• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.3
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• pp.274-279
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• 2008

Roll to roll (R2R) manufacturing process, also known as 'web processing', has been tried for producing electronic devices on a flexible plastic or metal foil. To increase the performance and productivity the R2R process, effective control and on-line supervision for web quality becomes very important. Wrinkle is one of the defects, which is incurred due to compressive stresses. A system for on-line measurement of wrinkle is developed using area scan camera and machine vision laser. The 2D image, obtained by area scan camera, is produced by Gaussian regression method to characterize the wrinkle on a transparent web. The experiment proves that 0.3mm wrinkle height can be measured successfully with 74fps.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1539-1543
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• 2006

We have developed self-aligned imprint lithography (SAIL) technology, an innovative method for roll-to-roll (R2R) fabrication of electronic devices on flexible plastic substrates. In this paper, we present the first R2R-produced ${\alpha}$-Si TFTs built on a polyimide substrate using the SAIL process, and prove the feasibility of this technology to enable R2R fabrication of flexible display active matrix (AM) backplanes with high precision and throughput.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.808-810
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• 2005

Inexpensive large area arrays of thin film transistors (TFTs) on flexible substrates will enable many new display products that cannot be cost effectively manufactured by conventional means. This paper presents a new approach for low cost manufacturing of electronic devices using roll-to-roll (R2R) processes exclusively. It was developed in partnership by Hewlett Packard Laboratories and Iowa Thin Film Technologies (ITFT), a solar cell manufacturer. The approach combines ITFT's unique processes for vacuum deposition and etching of semiconductors, dielectrics and metals on continuous plastic webs with a method HP has invented for the patterning and aligning the multiple layers of a TFT with sub-micron accuracy and feature size.

• Journal of Welding and Joining
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• v.31 no.5
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• pp.59-63
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• 2013

A bendable electronic module has been developed for a mobile application by using a low-cost roll-to-roll manufacturing process. In flexible embedded electronic module, a thin silicon chip was embedded in a polymer-based encapsulating adhesive between flexible copper clad polyimide layers. To confirm reliability and durability of prototype bendable module, the following tests were conducted: Moisture sensitivity level, thermal shock test, high temperature & high humidity storage test, and pressure cooker tester. Those experiments to induce failure of the module due to temperature variations and moisture are the experiment to verify the reliability. Failure criterion was 20% increase in bump resistance from the initial value. The mechanism of the increase of the bump resistance was analyzed by using non-destructive X-ray analysis and scanning acoustic microscopy. During the pressure cooker test (PCT), delamination occurred at the various interfaces of the bendable embedded modules. To investigate the failure mechanism, moisture diffusion analysis was conducted to the pressure cooker's test. The hygroscopic characteristics of the encapsulating polymeric materials were experimentally determined. Analysis results have shown moisture saturation process of flexible module under high temperature/high humidity and high atmosphere conditions. Based on these results, stress factor and failure mechanism/mode of bendable embedded electronic module were obtained.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.51-58
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• 2018

In this paper, the organic material Poly(methyl methacrylate) PMMA is used with inorganic $Al_2O_3$ to fabricate organic-inorganic multilayer barrier thin films. The organic thin films are developed using a roll-to-roll electrohydrodynamic atomization system, whereas the inorganic are grown using a roll-to-roll low-temperature atmospheric pressure atomic layer deposition system. For the first time, these two technologies are used together to develop organic-inorganic multilayer barrier thin films in atmospheric condition. The films are grown under optimized parameters and classified into three classes based on the layer structures, when the total thickness of the barrier is maintained at ~ 160 nm. All classes of barriers show good morphological, optical and chemical properties. The $Al_2O_3$ films with a low average arithmetic roughness of 1.58 nm conceal the non-uniformity and irregularities in PMMA thin films with a roughness of 5.20 nm. All classes of barriers show a notably good optical transmission of ~ 85 %. The hybrid organic-inorganic barriers show water vapor and oxygen permeation in the range of ${\sim}3.2{\times}10^{-2}g/m^2/day$ and $0.015cc/m^2/day$ at $23^{\circ}C$ and 100% relative humidity. It has been confirmed that it can be mass-produced and used as a low-cost barrier thin film in various printing electronic devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.6
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• pp.462-467
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• 2013

In this paper, we analyzed the effects of doctoring process on the patterns of Ag ink in gravure off-set printing. The parameters of doctoring process were the angle and the pressure, which was represented by the depth of blade movement to the gravure roll, of doctor blade to the surface of gravure roll, and the angle of patterns engraved on the gravure roll to the doctor blade moving direction. The proper parameters were extracted for the fine patterns and they were 15 mm for the pressure, $60^{\circ}$ for the blade angle. And the angle of patterns with respect to the blade movement should be less than $40^{\circ}$ for the best results. The gravure off-set printing with the above parameters was carried out to print gate electrodes and scan bus lines of OTFT-backplane for e-paper. The line width of $50{\mu}m$ was successfully obtained. The thickness of electrodes was $2.5{\mu}m$ and the surface roughness was $0.65{\mu}m$ and the sheet resistance was $15.8{\Omega}/{\Box}$.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.524-524
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• 2006

For decades, the pursuit of volume commercialization of low-power reflective displays with a paper-like look has been an unfulfilled dream. While steady technical progress was made throughout the late 1990s, there were still no volume products incorporating electronic paper displays (EPD) on the market. Now, microencapsulated electrophoretic display technology, also called electronic ink, has moved into volume production with a frontplane laminate (FPL) display component called E Ink Imaging Film™. This film is coated roll to roll on a flexible plastic substrate and integrated into a display module. Today, all-plastic segmented displays are being shipped as well as displays with electronic ink FPL being driven by glass TFT backplanes. A roadmap to active matrix flexible electrophoretic displays is being enabled by rapid technical progress on flexible TFT backplanes by a variety companies. Each of the approaches to these backplanes and flexible active matrix displays has different advantages for the various market segments being pursued including large format flexible displays for e-news and other reader applications, rollable displays for compact readers, and high resolution small format displays up to 400 ppi that can have fully integrated drive electronics to reduce size and drive down costs. Backplane approaches include Si on plastic, organic transistors on plastic, and Si transistors on flexible stainless steel substrate. Progress is also being made on next generation inks, including more reflective inks with higher contrast ratios. A full color 6 inch, 170 pixel per inch (PPI) active matrix display using a newer generation ink has been developed and this will be described and demonstrated. Large format segmented flexible displays will also be described.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.6
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• pp.1422-1428
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• 2014

This paper has analyzed threshold voltage roll-off for bottom gate voltages of asymmetric double gate(DG) MOSFET. Since the asymmetric DGMOSFET is four terminal device to be able to separately bias for top and bottom gates, the bottom gate voltage influences on threshold voltage. It is, therefore, investigated how the threshold voltage roll-off known as short channel effects is reduced with bottom gate voltage. In the pursuit of this purpose, off-current model is presented in the subthreshold region, and the threshold voltage roll-off is observed for channel length and thickness with a parameter of bottom gate voltage as threshold voltage is defined by top gate voltage that off-currnt is $10^{-7}A/{\mu}m$ per channel width. As a result to observe the threshold voltage roll-off for bottom gate voltage using this model, we know the bottom gate voltage greatly influences on threshold voltage roll-off voltages, especially in the region of short channel length and thickness.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.5
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• pp.330-334
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• 2018

With the development of the Internet of Things, the use of flexible displays has become widespread. In particular, the use of curved, bendable, and rollable displays is increasing. Flexible display production processes include various important components such as lamination material, flexible substrates, and adhesives. Among them, improvement of the lamination process comprises a large proportion of efforts for further development. In this paper, we attempt to improve the transmittance of the display substrate by performing a bubble removal process after adhesion. The transmittance of the glass substrate with the bubble removal process was 5~12% higher than that of the substrate without the bubble removal process. The fill-strength after the bubble removal process was improved by 21.4%, and the shear-strength was improved by 43.9%.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.4
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• pp.473-481
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• 2012

For a mesa-isolated small geometry SOI MOSFET, the potentials in the silicon film, front, back, and side-wall oxide layers can be derived three-dimensionally. Using Taylor's series expansions of the trigonometric functions, the derived potentials are written in terms of the natural length that can be determined by using the derived formula. From the derived 3-D potentials, the minimum values of the front and the back surface potentials are derived and used to obtain the closed-form expressions for the front and back gate threshold voltages as functions of various device parameters and applied bias voltages. Obtained results can be found to explain the drain-induced threshold voltage roll-off and the narrow width effect of a fully depleted small geometry SOI MOSFET in a unified manner.