Bi-Cu film deposition in aqueous solutions
(1. Taiho Kogyo Co. Ltd., Hosoya-cho, Toyota-City, Aichi. 471-8502, Japan;
2. Department of Materials Science and Engineering, Nagoya University, Furo-cho,
Chikusa-ku Nagoya 464-8603, Japan)
2. Department of Materials Science and Engineering, Nagoya University, Furo-cho,
Chikusa-ku Nagoya 464-8603, Japan)
Abstract: The relatively uniform bismuth-copper film was electrodeposited between −15 and −20 mV in the sulfate electrolyte containing 4 mmol/L bismuth ion and 2 mmol/L copper ion. Only copper was electrodeposited at −5 mV. The dendritic bismuth-copper film was electrodeposited under −20 mV. The cathodic current became constant between −20 and −400 mV. Therefore, bismuth-copper electrodeposition changes from charge transfer controlling to diffusion controlling at −20 mV. On the other hand, the uniform bismuth-copper film was electrodeposited between −5 and −35 mV in the methanesulfonate electrolyte containing 4 mmol/L bismuth ion and 2 mmol/L copper ion. The dendritic bismuth-copper film was electrodeposited under −35 mV. The potential region for good electrodepositon in methanesulfonate electrolyte is wider than that in sulfate electrolyte. Therefore, it is easy to control electrodeposition conditions by using methanesulfonate electrolyte.
Key words: electrodepositon; lead-free electrolyte; Bi-Cu film; current efficiency