Electrodeposition of soft gold from a thiosulfate-sulfite bath for electronics applications

T. Osaka*, A. Kodera, T. Misato, T. Homma, Y. Okinaka, O. Yoshioka

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

106 Citations (Scopus)


The possibility of electrodeposition of soft gold from a thiosulfate-sulfite bath was explored for electronics applications. The bath does not contain cyanide, and it is operated at a near neutral pH and a mildly elevated temperature. The bath is stable, does not undergo spontaneous decomposition without the addition of any stabilizer, and yields gold deposits with a hardness sufficiently low for use as gold bumps on semiconductor devices. Factors affecting the hardness were investigated in detail. It is shown that the use of high concentrations of the complexing agents and/or the addition of thallium(I) ions decreases both hardness and sulfur content of the deposit. The lowest Vickers hardness values achieved were approxiraately 80 kg mm-2 in the as-deposited state and 50 kg mm-2 after annealing at 350°C for 30 min in air. The relationship between hardness and microstructure of the deposit was also examined.

Original languageEnglish
Pages (from-to)3462-3469
Number of pages8
JournalJournal of the Electrochemical Society
Issue number10
Publication statusPublished - 1997 Oct

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Surfaces, Coatings and Films
  • Electrochemistry
  • Materials Chemistry


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