• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.267-270
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• 2009

In the present investigation, we are newly developing a new forming process which can fabricate micro patterns on large-area polymeric substrates for high speed mass production. The key idea of the new process is to pressurize multiple vacuum-packed substrate-mold stacks above the glass transition temperature ($T_g$) of the polymeric substrates. The new process is thought to be promising micro-pattern fabrication technique in three aspects; firstly, isostatic pressing ensures the uniform micro-pattern replicating condition regardless of the substrate area. Secondly, the control of forming condition such as temperature and pressure can realize well-defined process condition exploited in the conventional hot embossing research field. Thirdly, multiple substrates can be patterned at the same time. A prototype forming machine for the new process was developed with the design consideration realizing the present idea. With a developed machine, micro prismatic array patterns with 50 um in size were successfully made on the $380{\times}300{\times}6\;mm$ PMMA plate.

• Transactions of Materials Processing
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• v.21 no.3
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• pp.202-206
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• 2012

Marking is a process that engraves letters or a pattern onto the surface of sheet metal. During marking, it is important to set the proper working conditions for clarity of the letters. In this study a simple case for forming circular protrusions by half-piercing and embossing was initially attempted to determine the working conditions which gave good results with respect to shape accuracy. Corner-radius and flatness of circular protrusions made under several experimental conditions were measured and compared. It is shown that the precision of protrusions by half-piercing is superior to that of embossing, and the clearance between punch and die exerts a strong influence on the shape accuracy rather than the penetration percentage into the thickness of the sheet metal. The marking dies for "SNUT" letters, as an example, by applying the above results were manufactured with four different clearances. The working variables for the experiment were clearance and marking depth. For the very shallow depth of 0.1mm the letters were not clearly read. Letters marked under other conditions were easily distinguished with increasing marking depth. It was confirmed that the half-piercing technique with proper values of the working variables gives good quality for the marking of sheet metal.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.571-572
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• 2006

RTP (rapid thermal pressing), one of micro-pattern replication techniques like hot embossing, is focused on achieving shorter cycle time. DFSS(Design for Six Sigma) has been applied in order to enhance the completeness of the development process for RTP system. According to DIDOV roadmap, we derived design concepts and subsequently decided the main performances, design factors, and components for RTP system. In the design process of RTP system using finite element analysis, it was realized that its structural characteristics affect large area replicability. Optimizing structural design factors, based on CAE, it was checked out that its large area replicability could be improved in a virtual test. Finally, we have a plan to validate the large area replicability of the developed RTP system, by performing micro-pattern replication tests with polymeric sheets.

• Design & Manufacturing
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• v.2 no.6
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• pp.28-32
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• 2008

Polymer solar cells are a type of organic solar cell (also called plastic solar cell), or organic photovoltaic cell that produce electricity from sunlight using polymers. It is a relatively novel technology, they are being researched by universities, national laboratories and several companies around the world. In this paper, stamping mold of barrier ribs for polymer solar cells was manufactured by lithography and electroforming which can control the height of pattern and 80nl of barrier ribs was manufactured by using hot embossing.

• Journal of the Korean institute of surface engineering
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• v.41 no.6
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• pp.331-334
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• 2008

The replica of highly ordered nano-sphere array patterns were fabricated using hot embossing method. First, silica nano-sphere array on Si substrate was transferred to PVC film at $130^{\circ}C$ and 7 bar using hot embossing process. Then, silica nano-sphere array on PVC template was removed by soaking the PVC film in buffered oxide etcher. In order to form anti-stiction layer, the PVC template was coated with silicon dioxide layer and self-assembled monolayer. Through UV nanoimprint lithography with the fabricated flexible PVC template, highly ordered nano-sphere array pattern was imprinted on curved substrates with high fidelity.

• Membrane Journal
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• v.3 no.1
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• pp.22-28
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• 1993

Fabrics of polyester, polyacrylics, nylon and cotton were tested to investigate the possibility. of using these matehals as a membrane support sheet. Considering the physical properties such as compaction rate, membrane embossing, water flux, the chemical and mechanical properties, 50 denlet polyester fabrics was found to be the appropriate material as a membrane support sheet among the tested materials. The experimental parameters such as pressure drop, compression pressure and viscosity were changed to investigate the effects of these parameters on the flow patten in this membrane support sheet. As a result, it was shown that Darcy's law could be satisfactorily applied to describe the flow pattern in this membrane support sheet.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.423-427
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• 2005

Sandwich structures, which are composed of a thick core between two thin faces, are commonly used in many engineering applications because they combine high stiffness and strength with low weight. Depending on the application of a particular sandwich structure, various types of cores can be used. The production of sandwich sheets by a rolling process, which is a more efficient and economical approach compared to other types of processes, has become an increasingly important subject of study. In this paper, we have studied the embossing structure of sheet type and developed embossing roll mold with $\Phi3$ pattern and roll forming system.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.2
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• pp.130-138
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• 2006

We have investigated pattern scaling down of silicon stamps through the oxidation technique, During oxidizing the silicon stamps, silicon dioxide that has 300 nm and 500 nm thickness was grown, and critical deformations were not observed in the patterns. There was positive effect to reduce size of patterns because vertical and horizontal patterns have different orientation. We achieved pattern reduction rate of $26\%$. In addition, the formation of polymer patterns had been investigated with varied temperature and pressure conditions to improve the filling characteristics of polymers during nanoimprint lithography when pattern sizes were few micrometers. In these varied conditions, polymers had been affected by free space compensation and elastic stress relaxation for filling the cavities. Based on the results, defect control which is an important issue in the nanoimprint lithography were facilitated.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.5
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• pp.871-878
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• 2013

Roll-to-roll (R2R) hot embossing systems have been developed and are widely used in various industrial domains. These systems press and heat flexible films between a press roll and a back-up roll, as said films pass through the two rolls. In previous studies, a heating roll was used for heating. However, in this study, a hybrid roll for R2R hot embossing is conceptualized and developed. This R2R system can be used for generating fine patterns on large and continuous films. The hybrid roll of our system can cool and heat the films simultaneously, thus affording greater flexibility in process design. Thermal and structural analyses were performed for developing the hybrid roll. In addition, a hybrid roll was designed based on analytical results. Experiments were conducted for measuring the performance of the developed hybrid roll.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.3895-3899
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• 2012

In this study, the start-type molded material, silicone resin(RTV-3040) was used to develop a mold that is utilized for embossing pattern. After selecting a required pattern using the commercial package (Freeform), we examined whether this is applicable to components creating projective embossed side on the surface. We responded to products that require corrosive pattern, such as aluminum mold, by making the starting type when small amounts of components are developing. However, the development of silicone mold that is applied to corrosive pattern showed the possible reduction in time and cost.