TY - JOUR
T1 - Atomic insights into the ordered solid solutions of Ni and Au in η-Cu6Sn5
AU - Yang, Wenhui
AU - Tran, Xuan Quy
AU - Yamamoto, Tomokazu
AU - Aso, Kohei
AU - Somidin, Flora
AU - Tan, Xin Fu
AU - Kawami, Youichirou
AU - Nogita, Kazuhiro
AU - Matsumura, Syo
N1 - Funding Information:
This work was supported by the Progress 100 program at Kyushu University (KU), a “UQ-KU project” at the University of Queensland (UQ), which assists research collaborations between UQ and KU, and the Australian Research Council Discovery Project grant (DP200101949). XRD experiments were performed at the Australian Synchrotron (AS) Powder Diffraction Beam Line (Project ID: AS101/PD2249 and AS111/PD3364). The authors would like to thank Dr. Q.F. Gu (AS) for his support with the XRD experiments and Dr. S. Liu at The University of Queensland (UQ) for the sample preparation. W. Yang is financially supported by a China Scholarship Council (CSC) Scholarship. The authors also would like to thank anonymous reviewers for useful comments to improve the quality of the paper.
Funding Information:
This work was supported by the Progress 100 program at Kyushu University (KU), a “UQ-KU project” at the University of Queensland (UQ), which assists research collaborations between UQ and KU, and the Australian Research Council Discovery Project grant (DP200101949). XRD experiments were performed at the Australian Synchrotron (AS) Powder Diffraction Beam Line (Project ID: AS101/PD2249 and AS111/PD3364). The authors would like to thank Dr. Q.F. Gu (AS) for his support with the XRD experiments and Dr. S. Liu at The University of Queensland (UQ) for the sample preparation. W. Yang is financially supported by a China Scholarship Council (CSC) Scholarship. The authors also would like to thank anonymous reviewers for useful comments to improve the quality of the paper.
Publisher Copyright:
© 2021 Acta Materialia Inc.
PY - 2022/2/1
Y1 - 2022/2/1
N2 - The Cu6Sn5 intermetallic, which commonly forms at the solder interconnects, is a critical component contributing to the reliability of today's electronic products. It has been established that the structural control of its hexagonal η-Cu6Sn5 polymorph can be achieved over a wide temperature range of service conditions via chemical doping with Ni or Au, effectively suppressing the undesirable hexagonal to monoclinic (ƞ → ƞ′) phase transition at 186 °C and its associated volume change. In this study, we further investigate the effects of Ni (26.5 at%) and Au (9 at%), with high doping/alloying contents, on the atomic-scale structure of η-Cu6Sn5 using a suite of microscopy techniques including atomic-resolution imaging, chemical mapping, electron diffraction, and in-situ heating, coupled with advanced data informatics. Our study reveals that while Ni occupancy takes place in both the Cu1 and Cu2 sites of η-Cu6Sn5 in substantial amounts, Au is mostly substituted at the Cu1 sites of η-Cu6Sn5. Most interestingly, characteristic occupational modulations of the Cu6Sn5 structure arise with each type of dopants: a three-fold ordered structure for Ni accompanied by a displacive modulation of the constituent atoms, but a two-fold layer-like structure for Au. Moreover, with a high content of Ni, the unit cell of η-Cu6Sn5 is found to contract along its hexagonal ah axis relative to the Ni-dilute case, but anisotropically expands the ch axis in a bimodal fashion; in contrast, the effect of Au appears to be of an isotropically expanding nature.
AB - The Cu6Sn5 intermetallic, which commonly forms at the solder interconnects, is a critical component contributing to the reliability of today's electronic products. It has been established that the structural control of its hexagonal η-Cu6Sn5 polymorph can be achieved over a wide temperature range of service conditions via chemical doping with Ni or Au, effectively suppressing the undesirable hexagonal to monoclinic (ƞ → ƞ′) phase transition at 186 °C and its associated volume change. In this study, we further investigate the effects of Ni (26.5 at%) and Au (9 at%), with high doping/alloying contents, on the atomic-scale structure of η-Cu6Sn5 using a suite of microscopy techniques including atomic-resolution imaging, chemical mapping, electron diffraction, and in-situ heating, coupled with advanced data informatics. Our study reveals that while Ni occupancy takes place in both the Cu1 and Cu2 sites of η-Cu6Sn5 in substantial amounts, Au is mostly substituted at the Cu1 sites of η-Cu6Sn5. Most interestingly, characteristic occupational modulations of the Cu6Sn5 structure arise with each type of dopants: a three-fold ordered structure for Ni accompanied by a displacive modulation of the constituent atoms, but a two-fold layer-like structure for Au. Moreover, with a high content of Ni, the unit cell of η-Cu6Sn5 is found to contract along its hexagonal ah axis relative to the Ni-dilute case, but anisotropically expands the ch axis in a bimodal fashion; in contrast, the effect of Au appears to be of an isotropically expanding nature.
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U2 - 10.1016/j.actamat.2021.117513
DO - 10.1016/j.actamat.2021.117513
M3 - Article
AN - SCOPUS:85120316529
VL - 224
JO - Acta Materialia
JF - Acta Materialia
SN - 1359-6454
M1 - 117513
ER -