• Korean Journal of Materials Research
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• v.22 no.12
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• pp.643-649
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• 2012

Coatings composited with alumina and Perfluoro alkoxyalkane (PFA) resin were deposited on stainless steel plate (SUS304) to further improve corrosion resistance. Plate (ca. $10{\mu}m$) and/or nanosize (27~43 nm) alumina used as inorganic additives were mixed in PFA resin to make alumina-fluoro composite coatings. These coatings were deposited on SUS304 plate with wet spray coating and then the film was cured thermally. According to the amount and ratio of the two kinds of alumina having plate morphology and nano size, corrosion resistance of the film was evaluated under strong acids (HF, HCl) and a strong base (NaOH). The film prepared with the addition of 5~10 wt% alumina powders in PFA resin showed corrosion resistance superior to that of pure PFA resin film. However, for the film prepared with alumina content above 10 wt%, the corrosion resistance did not improve with the physical properties, such as surface hardness and adhesion. The film prepared with plate/nanosize (weight ratio = 1/2) alumina especially enhanced the surface hardness and corrosion resistance. This can be explained as showing that the plate and the nanosize alumina dispersed in PFA resin effectively suppressed the penetration of cations and anions due to the long penetration length and fewer defects that accompany the improved surface hardness under a serious environment of 10% HF solution for over 120 hrs.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.3
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• pp.77-82
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• 2012

In this paper, the research of IC embedded PCB process is carried out. For embedding chips into PCB, solder-balls on chips were etched out and ABF(Ajinomoto Build-ip Film), prepreg and Cu foil was laminated on that to fabricate 6 layer build-up board. The chip of which solder ball was removed was successfully interconnected with PCB by laser drilling and Cu plating. However, de-lamination phenomenon occurred between chip surface and ABF during reflow and thermal shock. To solve this problem, de-smear and plasma treatment was applied to PI(polyimide) passivation layer on chip surface to improve the surface roughness. The properties of chip surface(PI) was investigated in terms of AFM(Atomic Force Micrometer), SEM and XPS (X-ray Photoelectron Spectroscopy). As results, nano-size anchor was evenly formed on PI surface when plasma treatment was combined with de-smear(NaOH+KMnO4) process and it improved thermal shock reliability ($260^{\circ}C$-10sec solder floating).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.9
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• pp.558-565
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• 2017

Hybrid insulators that have the advantages of both porcelain (high mechanical strength and chemical stability) as well as polymer (light weight and high resistance to pollution) insulators, can be used in place of individual porcelain and polymer insulators that are used for both mechanical support as well as electrical insulation of overhead power transmission lines. The most significant feature of hybrid insulators is the presence of porcelain/polymer interfaces where the porcelain and polymer are physically bonded. Individual porcelain and polymer insulators do not have such porcelain/polymer interfaces. Although the interface is expected to affect the mechanical/electrical properties of the hybrid insulator, systematic studies of the adhesion properties at the porcelain/polymer interface and the effect of the interface on the insulation characteristics and electric field distribution of the hybrid insulator have not been reported. In this study, we fabricated small hybrid insulator specimens with various types of interfaces and investigated the effect of the porcelain/polymer interface on the microstructure, insulating characteristics, and electric field distribution of the hybrid insulators. It was observed that the porcelain/polymer interface of the hybrid insulator does not have a significant effect on the insulating characteristics and electric field distribution, and the hybrid insulator can exhibit electrical insulating properties that are similar or superior to those of individual porcelain and polymer insulators.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.21-21
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• 2009

후막 광식각 기술을 이용하여 형성된 Ag 전극과 LTCC 기판 사이의 접착력을 향상시키기 위하여 무기 바인더로서 anorthite, diopside 및 MLS-62 glass frit을 첨가하여 감광성 Ag paste를 제조하였다. 소성 후의 glass pool effect를 감소시키기 위해 attrition mill을 통하여 미세 glass 분말을 준비하였다. Glass frit은 Ag powder의 5vol%~25vol%의 함량으로 첨가하여 감광성 Ag paste를 제조하였고 패턴 형성 후 $850^{\circ}C$에서 1시간 소결하였다. 전극과 기판 사이의 접착력은 micro-ball shear test 법으로 측정하였으며, Ag 전극 부착력은 glass frit의 함량 증가에 따라 증가하다가 감소하는 경향을 보이는데, 이는 과량의 glass frit 첨가로 인한 전극 내부에 액상 풀의 형성에 기인한 것으로 보여진다. Ag 전극의 면저항은 glass frit의 함량이 증가함에 따라 $0.13m{\Omega}{/\square}$에서 $2.06m{\Omega}{/\square}$까지 증가하는 경향을 나타내었다. 소성 전후의 전극 패턴의-수축율은 $100{\mu}m$의 선폭을 기준으로 glass frit의 첨가랑이 증가할수록 43.3%에서 35.0%로 감소하였으며, 그 결과 최소 선폭 $25{\mu}m$의 미세 전극 패턴의 형성이 가능하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.6
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• pp.425-428
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• 2013

In this paper, we present a novel hydrophilic coating material (Wellture Finetech, Korea) which can be utilized as a coating layer for anti-contamination for electrical and electronic system. The coating material was deposited on 4 inch silicon wafer with several different film thickness. The film thickness was controlled by spin coating speed. After curing of the film, we have scratched by permanent marker to check self-cleaning property of the film. Also we have executed several mechanical tests of the films. As the spin coating speed is increased, the film thickness was thinned from 230 nm to 125 nm. Contact angle of the film was lowered from $30^{\circ}$ to $12^{\circ}$ as the spin coating speed is increased from 700 to 2,500 rpm. On permanent marker scratched film surface coated at 1,000 rpm, we have poured regular city water to investigate self cleaning property of the film. The scratches were gradually separated from the film surface due to super-hydrophilicity of the film. Hardness of spin coated film was 9H measured by ASTM D3363 method. and adhesion of all film was 5B tested by ASTM D3359 method. Also, to get exact hardness value of the film, we have utilized a nano-indenter. As spin speed is increased, the hardness of film was increased from 3 GPa to 5 GPa.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.2007-2013
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• 2017

In order to give hydrophobic surface properties on carbon steel, the fluorinated amorphous carbon films were prepared by using linear 2.45GHz microwave PECVD device. Two different process approaches have been tested. One is direct deposition of a-C:H:F films using admixture of $Ar/CH_4/CF_4$ working gases and the other is surface treatment using $CF_4$ plasma after deposition of a-C:H film with $Ar/CH_4$ binary gas system. $Ar/CF_4$ plasma treated surface with high $CF_4$ gas ratio shows best hydrophobicity and durability of hydrophobicity. Nanometer scale surface roughness seems one of the most important factors for hydrophobicity within our experimental conditions. The properties of a-C:H:F films and $CF_4$ plasma treated a-C:H films were investigated in terms of surface roughness, hardness, microstructure, chemical bonding, atomic bonding structure between carbon and fluorine, adhesion and water contact angle by using atomic force microscopy (AFM), nano-indentation, Raman analysis and X-ray photoelectron spectroscopy (XPS).

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.42.2-42.2
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• 2011

$TiO_2$ films were modified by adding a glass frit as a light scattering particle and applied to an anode electrode in dye-sensitized solar cells (DSSCs) to enhance the adhesion between $TiO_2$ and fluorine doped transparent oxide (FTO). Low melting point glass frits at contents of (3 to 7wt%) were added to the nano crystalline $TiO_2$ films. The light scattering properties, photovoltaic properties and microstructures of the photo electrodes were examined to determine the role of the low glass transition temperature ($T_g$) glass frit. Electrochemical impedance spectroscopy, Brunauer-Emmett-Teller method and scratch test were conducted to support the results. The DSSC with the $TiO_2$ film containing 3wt% low Tg glass frit showed optimal performance (5.1%, energy conversion efficiency) compared to the $TiO_2$-based one. The photocurrent density slightly decreased by adding 3wt% of the frit due to its large size and non conductivity. However, the decrease of current density followed by the decrease of electron transfer due to the large frit in $TiO_2$ electrode was compensated by the scattering effect, high surface area and reduced the electron transfer impedance at the electrolyte-dye-$TiO_2$ interface. The stability of the photo electrodes was improved by the frit, which chemically promoted the sintering of $TiO_2$ at relatively low temperature ($450^{\circ}C$).

• Macromolecular Research
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• v.13 no.2
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• pp.120-127
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• 2005

Conventional poly(methyl methacrylate) (PMMA) bone cement has been widely used as an useful biopolymeric material to fix bone using artificial prostheses. However, many patients had to be reoperated, due to the poor mechanical and thermal properties of conventional PMMA bone cement, which are derived from the presence of unreacted MMA liquid, the shrinkage and bubble formation that occur during the curing process of the bone cement, and the high curing temperature ($above 100^{\circ}C$) which has to be used. In the present study, a composite PMMA bone cement was prepared by impregnating conventional PMMA bone cement with ultra high molecular weight polyethylene (UHMWPE) powder, in order to improve its mechanical and thermal properties. The UHMWPE powder has poor adhesion with other biopolymeric materials due to the inertness of the powder surface. Therefore, the surface of the UHMWPE powder was modified with two kinds of silane coupling agent containing amino groups (3-amino propyltriethoxysilane ($TSL 8331^{R}$) and N-(2-aminoethyl)-3-(amino propyltrimethoxysilane) ($TSL 8340^{R}$)), in order to improve its bonding strength with the conventional PMMA bone cement. The tensile strengths of the composite PMMA bone cements containing $3 wt\%$ of the UHMWPE powder surface-modified with various ratios of $TSL 8331^{R}$ and $TSL 8340^{R}$ were similar or a little higher than that of the conventional PMMA bone cement. However, no significant difference in the tensile strengths between the conventional PMMA bone cement and the composite PMMA bone cements could be found. However, the curing temperatures of the composite PMMA bone cements were significantly decreased.

• Journal of the Korean Vacuum Society
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• v.15 no.4
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• pp.354-359
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• 2006

Recently, the interest in lithography without photo exposure has been increased compare to the conventional photolithography in nano meter and micrometer size patterning area. We studied a self aligned dipping of Ag solution through micro contact printing (${\mu}-CP$) with octadecyltrichlorosilane (OTS) treated polydimethylsiloxane (PDMS) soft mold. The OTS monolayer on the patterned PDMS was formed by dipping it into OTS solution. We transferred the OTS monolayer from PDMS mold to the glass. The OTS monolayer changed the surface energy from hydrophilic surface to hydrophobic surface, And then we made self aligned Ag solution patterns just after dipping the substrate, using adhesion difference of Ag solution between OTS treated hydrophobic area and non-OTS treated hydrophilic area. We finally get the Ag patterns through only dip-coating after the ${\mu}-CP$ process. And we observed surface energies on the glass substrate through the contact angle measurements as time goes on.

• The Journal of Advanced Prosthodontics
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• v.10 no.3
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• pp.211-217
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• 2018

PURPOSE. To evaluate the effect of prolonged sandblasting on the bond durability of dual-cure adhesive resin cement to computer-aided design and computer-aided manufacturing (CAD/CAM) restoratives. MATERIALS AND METHODS. Nano-ceramic LAVA Ultimate and hybrid-ceramic VITA Enamic CAD/CAM blocks were used for this study. Each CAD/CAM block was sectioned into slabs of 4-mm thickness for the microtensile test (${\mu}TBS$) test and 2-mm thickness for the surface roughness test. Three groups were created according to the sandblasting protocols; group 1: specimens were sandblasted for 15 seconds, group 2: specimens were sandblasted for 30 seconds, and group 3: specimens were sandblasted for 60 seconds. After sandblasting, all specimens were luted using RelyX Ultimate Clicker. Half the specimens were subjected to ${\mu}TBS$ tests at 24 hours, and the other half were subjected to tests after 5000 thermocycles. Additionally, a total of 96 CAD/CAM block sections were prepared for surface roughness tests and scanning electron microscopy (SEM) evaluations. The Mann-Whitney U test, Kruskal-Wallis one-way analysis of variance, and Dunn's post hoc test were used to compare continuous variables among the groups. RESULTS. At baseline, group 1, group 2, and group 3 exhibited statistically similar ${\mu}TBS$ results for LAVA. However, group 3 had significantly lower ${\mu}TBS$ values than groups 1 and 2 for VITA. After 5000 thermocycles, ${\mu}TBS$ values significantly decreased for each block (P<.05). CONCLUSION. It is important to perform controlled sandblasting because it may affect bond strength results. Sixty seconds of sandblasting disturbs the initial ${\mu}TBS$ values and the stability of adhesion of CAD/CAM restoratives to dual-cure adhesive resin cement for VITA Enamic.