Interfacial Reactions between Ga and Cu-10Ni Substrate at Low Temperature

Shiqian Liu; Guang Zeng; Wenhui Yang; Stuart McDonald; Qinfen Gu; Syo Matsumura; Kazuhiro Nogita

doi:10.1021/acsami.0c02032

Interfacial Reactions between Ga and Cu-10Ni Substrate at Low Temperature

ACS Appl Mater Interfaces. 2020 May 6;12(18):21045-21056. doi: 10.1021/acsami.0c02032. Epub 2020 Apr 22.

Authors

Shiqian Liu¹, Guang Zeng², Wenhui Yang³, Stuart McDonald¹, Qinfen Gu⁴, Syo Matsumura⁵, Kazuhiro Nogita¹

Affiliations

¹ Nihon Superior Centre for the Manufacture of Electronic Materials (NS CMEM), School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia.
² School of Materials Science and Engineering, Central South University, Changsha 410083, China.
³ Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Motooka 744, Nishi-ku, Fukuoka 819-0395, Japan.
⁴ Powder Diffraction Beamline, The Australian Synchrotron (ANSTO), Clayton, Victoria 3168, Australia.
⁵ The Ultramicroscopy Research Center, Kyushu University, Motooka 744, Nishi-ku, Fukuoka 819-0395, Japan.

PMID: 32272014
DOI: 10.1021/acsami.0c02032

Abstract

Ga alloys have been attracting significant renewed attention for low-temperature bonding applications in electronic packaging. This study systematically investigates the interfacial reaction between liquid Ga and Cu-10Ni substrates at 30 °C. In addition to CuGa₂ formed from binary Ga/Cu couples, a layer of nanocrystalline Ga₅Ni and CuGa₂ formed between the Cu-10Ni substrate and the blocklike micrometer scale CuGa₂ layer. The growth of interfacial intermetallics (IMCs) on the Cu-10Ni substrate was substantially accelerated compared to the IMC growth in binary Ga/Cu couples. Reaction kinetics study shows the IMC growth from the Cu-10Ni substrate was controlled by reaction and volume diffusion, while the IMC growth from the Cu substrate was controlled by volume diffusion. It is also found that the presence of Ni within the CuGa₂ phase resulted in improved thermal stability and a smaller coefficient of thermal expansion during heating from 25 to 300 °C, using synchrotron XRD analysis. There was least thermal expansion anisotropy among most of the IMCs that form in conventional Sn-based solder alloys, including Cu₆Sn₅ and so forth. It is concluded that using a Cu-10Ni substrate as opposed to a Cu substrate could achieve sufficient metallurgical bonding within shorter processing time. The results have implications for broadening the application temperatures when using Ga as a low-temperature joining material.

Keywords: gallium; intermetallics; soldering; synchrotron diffraction; transmission electron microscopy.