Novel silver-enhanced hard gold electrodeposit applied for electrical contacts: comparison with conventional gold–cobalt alloy

ABSTRACT

An Au–Ag coating has been envisaged as an alternative to the conventional Au–Co electrodeposit. In this study, an Au–Ag coating was electrodeposited on Cu substrates pre-coated with a Ni layer. The contact resistance of the Au–Ag coating was observed to be lower than that of the Au–Co coating. Under extended aging, the Au–Ag coating demonstrated a slightly increased contact resistance, while the contact resistance of the Au–Co coating increased significantly. Additionally, the solderability of the Au–Ag coating surpassed that of the Au–Co coating. Qualitative analyses demonstrate that, in the case of Au–Co coating, a considerable amount of Ni diffused through the Au layer to react with O₂ in the air to form oxides during aging. The Co elements also oxidised due to aging. The formation of the oxide layer induced an increased contact resistance and diminished solderability. In addition, the Au–Co coating consisted of finer grains than the Au–Ag coating, promoting the Ni diffusion through the Au layer.

KEYWORDS:

• Hard gold
• gold–cobalt alloy
• gold–silver alloy
• electrodeposition
• contact resistance
• solder
• electrical contact
• aging

Acknowledgements

This work was funded by the National Research Foundation of Korea (NRF) grant sponsored by the Korean government (Ministry of Education) (NRF- 2020R1A2C1014604).

This paper is based on a presentation given by the authors at Interfinish2020 on-line, 6–8 September 2021, organised by The Surface Finishing Society of Japan, co-organised by Nagoya University and supported by the International Union for Surface Finishing (IUSF)

Disclosure statement

No potential conflict of interest was reported by the author(s).