• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.143-144
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• 2006

In this paper, we proposed XP KMPR-1050 negative tone resist to replace SU-8 resist for multi-layer micro-structures and thick plating mold fabrication using UV-LIGA process. XP KMPR resist proposed in this paper can be easily striped using a common stripping solution such as NMP without damage of micro-structure. The conditions for the fabrication of XP KMPR micro-structure were optimized by adjustment of exposure and post-exposure bake(PEB). The $140{\mu}m$ -thick and an aspect ratio at least 10 micro-structure and multi-layer structures were successfully fabricated through the process conditions. Through-mold electroplating and PR striping of XP KMPR has been successfully demonstrated.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.04a
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• pp.23-23
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• 2006

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.8
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• pp.1242-1245
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• 2001

Plastic microlenses play an important role in reducing the size, weight, and the cost of the systems in the fields of optical data storage and optical communication. In the present study, plastic microlens arrays were fabricated using micro-compression molding process. The design and fabrication procedures for mold insert were simplified by using silicon instead of metal. A simple but effective micro compression molding process, which uses polymer powder, were developed for microlens fabrication. The governing process parameters were temperature and pressure histories and the micromolding process was controlled such that the various defects developing during molding process were minimized. The radius and magnification ratio of the fabricated microlens were 125$\mu\textrm{m}$ and over 3.0, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.2
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• pp.68-72
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• 2003

In this paper, we developed a new thick photoresist fabrication technology for 3-dimensional microstructures. In general, like as AZ photoresist was coated with thin film thickness about 1 $\mu\textrm{m}$ to 30 $\mu\textrm{m}$, but photoresist like SU-8 has thickness of several tens $\mu\textrm{m}$ or more and high aspect ratio. When we fabricate a microstructure using the thick photoresist like SU-8, cracks on the SU-8 thick photoresist are appeared by stress which was caused by sudden cooling down during bake of the thick photoresist spun on wafer. Thus, it was hard to fabricate the microstructure using the thick photoresist for electroplating. In this paper, we developed a new process to produce a 3-dimensional microstructure without the crack by stress through a suitable thick photoresist coating, time control of cool down and time control of PEB (Post Expose Bake).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.1982-1988
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• 2002

Micro-injection molding and microfluidic devices with the help of MEMS technologies including the LIGA process are expected to play important roles in micro-system industries, in particular the bio-application industry, in the near future. Understanding fluid flows in micro-channels is important since micro-channels are typical geometry in various microfluidic devices and mold inserts for micro-injection molding. In the present study, Part 1, an experimental investigation has been carried out to understand the detailed flow phenomena in micro-channel filling process. Three sets of micro-channels of different thickness (40um,30um and 2011m) were fabricated using SU-8 on silicon wafer substrate. And a flow visualization system was developed to observe the filling flow into the micro-channels. Experimental flow observations are extensively made to find the effects of pressure, inertia force, viscous force and surface tension. A dimensional analysis for experimental results was carried out and several relationships A dimensionless parameters are obtained.

• Design & Manufacturing
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• v.17 no.2
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• pp.22-26
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• 2023

As Light-Emitting Diodes(LEDs) continue to advance in performance, their application in automotive lamps is increasing. Automotive LEDs utilize light guides not only for aesthetics but also to control light quantity and direction. Light guides employ patterns of a few hundred micrometers(㎛) to regulate the light, and the surface roughness(Ra) of these patterns can reach tens of nanometers(nm). Given that these light guides are produced through injection molding, mold processing technology with high surface quality micro-patterns is required. This study serves as a preliminary investigation into the development of high surface quality micro-pattern processing technology. It examines the surface roughness of the workpiece based on the cutting direction of the pattern and the cutting fluid type when cutting micro-patterns on STAVAX steel using cubic Boron Nitride(cBN) tools. The experiments involved machining a step-shaped micro-pattern with a height of 60 ㎛ and a pitch of 400 ㎛ in a 22×22 mm area under identical cutting conditions, with only the cutting direction and cutting fluid type being varied. The machining results of four cases were compared, encompassing two cases of cutting direction(parallel to the pattern, orthogonal to the pattern) and two cases of cutting fluid type (flood, mist). Consequently, the Ra value was found to be the highest(Ra 128.33 nm) when machining with the flood type in parallel to the pattern, while it was the lowest(Ra 95.22 nm) when machining with the mist type orthogonal to the pattern. These findings confirm that there is a difference of up to 25.8 % in the Ra value depending on the cutting direction and cutting fluid type.

• Design & Manufacturing
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• v.17 no.3
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• pp.8-14
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• 2023

In this study, basic research was conducted on manufacturing technology of thick-walled light guide a component that controls the light source of automobile lamps. As a preliminary study for manufacturing the final injection molded parts, a model for analyzing the influence of micro patterns on light guides is presented. The optical characteristics of the light guide were analyzed according to the change of the curvature radius of the micro-optical pattern, and the injection molding characteristics of the light guide according to the change of injection molding conditions were analytically evaluated. It was confirmed that the luminance uniformity improves as the R value decreases for changes in the micro-pattern R value, but it was confirmed that there are technical limitations in actual injection mold core processing and high-replication injection molding. Injection molding analysis showed that cooling channel design is very important compared to general injection molding due to thick-wall characteristics and thickness variation. It was also confirmed that the cooling channel has a great influence on the cycle time and birefringence result due to residual stress. As a result of analyzing the influence of filling time, holding condition, and cooling on shrinkage, it was found that the cooling water temperature has a significant effect on the shrinkage of ultra-fine light guide parts, and the holding condition also has a significant effect.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.9
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• pp.1429-1434
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• 2004

Immunoassay is one of the important analytical methods for clinical diagnoses and biochemical studies, but needs a long time, troublesome procedures and expensive reagents. In this study, therefore, we propose the micro filter chip with microbeads for immunoassay, which has pillar structures. The advantage of the proposed micro filter chip is to use simple fabrication process and cheap materials. The mold was made by the photolithography technique with Si wafer and negative photoresist SU-8. The replica was made of PDMS, bonded on the pyrex glass. The micro filter chip consists of inlet channel, filter chamber and outlet channel. HBV (Hepatitius B virus) monoclonal antibody (Ag1) labeled with biotin were immobilized onto streptavidin coated beads of 30∼50 $\mu$m size. Fluorescein isothiocyanate (FITC)-labeled HBV monoclonal antibody (Ag8) was used to detect HBsAg (Hebatitis B virus surface Antigen), and fluorescence intensity was monitored by epi-fluorescence microscope. In this study, the immune response of less than 30 min was obtained with with the use of 100 $m\ell$ of sample.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.216-216
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• 2009

This paper describes a novel processing technique for the fabrication of polymer-derived SiCN (silicone carbonitride) microstructures for extreme microelectromechanical system (MEMS) applications. A polydimethylsiloxane (PDMS) mold was formed on an SU-8 pattern using a standard UV photolithographic process. Next, the liquid precursor, polysilazane, was injected into the PDMS mold to fabricate free-standing SiCN microstructures. Finally, the solid polymer SiCN microstructure was cross-linked using hot isostatic pressure at $400^{\circ}C$ and 205 bar. The optimal pyrolysis and annealing conditions to form a ceramic microstructure capable of withstanding temperatures over $1400^{\circ}C$ were determined. Using the optimal process conditions, the fabricated SiCN ceramic microstructure possessed excellent characteristics includingshear strength (15.2 N), insulation resistance ($2.163{\times}10^{14}\;{\Omega}$, and BDV (1.2 kV, minimum). Since the fabricated ceramic SiCN microstructure has improved electrical and physical characteristics compared to bulk Si wafers, it may be applied to harsh environments and high-power MEMS applications such as heat exchangers and combustion chambers.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.2
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• pp.236-240
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• 2013

In this presentation, we propose a fabrication method of PDMS stencil to apply into a localized culture of NIH/3T3 cells. PDMS stencil was fabricated by nitrogen gas blowing and soft lithography from preparing SU-8 master mold by photolithography. PDMS stencil pattern was production of the circle size 20 to $500{\mu}m$. In the culture test of PDMS stencil, a stencil was placed on a glass disk. The NIH/3T3 cells were successfully cultured into micropatterns by using the PDMS stencil. The results showed that cells could be cultured into micropatterns with precisely controlled manner at any shapes and specific size for bioscience study and bioengineering applications.