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25. Microstructure and mechanical property of thick Cu/AlN joints formed at low temperature.

Author

Chen, Shu, Xu, Zhiwu, Ma, Zhongwei, Li, Zhengwei, and Yan, Jiuchun

Subjects
COPPER, LOW temperatures, MICROSTRUCTURE, TELECOMMUNICATION, BOND strengths
Abstract

The bonding of thick Cu and AlN is necessary in power modules with the development of high‐frequency communication technology. In this work, 2 mm‐thick Cu was successfully bonded with AlN by using Sn9Zn solder with the assistance of ultrasonication at 230°C. Results showed that an AlN/Sn9Zn/Cu joint without crack was manufactured with a cooling rate of 7°C/min. Nonreactive wetting was realized between AlN and Sn9Zn, forming an amorphous transition layer. CuZn2 and CuZn were formed at the Sn9Zn/Cu interface. A joint with the highest bonding strength of 30.07 MPa was obtained, in which the AlN/Sn9Zn interface was no longer the weakest location. This work provides a low‐temperature manufacturing method for thick Cu/AlN joints. [ABSTRACT FROM AUTHOR]

Published
2024
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43. GROWTH STRUCTURE EFFECT ON THE CORROSION RESISTANCE AND MECHANICAL PROPERTIES OF CrNx COATING.

Author

DU, JIAOJIAO, ZHOU, HAIBIN, SUN, CAIXIA, KOU, HAIJIANG, MA, ZHONGWEI, WANG, XIAOYAN, and DAI, JINGJIE

Subjects
ARTIFICIAL seawater, CORROSION resistance, MAGNETRON sputtering, SURFACE coatings, CRYSTAL grain boundaries
Abstract

A new approach was adopted to improve the corrosion behavior of the chromium nitride (CrNx) hard coating through magnetron sputtering deposition at different nitrogen flow rates. The influence of the nitrogen flow rates on the chemical composition, microstructure, mechanical property and corrosion behavior in artificial seawater of the CrNx coatings was investigated. The results show that with the increase of the nitrogen flow rates, the growth structure of the coatings varied from dense granular growth to coarse columnar growth. Increasing the nitrogen flow rates was helpful to decrease the Cr/N ratio and induce the phase transforming from mixed hexagonal Cr2N and face-centered cubic CrN to single CrN. However, the coatings under different nitrogen flow rates significantly improved the corrosion resistance and hardness of the steel substrate. Furthermore, at high nitrogen flow rate, the coating had high corrosion velocity and low protective capability against the substrate corrosion due to the fast corrosion channels acted by the columnar grain boundaries. While at the middle nitrogen flow rate, the coating with CrN phase, densely granular growth structure and moderate grain size resulted in excellent corrosion resistance and highest hardness. [ABSTRACT FROM AUTHOR]

Published
2020
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50. Magnetic interactions possessing point group symmetry and their application to ruby

Author

Yang Zhenguo, Ma Zhongwei, and Zhao Minguang

Subjects
Condensed matter physics, Magnetic moment, Chemistry, Molecular symmetry, State (functional analysis), Singlet state, Symmetry (physics)
Abstract

By utilizing the magnetic interactions possessingC3v symmetry, the author has deduced the general expressions for theg-factors, zero-field splitting and effective magnetic moment of the ground singlet orbital state in d3-complex. For ruby (Al2O3: Cr3+) the results are in good agreement with experiments: theoretical values:g‖=1.9835;g⊥=1.9876; 2D=−0.3731 cm−1;μ‖=3.857β;μ⊥=3.861β; experimental values:g‖=1.9840±0.006,g⊥=1.9867±0.0006, 2D=−0.3831±0.0002 cm−1,μ=3.8−3.9β.

Published
1982

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