• 마이크로전자및패키징학회지
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• 제24권1호
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• pp.27-34
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• 2017

Recently, a demand in sustainable green technologies is requiring the lead free bonding for high power module packaging due to the environmental pollution. The Transient-liquid phase (TLP) bonding can be a good alternative to a high Pb-bearing soldering. Basically, TLP bonding is known as the combination of soldering and diffusion bonding. Since the low melting temperature material is fully consumed after TLP bonding, the remelting temperature of joint layer becomes higher than the operating temperature of the power module. Also, TLP bonding is cost-effective process than metal nanopaste bonding such as Ag. In this paper, various TLP bonding techniques for power semiconductor were described.

• 환경위생공학
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• 제13권1호
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• pp.174-184
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• 1998

Biosorption characteristics were investigated to discuss the use of agar entrapped Spirulina to remove of heavy metal ions from polluted waters. Agar immobilized algae were used as bioadsorbent in continuous reactor for heavy metal ions removal. The process solution contains Pb, Cu, and Cd as single ion and binary ions. In the adsorption of single heavy metal ions by agar immobilized Spirulina, the adsorption reached within 1hr and observed diffusion limitation differed from the free algal cell adsorption. The optimum pH for the adsorption of heavy metals was 4.5 but the influence of pH decreased less than that of free algal cell. Also, the adsorption characteristics of single heavy metal ions with agar immobilized Spirulina fitted the BET isotherm. Both of experiments of free algal cell and agar immobilized algae showed higher removal efficiency in the single ion solutions than binary ions solutions. The experimental results in the packed column with agar immobilized algae were over 90% of removal efficiency for the Pb, Cu, and Cd in single ion solutions.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.41-43
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• 2004

Dielectric thin films of $(Pb_{0.72}La_{0.28})Ti_{0.93}O_3$ were deposited on $Pt(111)/Ti/SiO_2/Si$ substrates in situ by pulsed laser deposition(PLD) and annealed with different gases which are forming gas and oxygen gas, respectively. The diffusion of hydrogen into the ferroelectric film was caused by annealing process and resulted in the destruction of polarization. The dielectric properties of forming gas annealed PLT thin films, which are dielectric constant, ferroelectric characteristic, and leakage current characteristics, were degraded

• 마이크로전자및패키징학회지
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• 제5권1호
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• pp.7-18
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• 1998

In the flip chip interconnection on organic substrates using eutectic Pb/Sn solder bumps highly reliable Under Bump Metallurgy (UBM) is required to maintain adhesion and solder wettability. Various UBM systems such as 1$\mu$m Al/0.2$\mu$m Pd/1$\mu$m Cu, laid under eutectic Pb/Sn solder were investigated with regard to their interfacial reactions and adhesion proper-ties. The effects of numbers of solder reflow and aging time on the growth of intermetallic compounds (IMCs) and on the solder ball shear strength were investigated. Good ball shear strength was obtained with 1$\mu$m Al/0.2$\mu$m Ti/5$\mu$m Cu and 1$\mu$m Al/0.2$\mu$m ni/1$\mu$m Cu even after 4 solder reflows or 7 day aging at 15$0^{\circ}C$. In contrast 1$\mu$m Al/0.2$\mu$m Ti/1$\mu$m Cu and 1$\mu$mAl/0.2$\mu$m Pd/1$\mu$m 쳐 show poor ball shear strength. The decrease of the shear strength was mainly due to the direct contact between solder and nonwettable metal such as Ti and Al resulting in a delamination. In this case thin 1$\mu$m Cu and 0.2$\mu$m Pd diffusion barrier layer were completely consumed by Cu-Sn and pd-Sn reaction.

• 공업화학
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• 제10권3호
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• pp.331-335
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• 1999

진이급속 산화물은 전기화학적 산소 발생/환원에 대한 bifunctional 촉매효과가 있어 금속-공기 이차전지와 같은 에너지 저장기술 개발에 연구대상이 되어왔다. Amorphous citrate precursor법을 이용하여 perovskite 구조를 갖는 La-Ca-Co 산화물과 pyrochlore 구조를 갖는 Pb-Ru 산화물을 제조하고, 이후 열처리법으로 표면적이 큰 전이금속 산화물 촉매분말을 제조하였다. PTFE 결합 기체확산형 전극의 충방전 실험을 통하여 전기화학적 산소발생/환원에 대한 좋은 촉매능을 가짐을 확인하였고, ${\pm}25mA/cm^2$의 전류밀도를 가하고 공기를 공급하면서 충방전 실험한 결과 100시간 이내에서 두촉매분말 모두 안정하였다. ACP법으로 제조한 perovskite 구조의 La0.6Ca0.4CoO3과 pyrochlore 구조의 Pb2Ru2O6가 이차전지용 공기전극 재료로 사용할 수 있음을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제16권9호
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• pp.819-823
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• 1995

Thin films of two kinds of Prussian Blue (PB)-modified, using iron(Ⅲ) complex instead of conventional FeCl3, were prepared on a gold substrate and these films were able to be electrochemically reduced in potassium nitrate solution. In case of PB-modified films prepared from Fe(Ⅲ)-ethylenediamine-N,N'-diacetic acid (FeEN3+)/K3Fe(CN)6 solution, the mid-peak potential was 0.156 V in 0.1 M KNO3 and it was found that potassium ion migrates into or out of the film during the electrolysis. These films were shown to be electrochromic. These films exhibited smaller peak separation than those formed from Fe(Ⅲ)-tartaric acid (FeTA3+)/K3Fe(CN)6 system. The diffusion coefficient of Fe(CN)63-/4- redox couple, evaluated using the fabricated Au rotating disc electrode(rde) previously reported, was in good agreement with the existing data. Two experimental procedures, including the voltammetry at relatively low scan rates and the rde study, have been used in order to characterize the electrode kinetics. The electrode kinetics of some redox couples (FeEN2+-FeEN3+ and FeTA2+-FeTA3+) on both PB-modified thin films and bare Au electrode were studied using a Au rde. In all cases the rate constants of electron transfer obtained with the PB-modified film electrodes were only slightly less than those obtained for the same reaction on bare Au disc electrodes. The conductivities, as determined from the slopes of the i-V curves for a ca. 1 mm sample for dried PB-modified potassium-rich and deficient bulk samples pressed between graphite electrodes, were 6.21 × 10-7 and 2.03 × 10-7(Ω·cm)-1, respectively.

• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3391-3398
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• 2013

The carboxylated multiwall carbon nanotubes (MWCNT-COOH) and functionalized with isatin derivative (MWCNT-isatin) have been used as efficient adsorbents for the removal of lead (Pb) from aqueous solutions. The influence of variables including pH, concentration of the lead, amount of adsorbents and contact time was investigated by the batch method. The adsorption of the lead ions from aqueous solution by modified MWCNTs was studied kinetically using different kinetic models. The kinetic data were fitted with pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. The sorption process with MWCNT-COOH and MWCNT-isatin was well described by pseudo-second-order and pseudo-first-order kinetics, respectively which it was agreed well with the experimental data. Also, it involved the particle-diffusion mechanism. The values of regression coefficient of various adsorption isotherm models like Langmuir, Freundlich and Tempkin to obtain the characteristic parameters of each model have been carried out. The Langmuir isotherm was found to best represent the measured sorption data for both adsorbent.

• 한국결정성장학회지
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• 제4권2호
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• pp.199-209
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• 1994

Titanium tetra iso-propoxide와 Lead acetate trihydrate를 출발물질로 사용하여 제조한 졸을 현미경용 soda-lime-silica 슬라이드 유리, Si-Wafer 및 Sapphire 기판 위에 Dip-coating법으로 박막을 제조하였으며, 안정한 졸을 얻기 위하여 Acetylacetone을 첨가하였다. 졸의 점도, 조성등의 영향을 조사하였고, 조성변화, 막의 두께 변화, 열처리 온도에 따른 가시영역에서의 투과율과 굴절율 및 IR Spectra를 측정하였으며, $PbTiO_3$ 박막의 결정 생성 유무를 XPD로 검토하였다. 또하 EDX로 슬라이드 유리에서 박막으로의 확산 유무를 조사하였다. 제조된 졸은 20일동안 침전없는 안정한 상태를 유지하였다. 가시영역에서의 투과율은 열처리온도와 막의 두께가 증가함에 따라 감소하였고, flat한 투과특성을 나타내었다. 슬라이드 유리 위에 코팅한 $PbTiO_3$ 박막은 $600^{\circ}C$에서 열처리한 경우 Pyrochlore형이 나타났고, Si-Wafer와 Sapphire 기판 위에 코팅할 경우에는 $600^{\circ}C$에서 Pyrochlore형이 나타나기 시작하였으며, 열처리 온도가 높아짐에 따라 $800^{\circ}C$에서 $PbTi_3O_7$상이 나타났다.

• 한국재료학회지
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• 제11권4호
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• pp.305-311
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• 2001

PDP용 투명유전체 재료로 사용되는 $PbO-B_2O_3-SiO_2-Al_2O_3$계의 소성과정 중에서 투명전극 (ITO)과의 반응성 및 광학적, 열적, 전기적 특성을 조사하였다. 본 연구에서 유전체막.두께는 12$\mu\textrm{m}$으로, 온도는 550-58$0^{\circ}C$에서 소성한 후 여러 물성을 평가하였다 그 결과로, 유전체와 투명전극(ITO)의 반용에서, In 이온이 유전체층으로 확산이동하였으며, Sn 확산은 거의 발생하지 않았다. 선팽창계수, 유전상수, 유리전이온도,광 투과율은 유전체 조성의 PbO 양에 큰 영향을 받았다. PbO양 증가는 선팽창계수와 유전상수를 증가시킨 반면, 유리전이온도와 광 투과율온 저하시켰다. $Al_2O_3/B_2O_3$ 비가 증가함에 따라서는 선팽창계수는 감소, 유전상수는 증가, 광 투과율은 감소하였으며, 유리 전이점 변화는 거의 나타나지 않았다.

• 한국세라믹학회지
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• 제29권1호
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• pp.65-73
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• 1992

The effect of grain size on the time-dependent piezoelectrice degradation of a poled PZT of MPB composition Pb0.988Sr0.012 (Zr0.52Ti0.48)O3 with 2.4 mol% of Nb2O5 was studied, and the degradation mechanism was discussed. Changes in the internal bias field and the internal stress both responsible for the time-dependent degradation of poled PZT were examined by the polarization reveral technique, XRD and Vickers indentation, respectively. The piezoelectric degradation increased with increasing time and grain size, and the internal bias field due to space charge diffusion decreased with increasing grain size of poled PZT. The internal bias field, however, was almost insensitive to the degradation time regardless of the grain size. On the other hand, both the x-ray diffraction peak intensity ratio of (002) to (200) and the fracture behavior including the crack propagation support that the ferroelectric domain rearrangement of larger grain size showed rapid relaxation of the internal stress compared with smaller one, which is thought the origin of the larger piezoelectric degradation in the former. In conclusion, the contribution of space charge diffusion on the piezoelectric degradation of PZT is strongly dependent on both the grain size and the composition. Thus, the relaxation of internal stress due to the ferroelectric domain rearrangement as well as the amount and time-dependence of the internal bias field due to space charge diffusion should be considered simultaneously in the degradation mechanism of PZT.