Atomic insights into the ordered solid solutions of Ni and Au in η-Cu6Sn5

Wenhui Yang, Xuan Quy Tran, Tomokazu Yamamoto, Kohei Aso, Flora Somidin, Xin Fu Tan, Youichirou Kawami, Kazuhiro Nogita, Syo Matsumura

研究成果: ジャーナルへの寄稿学術誌査読

抄録

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.

本文言語英語
論文番号117513
ジャーナルActa Materialia
224
DOI
出版ステータス出版済み - 2月 1 2022

!!!All Science Journal Classification (ASJC) codes

  • 電子材料、光学材料、および磁性材料
  • セラミックおよび複合材料
  • ポリマーおよびプラスチック
  • 金属および合金

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