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Focused-Infrared-Light Assisted Roll-to-Roll Hot Embossing
조정대(Jeongdai Jo),김우섭(Wooseop Kim),김광영(Kwang-Young Kim),최영만(Young-Man Choi) Korean Society for Precision Engineering 2017 한국정밀공학회지 Vol.34 No.3
Hot embossing techniques are used to engrave patterns on plastic substrates. Roll based hot embossing uses a heated roll for a continuous process. A heated roll with relief patterns is impressed on a preheated plastic substrate. Then, the substrate is cooled down quickly to prevent thermal shrinkage. The roll speed is normally very slow to ensure substrate temperature increase up to the glass transition temperature. In this paper, we propose a noncontact preheating technique using focused infrared light. The infrared light is focused as a line beam on a plastic substrate using an elliptical mirror just before entering the hot embossing roll. The mid range infrared light efficiently raises the substrate temperature. For preliminary tests, substrate deformation and temperature changes were monitored according to substrate speed. The experiments show that the proposed technique is a good possibility for high speed hot embossing.
마이크로 구조물 형성을 위한 핫 엠보싱용 플라스틱 스탬프 제작
차남구,박창화,임현우,박진구,정준호,이응숙,Cha Nam-Goo,Park Chang-Hwa,Lim Hyun-Woo,Park Jin-Goo,Jeong Jun-Ho,Lee Eung-Sug 한국재료학회 2005 한국재료학회지 Vol.15 No.9
Nanoimprinting lithography (NIL) is known as a suitable technique for fabricating nano and micro structures of high definition. Hot embossing is one of NIL techniques and can imprint on thin films and bulk polymers. Key issues of hot embossing are time and expense needed to produce a stamp withstanding a high temperature and pressure. Fabrication of a metal stamp such as an electroplated nickel is cost intensive and time consuming. A ceramic stamp made by silicon is easy to break when the pressure is applied. In this paper, a plastic stamp using a high temperature epoxy was fabricated and tested. The plastic stamp was relatively inexpensive, rapid to produce and durable enough to withstanding multiple hot embossing cycles. The merits of low viscosity epoxy solutions were a fast degassing and a rapid filling the microstructures. The hot embossing process with plastic stamp was performed on PMMA substrates. The hot embossing was conducted at 12.6 bar, $120^{\circ}C$ and 10 minutes. An imprinted PMMA wafer was almost same value of the plastic stamp after 10 times embossing. Entire fabrication process from silicon master to plastic stamp was completed within 12 hours.
Recent Research Trend of Micro Hot-Embossing
이승현(Seung-Hyun Lee),조정대(Jeongdai Jo),김광영(Kwang-Young Kim),최영만(Young-Man Choi) Korean Society for Precision Engineering 2018 한국정밀공학회지 Vol.35 No.11
Micro hot-embossing is a powerful tool in the agile additive manufacturing industry. Its applications include optical components, micro-fluidic devices, MEMS, hydrophobic/hydrophilic surfaces, and energy harvesting devices. To overcome a drawback of low-process speed, the R2R process has been innovated, with novel embossing mechanisms and process optimization. Also, new materials beyond thermoplastic polymers have been applied to develop new devices, or enhance device performance. This review surveys recent progress in micro hot-embossing technology, in terms of new mold fabrication process, process innovation, and various applications.
Hot Embossing기술을 이용한 병렬 광접속용 고분자 광도파로 제작
최춘기,김병철,한상필,안승호,정명영 한국광학회 2002 한국광학회지 Vol.13 No.3
병렬 광접속용 다중모드 고분자 광도파로를 제작하였으며, 도파로 구조는 LIGA 공정에 의해 제작된 니켈 성형 마스터에 의해 hot embossing기술을 이용하여 성형하였다. 도파로 크기가 48$\times$47$\mu\textrm{m}$$^{2}$인 다중모드 광도파로를 단순 2단계 공정에 의해 제작하였으며, 0.85$\mu\textrm{m}$과 1.3$\mu\textrm{m}$ 파장대역에서 측정한 다중모드 광도파로의 도파손실은 각각 0.38dB/cm와 0.66dB/cm이었다. Polymeric multi-mode optical waveguides were fabricated for parallel optical interconnection. Waveguide structures were molded by a Ni mold master using a hot embossing technique. The Ni mold master was manufactured by LIGA process. Multimode optical waveguides with a 48$\times$47 ${\mu}{\textrm}{m}$$^2$cross-section were produced by a simple two-step process. The propagation losses of the multimode waveguide measured at 0.85 ${\mu}{\textrm}{m}$ and 1.3 ${\mu}{\textrm}{m}$ wavelengths were 0.38 dB/cm and 0.66 dB/cm, respectively.
Numerical simulation of hot embossing filling stage using a viscoelastic constitutive model
박장민,강태곤,박성진 한국유변학회 2011 Korea-Australia rheology journal Vol.23 No.3
A finite element analysis system is developed to investigate the viscoelastic deformation of polymer during hot embossing process, employing a nonlinear viscoelastic model as a polymer constitutive model. The interface between air and polymer is captured by a level set method. The viscoelastic flow problem is solved using a discrete elastic-viscous stress splitting (DEVSS) formulation along with a matrix logarithm of the conformation tensor. A discontinuous Galerkin formulation is employed to treat convective problems. The developed method is applied to the filling stage of hot embossing for a two-dimensional cavity. The details of the polymer viscoelastic deformation are investigated in terms of the conformation tensor distribution at the end of the embossing. The embossing speed and the cavity aspect ratio are found to have significant effects on the polymer conformation development in the molded part. As for the difference in filling pattern between the Newtonian viscous fluid and the viscoelastic fluid, the difference grows with time, but not significant in the particular geometry and processing conditions chosen.
Numerical simulation of hot embossing filling stage using a viscoelastic constitutive model
Park, Jang-Min,Kang, Tae-Gon,Park, Seong-Jin 한국유변학회 2011 Korea-Australia rheology journal Vol.23 No.3
A finite element analysis system is developed to investigate the viscoelastic deformation of polymer during hot embossing process, employing a nonlinear viscoelastic model as a polymer constitutive model. The interface between air and polymer is captured by a level set method. The viscoelastic flow problem is solved using a discrete elastic-viscous stress splitting (DEVSS) formulation along with a matrix logarithm of the conformation tensor. A discontinuous Galerkin formulation is employed to treat convective problems. The developed method is applied to the filling stage of hot embossing for a two-dimensional cavity. The details of the polymer viscoelastic deformation are investigated in terms of the conformation tensor distribution at the end of the embossing. The embossing speed and the cavity aspect ratio are found to have significant effects on the polymer conformation development in the molded part. As for the difference in filling pattern between the Newtonian viscous fluid and the viscoelastic fluid, the difference grows with time, but not significant in the particular geometry and processing conditions chosen.
글라스 주형을 이용한 폴리머 미세 형상 핫-엠보싱 공정 연구
김주한(Joohan Kim),신기훈(Ki Hoon Shin) 한국생산제조학회 2007 한국생산제조학회지 Vol.16 No.6
A ceramic glass mold was developed for micro hot-embossing and replicated polymer parts are fabricated. The glass-ceramic micro mold could be fabricated with a laser process and a wet etching process and the fabrication time could be saved a lot. Various polymer micro structures can be obtained by hot-embossing. The process parameters such as ho-embossing temperatures or pressures were investigated and optimized. This process can be applied for fabrication of micro structures for flip-chips or micro fluidic channels for bio-engineering. The advantages and disadvantages of this process are discussed, too.
Direct writing 기법을 이용한 유기태양전지용 격벽 stamper 금형 제작 및 성형에 관한 연구
황철진,김종선,홍석관,오정길,강정진,Hwang, C.J.,Kim, J.S,Hong, S.K.,Oh, J.G.,Kang, J.J. 한국금형공학회 2008 한국금형공학회지 Vol.2 No.6
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.
Effect of Forming Conditions on Linear Patterning of Polymer Materials by Hot Embossing Process
Lee, Chang-Su,Kang, Chung-Gil,Youn, Sung-Won 한국정밀공학회 2010 International Journal of Precision Engineering and Vol.11 No.1
In this work we demonstrate the hot-embossing process under different forming conditions such as forming temperature, load, and holding time in pressing, in order to determine the suitable conditions required for linear patterning on polymer plates (PMMA and PC). Results showed that the replicated pattern depth increased in proportion to an increase in the forming temperature, load, and time. The reduction of the workpiece thickness increased according to the holding time in the pressing process. In the process of time, the reduction ratio of the workpiece thickness decreased due to the surface area increment of the workpiece, while the pressure on the workpiece declined. In order to reduce the bulging ratio we introduced a temperature difference between the upper and the lower punch.
글라스 주형을 이용한 폴리머 미세 형상 핫-엠보싱 공정 연구
김주한(Joohan Kim),신기훈(Ki Hoon Shin) 한국생산제조학회 2007 한국공작기계학회 춘계학술대회논문집 Vol.2007 No.-
A ceramic glass mold was developed for micro hot-embossing and replicated polymer parts are fabricated. The glass-ceramic micro mold could be fabricated with a laser process and a wet etching process and the fabrication time could be saved a lot. Various polymer micro structures can be obtained by hot-embossing. The process parameters such as ho-embossing temperatures or pressures were investigated and optimized. This process can be applied for fabrication of micro structures for flip-chips or micro fluidic channels for bio-engineering. The advantages and disadvantages of this process are discussed, too.