• Journal of the Microelectronics and Packaging Society
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• v.17 no.2
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• pp.41-47
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• 2010

The effect of PCB and BGA pad designs was investigated on the mechanical property of Pb-free solder joints. The mechanical property of solder joint was tested by three different test methods of drop impact tests, bending impact test, and high speed shear test. Two kinds of pad design such as NSMD (Non-Solder Mask Defined) and SMD (Solder Mask Defined) were applied with the OSP finished Pb-free solder (Sn-3.0Ag-0.5Cu, Sn-1.2Ag-0.5Cu). in the drop impact test and bending impact test, the characterized lifetime showed the same tendency, and SMD design showed better mechanical property of solder joint than NSMD regardless of test method, which was due to the different crack path. The fracture crack on SMD pad was propagated along the intermetallic compound (IMC) layer of solder joint, while the fracture crack on NSMD pad propagated through upper edge of land which shields pattern. In the high speed shear test, pad lift occurred on the solder joint of NSMD. SMD/SMD combination of pad design consequently illustrated the best mechanical property of BGA/PCB solder joint, followed by SMD/NSMD, NSMD/SMD, and NSMD/NSMD.

• Journal of Korean Society of Forest Science
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• v.99 no.6
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• pp.885-890
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• 2010

This study was conducted to confirm the application as ingredients of cosmetics through an examination of the function for anti-oxidant activity of the fraction isolated from Pyrus ussuriensis leaves. The dried leaf of Pyrus ussuriensis were extracted with acetone-$H_2O$ (6:4, v/v), concentrated and fractionated with the upper layer of acetone on a separatory funnel. Each fraction was freeze dried, then a portion of acetone soluble powder was chromatographed on a Sephadex LH-20 column using a series of aqueous methanol as eluents and also used the MIC-gel using a series of aqueous methanol as developing solvent. The isolated compounds were identified by silica-gel TLC. The concentration of total phenolic compound of Pyrus ussuriensis acetate soluble fraction was high, 914 mg/g. The results obtained from the analyses of the anti-oxidanat effects of Pyrus ussuriensis acetate fraction can be summarized as follows: In the result of DPPH scavenging radical activity, Pyrus ussuriensis acetate soluble fraction showed more than 80% at 100 ppm. SOD-like activity of one of Pyrus ussuriensis acetate soluble fractions was 77% at 1000 ppm. Xanthine oxidase inhibition of Pyrus ussuriensis acetate soluble fraction was 38% at 100 ppm. From these results, we confirmed that acetate fraction of Pyrus ussuriensis has a great potential as a natural ingredients with a natural antioxidant and antimicrobial source.

• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.88-99
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• 1992

For the development of semiconducting photoelectrode to be more stable and efficient in the process of photoelectrolysis of the water, pure titanium rods were oxidized by anodic oxidation, furance oxidation and flame oxidation and used as electrodes. The Indium islands were formed by electrodeposition of "In" thin film on $TiO_2$ and Ti by electrodeposition. Also $A1_2O_3$ and NiO islands were coated on Ti by the electron-beam evaporation technique. The maximum photoelectrochemical conversion efficiency(${\eta}$) was 0.98% for flame oxidized electrode($1200^{\circ}C$ for 2min in air). Anodically oxidized electrodes have photoelectrochemical conversion efficiency of 0.14%. Furnace oxidized electrode($800^{\circ}C$ for 10min in air) has 0.57% of photoelectrochemical efficiency and shows a band-gap energy of about 2.9eV. The $In_2O_3$ coated $TiO_2$ exhibits 0.8% of photoelectrochemical efficiency but much higher value of ${\eta}$ was obtained with the Increase of applied blas voltage. However, $Al_2O_3$ or NiO coated $TiO_2$ shows much low value of ${\eta}$. The efficiency was dependent on the presence of the metallic interstitial compound $TiO_{0+x}$(x<0.33) at the metal-semiconductor interface and the thickness of the suboxide layer and the external rutile scale.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.65-70
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• 2008

The mechanical shear strength of BGA(Ball Grid Array) solder joints under high impact loading was investigated. The Sn-37Pb solder balls with a diameter of $500{\mu}m$ were placed on the pads of FR-4 substrates with ENIG(Electroless Nickel Immersion Gold) surface treatment and reflowed. For the High Temperature Storage(HTS) test, the samples were aged a constant testing temperature of $120^{\circ}C$ for up to 250h. After the HTS test, high speed shear tests with various shear speed of 0.01, 0.1, 1, 3 m/s were conducted. $Ni_3Sn_4$ intermetallic compound(IMC) layer was observed at the solder/Ni-P interface and thickness of IMC was increased with aging process. The shear strength increased with increasing shear speed. The fracture surfaces of solder joints showed various fracture modes dependent on shear speed and aging time. Fracture mode was changed from ductile fracture to brittle fracture with increasing shear speed.

• Microbiology and Biotechnology Letters
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• v.34 no.3
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• pp.204-210
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• 2006

Ethyl (S)-4-chloro-3-hydroxybutyrate is a useful intermediate for the synthesis of Atorvastatin, a chiral drug to hypercholesterolemia. In this research, two 4-chloro-3-hydroxybutyro-nitrile-degrading strains were isolated from soil sample. They were identified as Rhodococcus erythropolis strains by 16S rRNA analysis. The nitrile-degrading enzyme(s) were suggested to be nitrile hydratase and amidase rather than nitrilase from the result of thin layer chromatography analysis. The corresponding genes were obtained by PCR cloning method. The predicted protein sequences had identities more than 96% with nitrile hydratase ${\alpha}-subunit$, nitrile hydratase ${\beta}-subunit$, and amidase of R. erythropolis. The 4-chloro-3-hydroxybutyronitrile-hydrolyzing activities in both strains were increased dramatically by ${\varepsilon}-caprolactam$ which was known as good inducer for nitrile hydratase. Both intact cells and cell-free extract could hydrolyze the nitrile compound. So, the intact cell and the enzymes could be used as potential biocatalyst for the production of 4-chloro-3-hydroxybutyric acid.

• Journal of the Korean Society of Radiology
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• v.14 no.2
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• pp.149-155
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• 2020

Most of radiation protection clothing is made of lead with excellent radiation shielding because it has excellent process ability and economic efficiency and has a high atomic number. However, lead is classified as a hazardous heavy metal, and there is a risk of lead poisoning. Recently, research to replace lead has been actively conducted. In this study, a research on a shielding sheet with improved physical properties while maintaining the radiation shielding ability equivalent to that of conventional materials by mixing two materials that are harmless to the human body, such as BaSO₄ and Bi₂O₃, and a silicone material binder Was performed. For comparison evaluation with the existing lead shielding sheet, the shielding rate was evaluated using a 40 degree shielding sheet having the highest porosity. As a result, it was analyzed that the shielding rate was superior to 9 % or more at the same thickness. In addition, as a result of studies to improve the physical properties of the shielding sheet, it was analyzed that the shielding sheet mixed with BaSO₄/nylon/Bi₂O₃ was the best.

• Korean Journal of Food Science and Technology
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• v.17 no.4
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• pp.248-252
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• 1985

Prunus tomentosa Thunberg seed was investigated to evaluate its possibility for use as food resources of fats and proteins. The seed contained 40.38% of crude fat and 26.59% of crude protein. The lipid fractions obtained by silicic acid column chromatography were mainly composed of 95.49% of neutral lipids, whereas compound lipids were only 4.51%. Among the neutral lipid components by thin-layer chromatography, triglycerides were 89.86%, sterols, monoglycerides, sterol esters, free fatty acids and diglycerides were 4.14%, 2.98%, 1.77%, 1.07%, and 0.18%, respectively. Oleic acid (65.06-66.05%) and linoleic acid (26.56-28.40%) were the main fatty acids in the total lipid, neutral lipid and triglyceride fractions. In the glycolipid and phospholipid fractions, predominant fatty acids were oleic acid (40.55-51.46%), linoleic acid (20.26-30.89%) and palmitic acid (17.64-21.43%). The extractability of salt soluble protein of seed was 60%, and recovery rate of main protein fraction separated by Sephadex G-200 was about 46.5%. The electrophoretic analysis showed 7 bands in seed protein.

• Korean Journal of Veterinary Research
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• v.24 no.2
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• pp.149-162
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• 1984

The research was conducted(1) to confirm the agent(s) responsible for the antimicrobial activity contained in the fermented tomato juice with L. acidophilus(2) to extract and purify the antimicrobial agent(s)(3) to find the biological, physical and chemical properties of the agent(s). The following results were obtained and summarized as followings; 1. The agent responsible for the inhibitory activity was confirmed by both well assay method using fermented tomato juice with L. acidophilus and turbidimetric technique using the cell-free filtrate or neutralized filtrate of tomato acidohilus culture and found exerted antimicrobial agent other than lactic acid. 2. The procedures of purification : The isolation and purification of antimicrobial agent from the lyophilized acidophilus tomato culture were carried out by (1) methanol extraction (2) acetone extraction, (3) Sephadex G-50 gel filtration (4) paper chromatography and (5) thin layer chromatography. 3. The biological, physical and chemical properties of antimicrobial agent: The biological, physical, chemical properties of the purified antimicrobial agent were: (1) The antimicrobial activity was strong against test organisms; Bacillus subtilis(ATCC 6633), Escheichia coli(ATCC 25922), Staphylococcus aureus(ATCC 167), Pseudomonas fluorescens(KFCC 32394), Proteus vulgaris and Shigella dysenteriae. (2) The pH value of the agent was 2.0 and the inhibitory activity was lost when it was neutralized at 7.0 of pH and the agent was heat stable at $121^{\circ}C$ for 60 minutes. (3) The ultraviolet light absorption spectra of methanol-acetone extract and TLC fraction exhibited a maximum absorption at 260nm and 224nm respectively. (4) The most purified agent from TLC plate increased about 130-fold in activity. (5) The agent isolated from TLC plate was free from $H_2O_2$ or lactic acid. 4. Bioautographic assy: By means of bioautography of the agent on silica gel of TLC plate a strong inhibitory activity against B. subtilis was demonstrated. 5. Mass spectrometry: The agent obtained from TLC plate was analyzed by mass spectrometry which show the parent peak at m/e 264 suggesting the molecular weight of the compound and molecular group such as [$C_2H{^+}_4$], [CO], [CH=NH], [$C_3{H^}4_7$], [$\begin{array}{rcl}O\\{\parallel}\\CH_3-C\\\end{array}$], [$C_6-H{^+}_{11}$], [$C_5H{^+}_{11}$], [$\begin{array}{rcl}O\\{\parallel}\\C_5H_7-C^+\\\end{array}$] were suggested.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1999.04a
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• pp.5-5
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• 1999

The Principal deficiency of the existing notion about the sintering-mixtures consists in the fact that almost no attention is focused on the Phenomenon of alloy formation during sintering, its connection with dimensional changes of powder bodies, and no correct ideas on the driving force for the sintering process in the stage of establishing chemical equilibrium in a system are available as well. Another disadvantage of the classical sintering theory is an erroneous conception on the dissolution mechanism of solid in liquid. The two-particle model widely used in the literature to describe the sintering phenomenon in solid state disregards the nature of the neighbouring surrounding particles, the presence of pores between them, and the rise of so called arch effect. In this presentation, new basic scientific principles of the driving forces for the sintering process of a two-component powder body, of a diffusion mechanism of the interaction between solid and liquid phases, of stresses and deformation arising in the diffusion zone have been developed. The major driving force for sintering the mixture from components capable of forming solid solutions and intermetallic compounds is attributed to the alloy formation rather than the reduction of the free surface area until the chemical equilibrium is achieved in a system. The lecture considers a multiparticle model of the mixed powder-body and the nature of its volume changes during solid-state and liquid-phase sintering. It explains the discovered S-and V-type concentration dependencies of the change in the compact volume during solid-state sintering. It is supposed in the literature that the dissolution of solid in liquid is realised due to the removal of atoms from the surface of the solid phase into the melt and then their diffusicn transfer from the solid-liquid interface into the bulk of liquid. It has been shown in our experimental studies that the mechanism of the interaction between two components, one of them being liquid, consist in diffusion of the solvent atoms from the liquid into the solid phase until the concentration of solid solutions or an intermetallic compound in the surface layer enables them to pass into the liquid by means of melting. The lecture discusses peculimities of liquid phase formation in systems with intermediate compounds and the role of the liquid phase in bringing about the exothermic effect. At the frist stage of liquid phase sintering the diffusion of atoms from the melt into the solid causes the powder body to grow. At the second stage the diminution of particles in size as a result of their dissolution in the liquid draws their centres closer to each other and makes the compact to shrink Analytical equations were derived to describe quantitatively the porosity and volume changes of compacts as a result of alloy formation during liquid phase sinteIing. Selection criteria for an additive, its concentration and the temperature regime of sintering to control the density the structure of sintered alloys are given.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.102-102
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• 2018

Electronic industry had required the finer size and the higher performance of the device. Therefore, 3-D die stacking technology such as TSV (through silicon via) and micro-bump had been used. Moreover, by the development of the 3-D die stacking technology, 3-D structure such as chip to chip (c2c) and chip to wafer (c2w) had become practicable. These technologies led to the appearance of HBM (high bandwidth memory). HBM was type of the memory, which is composed of several stacked layers of the memory chips. Each memory chips were connected by TSV and micro-bump. Thus, HBM had lower RC delay and higher performance of data processing than the conventional memory. Moreover, due to the development of the IT industry such as, AI (artificial intelligence), IOT (internet of things), and VR (virtual reality), the lower pitch size and the higher density were required to micro-electronics. Particularly, to obtain the fine pitch, some of the method such as copper pillar, nickel diffusion barrier, and tin-silver or tin-silver-copper based bump had been utillized. TCB (thermal compression bonding) and reflow process (thermal aging) were conventional method to bond between tin-silver or tin-silver-copper caps in the temperature range of 200 to 300 degrees. However, because of tin overflow which caused by higher operating temperature than melting point of Tin ($232^{\circ}C$), there would be the danger of bump bridge failure in fine-pitch bonding. Furthermore, regulating the phase of IMC (intermetallic compound) which was located between nickel diffusion barrier and bump, had a lot of problems. For example, an excess of kirkendall void which provides site of brittle fracture occurs at IMC layer after reflow process. The essential solution to reduce the difficulty of bump bonding process is copper to copper direct bonding below $300^{\circ}C$. In this study, in order to improve the problem of bump bonding process, copper to copper direct bonding was performed below $300^{\circ}C$. The driving force of bonding was the self-annealing properties of electrodeposited Cu with high defect density. The self-annealing property originated in high defect density and non-equilibrium grain boundaries at the triple junction. The electrodeposited Cu at high current density and low bath temperature was fabricated by electroplating on copper deposited silicon wafer. The copper-copper bonding experiments was conducted using thermal pressing machine. The condition of investigation such as thermal parameter and pressure parameter were varied to acquire proper bonded specimens. The bonded interface was characterized by SEM (scanning electron microscope) and OM (optical microscope). The density of grain boundary and defects were examined by TEM (transmission electron microscopy).