• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.4
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• pp.759-764
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• 2012

Copper Pillar Tin Bump (CPTB) was investigated for high density chip interconnect technology development, which was prepared by electroplating and electro-less plating methods. Copper pillar tin bumps that have $100{\mu}m$ pitch were introduced with fabrication process using a KM-1250 dry film photoresist (DFR), with copper electroplating for Copper Pillar Bump (CPB) formation firstly, and then tin electro-less plating on it for control oxidation. Electric resistivity and mechanical shear strength measurements were introduced to characterize the oxidation effects and bonding process as a function of thermo-compression. Electrical resistivity increased with increasing oxidation thickness, and shear strength had maximum value with $330^{\circ}C$ and 500 N at thermo-compression process. Through the simulation work, it was proved that the CPTB decreased in its size of conduction area as time passes, however it was largely affected by the copper oxidation.

• Journal of the Korean Wood Science and Technology
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• v.41 no.1
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• pp.33-41
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• 2013

This study was performed to analyse cause of quality deterioration using byproduct of plywood and to determine physical and mechanical properties of particleboard used new bonding condition we found. The result of bending strength of Com-Ply board using EMDI is 57.7 $N/mm^2$ on linear direction and 25.1 $N/mm^2$ on vertical direction. EMDI has better water-resisting qualities than Urea formaldehyde adhesive according to result of thickness swelling and water absorption test. Pre-treatment soaked particle 72 hours in water caused increase of HCHO emission.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.726-729
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• 2010

Copper Pillar Tin Bump (CPTB) was investigated for high density chip interconnect technology development, which was prepared by electroplating and electro-less plating methods. Copper pillar tin bumps that have $100{\mu}m$ pitch were introduced with fabrication process using a KM-1250 dry film photoresist (DFR), with copper electroplating for Copper Pillar Bump (CPB) formation firstly, and then tin electro-less plating on it for control oxidation. Electric resistivity and mechanical shear strength measurements were introduced to characterize the oxidation effects and bonding process as a function of thermo-compression. Electrical resistivity increased with increasing oxidation thickness, and shear strength had maximum value with $330^{\circ}C$ and 500 N thermo-compression process. Through the simulation work, it was proved that when the CPTB decreased in its size, it was largely affected by the copper oxidation.

• Applied Microscopy
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• v.34 no.4
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• pp.277-283
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• 2004

This paper reports that the ultrastructural nature of the interface process between the implants and surrounding bone has been studied after in vivo 1, 4, 8, 12 weeks of implantation of smooth machined implants into rabbit tibias. There was no indication of the fibrous connective tissue formation around the implant that imply intolerance of the bone tissue towards the implant after 1 week of implantation. The regions showing direct bone tissue bonding to the smooth machined implant contained osteoblast activating across the interface in the direction after 4 weeks of implantation. The reaction of a smooth machined implant caused in the first instance formation of an amorphous woven bone, which transformed into a mineralized bone containing collagen fibers. After 8 weeks of implantation, the activities of osteoblast initiated osseointegration forming bone matrix at the interface. During this period, the osteoblast surrounded with a matrix consisting of collagen bundles running in various directions. In the interface area between newly formed bone tissue and implants which has been inserted in rabbit tibias for 12 weeks, the implant and mineralized bone was separated by an amorphous electron dense material layer about $1{\sim}1.5{\mu}m$ in thickness.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.1
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• pp.7-11
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• 2006

Since ceramic layers coated on machinery components inevitably experience the changes in their properties it is necessary to evaluate the characteristics of ceramic coating layers nondestructively for a reliable use of coated components and 4heir remaining life prediction. To address such a need, in the present study, an ultrasonic backward radiation technique is applied to investigate the characteristics of leaky Rayleigh surface waves propagating through the very thin TiN ceramic layers coated on AISI 1045 steel or austenitic 304 steel substrate with three different conditions of surface roughness, coating layer thickness and wear condition. In the experiments performed in the present work, the peak angle and the peak amplitude of ultrasonic backward radiation profile varied sensitively according to three specimen preparation renditions. in fact, this result demonstrates a high possibility of the ultrasonic backward radiation as an effective tool for the nondestructive characterization of the resting layers even in such a thin regime.

• Journal of Sensor Science and Technology
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• v.11 no.1
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• pp.54-59
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• 2002

This paper describes a new process technique for batch process of SOI(Si-on-Insulator) structures with buried cavities for MEMS(Micro Electro Mechanical System) applications by SDB(Si-wafer Direct Bonding) technology and electrochemical etch-stop. A low-cost electrochemical etch-stop method is used to control accurately the thickness of SOI. The cavities were made on the upper handling wafer by Si anisotropic etching. Two wafers are bonded with an intermediate insulating oxide layer. After high-temperature annealing($1000^{\circ}C$, 60 min), the SDB SOI structure with buried cavities was thinned by electrochemical etch-stop. The surface of the fabricated SDB SOI structure have more roughness that of lapping and polishing by mechanical method. This SDB SOI structure with buried cavities will provide a powerful and versatile substrate for novel microsensors arid microactuators.

• Polymer(Korea)
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• v.28 no.4
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• pp.305-313
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• 2004

A vacuum pressure-difference technique for making a nano-precision replica is investigated for various applications. Master patterns for replication were fabricated using a nano-replication printing (nRP) process. In the nRP process, any picture and pattern can be replicated from a bitmap figure file in the range of several micrometers with resolution of 200nm. A liquid-state monomer is solidified by two-photon absorption (TPA) induced by a femto-second laser according to a voxel matrix scanning. After polymerization, the remaining monomers were removed simply by using ethanol droplets. And then, a gold metal layer of about 30nm thickness was deposited on the fabricated master patterns prior to polydimethylsiloxane molding for preventing bonding between the master and the polydimethylsiloxane mold. A few gold particles attached on the polydimethylsiloxane stamp during detaching process were removed by a gold selecting etchant. After fabricating the polydimethylsiloxane mold, a nano-precision polydimethylsiloxane replica was reproduced. More precise replica was produced by the vacuum pressure-difference technique that is proposed in this paper. Through this study, direct patterning on a glass plate, replicating a polydimethylsiloxane mold, and reproducing polydimethylsiloxane replica are demonstrated with a vacuum pressure-difference technique for various micro/nano-applications.

• Korean Journal of Metals and Materials
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• v.48 no.11
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• pp.1035-1040
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• 2010

The research efforts on GaN-based light-emitting diodes (LEDs) keep increasing due to their significant impact on the illumination industry. Surface mount technology (SMT) is widely used to mount the LED packages for practical application. In surface mount soldering both the device body and leads are intentionally heated by a reflow process. We studied on the effects of multiple reflows on microstructural variation and joint strength of the solder joints between the LED package and the substrate. In this study, Pb-free Sn-3.0Ag-0.5Cu solder and a finished pad with organic solderability preservatives (OSP) were employed. A $Cu_6Sn_5$ intermetallic compound (IMC) layer was formed during the multiple reflows, and the thickness of the IMC layerincreased with an increasing number of reflows. The shear force decreased after three reflows. From the observation of the fracture surface after a shear test, partially brittle fractures were observed after five reflows.

• Composites Research
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• v.29 no.3
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• pp.117-124
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• 2016

The failure strength of composite single-lap joint repaired using scarf patch was investigated by test and finite element method. A total of 45 specimens were tested changing scarf ratio, stacking pattern, and defect size to study the failure strength and mode. Except for one case, all repaired specimens showed the equal or higher strength than the sound specimens and the effect of considered repair parameters was not remarkable. It was found through the failure mode inspection that the surface treatment for bonding was not enough in the case which failed at the lower load than the sound specimen. Three-dimensional finite element analysis was conducted to verify the test results. It was confirmed that the considered repair parameters do not significantly affect the stress distribution of the specimens. It was also observed that the applied tensile load is relieved passing through the overlapped region thickness of which is almost double. From this study, it is concluded that if the bonding procedure for adherends and patch including surface treatment for fabric layer is thoroughly followed, the strength of repaired single-lap joint can be restored up to the strength of sound one.

• Journal of the Korean Wood Science and Technology
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• v.45 no.5
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• pp.559-571
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• 2017

This study was conducted to determine the adhesive performances of plywoods affected by layering direction and the amounts of thermoplastic films. The face and back layers of veneer were hardwood species (Mixed light hardwood) and core layer veneer was radiata pine (Pinus radiata D. Don). Thermoplastic film used as adhesive were polypropylene (PP) film and polyethylene (PE) film. Thermal analysis and tensile strength were investigated on each films. As a result, the melting temperature of PP and PE films were $163.4^{\circ}C$ and $109.7^{\circ}C$, respectively, and the crystallization temperature were $98.9^{\circ}C$ and $93.6^{\circ}C$, respectively. Tensile strength and elongation of each films appeared higher on the width direction than length direction. Considering the characteristics of the thermoplastic films, the test for the amount of film used was carried out by layering film to the target thickness on veneer. The effecting of layering direction of film on plywood manufacturing was conducted by laminating in the length and width directions of the film according to the grain direction of veneer. Tensile-shear strength of plywood in wet condition was satisfied with the quality standard (0.7 MPa) of KS F 3101 when the film was used over 0.05 mm of PP film and over 0.10 mm of PE film. Tensile-shear strength of plywood after cyclic boiling exceeded the KS standard when PP film was used 0.20 mm thickness. Furthermore, higher bonding strength was observed on a plywood made with width direction of film according to grain direction of veneer than that of length direction of film. Based on microscopic analysis of the surface and bonding line of plywood, interlocking between veneers by penetration of a thermoplastic film into inner and cracks were observed.