• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.12
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• pp.949-954
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• 2011

In this study, the characteristics and error ranges of the mechanical bonding strength were analyzed according to before and after thermal shock test for various chips of automotive application component using Sn-3.0Ag-0.5Cu solder. In the after thermal shock test, the mechanical bonding strengths tend to decrease, meanwhile decreasing rates of mechanical strengths were less then 12% at specimen's bonding area below 3.5$mm^2$, and were from 17 to 21% at specimen's bonding area above 12 $mm^2$. On the other hand, Specimen's mean deviation rates were about 5% at specimen's bonding area more than 12 $mm^2$. Inversely, at specimen's bonding area is less then 3.5 $mm^2$, mean deviation rates were increased to about 8%. It means that the smaller device size is, the larger mean deviation rate. In addition, error ranges and deviation rates of the mechanical bonding strengths may differ slightly depending on their bonding area. Furthermore, process conditions as well as method of mechanical reliability evaluation should be established to reduce the error ranges of bonding strength.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.2
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• pp.1-8
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• 2018

In the soldering industry, a variety of lead-free solders have been developed as a part of restricting lead in electronic packaging. Sn-Ag-Cu (SAC) lead-free solder is regarded as one of the most superior candidates, owing to its low melting point and high solderability as well as the mechanical property. On the other hand, the mechanical property of SAC solder is directly influenced by intermetallic compounds (IMCs) in the solder joint. Although IMCs in SAC solder play an important role in bonding solder joints and impart strength to the surrounding solder matrix, a large amount of IMCs may cause poor strength, due to their brittle nature. In other words, the mechanical properties of SAC solder are of some concern because of the formation of large and brittle IMCs. As the IMCs grow, they may cause poor device performance, resulting in the failure of the electronic device. Therefore, new solder technologies which can control the IMC growth are necessary to address these issues satisfactorily. There are an advanced nanotechnology for microstructural refinement that lead to improve mechanical properties of solder alloys with nanoparticle additions, which are defined as nano-reinforced solders. These nano-reinforced solders increase the mechanical strength of the solder due to the dispersion hardening as well as solderability of the solder. This paper introduces the nano-reinforced solders, including its principles, types, and various properties.

• Journal of the Korean Society of Clothing and Textiles
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• v.37 no.7
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• pp.874-881
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• 2013

Dansam (Salvia miltiorrhiza Bunge) is a perennial plant that belongs to the Labiatae family and is characterized by red pigment found in the epidermis of its roots. Research on the dyeability of Dansam extract was performed with repeated trials under various conditions such as temperature, time, and mordant treatment. Silk fabrics were dyed with Dansam extract and mordanted with various agents such as Al, Fe, Cu, and Sn to evaluate the dyeability and functionality of Dansam extract; subsequently, the K/S value and the change of surface color were analyzed using a colorimeter. In addition, the dyeability of dyed fabrics (such as color fastness to washing, dry cleaning fastness, rubbing fastness and light fastness) and functionality (such as antibacterial activity and deodorization) were analyzed. The surface colors of all dyed fabrics were recorded and the results showed the presence of mostly YR series of colors; in addition, a GY color series appeared in the Fe pre-mordants of the silk fabric. The highest K/S values were recorded in Fe post-mordants. The washing fastness were Level 3 and Level 4; in addition, the dry-cleaning fastness showed excellent results at Level 4 and Level 5. The rubbing fastness was satisfactory at Level 3 and Level 4 and the light fastness was satisfactory at Level 4. The results of the measurements (that pertained to the antibacterial activity of fabrics dyed with Dansam extract) showed a 99.9% bacteria reduction rate of Staphylococcus aureus and Klebsiella pneumoniae. In regards to deodorization ability, dyed fabrics were found to have higher deodorization rates than those not dyed. The dyed fabric demonstrated exceptional deodorization qualities.

• Journal of Korean Society for Atmospheric Environment
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• v.29 no.3
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• pp.317-324
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• 2013

This research assessed the surface properties of modified activated carbons with three different acids and five different metals for ammonia gas removal. Raw bituminous coal-based activated carbon ($4{\times}8$ mesh) had low adsorption capacity of 0.72 mg $NH_3/g$ based on the analysis in the column adsorption experiment. Adsorption capacities of carbons modified with $CH_3COOH$, $H_3PO_4$, and $H_2SO_4$ increased up to 3.34, 21.00, and 35.21 mg $NH_3/g$, respectively. Those of carbons with Cu, Zn, Zr, Fe, and Sn were 9.63, 9.13, 7.09, 25.12 and 15.03 mg $NH_3/g$. Ammonia adsorption was enhanced by the presence of surface oxygen groups on carbon materials, which influenced pH of carbon surface. BET surface area of raw carbon was analyzed to be $1087m^2/g$, but it decreased by carbon surface modification. Fe-impregnated carbon showed $503.02m^2/g$ of surface area. These observations were mostly caused by chemical adsorption.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.4
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• pp.237-240
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• 2016

The improvement of irradiation intensity and irradiation uniformity is essential for large area and high power UVA light source application. In this study, large number of chips bonded by micro soldering technique were driven by low current, and current limiting diodes were configured to supply constant current to parallel circuits consisting of large number of series strings. The dimension of light source module circuit board was $350{\times}90mm^2$ and 16,650 numbers of 385 nm flip chip LEDs were used with a configuration of 90 parallel and 185 series strings. The space between LEDs in parallel and series strings were maintained at 1.9 mm and 1.0 mm distance, respectively. The size of the flip chip was $750{\times}750{\mu}m^2$ were used with contact pads of $260{\times}669{\mu}m^2$ size, and SAC (96.5 Sn/3.0 Ag/0.5 Cu) solder was used for flip chip bonding. The fabricated light source module with 7.5 m A supply current showed temperature rise of $66^{\circ}C$, whereas irradiation was measured to be $300mW/cm^2$. Inaddition, 0.23% variation of the constant current in each series string was demonstrated.

• Progress in Medical Physics
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• v.27 no.3
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• pp.125-130
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• 2016

Dual energy computed tomography (DECT) is used to classify two materials and quantify the mass density of each material in the human body. An energy modulation filter based DECT could acquire two images, which are generated by the low- and high-energy photon spectra, in one scan, with one tube and detector. In the case of DECT using the energy modulation filter, the filter should perform the optimization process for the type of materials and thicknesses for generating two photon spectra. In this study, Geant4 Monte-Carlo simulation toolkit was used to execute the optimization process for determining the property of the energy modulation filter. In the process, various materials used for the energy modulation filter are copper (Cu, $8.96g/cm^3$), niobium (Nb, $8.57g/cm^3$), stannum (Sn, $7.31g/cm^3$), gold (Au, $19.32g/cm^3$), and lead (Pb, $11.34g/cm^3$). The thickness of the modulation filter varied from 0.1 mm to 1.0 mm. To evaluate the overlap region of the low- and high-energy spectrum, Geant4 Monte-Carlo simulation is used. The variation of the photon flux and the mean energy of photon spectrum that passes through the energy modulation filter are evaluated. In the primary photon spectrum of 80 kVp, the optimal modulation filter is a 0.1 mm lead filter that can acquire the same mean energy of 140 kVp photon spectrum. The lead filter of 0.1 mm based dual energy CBCT is required to increase the tube current 4.37 times than the original tube current owing to the 77.1% attenuation in the filter.

• Journal of Surface Science and Engineering
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• v.41 no.6
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• pp.335-340
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• 2008

Cutting performance and wear behavior were studied with the diamond micro-blade of Cu/Sn bond materials containing various amount of lubricant materials such as graphite and $MoS_2$. Measurement of instantaneous electric power consumption for cutting glass workpiece at the constant velocity was conducted and proposed as a method to assess cutting efficiency. The energy consumption of micro-blade for glass cutting decreased with the content of graphite and $MoS_2$ while wear amount of blade in volume increased with the amount of lubricant addition during the dicing test. It is because that hardness, flexural strength, and fracture toughness ($K_{IC}$) reduced with the amount of lubricant addition. Blades with $MoS_2$ additive showed higher mechanical properties than those with graphite additives when the same amount of the lubricant additive in wt.% was added. Due to the lower density of graphite than $MoS_2$, higher volume fraction of graphite could result in stronger effect on lowering electric power consumption by reducing the friction between blade and work piece however increasing wear rate due to the reduction in strength and fracture toughness. Adhesive wearing mode of micro blade could be remarkably improved by the addition of graphite as well as $MoS_2$.

• Journal of Conservation Science
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• v.29 no.3
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• pp.231-241
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• 2013

Analysis of the bronze bodhisattva from Pangyo-dong sites in Seongnam by computed tomography, ICP-AES, metallurgical microscope and SEM-EDS had to know manufacturing technique. And the origin of the raw material, was investigated using TIMS. Results with computed tomography, two bronze bodhisattva produced by lost-wax casting technique with hollow inside and could see the core of the inside. Result of component analysis and microstructure observation, material is alloy of copper-tin-lead and made by casting without artificial treatment. According to lead isotope ratio analysis result of bronze bodhisattva could be made into galena of the Gyeonggi massif in Korea South.

• Microbiology and Biotechnology Letters
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• v.20 no.2
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• pp.150-155
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• 1992

- Some properties of an extracellular cytosine deaminase excreted from an isolate from soil samples were examined after 20~80%' ammonium sulfate fractionation. The enzyme catalyzed the conversion of cytosine and 5-fluorocytosine into uracil and 5-fluorouracil by substrate specificity, respectively. The optimum temperature and storage time on the stability of the enzvme preparation were below $50^{\circ}C$ keeping above 90% of the residual activity and near 4 days keeping above 80% of the residual one in Tris-HCI buffer. The maximum activity was also obtained at 8.0 in pH and 37'C in temperature. The pHs and temperatures for enzyme activity ranged from 8.0~8.5 and from 37~$45^{\circ}C$. respectively. The presence of $Ag^-,Hg^{2-}, Zn^{2-}, Cu^{2-}, Sn^{2-}, \; or\; Pb^{2-}$ in the reaction mixture resulted in the marked inhibition in enzyme activity, but 1 mM of $K^+, Fe^[3+}, Mg^{2+}, \; or \; Na^+$. slightly increased the activity. The enzyme preparation was heavily affected by most of inhibitors tested such as 1 mM of EIITA, NaCN and pentachlorophenol, and completely inactivated by p-CMB and TCA of 1 mM, or 10 mM.

• The Korean Journal of Physiology and Pharmacology
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• v.14 no.5
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• pp.249-256
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• 2010

Gender differences in the trace elements of monkey sino-atrial (SA) node were investigated in a process of age-dependent alterations. Sixty hearts from Japanese and rhesus monkeys (30 male and 30 female) used were aged ranging from 1-day- to 30-year-old. The elements were analyzed using an inductively coupled plasma-atomic emission spectrometer (ICP-AES). Advancing age decreased all the trace elements. Ca, P, S and Mg significantly decreased. The correlation coefficients of Ca and P were $-0.178{\pm}0.081$ (p<0.05) and $-0.088{\pm}0.022$ (p<0.05) in male (n=30), and $-0.095{\pm}0.026$ (p<0.05) and $-0.069{\pm}0.017$ (p<0.05) in female (n=30), respectively. The age-dependent coefficients for Fe/Ca, Zn/Ca, Fe/P, Fe/S, Zn/S, Fe/Mg and Zn/Mg were exhibited markedly in male, but all was less in female. In gender-related differences, only a ratio of P/Ca (p<0.05) was significantly observed with ageing. The trace elements such as Cu, Se and Sn were less detected in the SA nodes. These results indicate that the age-dependent changes in the ratios of elements are appeared more rapidly in male monkey SA node, and the gender difference is observed in ratio of P/Ca. The different attenuations may be involved with the age- and gender-related SA nodal functions.