• Journal of the Korean Electrochemical Society
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• v.22 no.1
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• pp.36-42
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• 2019

A macroporous Sn thick film as a high capacity negative electrode for a lithium ion secondary battery was prepared by using a chemical etching method using nitric acid for a Sn film having a thickness of $52{\mu}m$. The porous Sn thick film greatly reduced the over-voltage for the alloying reaction with lithium by the increased reaction area. At the same time. The porous structure of active Sn film plays a part in the buffer and reduces the damage by the volume change during cycles. Since the porous Sn thick film electrode does not require the use of the binder and the conductive carbon black, it has substantially larger energy density. As the concentration of nitric acid in etching solution increased, the degree of the etching increased. The etching of the Sn film effectively proceeded with nitric acid of 3 M concentration or more. The porous Sn film could not be recovered because the most of Sn was eluted within 60 seconds by the rapid etching rate in the 5 M nitric acid. In the case of etching with 4 M nitric acid for 60 seconds, the appropriate porous Sn film was formed with 48.9% of weight loss and 40.3% of thickness change during chemical acid etching process. As the degree of etching of Sn film increased, the electrochemical activity and the reversible capacity for the lithium storage of the Sn film electrode were increased. The highest reversible specific capacity of 650 mAh/g was achieved at the etching condition with 4 M nitric acid. The porous Sn film electrode showed better cycle performance than the conventional electrode using a Sn powder.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.338-338
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• 2013

Monolithic three-dimensional integrated circuits (3D-ICs) 구현 시 bonding 과정에서 발생되는 aluminum (Al) 이나 copper (Cu) 등의 interconnect metal의 확산, 열적 스트레스, 결함의 발생, 도펀트 재분포와 같은 문제들을 피하기 위해서는 저온 공정이 필수적이다. 지금까지는 polymer 기반의 bonding이나 Cu/Cu와 같은 metal 기반의 bonding 등과 같은 저온 bonding 방법이 연구되어 왔다. 그러나 이와 같은 bonding 공정들은 공정 시 void와 같은 문제가 발생하거나 공정을 위한 특수한 장비가 필수적이다. 반면, 두 물질의 합금을 이용해 녹는점을 낮추는 eutectic bonding 공정은 저온에서 공정이 가능할 뿐만 아니라 void의 발생 없이 강한 bonding 강도를 얻을 수 있다. Aluminum-germanium (Al-Ge) 및 aluminum-indium (Al-In) 등의 조합이 eutectic bonding에 이용되어 각각 $424^{\circ}C$ 및 $454^{\circ}C$의 저온 공정을 성취하였으나 여전히 $400^{\circ}C$이상의 eutectic 온도로 인해 3D-ICs의 구현 시에는 적용이 불가능하다. 이러한 metal 조합들에 비해 indium (In)과 tin (Sn)은 각각 $156^{\circ}C$ 및 $232^{\circ}C$로 굉장히 낮은 녹는점을 가지고 있기 때문에 In-Sn 조합은 약 $120^{\circ}C$ 정도의 상당히 낮은eutectic 온도를 갖는다. 따라서 본 연구팀은 In-Sn 조합을 이용하여 $200^{\circ}C$ 이하에서monolithic 3D-IC 구현 시 사용될 eutectic bonding 공정을 개발하였다. 100 nm SiO2가 증착된 Si wafer 위에 50 nm Ti 및 410 nm In을 증착하고, 다른Si wafer 위에 50 nm Ti 및 500 nm Sn을 증착하였다. Ti는 adhesion 향상 및 diffusion barrier 역할을 위해 증착되었다. In과 Sn의 두께는 binary phase diagram을 통해 In-Sn의 eutectic 온도인 $120^{\circ}C$ 지점의 조성 비율인 48 at% Sn과 52 at% In에 해당되는 410 nm (In) 그리고 500 nm (Sn)로 결정되었다. Bonding은 Tbon-100 장비를 이용하여 $140^{\circ}C$, $170^{\circ}C$ 그리고 $200^{\circ}C$에서 2,000 N의 압력으로 진행되었으며 각각의 샘플들은 scanning electron microscope (SEM)을 통해 확인된 후, 접합 강도 테스트를 진행하였다. 추가로 bonding 층의 In 및 Sn 분포를 확인하기 위하여 Si wafer 위에 Ti/In/Sn/Ti를 차례로 증착시킨 뒤 bonding 조건과 같은 온도에서 열처리하고secondary ion mass spectrometry (SIMS) profile 분석을 시행하였다. 결론적으로 본 연구를 통하여 충분히 높은 접합 강도를 갖는 In-Sn eutectic bonding 공정을 $140^{\circ}C$의 낮은 공정온도에서 성공적으로 개발하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.4
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• pp.589-598
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• 1997

The effects of PT/PZ ratio variations in a modified PZT system on crystal structure and electrical properties were studied. $0.05Pb(Sn_{0.5}Sb_{0.5})O_3＋xPbTiO_3＋yPbZrO_3$＋0.4Wt% $MnO_2$(＝0.55PSS＋0.11PT＋0.84PZ＋0.4wt%$MnO_2$ ; x＋y=0.95) systems with variations of PT/PZ from 0.50/0.45 to 0.l1/0.84 were sintered at $1250^{\circ}C$ for 2 hr, and then sintering density, crystal structure, dielctric, piezoelectric, pyroelectic and voltage responsity to infrared were investigated. Sintering density was increased from 7.52g/$\textrm {cm}^3$ to 7.82g/$\textrm {cm}^3$ with increasing PZ content. Dielectric constants at 1 KHz were decreased from 1147 to 193 with variation of PT/PZ from 0.50/0.45 to 0.l1/0.84 after poling of $4 KV_{DC}$/mm at $140^{\circ}C$ for 20 minutes. All Dielectric losses at 1 KHz were less than 1 % in all specimens. $K_{p}$ was increased near to 1 of PT/PZ, and maximun value of 48.2 % was .at 0.45/0.50. Pyroelectric coefficient of PT/PZ with 0.l1/0.84 was maximun value, 0.0541 C/$\m^2$K, and voltage responsity to infrared was 1.5 V.

• Journal of Surface Science and Engineering
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• v.36 no.5
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• pp.373-378
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• 2003

With increasing environmental concerns, application of lead-free solder and fluxless soldering process have been taken attention from the electronic packaging industry. Plasma treatment is one of the soldering methods for the fluxless soldering, and it can prevent environmental pollution cased by flux. On this study fluxless soldering process under $Ar-H_2$plasma using lead free solders such as Sn-3.5 wt%Ag, Sn-3.5 wt%Ag-0.7 wt%Cu and Sn-37%Pb for a reference was investigated. As the plasma reflow has higher soldering temperature than normal air reflow, the effects of UBM(Under Bump Metallization) thickness on the interfacial reaction and bonding strength can be critical. Experimental results showed in case of the thin UBM, Au(20 nm)/Cu(0.3 $\mu\textrm{m}$)/Ni(0.4 $\mu\textrm{m}$)/Al(0.4 $\mu\textrm{m}$), shear strength of the soldered joint was relatively low as 19-27㎫, and it's caused by the crack observed along the bonded interface. The crack was believed to be produced by the exhaustion of the thin UBM-layer due to the excessive reaction with solder under plasma. However, in case of thick UBM, Au(20 nm)/Cu(4 $\mu\textrm{m}$)/Ni(4 $\mu\textrm{m}$)/Al(0.4 $\mu\textrm{m}$), the bonded interface was sound without any crack and shear strength gives 32∼42㎫. Thus, by increasing UBM thickness in this study the shear strength can be improved to 50∼70%. Fluxed reflow soldering under hot air was also carried out for a reference, and the shear strength was 48∼52㎫. Consequently the fluxless soldering with plasma showed around 65∼80% as those of fluxed air reflow, and the possibility of the $Ar-H_2$ plasma reflow was evaluated.

• Journal of the Korean Chemical Society
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• v.32 no.1
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• pp.48-52
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• 1988

Kinetics of the reaction of 2-phenethyl p-bromobenzenesulfonate with substituted pyridines in acetonitrile were investigated by an electric conductivity method at 1-2000 bars and $45{\sim}55{\circ}C$. The rates of these reactions were increased with raising temperatures, pressures and by changing electron-donating substitutents in pyridine. When raising pressure the Hammett reaction parameter $I{\rho}I$ and Bronsted ${\beta}$ values were increased, and isokinetic temperature observed from isokinetic relations hip between ${\Delta}H^{\neq}$ and TEX>${\Delta}S^{\neq}$ was decreased. These results indicate that the $S_N2$ characters were increased with raising pressure.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.10
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• pp.1438-1446
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• 2011

Palmitoyl-oleoyl-oleoyl (POO) and palmitoyl-oleoyl-palmitoyl triacylglycerol rich fraction (PSL) was obtained from the acetone fractionation of palm stearin. The fatty acid composition (total and positional), tri-acylglycerol species, and solid fat index (SFI) were compared among the blends of natural vegetable fats (sal fat, illipe fat, kokum fat, shea stearin fat, and shea butter) and PSL with different ratios (50:50, 60:40, 65:35, 70:30). In total fatty acid composition of PSL, palmitic, oleic, and linoleic acids were the major fatty acids, whereas in natural vegetable fats stearic and palmitic acids were the major fatty acids. Moreover, oleic acid was a major fatty acid at sn-2 position in sal fat, illipe fat, and kokum fat. The TAG species was analyzed by reversed-phase HPLC, from which the PN value ranged from 46 to 54. When natural vegetable fats and PSL were blended with different ratios, decreasing the amount of PSL resulted in increasing SFI in most cases. Among blends, the SFI of sal fat and PSL were most similar to commercial cocoa butter equivalent (CBE).

• The Journal of Korean Academy of Prosthodontics
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• v.23 no.1
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• pp.39-59
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• 1985

The purpose of this study was to investigate how gap distances of 0.13mm, 0.15mm, 0.20mm, and 0.30mm affects solder joint strength from gold alloys and nickel-chromium base alloys and to examine the composition of solder gold, the solder joint of gold alloys and nickel-chromium base alloys. The tensile test specimens were prepared in the split stainless steel mold with a half dumbbell shape 2.5mm in diameter and l2mm in length. 6 pairs of specimens of each gap distance group of gold alloys and nickel-chromium base alloys were made and 48 pairs of all specimens were soldered with solder gold of 666 fineness. All soldered specimens were machined to a uniform diameter and then a tensile load was applied at a cross-head speed of 0.10mm/min using Instron Universal Testing Machine, Model 1115. The fractured specimens at solder gold of solder joint fracture with each gap distance of 0.13mm, 0.15mm, 0.20mm, and 0.30mm were examined under the Scanning Electron Microscope, JSM-35c and the composition of solder gold, the solder joint of gold alloys and nickel-chromium base alloys was analyzed by Electron Probe Micro Analyzer. The results of this study were obtained as follows: 1. In case of soldering of gold alloys, the tensile strength between gold alloys showed $37.33{\pm}2.52kg/mm^2$ at 0.13, $39.14{\pm}3.35kg/mm^2$ at 0.15mm, $43.76{\pm}2.97kg/mm^2$ at 0.20mm, and $49.18{\pm}4.60kg/mm^2$ at 0.30mm. There was statistically significant difference at each gap distance, and so the greater increase of gap distance showed the greater tensile strength. 2. In case of soldering of nickel-chromium base alloys, the tensile strength between nickel-chromium base alloys showed $34.84{\pm}4.26kg/mm^2$ at 0.13mm, $37.25{\pm}2.49kg/mm^2$ at 0.15mm, $42.91{\pm}4.32kg/mm^2$ at 0.20mm, and $46.93{\pm}4.21kg/mm^2$ at 0.30mm. There was not statistically significant difference only between 0.13mm and 0.15mm and bet ween 0.20 mm and 0.30mm, but generally the greater increase of gap distance showed the greater tensile strength. 3. The greater increase of gap distance shoed less porosities in solder gold at solder joint fracture. 4. In solder gold Au, Cu, Ag, Zn, and Sn were composed and Au and Cu were mostly distributed uniformly. 5. In solder joints of solder gold and gold alloys Au, Cu, Ag, Zn, and Sn were composed in solder gold and Au, Cu, Ag, Pt, and Pd were composed in gold alloys. Au and Cu of solder gold and gold alloys were mostly distributed uniformly and the diffusion of other elements except Pt and Pd around the solder joint was not almost found. In solder joints of solder gold and nickel-chromium base alloys Au, Cu, Ag, Zn, and Sn were composed in solder gold and Ni, Cr, and Al were composed in nickel-chromium base alloys. Au and Cu of solder gold and Ni and Cr of nickel-chromium base alloys were mostly distributed uniformly and the diffusion of other elements except Cr around the solder joint was not almost found.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.37 no.6
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• pp.457-463
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• 2011

Introduction: This study evaluate the soft tissue changes to the upper lip and nose after Le Fort I maxillary posterosuperior rotational movement. Materials and Methods: Twenty Skeletal class III patients, who had undergone bimaxillary surgery with a maxillary Le Fort I osteotomy and bilateral sagittal split ramus osteotomy, were included in the study. The surgical plan for maxilla was posterosuperior rotational movement, with the rotation center in the anterior nasal spine (ANS) of maxilla. Soft and hard tissue changes were measured by evaluating the lateral cephalograms obtained prior to surgery and at least 6 months after surgery. For cephalometric analysis, four hard tissue landmarks ANS, posterior nasal spine [PNS], A point, U1 tip), and five soft tissue landmarks (pronasale [Pn], subnasale [Sn], A' Point, upper lip [UL], stomion superius [StmS]) were marked. A paired t test, Pearson's correlation analysis and linear regression analysis were used to evaluate the soft and hard tissue changes and assess the correlation. A P value <0.05 was considered significant. Results: The U1 tip moved $2.52{\pm}1.54$ mm posteriorly in the horizontal plane (P<0.05). Among the soft tissue landmarks, Pn moved $0.97{\pm}1.1$ mm downward (P<0.05), UL moved $1.98{\pm}1.58$ mm posteriorly (P<0.05) and $1.18{\pm}1.85$ mm inferiorly (P<0.05), and StmS moved $1.68{\pm}1.48$ mm posteriorly (P<0.05) and $1.06{\pm}1.29$ mm inferiorly (P<0.05). The ratios of horizontal soft tissue movement to the hard tissue were 1:0.47 for the A point and A' point, and 1:0.74 for the U1 tip and UL. Vertically, the movement ratio between the A point and A' point was 1:0.38, between U1 tip and UL was 1:0.83, and between U1 tip and StmS was 1:0.79. Conclusion: Posterosuperior rotational movement of the maxilla in Le Fort I osteotomy results in posterior and inferior movement of UL. In addition, nasolabial angle was increased. Nasal tip and base of the nose showed a tendency to move downward and showed significant horizontal movement. The soft tissue changes in the upper lip and nasal area are believed to be induced by posterior movement at the UL area.

• Journal of Food Hygiene and Safety
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• v.3 no.1
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• pp.7-18
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• 1988

In 1987, the level of heavy metals were determined ina total of 200 samples of 9 species of shellfish of Korea. The samples were collected at the fish. markets by 10 Public Institute of Health. The samples were whelk (Buccinum striatiBBimum), oyster (Crassostrea gigas), ark shell(Tegillarca granesa), shartnecked clam (Venerupis semidecussta), hard clam (Meretrix lusoria), top shell (Turbo cornutus), abalone (Haliotis gigantea), ark shell (Scapharea broughtonii), sea-mussel (Mytilus conuscus gould), respectively. The levels of total mercury, lead, cadmium, arsenic, copper, zinc and manganese were determined. The total mercury levels were determined by mercury analyzer using the combustion gold amalgamation method. The arsenic level were determined by spectrophotometry using colorimetric sil ver diethyldithiocarbamate method after dry ash dige8tion of the samples with magnesium oxide and magnesium nitrate. The levels of other metals were determined by inductively coupled pluma spectrophotometry after wet digestion of the samples with nitric acid and su1furic acid. The results were summerized as follows; 1. The overallranges and mean(ppm) were; Hg, ND-O.221 (0.036); Pb, 0.05-1.51 (0.37); Cd, 0.02-1.86 (0.61); As, 0.5-3.97 (1.22); Cu, 0.14-54.16 (4.93); Zn, 7.40-207.17 (30.09); Mn, 0.13-s.72 (3.40). 2. The levels of all 6 metals were found to be below the maximum permissible Iimits set by the Japan lor mercury, the Netherland for lead the Hong Kong for cadmium. The Finland for Arsenic no statutory Iimits for Zn and Mn in shellfish in any countries. 3. The results show that all the 9 species of shellfish studied, none have accumulated levels dangerous enough to pose a health problem.roblem.