Humidity Sensor Using an Air Capacitor

최진문,김태완 한국전기전자재료학회 2013 Transactions on Electrical and Electronic Material Vol.14 No.4

We studied the possibility that an air capacitor can be used as a humidity sensor by measuring capacitance change. In order to investigate the possibility, the change of capacitance of an air capacitor due to moisture in air was first considered theoretically, and was then experimentally verified. The capacitance was measured by an LCR impedance meter with a 100-kHz and 1-V ac. The results revealed that the changes in the experimentally measured capacitances were greater than those in the theoretically calculated values. Based on this fact, we knew that an air capacitor could be used as part of a humidity sensing device. We expect the humidity sensor with an air capacitor has characteristics of fast response time, high reliability, and high durability compared with other conventional methods.

Surface Modification by Atmospheric Pressure DBDs Plasma: Application to Electroless Ni Plating on ABS Plates

송호식,최진문,김태완 한국전기전자재료학회 2013 Transactions on Electrical and Electronic Material Vol.14 No.3

Acrylonitrile-butadiene-styrene (ABS) plastic is a polymer material extensively used in electrical and electronic applications. Nickel (Ni) thin film was deposited on ABS by electroless plating, after its surface was treated and modified with atmospheric plasma generated by means of dielectric barrier discharges (DBDs) in air. The method in this study was developed as a pre-treatment for electroless plating using DBDs, and is a dry process featuring fewer processing steps and more environmentally friendliness than the chemical method. After ABS surfaces were modified,surface morphologies were observed using a scanning electron microscope (SEM) to check for any physical changes of the surfaces. Cross-sectional SEM images were taken to observe the binding characteristics between metallic films and ABS after metal plating. According to the SEM images, the depths of ABS by plasma are shallow compared to those modified by chemically treatment. The static contact angles were measured with deionized (DI) water droplets on the modified surfaces in order to observe for any changes in chemical activities and wettability. The surfaces modified by plasma showed smaller contact angles, and their modified states lasted longer than those modified by chemical etching. Adhesion strengths were measured using 3M tape (3M 810D standard) and by 90° peel-off tests. The peel-off test revealed the stronger adhesion of the Ni films on the plasma-modified surfaces than on the chemically modified surfaces. Thermal shock test was performed by changing the temperature drastically to see if any detachment of Ni film from ABS would occur due to the differences in thermal expansion coefficients between them. Only for the plasma-treated samples showed no separation of the Ni films from the ABS surfaces in tests. The adhesion strengths of metallic films on the ABS processed by the method developed in this study are better than those of the chemically processed films.

An Environment-Friendly Surface Pretreatment of ABS Plastic for Electroless Plating Using Chemical Foaming Agents

강동호,최진철,최진문,김태완 한국전기전자재료학회 2010 Transactions on Electrical and Electronic Material Vol.11 No.4

We have developed an environment-friendly etching process, an alternative to the dichromic acid etching process, as a pretreatment of acrylonitrile-butadiene-styrene (ABS) plastic for electroless plating. In order to plate ABS plastic in an electroless way, there should be fine holes on the surface of the ABS plastic to enhance mechanically the adhesion strength between the plastic surface and the plate. To make these holes, the surface was coated uniformly with dispersed chemical foaming agents in a mixture of environmentally friendly dispersant and solvent by the methods of dipping or direct application. The solvent seeps into just below the surface and distributes the chemical foaming agents uniformly beneath the surface. After drying off the surface, the surface was heated at a temperature well below the glass transition temperature of ABS plastic. By pyrolysis, the chemical foaming agents made fine holes on the surface. In order to discover optimum conditions for the formation of fine holes, the mixing ratio of the solvent, the dispersant and the chemical foaming agent were controlled. After the etching process, the surface was plated with nickel. We tested the adhesion strength between the ABS plastic and nickel plate by the cross-cutting method. The surface morphologies of the ABS plastic before and after the etching process were observed by means of a scanning electron microscope.

A Composite of Metal and Polymer Films: Thin Nickel Film Coated on a Polypropylene Film after Atmospheric Plasma Induced Surface Modification

Ho Shik Song,최진문,김태완 한국전기전자재료학회 2011 Transactions on Electrical and Electronic Material Vol.12 No.3

Polymeric films of high chemical stability and mechanical strength covered with a thin metallic film have been extensively used in various fields as electric and electronic materials. In this study, we have chosen polypropylene (PP) as the polymer due to its outstanding chemical resistance and good creep resistance. We coated thin nickel film on PP films by the electroless plating process. The surfaces of PP films were pre-treated and modified to increase the adhesion strength of metal layer on PP films, prior to the plating process, by an environment-friendly process with atmospheric plasma generated using dielectric barrier discharges in air. The surface morphologies of the PP films were observed before and after the surface modification process using a scanning electron microscope (SEM). The static contact angles were measured with deionized water droplets. The cross-sectional images of the PP films coated with thin metal film were taken with SEM to see the combined state between metallic and PP films. The adhesion strength of the metallic thin films on the PP films was confirmed by the thermal shock test and the cross-cutting and peel test. In conclusion, we made a composite material of metallic and polymeric films of high adhesion strength.

Red Electroluminescence Device Using a Cu-Coated CaS:Eu2+ Phosphor

Jun-Seok Park,최진철,최진문,Boo-Won Park,김종수 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.1

Cu-coated CaS:Eu2+ phosphors are synthesized by using a wet-processing method. The alternat- ing current(A.C.) powder electroluminescence devices are fabricated by a screen-printing method: ITO PET lm/phosphor layer (Cu-coated CaS:Eu2+)/dielectric layer (BaTiO3)/silver electrode. Their electroluminescence spectra show a deep red emission peaking at 650 nm due to the f-d tran- sitions of Eu2+ ions in CaS:Eu2+ phosphor, indicating that the purity of red color is superior to that with a commercial ZnS:Mn2+ phosphor. With increasing Cu concentration, the electroluminescent intensity is maximized at an optimal Cu concentration and then decreases, which is explained by two competing factors, an improved conductivity and a reduced transparency. Cu-coated CaS:Eu2+ phosphors are synthesized by using a wet-processing method. The alternat- ing current(A.C.) powder electroluminescence devices are fabricated by a screen-printing method: ITO PET lm/phosphor layer (Cu-coated CaS:Eu2+)/dielectric layer (BaTiO3)/silver electrode. Their electroluminescence spectra show a deep red emission peaking at 650 nm due to the f-d tran- sitions of Eu2+ ions in CaS:Eu2+ phosphor, indicating that the purity of red color is superior to that with a commercial ZnS:Mn2+ phosphor. With increasing Cu concentration, the electroluminescent intensity is maximized at an optimal Cu concentration and then decreases, which is explained by two competing factors, an improved conductivity and a reduced transparency.

Room Temperature Luminescence from ion Beam or Atmospheric Pressure Plasma Treated SrTiO3

송진호,석재권,여창수,이관호,송종한,신상원,최진문,조만호 한국진공학회 2013 한국진공학회 학술발표회초록집 Vol.2013 No.2

소성 온도에 따른 Cu-coated CaS:Eu2+의 A.C. powder EL 발광 특성 연구

박준석 ( Jun Seok Park ),백운일 ( Un Il Baek ),최진철 ( Jin Chul Choi ),최진문 ( Jin Moon Choi ) 한국화상학회 2007 한국화상학회지 Vol.13 No.4