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- Title
In Situ Study of Reduction Process of CuO Paste and Its Effect on Bondability of Cu-to-Cu Joints.
- Authors
TAKAFUMI YAO; TOMOKI MATSUDA; TOMOKAZU SANO; CHIAKI MORIKAWA; ATSUSHI OHBUCHI; HISASHI YASHIRO; AKIO HIROSE
- Abstract
A bonding method utilizing redox reactions of metallic oxide microparticles achieves metal-to-metal bonding in air, which can be alternative to lead-rich high-melting point solder. However, it is known that the degree of the reduction of metallic oxide microparticles have an influence on the joint strength using this bonding method. In this paper, the reduction behavior of CuO paste and its effect on Cu-to-Cu joints were investigated through simultaneous microstructure-related x-ray diffraction and differential scanning calorimetry measurements. The CuO microparticles in the paste were gradually reduced to submicron Cu2O particles at 210-250°C. Subsequently, Cu nanoparticles were generated instantaneously at 300-315°C. There was a marked difference in the strengths of the joints formed at 300°C and 350°C. Thus, the Cu nanoparticles play a critical role in sintering-based bonding using CuO paste. Furthermore, once the Cu nanoparticles have formed, the joint strength increases with higher bonding temperature (from 350°C to 500°C) and pressure (5-15 MPa), which can exceed the strength of Pb-5Sn solder at higher temperature and pressure.
- Subjects
COPPER oxide; JOINTS (Engineering); X-ray diffraction; METAL microstructure; CHEMICAL bonds; OXIDATION-reduction reaction
- Publication
Journal of Electronic Materials, 2018, Vol 47, Issue 4, p2193
- ISSN
0361-5235
- Publication type
Article
- DOI
10.1007/s11664-017-6049-9