• Journal of Conservation Science
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• v.35 no.5
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• pp.508-517
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• 2019

This study analyzed on alloys and by-product samples produced through the reproduction experiment of bronze mirror with geometric designs. The alloy ratio used in the first and second reproduction experiments was based on the analysis results of bronze mirror with geometric designs(Cu 61.68%, Sn 32.25%, Pb 5.46%) which is the national treasure No. 141. As a result of portable X-ray fluorescence analysis on the raw materials used in the reproduction experiment, the contents of copper raw materials were 98.85 wt% for Cu, tin raw materials were 99.03 wt% for Sn, and lead raw materials were 70.19 wt% for Pb, and 21.81 wt% for Sn. Sn and Pb were added 5 wt% more considering the evaporation amount of tin and lead during alloy melting. The result produced by the first reproduction experiment were 58.75 wt% for Cu, 36.87 wt% for Sn, 4.39 wt% for Pb, and the other result produced by the second reproduction experiment were 58.66 wt% for Cu, 35.89 wt% for Sn, and 5.50 wt% for Pb. The composition of the components was about 3.00 wt% in Cu and Sn respectively, and the microstructure was similar to the previous studies because the δ phase was observed mainly. The results of this study will be used as basic data for the materialistic characteristics of ancient bronze mirror in the future.

• Journal of Conservation Science
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• v.36 no.3
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• pp.178-186
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• 2020

Verdigris is a traditional artificial pigment reported on old research papers and according to the methods mentioned in the literature, it is manufactured by the corrosion of copper or copper alloys using vinegar and by further scraping the generated rust. Since the Three Kingdoms Period, various household products with copper alloys, such as bronze and brass, have been used, and pigment analysis of these cultural heritage items has revealed the presence of tin, zinc, lead, and copper in green pigments. Based on these data, five types of verdigris were prepared from copper and copper alloys, and analyzed. the analysis results revealed a bluish green pigmentation, and the chromaticity, particle shape, and oil absorption quantity of each verdigris differed based on the type of copper alloy used in its preparation. The main components of verdigris are Cu, Sn, Zn and Pb, and their proportions depended on the type of copper alloy used during manufacturing. However, the main constituent mineral of the pigments is the same as 'hoganite[Cu(CH₃COO)₂·H₂O]', regardless of the copper alloy used. The result of accelerated weathering test for stability evaluation revealed that verdigris was discolored rapidly, thereby indicating that its stability was low, in particular, the pigments comprising lead presented relatively lower stability.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2001.11a
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• pp.7-7
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• 2001

The increasing interest in light weight materials coupled to the need for cost -effective processing have combined to create a significant opportunity for aluminum P/M. particularly in the automotive industry in order to reduce fuel emissions and improve fuel economy at affordable prices. Additional potential markets for Al PIM parts include hand tools. Where moving parts against gravity represents a challenge; and office machinery, where reciprocating forces are important. Aluminum PIM adds light weight, high compressibility. low sintering temperatures. easy machinability and good corrosion resistance to all advantages of conventional iron bm;ed P/rv1. Current commercial alloys are pre-mixed of either the AI-Si-Mg or AL-Cu-Mg-Si type and contain 1.5% ethylene bis-stearamide as an internal lubricant. The powder is compacted in closed dies at pressure of 200-500Mpa and sintered in nitrogen at temperatures between $580~630^{\circ}C$ in continuous muffle furnace. For some applications no further processing is required. although most applications require one or more secondary operations such as sizing and finishing. These sccondary operations improve the dimension. properties or appearance of the finished part. Aluminum is often considered difficult to sinter because of the presence of a stable surface oxide film. Removal of the oxide in iron and copper based is usually achieved through the use of reducing atmospheres. such as hydrogen or dissociated ammonia. In aluminum. this occurs in the solid st,lte through the partial reduction of the aluminum by magncsium to form spinel. This exposcs the underlying metal and facilitates sintering. It has recently been shown that < 0.2% Mg is all that is required. It is noteworthy that most aluminum pre-mixes contain at least 0.5% Mg. The sintering of aluminum alloys can be further enhanced by selective microalloying. Just 100ppm pf tin chnnges the liquid phase sintering kinetics of the 2xxx alloys to produce a tensile strength of 375Mpa. an increilse of nearly 20% over the unmodified alloy. The ductility is unnffected. A similar but different effect occurs by the addition of 100 ppm of Pb to 7xxx alloys. The lend changes the wetting characteristics of the sintering liquid which serves to increase the tensile strength to 440 Mpa. a 40% increase over unmodified aIloys. Current research is predominantly aimed at the development of metal matrix composites. which have a high specific modulus. good wear resistance and a tailorable coefficient of thermal expnnsion. By controlling particle clustering and by engineering the ceramic/matrix interface in order to enhance sintering. very attractive properties can be achicved in the ns-sintered state. I\t an ils-sintered density ilpproaching 99%. these new experimental alloys hnve a modulus of 130 Gpa and an ultimate tensile strength of 212 Mpa in the T4 temper. In contest. unreinforcecl aluminum has a modulus of just 70 Gpa.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.2
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• pp.91-97
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• 2014

With Pb-free solder joints containing Sn-Ag-Cu-based ternary alloys (Sn-1.0 wt.%Ag-0.5Cu and Sn-4.0Ag-0.5Cu) and Sn-Ag-Cu-In-based quaternary alloys (Sn-1.0Ag-0.5Cu-1.0In, Sn-1.2Ag-0.5Cu-0.4In, Sn-1.2Ag-0.5Cu-0.6In, and Sn-1.2Ag-0.7Cu-0.4In), fracture-mode change, shear strengths, and fracture energies were observed and measured under a high-speed shear test of 500 mm/s. The samples in each composition were prepared with as-reflowed ones or solid-aged ones at $125^{\circ}C$ to 500 h. As a result, it was observed that ductile or quasi-ductile fracture modes occurs in the most of Sn-Ag-Cu-In samples. The happening frequency of a quasi-ductile fracture mode showed that the Sn-Ag-Cu-In joints possessed ductile fracture properties more than that of Sn-3.0Ag-0.5Cu in the high-speed shear condition. Moreover, the Sn-Ag-Cu-In joints presented averagely fracture energies similar to those of Sn-Ag-Cu joints. While maximum values in the fracture energies were measured after the solid aging for 100 h, clear decreases in the fracture energies were observed after the solid aging for 500 h. This result indicated that reliability degradation of the Sn-Ag-Cu-In solder joints might accelerate from about that time.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.475-480
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• 2002

The reliability of the solder joint is affected by type and extent of the interfacial reaction between solder and substrates. Therefore, understanding of intermetallic compounds produced by soldering in electronic packaging is essential. In-based alloys have been favored bonding devices that demand low soldering temperatures. For photonic and fiber optics packaging, m-based solders have become increasingly attractive as a soldering material candidate due to its ductility. In the present work, the interfacial reactions between indium solder and bare Cu Substrate are investigated. For the identification of intermetallic compounds, both Scanning Electron Microscopy(SEM) and X-Ray Diffraction(XRD) were employed. Experimental results showed that the intermetallic compounds, such as Cu$_{11}$In$_{9}$ was observed for bare Cu substrate. Additionally, the growth rate of these intermetallic compounds was increased with the reaction temperature and time. We found that the growth of the intermetallic compound follows the parabolic law, which indicates that the growth is diffusion-controlled.d.

• Conservation Science in Museum
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• v.21
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• pp.17-28
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• 2019

The term jinjuseon(眞珠扇), meaning literally a pearl fan, refers to a fan decorated with precious stones for use in royal wedding ceremonies. This study examined a jinjuseon housed in the National Palace Museum of Korea (NPMK) which currently lacks jeweled ornaments. In order to determine whether pearls or other gemstone settings originally ornamented the fan,the surface and composition of the gray materials remaining on the washers were investigated and the fan was compared with other artifacts decorated using similar techniques. The analysis revealed that the gray materials visible around the round rims of the washers contain tin-lead alloys. The traces of folded nails suggest that soldering was not applied. The remains of the infill observed in other artifacts with bezel settings indicate that this jinjuseon in the NPMK collection was produced using abezel setting technique wherein pearls or other gemstones were affixed by filling cylindrical bezels with tin-lead alloys.

• Korean Journal of Metals and Materials
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• v.47 no.12
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• pp.842-851
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• 2009

The long-term reliability of Sn-0.3wt%Ag-0.7wt%Cu solder joints was evaluated and compared with Sn-3.0wt%Ag-0.5wt%Cu under thermal shock conditions. Test vehicles were prepared to use Sn-0.3Ag-0.7Cu and Sn-3.0Ag-0.5Cu solder alloys. To compare the shear strength of the solder joints, 0603, 1005, 1608, 2012, 3216 and 4232 multi-layer ceramic chip capacitors were used. A reflow soldering process was utilized in the preparation of the test vehicles involving a FR-4 material-based printed circuit board (PCB). To compare the shear strength degradation following the thermal shock cycles, a thermal shock test was conducted up to 2,000 cycles at temperatures ranging from $-40^{\circ}C$ to $85^{\circ}C$, with a dwell time of 30 min at each temperature. The shear strength of the solder joints of the chip capacitors was measured at every 500 cycles in each case. The intermetallic compounds (IMCs) of the solder joint interfaces werealso analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results showed that the reliability of Sn-0.3Ag-0.7Cu solder joints was very close to that of Sn-3.0Ag-0.5Cu. Consequently, it was confirmed that Sn-0.3Ag-0.7Cu solder alloy with a low silver content can be replaced with Sn-3.0Ag-0.5Cu.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.439-449
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• 2002

This paper reviews our recent research works on the interconnection technologies in electronic packaging and assembly. At the aspect of advanced joining methods, laser-ultrasonic fluxless soldering technology was proposed. The characteristic of this technology is that the oxide film was removed through the vibration excitated by high frequency laser change in the molten solder droplet. Application researches of laser soldering technology on solder bumping of BGA packages were carried out. Furthermore, interfacial reaction between SnPb eutectic solder and Au/Ni/Cu pad during laser reflow was analyzed. At the aspect of soldered joints' reliability, the system for predicting and analyzing SMT solder joint shape and reliability(PSAR) has been designed. Optimization design method of soldered joints' structure was brought forward after the investigation of fatigue failure of RC chip devices and BGA packages under temperature cyclic conditions with FEM analysis and experimental study. At the aspect of solder alloy design, alloy design method based on quantum was proposed. The macroproperties such as melting point, wettability and strength were described by the electron parameters. In this way, a great deal of the experimental investigations was replaced, so as to realize the design and research of any kinds of solder alloys with low cost and high efficiency.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.3
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• pp.19-27
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• 2003

Surface finishes of PCB laminates are important in the solder joint reliability of flip chip package because the types and thicknesses of intermetallic compound(IMC), and compositions and hardness of solders are affected by them. In this study, effects of surface finishes of PCB on the low cycle fatigue resistance of Sn-based lead-free solders; Sn-3.5Ag, Sn-3.5Ag-XCu(X=0.75, 1.5), Sn-3.5Ag-XBi(X=2.5, 7.5) and Sn-0.7Cu were investigated for the Cu and Au/Ni surface finish treatments. Displacement controlled room temperature lap shear fatigue tests showed that fatigue resistance of Sn-3.5Ag-XCu(X=0.75, 1.5), Sn-3.5Ag and Sn-0.7Cu alloys were more or less the same each other but much better than that of Bi containing alloys regardless of the surface finish layer used. In general, solder joints on the Au/Ni finish showed better fatigue resistance than those on the Cu finish. Cross-sectional fractography revealed microcracks nucleation inside of the interfacial IMC near the solder mask edge, more frequently on the Cu than the Au/Ni surface finish. Macro cracks followed the solder/IMC interface in the Bi containing alloys, while they propagated in the solder matrix in other alloys. It was ascribed to the Bi segregation at the solder/IMC interface and the solid solution hardening effect of Bi in the $\beta-Sn$ matrix.

• Conservation Science in Museum
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• v.29
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• pp.133-152
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• 2023

This study references preceding studies to examine the history of paint application techniques using various paints in the past, with the aim to contribute to the long-term preservation of large military cultural heritage assets situated outdoors. To this end, the study compared the findings of preceding research with the findings of an analysis conducted on a H-13 helicopter housed at the War Memorial of Korea. Upon collecting and analyzing samples from three grounded WWII aircraft from above-ground by preceding studies, it was confirmed from each sample that the various chemical properties of chrome ensured the effectiveness of the protective coating. The compound was first tested as a corrosion-inhibiting pigment in the early 1940s and proved its excellent moisture-resistant properties over the course of 80 years, despite the deterioration of the paint layer and long-term exposure to the natural environment. For this reason, it has been widely used as a corrosion inhibitor for aluminum alloys in the aviation industry. In other word, the most widely-used material for preventing corrosion was an organic primer containing chromate. In this study, based on the paint analysis of a H-13 helicopter operated in the Korean War, it was shown that the second layer, consisting of the primer, contains chromium oxide (Cr₂O₃). In addition, it was estimated that red lead tetraoxide (Pb₃O₄) was used for the vehicle. Analysis results and data from previous studies can help to confirm the continued effectiveness of corrosion prevention function provided by chromate. Meanwhile, the result of infrared spectroscopy analysis confirmed the use of alkyd resin. In the future, comparisons with a more diverse range of artifacts will allow the identification of changes in the manufacturing technology of paints used to protect alloys from corrosion.