| Project/Area Number |
16560575
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical properties of metals
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
KAJIHARA Masanori Tokyo Institute of Technology, Dept.Materials Science and Engineering, Associate Professor, 大学院・総合理工学研究科, 助教授 (10161035)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2005: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2004: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Keywords | Conductor materials / Reactive diffusion / Intermetallics / Soldering / Electronic devices / Pb-free solders / Eco-materials / 電子材料 / 固相反応 / 固相接合 |
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| Research Abstract |
Sandwich Sn/(Au-Ag)/Sn diffusion couples were prepared from pure Sn and binary Au-Ag alloys with different Ag concentrations by a diffusion bonding technique. The diffusion couples were isothermally annealed at temperatures between 433 and 473 K for various times in an oil bath with silicone oil. For the cross-section of the annealed diffusion couple, the microstructure was observed by scanning electron microscopy and the chemical composition of each phase was determined by electron probe microanalysis. According to the observation, intermetallic layers consisting of binary Au-Sn and Ag-Sn compounds are formed at the interface of the diffusion couple due to the reactive diffusion between the binary Au-Ag alloy and pure Sn. The total thickness of the intermetallic layers is proportional to a power function of the annealing time. The exponent of the power function takes values between 0.3 and 0.5 depending on the composition of the Au-Ag alloy. When the exponent is equal to 0.5, the growth of the intermetallic layer is controlled by volume diffusion. On the other hand, grain boundary diffusion as well as volume diffusion contributes to the rate-controlling process, if the exponent is smaller than 0.5. Thus, the rate-controlling process varies depending on the composition of the Au-Ag alloy. The proportionality coefficient of the power function also changes depending on the composition of the Au-Ag alloy. The minimum value of the proportionality coefficient is realized for the concentration of 87 at% Ag. This means that the growth rate of the intermetallic layer is most sluggish for the Au-87Ag alloy. The intermetallic layer is brittle and possesses high electrical resistivity. As a result, it is concluded that the Au-87Ag alloy is an excellent conductor material with resistance against the reactive diffusion under usual energization heating conditions.
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