• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1724-1725
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• 2011

본 논문에서는 LED 패키지의 방열문제를 해결하기 위해 FR4 PCB에 Via-hole을 형성함으로써 열전달 능력을 향상시키고자 하였다. 또한 FR4 PCB의 면적과 Via-hole 크기 및 수량을 변화를 주어 그에 따른 K-factor를 측정 하였으며 열 저항 특성을 분석하였다. 결과로서, Via-hole을 형성한 FR4 PCB의 경우 초기 면적이 증가함에 따라 열 저항 및 접합온도가 급격히 감소하는 특성을 보였으며 200 [mm2]에서 안정화 되는 특성을 보였다. 또한 PCB 면적 및 Via-hole을 형성함에 따라 광 출력이 최대 17% 향상 되었다. 따라서 접합온도 및 열 저항에 있어서 PCB면적의 증가 및 Via-hole을 구성함에 있어 열전달 능력을 향상시킬 수 있음을 확인하였다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.2
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• pp.112-117
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• 2008

Vertical interconnection scheme using novel silicon-through-via for 3D MEMS devices or stacked package is proposed and fabricated to demonstrate its feasibility. The suggested silicon-through-via replaces electroplated copper, which is used as an interconnecting material in conventional through-via, with doped silicon. Adoption of doped silicon instead of metal eliminates thermal-mismatch-induced stress, which can make troubles in high temperature MEMS processes, such as wafer bonding and LP-CVD(low pressure chemical vapor deposition). Two silicon layers of $30{\mu}m$ thickness are stacked on the substrate. The through-via arrays with spacing $40{\mu}m$ and $50{\mu}m$ are fabricated successfully. Electrical characteristics of the through-via are measured and analyzed. The measured resistance of the silicon-through-via is $169.9\Omega$.

• Structural Engineering and Mechanics
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• v.64 no.1
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• pp.121-133
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• 2017

This paper proposes an analytical solution method for free vibration of curved functionally graded (FG) nonlocal beam supposed to different thermal loadings, by considering porosity distribution via nonlocal elasticity theory for the first time. Material properties of curved FG beam are assumed to be temperature-dependent. Thermo-mechanical properties of porous FG curved beam are supposed to vary through the thickness direction of beam and are assumed to be temperature-dependent. Since variation of pores along the thickness direction influences the mechanical and physical properties, porosity play a key role in the mechanical response of curved FG structures. The rule of power-law is modified to consider influence of porosity according to even distribution. The governing equations of curved FG porous nanobeam under temperature field are derived via the energy method based on Timoshenko beam theory. An analytical Navier solution procedure is used to achieve the natural frequencies of porous FG curved nanobeam supposed to thermal loadings with simply supported boundary condition. The results for simpler states are confirmed with known data in the literature. The effects of various parameters such as nonlocality, porosity volume fractions, type of temperature rising, gradient index, opening angle and aspect ratio of curved FG porous nanobeam on the natural frequency are successfully discussed. It is concluded that these parameters play key roles on the dynamic behavior of porous FG curved nanobeam. Presented numerical results can serve as benchmarks for future analyses of curve FG nanobeam with porosity phases.

• Bulletin of the Korean Chemical Society
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• v.35 no.11
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• pp.3249-3253
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• 2014

A novel triazole-functionalized phenolic resin was developed, and its thermal and flame-retardant properties were investigated. The triazole group was incorporated as a pendant unit on the phenolic resin via copper-mediated click chemistry between propargylated phenolic resin and benzyl azide. The newly-developed triazole-functionalized phenolic resin showed higher thermal stability and char yield, together with a reduced total heat release (THR), than the non-functionalized bare phenolic resin, indicating enhanced flame retardancy for the triazole-functionalized phenolic resin.

• Journal of the Korean Chemical Society
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• v.18 no.6
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• pp.447-452
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• 1974

A mechanistic possibility for the initiation of the thermal polymerization reactions are envisaged theoretically. As result of the considerations, it is assumed that the thermal polymerization reactions take place via the pseudo molecular complex which has been supposed to be an intermediate in the transition state of Diels-Alder reactions.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2009.11a
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• pp.15-16
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• 2009

Poly(vinyl alcohol) was crosslinked by UV irradiation in the presence of water soluble photoinitiators. The crosslinking of PVA films with 1,2,3,4-Butanetetracarboxylic acid(BTCA) and sodium phosphinate monohydrate(SPM) was also achieved via thermal curing. Different factors in the crosslinking including thermal and radiation methods were studied. Gel fraction of PVA films increased with increasing photoinitiator concentration. The maximum gel fraction on the crosslinking method was reached about 81%. The glass transition and maximum decomposition temperature improved by both thermal and radiation crosslinking.

• Bulletin of the Korean Chemical Society
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• v.22 no.2
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• pp.179-182
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• 2001

Photocyclizable poly(cinnam-4'-yl methyl methacrylate) derivatives bearing methoxy benzene (PMCMMA), anthracene (PACMMA), and coumarin (PCCMMA) have been synthesized via Heck type reaction. Three different types of polymers are photoreactable usin g linearly polarized UV light and applicable as liquid crystal alignment layer. Anthracence and coumarin containing polymers (PACMMA, PCCMMA) have better thermal stability than PMCMMA. This observation may be attributed to the glass transition temperature elevation due to the bulky size and another photocrosslinking site provided by anthracene or coumarin group.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.323-330
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• 1998

Mixed oxide compounds of potential usefulness for fibre coatings (hexagonal celsian, $BaAl_2Si_2O_8$ and lanthanum hexaluminate, $LaAl_{11}O_{18}$) or for matrix materials (yttrium aluminium garnet, $Y_3Al_5O_{12}$) were prepared by hybrid sol-gel synthesis and their thermal crystallisation was monitored by thermal analysis, X-ray diffraction and multinuclear solid state MAS NMR. All the gels convert to the crystalline phase below about $12200^{\circ}C$, via amorphous intermediates in which the Al shows and NMR resonance at 36-38 ppm sometimes ascribed to Al in 5-fold coordination. Additional information about the structural changes during thermal treatment was provided by $^{29}Si$, $^{137}Ba$ and $^{89}Y$ MAS NMR spectroscopy, showing that the feldspar framework of celsian begins to be established by about $500^{\circ}C$ but the Ba is still moving into its polyhedral lattice sites about $400^{\circ}C$ after the sluggish onset of crystallization. Lanthanum hexaluminate and YAG crystallise sharply at 1230 and $930^{\circ}C$ respectively, the former via $\gamma-Al_2O_3$, the latter via $YAlO_3$. Yttrium moves into the garnet lattice sites less than $100^{\circ}C$ after crystallisation.

• Journal of Powder Materials
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• v.30 no.2
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• pp.123-129
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• 2023

High-temperature and high-pressure post-processing applied to sintered thermoelectric materials can create nanoscale defects, thereby enhancing their thermoelectric performance. Here, we investigate the effect of hot isostatic pressing (HIP) as a post-processing treatment on the thermoelectric properties of p-type Bi_0.5Sb_1.5Te_3.0 compounds sintered via spark plasma sintering. The sample post-processed via HIP maintains its electronic transport properties despite the reduced microstructural texturing. Moreover, lattice thermal conductivity is significantly reduced owing to activated phonon scattering, which can be attributed to the nanoscale defects created during HIP, resulting in an ~18% increase in peak zT value, which reaches ~1.43 at 100℃. This study validates that HIP enhances the thermoelectric performance by controlling the thermal transport without having any detrimental effects on the electronic transport properties of thermoelectric materials.

• Proceedings of the Materials Research Society of Korea Conference
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• 1999.05a
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• pp.34-34
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• 1999