• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.640-644
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• 2000

The microstructure, wettability, shear strength and aging effect of Sn-3.5Ag/Cu and Alloy42 lead-frame solder joints were measured for comparison. In the case of Sn-3.5Ag/Cu, Ag$_3$Sn and Cu$\sub$6/Sn$\sub$5/ phases in the matrix Sn and 1∼2$\mu\textrm{m}$ thick Cu$\sub$6/Sn$\sub$5/ Phase at the interface of solder/lead-frame were formed. In the case of Sn-3.5AAg/A11oy42, only Ag$_3$Sn Phase of low density in the matrix Sn and 0.5∼1.5$\mu\textrm{m}$ thick FeSn$_2$phase at the interface of solder/lead-frame were formed. Comparing to Cu, Alloy42 shear strength of Alloy 42 solder joints was smaller than that of Cu and all declined after aging. After aging at 180$^{\circ}C$ for 1 week, η-Cu$\sub$6/Sn$\sub$5/ layer was formed on Cu lead-frame, while AgSn$_3$ phase in the matrix and thickened FeSn$_2$at the interface were formed on Alloy42 lead-frame.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.1
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• pp.10-16
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• 2010

The microstructure of Cu-Mg-P alloy sheet consisted of Cu matrix and very fine MgP precipitate, and it has been observed that the microstructure remains virtually unchanged by Ag additions up to 2%. Ag solutes were dissolved into the matrix and hardly found in the precipitates. The hardness increased with increase of the Ag content, while the conductivity slightly decreased. Strain hardening through cold rolling was found to be effective in improving the hardness, especially in high-Ag alloys. Aging treatment was conducted either before the first cold rolling or between the first and the final cold rolling, and the conductivity was significantly higher at the former case, regardless of the Ag content. Softening of Cu-Mg-P alloy sheet was remarkable above $400^{\circ}C$ and the Ag content did not show any significant effect on it.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.921.1-921.1
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• 2006

• Korean Journal of Metals and Materials
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• v.49 no.12
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• pp.995-1000
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• 2011

The microstructure of Cu-24 wt.%Ag filamentary nanocomposite fabricated by a thermo-mechanical process has been investigated by transmission electron microscopy (TEM) observations. This study is focused on the stability of Ag filaments formed by cold drawing; the effects of thermal treatment on the precipitation behavior and distribution of Ag-rich precipitates were also investigated. The Ag filaments elongated along the <111> orientation were observed in Cu-rich ${\alpha}$ phase of the as-drawn specimen and the copper matrix and the silver filament have a cube on cube orientation relationship. Annealing at temperatures lower than $200^{\circ}C$ for the as-drawn specimen caused insignificant change of the fibrous morphology but squiggly interfaces or local breaking of the elongated Ag filaments were easily observed with annealing at $300^{\circ}C$. When samples were annealed at $400^{\circ}C$, discontinuous precipitation was observed in supersaturated Cu solid solution. Ag precipitates with a thickness of 7-20 nm were observed along the <112> direction and the orientation relationship between the copper matrix and the Ag precipitates maintained the same orientation relationship in the as-drawn specimen. The interface between the copper matrix and the Ag precipitates is parallel to {111} and micro-twins were observed in the Ag precipitates.

• Korean Journal of Metals and Materials
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• v.46 no.3
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• pp.182-188
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• 2008

Carbon nanotubes(CNTs) have outstanding mechanical, thermal, and electrical properties. Thus, by placing nanotubes into appropriate matrix, it is postulated that the resulting composites will have enhanced properties. Cold spray can produce thick metal-based composite coatings with very high density, low oxygen content, and phase purity, which leads to excellent physical properties. In this study, we applied cold spray coating process for the consolidation of Cu/CNT composite powder. The precursor powder mixture, in which CNTs were filled into copper particles, was prepared to improve the distribution of the CNT in copper matrix. Pure copper coating was also conducted by cold spraying as a reference. Annealing heat treatment was applied to the coating to examine its effect on the properties of the composite coating. The hardness of Cu/CNT composite coating represented similar value to that of pure copper coating. It was importantly found that the electrical conductivity of the Cu/CNT composite coating significantly increased from 53% for the standard condition to almost 55% in the optimized condition, taking annealed ($500^{\circ}C/1hr$.) copper coating as a reference (100%). The thermal conductivity of Cu/CNT composite coating layer was higher than that of pure Cu coating. It was also found that the electrical and thermal conductivities of Cu/CNT composite could be improved through annealing heat treatment. The microstructural evolution of Cu/CNT coating was also investigated and related to the macroscopic properties.

• Journal of Powder Materials
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• v.13 no.1 s.54
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• pp.33-38
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• 2006

The effect of Cu content on microstructure and mechanical properties of nano-sized Cu dispersed $Al_2O_3(Al_2O_3/Cu)$ nanocomposites was investigated. The nanocomposites with Cu content of 2.5 to 10 vol% were prepared by reduction and hot-pressing of $Al_2O_3/CuO$ powder mixtures. The nanocomposites with Cu content of 2.5 and 5vol% exhibited the maximum fracture strength of 820MPa and enhanced toughness compared with monolithic $Al_2O_3$. The strengthening was mainly attributed to the refinement of $Al_2O_3$ matrix grains. The toughening mechanism was discussed by the observed microstructural feature based on crack bridging.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.366-367
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• 2006

Carbon nanotubes (CNTs) have attracted remarkable attention as reinforcement for composites owing to their outstanding mechanical properties. The CNT/Cu nanocomposite is fabricated by a novel fabrication process named molecular level process. The novel process for fabricating CNT/Cu composite powders involves suspending CNTs in a solvent by surface functionalization, mixing Cu ions with CNT suspension, drying, calcination and reduction. The molecular level process produces CNT/Cu composite powders whereby the CNTs are homogeneously implanted within Cu powders. The mechanical properties of CNT/Cu nanocomposite, consolidated by spark plasma sintering of CNT/Cu composite powders, shows about 3 times higher strength and 2 times higher Young's modulus than those of Cu matrix.

• Journal of Powder Materials
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• v.13 no.5 s.58
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• pp.366-370
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• 2006

The microstructure and mechanical properties of hot-pressed $Al_2O_3/Cu$ composites with a different sintering temperature have been studied. The size of matrix grain and Cu dispersion in composites increased with increase in sintering temperature. Fracture toughness of the composite sintered at high temperature exhibited an enhanced value. The toughness increase was explained by the thermal residual stress, crack bridging and crack branching by the formation of microcrack. The nanocomposite, hot-pressed at $1450^{\circ}C$, showed the maximum fracture strength of 707 MPa. The strengthening was mainly attributed to the refinement of matrix grains and the increased toughness.

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.11a
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• pp.174-176
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• 1996

In the YBCO matrix, 10wt.% Y$_2$BaCuO$\_$5/ (211 phase) was added, the final 211 content of YBCO made by MTG process could reach about 20wt.% which was the optimum value for the critical current density. And also 10wt.% Ag was added in the matrix of YBCO, which was nearly about the saturate solubility of silver in textured YBCO. SmBaCuO crystal was grown by the melted-condensed process. A 5${\times}$5${\times}$2㎣ single crystal of SmBaCuO was used to be the seed in the preparation of YBCO. It was proved the orientation of YBCO was the same as the orientation of the SmBaCuO seed. The oxygen absorption of bulk oriented YBCO was studied and the heat treatment of oxygen absorption would be in flowing oxygen, at 400$^{\circ}C$ for about 24 hours. the magnetic hysteresis loops were measured by Vibrating Smaple Magnetometer and the J$\_$c/ was calcuated by means of Bean's model.

• Korean Journal of Materials Research
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• v.20 no.2
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• pp.65-71
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• 2010

In this study, the effect of Sn and Mg on microstructure and mechanical properties of Cu-Fe-P alloy were investigated by using scanning electron microscope, transmission electron microscope, tensile strength, electrical conductivity, thermal softening, size and distribution of the precipitation phases in order to satisfy characteristic for lead frame material. It was observed that Cu-0.14wt%Fe-0.03wt%P-0.05wt%Si-0.1wt%Zn with Sn and Mg indicates increasing tensile strength compare with PMC90 since Sn restrained the growth of the Fe-P precipitation phase on the matrix. However, the electrical conductivity was decreased by adding addition of Sn and Mg because Sn was dispersed on the matrix and restrained the growth of the Fe-P precipitation. The size of 100 nm $Mg_3P_2$ precipitation phase was observed having lattice parameter $a:12.01{\AA}$ such that [111] zone axis. According to the results of the study, the tensile strength and the electrical conductivity satisfied the requirements of lead frame; so, there is the possibility of application as a substitution material for lead frame of Cu alloy.