• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.1 s.256
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• pp.51-61
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• 2007

This paper presents numerical and theoretical studies of acoustic wave interactions in slightly compressible liquids within piezoelectrically driven inkjet print heads. The interconnected flow channels may cause jet crosstalk, resulting in poor printing quality. It should be reduced by modifying the channel structure with the acoustic wave interactions considered. Compressible gas flow driven by the sudden movement of a top wall in the channel is calculated using Flow3D and is validated with the narrow gap theory. Limited compressibility model of the Flow3D is employed to calculate pressure waves of slightly compressible ink flow. It is found that reducing restrictor width can damp out the jet crosstalk by inhibiting the pressure wave propagation. The degree of crosstalk has been quantified using the maximum values of cross-correlations between neighboring channels and a critical channel dimension for acceptable crosstalk has been proposed. This finding is verified by drop visualization experiments using silicon-micromachined piezo inkjet print heads that are fabricated by our group.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.10 s.253
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• pp.1003-1011
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• 2006

Droplets are ejected onto a substrate through a nozzle by pushing liquids in flow channels of drop-on-demand devices. The behavior of ejection and formation of droplets is investigated to enhance the physical understanding of the hydrodynamics involved in inkjet printing. The free surface phenomenon of a droplet is described using $CFD-ACE^{TM}$ which employs the volume-of-fluid (VOF) method with the piecewise linear interface construction (PLIC). Droplet formation characteristics are analyzed in various flow regimes with different Ohnesorge numbers. The computational results show that the droplet formations are strongly dependent on the physical properties of working fluids and the inlet flow conditions. In addition, the wetting characteristics of working fluids on a nozzle influence the volume and velocity of a droplet produced in the device. This study may provide an insight into how a liquid droplet is formed and ejected in a piezoelectric inkjet printing device.

• Journal of the Semiconductor & Display Technology
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• v.10 no.2
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• pp.73-81
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• 2011

We manufactured the inkjet printing system for the application into the nano Ag finger line interconnection process in Si solar cells. The home-made inkjet printer consists of motion part for XY motion stage with optical table, head part, power and control part in the rack box with pump, and ink supply part for the connection of pump-tube-sub ink tanknozzle. The ink jet printing system has been used to conduct the interconnection process of finger lines on Si solar cell. The nano ink includes the 50 nm-diameter. Ag nano particles and the viscosity is 14.4 cP at $22^{\circ}C$. After processing of inkjet printing on the finger lines of Si solar cell, the nano particles were measured by scanning electron microscope. After the heat treatment at $850^{\circ}C$, the finger lines showed the smooth surface morphology without micropores.

• Journal of the Semiconductor & Display Technology
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• v.20 no.3
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• pp.51-56
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• 2021

Using an inkjet printing process, we have investigated a droplet formation of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) near the orifice of a piezoelectric inkjet head. With an attempt to form the smallest droplet without any satellites, we have applied various waveforms such as the unipolar, bipolar, and M-shaped waveforms. It is found that the droplet velocity and volume vary depending sensitively on the waveform width and voltage. Of those, the M-shaped waveform is shown to provide the smallest droplet volume, followed by the bipolar and then unipolar waveforms. The droplet printed on a PET film roll by the M-shaped waveform has the diameter as small as 46.1 ㎛. It is likely that the second short unipolar in the M-shape waveform increases the droplet velocity gradient, rendering the droplet smaller.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.105-105
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• 2006

IT 산업 및 반도체 산업이 발전함에 따라 초소형, 고집적화 시스템의 요구에 대응하기 위해서 고해상도 및 고정밀의 패턴 구현에 관한 많은 연구가 진행되고 있다. 이러한 연구는 각종 산업제품의 PCB(Printed Circuit Board) 및 디스플레이 장치인 PDP(Plasma Display Panel), LCD(Liquid Crystal Display) 등에 적용되어 널리 응용되고 있다. 현재 널리 사용되는 인쇄 회로 기판은 마스킹 후 선택적 에칭 방식을 적용하여 금속 배선을 형성하는 방식을 적용하고 있다. 이러한 방식은 설계가 변경될 경우 마스크를 다시 제작해야 하는 번거로움이 있어 설계 변경이 용이하지 않고 더욱 길어진 생산시간의 증가로 인하여 생산성 및 집적도가 떨어지게 된다. 따라서 최근에는 이러한 한계를 극복하기 위한 방안이 여러 가지 측면에서 시도되고 있으며, 그 중에서도 Inkjet Printing 기술에 대한 관심이 증가하고 있다. 본 연구에서는 Inkjet Printing 방식을 적용하여 금속 배선을 형성하고 선폭과 두께의 오차를 줄여 배선의 Tolerance 를 개선할 수 있는 방안을 제안하였다. Inkjet Printing 방식을 이용한 기존의 금속 배선 형성은 고해상도의 DPI(Dot Per Inch)에서 잉크 액적이 뭉치는 Bulge 현상이 발생되어 원하는 형상 및 배선의 폭을 구현하는데 어려움이 있었다. Bulge 현상은 배선의 불균일성을 야기할 뿐만 아니라 근접한 배선의 간섭에도 영향을 미처 금속 배선의 기능을 할 수 없는 단점을 발생시킨다. 따라서 본 연구에서는 이러한 Bulge 현상을 줄이고 배선간의 간섭을 방지하여 원하는 배선을 용이하게 형성할 수 있는 순차적 인쇄 방식을 적용하였다. 본 연구에서는 노즐직경 35um 의 Inkjet Head 와 나노 Ag 입자 잉크를 사용하여 Glass 표면 위에 배선을 형성하고 배선의 폭과 두께를 측정하였다. 또한 순차적 인쇄 방식을 적용하여 700DPI 이상의 고해상도에서 나타날 수 있는 Bulge 현상이 감소하였음을 관찰하였으며 금속 배선의 Tolerance를 10%내외로 유지할 수 있음을 확인하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.641-647
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• 2016

A drop-on-demand inkjet is used widely for various applications. Therefore, it is important to understand the jetting behavior of the drop from the piezo inkjet. In this study, to predict the jetting behavior, VOF (Volume-of-Fluid) simulation techniques were used and compared with the experimental results. The experimentally measured meniscus movement was used as the input data for the simulation. To verify the simulation, the measured jetting behavior of the mixture fluids of ethylene glycol and IPA (isopropyl alcohol), which has a mixing ratio of 50:50, was used. The numerical simulation of the drop formation using various mixture ratios and its comparison with the measured drop formation confirmed that the proposed method can predict the actual jetting. On the other hand, the satellite drop behavior showed slight differences because the small sized droplet is subject to a more aerodynamic effect during flight because the kinetic energy of the satellite droplet is far smaller than that of the main droplet.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.4
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• pp.455-460
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• 2012

The Electrostatic Inkjet system has many applications in cost and time effective manufacturing of printed electronics like RFIDs, OLEDs and flexible displays etc. This paper presents pneumatic ink supply system for an electrohydrodynamic deposition (EHD) setup for the precise pressure control to produce a small amount of discharge at the end of the capillary. The meniscus shape depends upon the applied pneumatic pressure to the ink supply system. Furthermore, this paper also compares meniscus shapes at different applied pneumatic pressures. It is concluded that patterning of constant line-width can be achieved better by controlling the meniscus shape using this technique.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.4
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• pp.369-375
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• 2015

This paper presents ejection of high viscosity fluids with magnetostrictive inkjet printhead(Magjet), which is not common with any other printhead. The MagJet uses a magnetostrictive material, Terfenol-D rod with 10-mm in diameter and 50-mm in length, as an actuation mechanism. It has been known that high viscosity is often an obstacle in ejecting small and mono-disperse droplets. We calculated required pressure with fluidic inertia (Bernoulli equation) and viscous loss (Hagen Poiseuille equation). The required pressure for ejecting a droplet is 1300kPa. The generated force and displacement with Terfenol-D rod are estimated to be 480N (2600kPa) and $28{\mu}m$, respectively. It was enough that Magjet eject high viscosity fluid (Max 1000cP). The experiments are performed to eject the high viscosity fluid with Magjet. The ejection of high viscosity fluids is successful with the aid of Terfenol-D's high performance.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.11a
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• pp.217-221
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• 2001

Poly-Si/SiO$_2$/Si의 하부기판구조 위에 Co금속을 E-beam evaporation 방식으로 증착하고 급속 열처리 방식을 통해 inkjet 프린터헤드의 heater로 사용 할 수 있는 코발트실리사이드를 형성하였다. RTA로 열처리 온도와 시간을 변수로하여 코발트실리사이드의 가장 안정적 결정상 및 성분분포를 찾고 이렇게 제작된 박막의 면저항과 표면특성을 통해 고온에서 사용 할 수 있는지를 연구하였다. 박막을 발열체(400~$600^{\circ}C$)로 사용하기 위해서는 발열체가 외부배선과의 접촉 저항보다 커야하고 저항이 고온에서 크게 변하면 안 된다. 코발트 실리사이드는 80$0^{\circ}C$ 20sec에서 발열체로 사용하기에 적당한 특성을 보였다. 그러나 실리사이드반응이 RTA에서 40$0^{\circ}C$ 20sec에서 형성되기 시작하지만 열처리 온도를 높일수록 박막의 면저항과 상변화가 일어남으로 발열체로 사용 할 수 없고, 90$0^{\circ}C$ 20sec 이상에서는 표면의 거칠어짐으로 인해 면저항이 증가하는 현상을 보여 역시 발열체로 사용 할 수 없음을 알 수 있었다.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1496-1499
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• 2005

This paper was represented an electrostatics distribution analysis using FEM(finite element method) with industrial type Inkjet plotter. Here, we know electronic value with each system position by experiment. these were decreased by discharge through earth and electricity shielding. According to industrial development, all fields using chemical instrument and material are generated an electrostatics. Based on these, the big large position of electrostatics was obtained metal base of controller, nonconductor fiber between two rubber roller, head controller by moving roller etc., Therefore these were showed an electrostatics generation source and by rubbing and meager profits electric charge.