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Gwangju, South Korea

Woo T.-G.,Chonbuk National University | Park I.-S.,Chonbuk National University | Jung K.-H.,Chonbuk National University | Jeon W.-Y.,Kwang Yang Health College | Seol K.-W.,Chonbuk National University
Electronic Materials Letters | Year: 2011

This study represents the results of an investigation of the peel strength and surface morphology according to the Ni sputtering power in producing Cu/Ni/PI structured flexible copper clad laminate (FCCL) using polyimide (PI). In order to analyze the surface morphologies of the sputtered Ni, Cu, and electrodeposited copper foil, and their crystal structure and interface binding structure, field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used. The surface roughness of the deposited layers and the crystal structure of the electrodeposited Cu layers varied according to the Ni sputtering power. In the range of RF output of 100~400 W in the Ni deposition process, the metal layers deposited at a power of about 300 W showed a homogeneous surface morphology and also exhibited a high peel strength for polyimide. The peeling that occurred at the interface of NiPI in the specimen fabricated using an Ni sputtering power of 300 W was due to the fact that the peeling usually occurs inside the polyimide. In the results of the XPS analysis on the separated Ni surface, the peaks of C and N, which are the major elements in polyimide, showed higher levels compared to those observed under the other conditions. © 2011 The Korean Institute of Metals and Materials and Springer Netherlands. Source


Park H.H.,Chonbuk National University | Park I.S.,Chonbuk National University | Kim K.S.,Jeonju Kijeon College | Jeon W.Y.,Kwang Yang Health College | And 4 more authors.
Electrochimica Acta | Year: 2010

The selection of bioactive and electrochemically stable materials for implants having effective corrosion resistance during long-term use in the body is essential. In this study, the bioactive and electrochemical properties of titanium implant materials with a nanotube surface treatment and various types of posttreatments were examined. Two types of amorphous TiO2 nanotubes were grown homogeneously on the surface: one with a larger diameter (approximately 85 nm) and one with a smaller diameter (approximately 50 nm). Amorphous TiO2 nanotubes were partially crystallized to anatase and rutile by heat treatment at 500°C for 2 h. The corrosion potential (E corr) of the heat-treated sample (HT) had a novel value of 0.102V due to the stable TiO2 crystal phase compared to the.0.106V observed in the anodic oxidation sample (AN). The corrosion current density (I corr) ranged from 0.20 to 0.64μA/cm2 according to the post-treatment conditions. However, at 0.6 V, where a passive layer had formed, the corrosion resistance of the HT was approximately ten times that of the AN and untreated (UT) samples. After evaluating the hydroxyapatite (HA)-forming ability by immersion in a simulated body fluid (SBF) solution, the CP process induced the adsorption of Ca and P onto HT. A comparison of the time-dependent amount of Ca and P adsorption showed that Ca adsorption plays a role in determining the rate at which hydroxyapatite (HA) is formed. For the induction of HA formation, a level of Ca adsorption above a critical level is required. © 2010 Elsevier Ltd. All rights reserved. Source


Woo T.-G.,Chonbuk National University | Park I.-S.,Chonbuk National University | Jung K.-H.,Chonbuk National University | Jeon W.-Y.,Kwang Yang Health College | And 2 more authors.
Electronic Materials Letters | Year: 2012

In microelectronics packaging, the reliability of the metal/polymer interface is an important issue because the adhesion strength between dissimilar materials is often inherently poor. This paper reports the peel strength and surface morphology of a Cu/Ni/PI structure flexible copper clad laminate (FCCL) based on polyimide(PI) according to the pre-treatment atmosphere and times. Field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) were used to analyze the surface morphology, crystal structure and interface binding structure, respectively, of the sputtered Ni, Cu, and electrodeposited copper foil layers. The surface roughness of the Ni and Cu sputtered deposition layers and the crystal structure of the electrodeposited Cu layer changed according to the pre-treatment atmosphere and times of PI. The PI surface etching speeds and surface shapes differed according to the gas used in plasma preprocessing. The highest peel strength (mean 15.8 gf/mm) can be obtained in a preprocessing process for 400 seconds in an O2 atmosphere due to the increase in mechanical binding force and change in chemical binding structure caused by the increase in polyimide surface roughness. © 2012 The Korean Institute of Metals and Materials and Springer Netherlands. Source


Woo T.-G.,Chonbuk National University | Park I.-S.,Chonbuk National University | Jeon W.-Y.,Kwang Yang Health College | Park E.-K.,Chonbuk National University | And 5 more authors.
Journal of Korean Institute of Metals and Materials | Year: 2010

This study examined the effect of copper and sulfuric acid concentrations on the surface morphology and physical properties of copper plated on a polyimide (PI) film. Electrochemical experiments with SEM and a four-point probe were performed to characterize the morphology and mechanical characteristics of copper electrodeposited in the composition of an electrolyte. The resistivity and peel strength were controlled using a range of electrolyte compositions. A lower resistivity and high flexibility were obtained when an electrolyte with 20 g/l of copper was used. However, a uniform surface was obtained when a high current density that exceeded 20 mA/cm2 was applied, which was maintained at copper concentrations exceeding 40 g/l. Increasing sulfuric acid to > 150 g/l decreased the peel strength and flexibility. The lowest resistivity and fine adhesion were detected at a Cu2+: H 2SO4 ratio of 50:100 g/l. Source


Woo T.-G.,Chonbuk National University | Park I.-S.,Chonbuk National University | Jung K.-H.,Chonbuk National University | Jeon W.-Y.,Kwang Yang Health College | Seol K.-W.,Chonbuk National University
Journal of Korean Institute of Metals and Materials | Year: 2011

This study represents the results of the peel strength and surface morphology according to the preprocessing times of polyimide (PI) in a Cu/Ni/PI structure flexible copper clad laminate production process based on the polyimide. Field emission scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopywere used to analyze the surface morphology, crystal structure, and interface binding structure of sputtered Ni, Cu, and electrodeposited copper foil layers. The surface roughness of Ni, Cu deposition layers and the crystal structure of electrodeposited Cu layers were varied according to the preprocessing times. In the RF plasma times that were varied by 100-600 seconds in a preprocessing process, the preprocessing applied by about 300-400 seconds showed a homogeneous surface morphology in the metal layers and that also represented high peel strength for the polyimide. Considering the effect of peel strength on plastic deformation, preprocessing times can reasonably be at about 400 seconds. Source

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