• Journal of the Korean Society of Manufacturing Process Engineers
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• 제20권6호
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• pp.100-107
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• 2021

As a significant technology in the smartization era promoted by the Fourth Industrial Revolution, the secondary battery industry has recently attracted significant attention. The demand for lithium-ion batteries (LIBs), which exhibit excellent performance, is considerably increasing in different industrial fields. During the manufacturing process of LIBs, it is necessary to join the cathode and anode sheets with thicknesses of several tens of micrometers to lead taps of the cathode and anode with thicknesses of several hundreds of micrometers. Ultrasonic welding exhibits excellent bonding when bonded with very thin plates, such as negative and positive electrodes of LIBs, and dissimilar and highly conductive materials. In addition, ultrasonic welding has a small heat-affected zone. In LIBs, Cu is mainly used as the negative electrode sheet, whereas Cu or Ni is used as the negative electrode tab. In this study, one or two electrode sheets (t0.025 mm Cu) were welded to one lead tab (t0.1 mm Cu). The welding energy and pressure were used as welding parameters to determine the welding strength of the interface between two or three welded materials. Finally, the effects of these welding parameters on the welding strength were investigated.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.490.2-490.2
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• 2014

Since the general solar cells accept sun light at the front side, excluding the electrode area, electrons move from the emitter to the front electrode and start to collect at the grid edge. Thus the edge of gridline can be important for electrical properties of screen-printed silicon solar cells. In this study, the improvement of electrical properties in screen-printed crystalline silicon solar cells by contact treatment of grid edge was investigated. The samples with $60{\Omega}/{\square}$ and $70{\Omega}/{\square}$ emitter were prepared. After front side of samples was deposited by SiNx commercial Ag paste and Al paste were printed at front side and rear side respectively. Each sample was co-fired between $670^{\circ}C$ and $780^{\circ}C$ in the rapid thermal processing (RTP). After the firing process, the cells were dipped in 2.5% hydrofluoric acid (HF) at room temperature for various times under 60 seconds and then rinsed in deionized water. (This is called "contact treatment") After dipping in HF for a certain period, the samples from each firing condition were compared by measurement. Cell performances were measured by Suns-Voc, solar simulator, the transfer length method and a field emission scanning electron microscope. According to HF treatment, once the thin glass layer at the grid edge was etched, the current transport was changed from tunneling via Ag colloids in the glass layer to direct transport via Ag colloids between the Ag bulk and the emitter. Thus, the transfer length as well as the specific contact resistance decreased. For more details a model of the current path was proposed to explain the effect of HF treatment at the edge of the Ag grid. It is expected that HF treatment may help to improve the contact of high sheet-resistance emitter as well as the contact of a high specific contact resistance.

• Journal of the Microelectronics and Packaging Society
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• 제31권1호
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• pp.29-34
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• 2024

The heating element utilizing the Joule heating generated when current flows through a conductor is widely researched and developed for various industrial applications such as moisture removal in automotive windshield, high-speed train windows, and solar panels. Recently, research utilizing heating elements with various nanostructures has been actively conducted to develop flexible heating elements capable of maintaining stable heating even under mechanical deformation conditions. In this study, flexible polyurethane possessing excellent flexibility was selected as the substrate, and silver (Ag) thin films with low electrical resistivity (1.6 μΩ-cm) were fabricated as the heating layer using magnetron sputtering. The 2D heating structure of the Ag thin films demonstrated excellent heating reproducibility, reaching 95% of the target temperature within 20 seconds. Furthermore, excellent heating characteristics were maintained even under mechanically deforming environments, exhibiting outstanding flexibility with less than a 3% increase in electrical resistance observed in repetitive bending tests (10,000 cycles, based on a curvature radius of 5 mm). This demonstrates that polyurethane/Ag planar heating structure bears promising potential as a flexible/wearable heating element for curved-shaped appliances and objects subjected to diverse stresses such as human body parts.

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제27권2호
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• pp.75-79
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• 2017

Honeycomb-shaped Ag-grid transparent conductive electrodes (TCEs) were fabricated using two different processes, high density plasma etching and lift-off, and the optical and electrical properties were compared according to the fabrication method. For the fabrication of the Ag-grid TCEs by plasma etching, etch characteristics of the Ag thin film in $10CF_4/5Ar$ inductively coupled plasma (ICP) discharges were studied. The Ag etch rate increased as the power increased at relatively low ICP source power or rf chuck power conditions, and then decreased at higher powers due to either decrease in $Ar^+$ ion energy or $Ar^+$ ion-assisted removal of the reactive F radicals. The Ag-grid TCEs fabricated by the $10CF_4/5Ar$ ICP etching process showed better grid pattern transfer efficiency without any distortion or breakage in the grid pattern and higher optical transmittance values of average 83.3 % (pixel size $30{\mu}m/line$ width $5{\mu}m$) and 71 % (pixel size $26{\mu}m/line$ width $8{\mu}m$) in the visible range of spectrum, respectively. On the other hand, the Ag-grid TCEs fabricated by the lift-off process showed lower sheet resistance values of $2.163{\Omega}/{\square}$ (pixel size $26{\mu}m/line$ width $18{\mu}m$) and $4.932{\Omega}/{\square}$ (pixel size $30{\mu}m/line$ width $5{\mu}m$), respectively.

• Journal of Industrial Convergence
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• 제20권10호
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• pp.33-38
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• 2022

In this paper, a simple method of forming a solution-based carbon nanotube (CNT) for use as a conductive material for electronic devices was studied. The CNT thin film coating was performed on the glass by applying the spin coating method and the argon atmospheric pressure plasma process. In order to observe changes in electrical and physical properties according to the number of coatings, samples formed in the same manner from times 1 to 5 were prepared, and surface shape, reflectance, transmittance, absorbance, and sheet resistance were measured for each sample. As the number of coatings increased, the transmittance decreased, and the reflectance and absorptivity increased in the entire measurement wavelength range. Also, as the wavelength decreases, the transmittance decreases, and the reflectance and absorption increase. In the case of electrical properties, it was confirmed that the conductivity was significantly improved when the second coating was applied. In conclusion, in order to replace CNT with a transparent electrode, it is necessary to consider the number of coatings in consideration of reflectivity and electrical conductivity together, and it can be seen that 2 times is optimal.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.116.1-116.1
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• 2011

Materials with a combination of high electrical conductivity and optical transparency are important components of many electronic and optoelectronic devices such as liquid crystal displays, solar cells, and light emitting diodes. In this study, to fabricate a low-resistance and high optical transparent electrode film for organic photovoltaic, the following steps were performed: the design and manufacture of an electroforming stamp mold, the fabrication of thermal roll imprinted (TRI) poly-carbonate (PC) patterned films, the manufacture of high-conductivity and low-resistance Ag paste which was filled into patterned PC film using a doctor blade process and then coated with a thin film layer of conductive polymer by a spin coating process. As a result of these imprinting processes the PC films obtained a line width of $10{\pm}0.5{\mu}m$, a channel length of $500{\pm}2{\mu}m$, and a pattern depth of $7.34{\pm}0.5{\mu}m$. After the Ag paste was used to fill part of the patterned film with conductive polymer coating, the following parameters were obtained: a sheet resistance of $9.65{\Omega}$/sq, optical transparency values were 83.69 % at a wavelength of 550 nm.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제21권2호
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• pp.280-286
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• 2020

Cards made from PVC and PET materials do not oxidize or decompose readily, so they are generally incinerated or landfilled after use and cause pollution problems, such as environmental hormones and combustion gases during incineration. In addition, there is a problem of environmental pollution because they are discarded as semi-permanent refuse without being decomposed at landfill. This study attempted to solve this problem using polylactic acid (PLA), which is a representative biodegradable material as a substitute material that can solve the issues with these cards. On the other hand, when the thin card core sheet is made from only PLA material, the physical properties of the material are insufficient, such as the low temperature impact strength, high temperature stability, and poor bending properties, so its use is limited. To solve this problem, the compositional ratio of PLA was reviewed, and the optimal biodegradable compound composition was determined through an examination of the compositions, such as crystallization nucleating agents, additives, and nano compound technology. The high functionalization as a biodegradable card was verified through a laminating process using annealing technology.

• KIEAE Journal
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• 제13권4호
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• pp.103-112
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• 2013

The Federal Democratic Republic of Nepal(Nepal) is one of the poorest country in the world. People in Nepal are having lots of housing problems including the lack of housing provision. Even Habitat for Humanity Nepal (HfH_Nepal) has developed various programs to diffuse ecological housing, still there are many problems due to financial and technological shortage. The purpose of this study is to verify the effects of suggestion of performance improvement for HfH_Nepal eco house with introduction of the housing situation and efforts to provide sustainable housing by HfH_Nepal in Terai plain. Ideas on CGI sheet roof with poor insulation, double panel bamboo wall and adobe brick wall which can overcome structural and waterproof flaws of the thin single panel bamboo wall. The experiment result shows that both ideas adapted to adobe brick house reduces daily temperature range 50.8% and humidity adjust effect. For the effective provision of adobe brick house, compressive strength was tested for the bricks made with locally available fiber materials. Brick with jute displayed 41.1% betterment than plain brick with closest packing condition while coconut and straw showed 25.1% and 7.9% improvement respectively. Technical and economic problems brought up during the building and experiment process were listed and countermeasures established. This kinds of building prototype houses and experiments can improve the living conditions of people in developing countries with little supplement of resources. Furthermore, consideration of locally available and affordable material can help the social and ecological sustainability in the world.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권5호
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• pp.490-496
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• 2015

We have grown AlN/GaN heterostructure which is a promising candidate for mm-wave applications. For the growth of the high quality very thin AlN barrier, indium was introduced as a surfactant at the growth temperature varied from 750 to $1070^{\circ}C$, which results in improving electrical properties of two-dimensional electron gas (2DEG). The heterostructure with barrier thickness of 7 nm grown at of $800^{\circ}C$ exhibited best Hall measurement results; such as sheet resistance of $215{\Omega}/{\Box}$electron mobility of $1430cm^2/V{\cdot}s$, and two-dimensional electron gas (2DEG) density of $2.04{\times}10^{13}/cm^2$. The high electron mobility transistor (HEMT) was fabricated on the grown heterostructure. The device with gate length of $0.2{\mu}m$ exhibited excellent DC and RF performances; such as maximum drain current of 937 mA/mm, maximum transconductance of 269 mS/mm, current gain cut-off frequency of 40 GHz, and maximum oscillation frequency of 80 GHz.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.255-255
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• 2011

Zinc oxide based thin films have been extensively studied in recent several years because they have very interesting properties and zinc oxide is non-poisonous, abundant and cheap material. ZnO films are employed in different applications like transparent conductive layers in solar cells, protective coatings and so on. Wide industrial application of the ZnO films requires of development of cheap, effective and scalable technology. Typically used technologies don't completely satisfy the industrial requirements. In the present work, we studied effect of the deposition parameters on the structure and properties of ZnO films deposited by DC arc plasmatron. The varied parameters were gas flow rates, precursor composition, substrate temperature and post-deposition annealing temperature. Vapor of Zinc acetylacetone was used as source materials, oxygen was used as working gas and argon was used as the cathode protective gas and a transport gas for the vapor. The plasmatron power was varied in the range of 700-1500 watts. Flow rate of the gases and substrate temperature rate were varied in the wide range to optimize the properties of the deposited coatings. After deposition films were annealed in the hydrogen atmosphere in the wide range of temperatures. Structure of coatings was investigated using XRD and SEM. Chemical composition was analyzed using x-ray photoelectron spectroscopy. Sheet conductivity was measured by 4-point probe method. Optical properties of the transparent ZnO-based coatings were studied by the spectroscopy. It was shown that deposition by a DC Arc plasmatron can be used for low-cost production of zinc oxide films with good optical and electrical properties. Increasing of the oxygen content in the gas mixture during deposition allow to obtain high-resistive protective and insulation coatings with high adhesion to the metallic surface.