• Transactions of Materials Processing
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• v.16 no.1 s.91
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• pp.48-53
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• 2007

LCD-BLU(Liquid Crystal Display - Back Light Unit) consists of several optical sheets: LGP(Light Guiding Plate), light source and mold frame. The LGP of LCD-BLU is usually manufactured by etching process and forming numerous dots with $50{\mu}m$ in diameter on the surface. But the surface roughness of LGP with etched dots is very high, so there is much loss of light. In order to overcome the limit of current etched dot patterned LGP, optical pattern design with microlens of $50{\mu}m$ diameter was applied in the present study. The microlens pattern fabricated by modified LiGA with thermal reflow process was applied to the optical design of LGP and optical simulation was carried out to know tendency of microlens patterned LGP simultaneously. The attention was paid to the effects of different aspect ratio(i.e. $0.2\sim0.5$) of optical pattern conditions to the brightness distribution of BLU with microlens patterned LGP. Finally, high aspect ratio microlens patterned LGP showed superior results to the one made by low aspect ratio in average luminance.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.2
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• pp.17-27
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• 2011

This paper describes an experimental study and finite element analysis (FEA) carried out for investigating thermal deformation behavior of solders, resulting from temperature change in the solder. With such a goal in mind, a shear specimen that was composed of two metal bars having different coefficient of thermal expansion and solder blocks placed between two bars was designed and fabricated. Two different types of solder blocks, eutectic solder (Sn/36Pb/ 2Ag) and lead-free solder (Sn/3.0Ag/0.5Cu) were tested as well. Fringe patterns for several temperature steps were recorded and analyzed for three temperature cycles using a real-time moir$\acute{e}$ setup. The experimental data was verified with FEA and used to evaluate the suitability for numerous solder constitutive models available in literatures. FEA employing Anand material model suggested by Darveaux et al. and Chang et al. were found to be in an excellent agreement with the experimental results for the eutectic solder and the lead-free solder, respectively. In addition, numerical predictions on bending displacement, shear strain and viscoplastic distortion energy are documented and viscoplastic deformation behavior of two types of solder material are compared.

• Applied Chemistry for Engineering
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• v.19 no.3
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• pp.351-356
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• 2008

Titania nanoparticles were prepared by controlled hydrolysis of titanium tetraisopropoxide (TTIP) in water-in-oil (W/O) and microemulsion stabilized with a nonionic surfactant, N P-10 (Polyoxyethylene Nonylphenol Ether: $C_9H_{19}C_6H_4(OCH_2CH_2)_{10}OH$)). The nanosized particles prepared in W/O microemulsion were characterized by FT-IR, TEM, XRD, TGA, and DTA. In addition, the photocatalytic degradation of p-nitrophenol has been studied by using a batch reactor in the presence of UV light in order to compare the photocatalytic activity of prepared nanosized titania. The nanaosized titania particles calcined at $300{\sim}600^{\circ}C$ showed an anatase structure, but it transformed to a rutile phase above $700^{\circ}C$ of calacination temperature. With an increase of $W_o$ ratio, the crystallite size increased but photocalytic activity decreased. The titania synthesized at $W_o=5$, R = 2, and calcined at $400{\sim}500^{\circ}C$ showed the highest activity on the photocatalytic degradation of p-nitrophenol.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.59-64
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• 2022

Effects of film stack structure and peeling rate on the peel strength of screen-printed (SP) Ag/polyimide (PI) systems were investigated by a 90° peel test. When PI film was peeled at PI/SP-Ag and PI/SP-Ag/electroplated (EP) Cu structures, the peel strength was nearly constant regardless of the peeling rate. When EP Cu was peeled at EP Cu/SP-Ag/PI structure, the peel strength continuously increased as peeling rate increased. Considering uniaxial tensile test results of EP Cu/SP-Ag film with respect to loading rate, the increase of 90° plastic bending energy and peel strength was attributed to increased flow stress and toughness. On the other hand, viscoelastic PI film showed little variation of flow stress and toughness with respect to loading rate, which was assumed to result in nearly constant 90° plastic bending energy and peel strength.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.2 s.31
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• pp.43-47
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• 2004

A coupler or divider is a microwave passive component used for power coupling or dividing. Regarding the trend of current telecommunication systems monolithic integration of passive components is highly desirable. In this study by the LTCC(Low temperature co-fired ceramics) technology a 2012 size type dual band coupler with multi-layer structure was fabricated. To achieve the desired coupling values for both DCS and EGSM bands, broad side coupled patterns were used with multi-layer structure. Its characteristics such as coupling, insertion loss, isolation and directivity values were measured and compared with simulation results.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.3
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• pp.69-75
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• 2001

Photoimageable thick film technology is a new technology in that the lithography process such as exposure and development is applied to the conventional thick film process. Line resolution of 25 $\mu\textrm{m}$ width and 25 $\mu\textrm{m}$ space could be obtained by laminating green sheet, printing photoimageable Ag paste, exposing the test patterns, developing, and co-firing. In case of using the alumina substrate, 20 $\mu\textrm{m}$ fine line could be also obtained by similar process. Test results showed that exposing power density and developing time were the most important processing parameters for the fine line formation. Microstrip and series gap resonators with well-defined line morphology and good transmission characteristics in high frequency were formed by this new technology, and thereby dielectric constant and loss of test substrate were calculated.

• Journal of the Microelectronics and Packaging Society
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• v.3 no.2
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• pp.27-38
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• 1996

Lithium fluorhectorite 결정상을 함유한 glass ceramics 분말의 형성과 제조된 glass ceramics 분말을 이용한 저온 소결기판의 특성평가를 하였다. Li2O-MgO-MgF2-SiO2 계 유 리로 핵형성 및 결정 성장을 실시하여 lithium fluorhectorite 결정상을 지닌 glass ceramics 를 제조하였다. 유리시편의 핵형성 온도는 46$0^{\circ}C$였고 결정성장온도는 600, 640, 110$0^{\circ}C$에서 나타났다. $600^{\circ}C$에서의 결정상으 Li2.4LiSi4O10F2가 나타났다. Li2.4Mg8LiSi4와 Li2.8Mg0.6SiO4은 lithium fluorhectorite 결정상으로 되기 위한 중간상임을 확인할수 있었다. 64$0^{\circ}C$에서 열처리 후 110$0^{\circ}C$에서 재열처리하여 형성된 결정은 lithium fluorhectorite 와 tridymite가 최종 결정 상으로 나타났다. 이것은 수중에서 water swelling 현상에 의하여 분말화할 수 있었다, 기판 제조용 slurry를 제조하기 위해 glass ceramics 분말에 Al2O3분말을 0,25,50wt%로 혼합한것 과 glass ceramics 분말에 potashborosilica-te glass 분말을 15, 30, 45, 60 wt% 로 배합하 여 doctor blade 법으로 green sheet를 제조하였다. green sheet 는 950~150$0^{\circ}C$로소성하여 기판의 특성을 평가하였다. 겉보기 기공율은 3.06~19,14%이었고, 전기적 특성으로 유전상수 는 3~5(100KHz)를 나타내었다.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.1
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• pp.120-127
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• 2013

A novel severe plastic deformation process named half channel angular extrusion (HCAE) is proposed in order to produce bulk UFG materials. In HCAE process, equal channel angular extrusion (ECAE) and conventional forward extrusion process is integrated to increase the strain per pass and effectiveness of the SPD process. Three-dimensional finite element analysis was carried out to study the deformation behavior of the materials in the HCAE process. HCAE process was performed experimentally on commercially pure aluminum (AA1050) and micro-Vickers hardness test was used to measure the distribution of hardness on the section of normal to the extrusion direction. The results show that HCAE is able to impose more intensive strains per pass and give rise to higher micro-hardness than ECAE.

• Korean Journal of Metals and Materials
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• v.50 no.11
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• pp.793-800
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• 2012

The effect of cold rolling on the microstructural evolution in 22Cr-0.2N micro-duplex stainless steel was investigated. The 22Cr-xNi-yMn-0.2N duplex stainless steel plates with various Ni and Mn contents were fabricated. The steels were vacuum induction melted and hot rolled, followed by annealing treatment at the temperature range of $1000-1100^{\circ}C$, in which both the austenite and ferrite phases were stable. The volume fraction of the ferrite phase depending on the alloy compositions of Ni and Mn increased with an increase in the annealing temperature. Grain growth in the ferrite phase occurred markedly after cold rolling followed by annealing, while fine recrystallised grains were still found in the austenite phase. A large number of martensite laths was found in the microstructure of cold rolled steels, which should be formed by strain-induced martensite from the austenite phase. The intersections of stacking faults were revealed by TEM observation. The volume fraction of the martensite phase increased with an increase of the reduction ratio by cold rolling.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2003.05a
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• pp.29-33
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• 2003

최근 이동 정보통신 분야의 발전에 따라 단말기 및 관련 부품들을 소형 경량화 하는 것이 매우 중요한 기술요소로 부각되고 있다. 이를 위해서는 기판의 배선밀도를 높이는 것과 개별 부품 또는 모듈의 크기와 무게를 줄이는 것이 절실히 필요하며, 이러한 요구에 부응하기 위해 기존의 다층 PCB 기술이나 MCM 기술에 비해 우수한 배선밀도와 양호한 전기적 특성을 갖는 저온 동시소성 세라믹(Low Temperature Co-fired Ceramic) 기술이 개발, 적용되고 있다. 본 논문에서는 이러한 LTCC 기판의 소결에 있어 기존의 소결 공정인 전기로 소결 공정과 microwave를 이용한 소결 공정을 이용하여 소결 하였을 때, LTCC 기판의 수축율과 무게감소, 그에 따른 밀도변화, SEM 을 이용한 표면형상 분석을 통해 급속가열을 통한 공정시간의 단축, 낮은 에너지 소비로 인한 제조단가의 절감, 균일한 가열로 인한 소결온도의 저하 등의 장점을 갖는 microwave sintering 을 적용할 수 있는 가능성을 제시하였다.