcome limitations due to traditional fabrication methods. To fabricate a micro/nano-scale structure, various manufacturing technologies such as lithography and etching were attempted. Since these manufacturing processes are limited by their materials, temperature and features, it is necessary to develop a new three-dimensional (3D) printing method. A novel nano-scale 3D printing system was developed consisting of the Nano-Particle Deposition System (NPDS) and the Focused Ion Beam (FIB) to overcome these limitations. By repeating deposition and machining processes, it was possible to fabricate micro/nano-scale 3D structures with various metals and ceramics. Since each process works in different chambers, a transfer process is required. In this research, nanoscale 3D printing system was briefly explained and an alignment algorithm for nano-scale 3D printing system was developed. Implementing the algorithm leads to an accepted error margin of 0.5% by compensating error in rotational, horizontal, and vertical axes.

• Tribology and Lubricants
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• v.24 no.6
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• pp.374-377
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• 2008

Due to the environmental concerns, especially the greenhouse effect and GWP (Global Warming Potential), the carbon dioxide was investigated as an alternative natural refrigerant to replace HFCs (HydroFluoroCarbons) in refrigerator or air conditioning systems. Because new compressor with carbon dioxide is going to be operated under the high pressure, the tribology of sliding surfaces in the compressor becomes very important. To improve of wear resistance in compressor parts, especially rotary type, the friction and wear characteristics of improved sliding surfaces between vane and flange were evaluated in this paper. The method of reformed sliding surface, such as micro-dimple processes, was applied on surfaces in order to improve the tribological characteristics, and their performances were evaluated experimentally. The vane-on-flange type lubricated sliding tests were performed with a high pressure wear tester using carbon dioxide. Test results showed that the reformed surfaces were very effective to reduce the friction and the wear amounts of vane surfaces. The method of improved surfaces showed good tribological properties at vane and flange.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3280-3286
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• 2009

In this paper, we designed and manufactured HD Switch Panel parts with micro-etched pattern. By using CAE analysis, we could predict weld-line positions and the amount of shrinkage during injection molding process. We measured the temperature distribution of the mold surface so that we could optimize the processing conditions such as mold temperature. In order to increase the transcription of micro-etched pattern, we applied the E-Mold technology and evaluated the effect of mold temperature on the surface quality. We concluded that the etched pattern was improved(more than 2.5$\to$1.5~1.7) through the measurement of surface gloss and the observation of both SEM and SPM images.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.6
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• pp.483-489
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• 2014

In this study, experiments were conducted for micro pattern printing to combine solution atomization process and stencil printing based on electrospray deposition. The stencil mask fabricated by etching the photosensitive glass placed below 0.3 mm distance to substrate has 100 um line width. The process parameters of electrospray deposition system for the atomization of the solution are applied voltage and supply flow rate of the solution. Meniscus angle of cone-jet was optimized by varying the supply flow rate from 0.3 ml/hr to 0.7 ml/hr. Voltage condition was verified having symmetric cone-jet angle and no pulsation at 8.5 kV applied voltage. In addition, a number of micro patterns are printed using a single 1 step process by solution atomization process. Variable line width of approximate 100 um was confirmed by changing conditions of solution atomization regardless of the pattern size of stencil mask.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.2
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• pp.113-120
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• 2010

An experimental investigation was carried out to examine the evaporative heat transfer characteristics of R-134a in a micro-channel heat exchanger. The micro-channel heat exchanger used in this study was a sort of plate heat exchanger. Micro-channels were fabricated on the SUS304 plate by the photo-etching process: 13 sheets of plates were stacked and bonded by the diffusion bonding process. The effects of the evaporating temperature, mass flux of R-134a, and inlet temperature of water were examined. As the difference between the inlet temperatures of R-134a and water increased, the heat transfer rate increased. The evaporative heat transfer coefficients obtained in this study range from 0.67 to 6.23 kW/$m^2{\cdot}^{\circ}C$. The experimental correlation for the Nusselt number as a function of the Reynold number and $\Theta$ was suggested for the micro-channel heat exchanger.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.207-208
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• 2002

In the present study, the friction and wear properties of boundary lubricated textured surfaces were investigated. The capability of textured surfaces to feed lubricant into the interface of a sliding contact and to isolate wear partices was studied and related to the properties of the textured surfaces. Well-defined surface textures were produced by lithography and anisotropic etching of silicon wafers. Different widths and distributions of parallel groves were manufactured and subsequently the wafers were PVD coated with thin wear resistant TiN or DLC coatings, retaining the substrate texture. The surfaces were evaluated in reciprocating sliding against a ball bearing steel ball under starved or boundary lubricated conditions.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.909-914
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• 2001

Fluid properties which are most commonly used to evaluate spray atomization characteristics, are important because they affect velocity and size distribution of droplets. The purpose of this study was to incorporate the significant characteristics in atomization process of industrial etching spray and how each of them affects the design of precise pressure-swirl nozzles. The experiment was carried out with different viscosity and density of fluid. The macro characteristics of liquid spray, such as the spray angle and shape were captured by PMAS and the micro characteristics of liquid spray, such as droplet size and velocity were obtained by PDA. The mean velocity and SMD of droplets were measured along axial and radial direction. It was found that the higher viscosity and density resulted in the larger SMD and the lower mean velocity of droplets.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.8
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• pp.152-156
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• 2004

A new tool of surface patterning technique for general purpose lithography was developed based on shadow mask method. This paper describes the fabrication of a new type of miniaturized shadow mask. The shadow mask is fabricated by photolithography and etching of 100-mm full wafer. The fabricated shadow mask has over 388 membranes with apertures of micrometer length scale ranging from 1${\mu}{\textrm}{m}$ to 100s ${\mu}{\textrm}{m}$ made on each 2mm${\times}$2mm large low stress silicon nitride membrane. It allows micro scale patterns to be directly deposited on substrate surface through apertures of the membrane. This shadow mask method has much wider choice of deposit materials, and can be applied to wider class of surfaces including chemical functional layer, MEMS/NEMS surfaces, and biosensors.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.40-44
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• 2002

The motivation of this work is to use SAM(Self-Assembled Monolayer) for developing a rapid and flexible non-photolithographic nano-structure fabrication technique which can be utilized in micro-machining of metals as well as silicon-based materials. The fabrication technique implemented in this work consists of a two-step process, namely, mechanical scribing followed by chemical etching. From the experimental results, it was found that thiol on copper surface could be removed even under a few nN normal load. The nano-tribological characteristics of thiol-SAM on various metals were largely dependent on the native oxide layer of metals. Based on these findings, nano-patterns with sub-micrometer width and depth on metal surfaces such as Cu, Au and Ag could be obtained using a diamond-coated tip.