Electrodeposition Mechanism and Process of a Novel Cyanide-Free Gold Sulfite Bath

Abstract

A novel cyanide-free gold sulfite process is introduced in this paper. In the bath, chloauric acid was directly employed as the main salt, and hydroxyethylidene diphosphonic acid (HEDP) was used as the stabilizer and coating grain refiner. The bath stability, the gold coating morphology and the mechanism of gold electrodeposition were studied in detail. The results showed that HEDP could significantly improve the bath stability. Moreover, the grains of the gold coating obtained from the gold sulfite bath without HEDP was rod-like, which grew gradually with the increasing of the deposition time, resulting in that the appearance of the coating turned from a golden yellow to a hazy reddish brown by the increase of the coating thickness. As HEDP was introduced into the gold sulfite bath, the gold grains were transformed to pyramidal, and the grain growth rate accompanying the increase of the coating thickness was much slower than that in the gold sulfite bath without HEDP, observing the golden bright appearance within 1 μm thickness. Electrochemical curves indicated that gold electrodeposition did not undergo a nucleation stage.

Keywords

cyanide-free gold plating / gold sulfite / hydroxyethylidene diphosphonic acid / electrodeposition / gold coating

References

[1] Inoue K, Sasaki N, Sasahira T, Watanabe T, Nakata T. The relationship between microstructure and the thermal equilibrium diagram of Au-Co alloy electrodeposit[J]. Mater. Trans., 2006, 47(6): 1546-1549.

[2] Togasaki N, Okinaka Y, Homma T, Osaka T. Preparation and characterization of electroplated amorphous gold-nickel alloy film for electrical contact applications[J]. Electro-chim. Acta, 2005, 51(5): 882-887.

[3] Okinaka Y, Hoshino M. Some recent topics in gold plating for electronics applications[J]. Gold Bull., 1998, 31(1): 3-13.

[4] Kato M, Okinaka Y. Some recent developments in non-cy-anide gold plating for electronics applications[J]. Gold Bull., 2004, 37(1-2): 37-44.

[5] Hydes P C, Middleton H. The sulfito complexes of gold. Their chemistry and applications in gold electrodeposition[J]. Gold Bull., 1979, 12(3): 90-95.

[6] He A, Liu Q, Ivey D G. Electroplating of gold from a solution containing tri-ammonium citrate and sodium sulphite[J]. J. Mater. Sci.-Mater. Electron., 2009, 20(6): 543-550.

[7] Josell D, Moffat T P. Superfilling damascene trenches with gold in a sulfite electrolyte[J]. J. Electrochem. Soc., 2013, 160(12): D3009-D3014.

[8] Osaka T, Kodera A, Misato T, Homma T, Okinaka Y, Yoshioka O. Electrodeposition of soft gold from a thiosulfate-sulfite bath for electronics applications[J]. J. Electrochem. Soc., 1997, 144(10): 3462-3469.

[9] Estrine E C, Riemer S, Venkatasamy V, Stadler B J H, Tabakovic I. Mechanism and stability study of gold electrodeposition from thiosulfate-sulfite solution[J]. J. Electro-chem. Soc., 2014, 161(12): D687-D696.

[10] Jin L, Yang J Q, Yang F Z, Zhan D P, Wu D Y, Tian Z Q. Novel and green chemical compound of HAu(Cys)(2): Toward a simple and sustainable electrolyte recipe for yanide-free gold electrodeposition[J]. ACS Sustain. Chem. Eng., 2020, 8(38): 14274-14279.

[11] Yang X W, An M Z, Zhang Y W, Zhang L. Electrochemical behavior of gold (III) in cyanide-free bath with 5,5′-dimethylhydantoin as complexing agent[J]. Electrochim. Acta, 2011, 58: 516-522.

[12] Ren X F, An M Z. Theoretical and experimental studies of the influence of gold ions and dmh on cyanide-free gold electrodeposition[J]. RSC Adv., 2018, 8(5): 2667-2677.

[13] Chen J S, Fang Y M, Qiu Q Y, You L X, Song J, Zhang G M, Chen G N, Sun J J. Electrodeposition of bright gold - a green path using hypoxanthine as a complexing agent[J]. Green Chem., 2011, 13(9): 2339-2343.

[14] Huang W, Jiang J Z, Chen L, Zhang B Q, Deng S F, Sun J J, Chen W K. Density functional theory and surface enhanced Raman spectroscopy studies of tautomeric hypoxanthine and its adsorption behaviors in electrochemical processes[J]. Electrochim. Acta, 2015, 164: 132-138.

[15] Jin L, Yang J Q, Yang F Z, Wu D Y, Tian Z Q. Electrochemistry and coordination behaviors of hypoxanthine-Au (III) ion in the cyanide-free gold electrodeposition[J]. J. Electrochem. Soc., 2020, 167(2): 22511.

[16] Green T A. Gold electrodeposition for microelectronic, optoelectronic and microsystem applications[J]. Gold Bull., 2007, 40(2): 105-114.

[17] Osaka T, Kato N, Sato J, Yoshizawa K, Homma T, Okinaka Y, Yoshioka O. Mechanism of sulfur inclusion in soft gold electrodeposited from the thiosulfate-sulfite bath[J]. J. Electrochem. Soc., 2001, 148(10): C659-C662.

[18] Green T A, Liew M J, Roy S. Electrodeposition of gold from a thiosulfate-sulfite bath for microelectronic applications[J]. J. Electrochem. Soc., 2003, 150(3): C104-C110.

[19] Yang J Q, Yu H H, Jin L, Yang F Z, Wu D Y, Zhan D P, Tian Z Q. Insights into the effects of chloride ions on cyanide-free gold electrodeposition[J]. J. Electrochem. Soc., 2020, 167(10): 102514.

[20] Yang J Q, Jin L, Xiao Y H, Yu H H, Yang F Z, Zhan D P, Wu D Y, Tian Z Q. Suppressing sulfite dimerization at a polarized gold electrode/water solution interface for high-quality gold electrodeposition[J]. Langmuir, 2021, 37(38): 11251-11259.

[21] Fang J L. Thoery and applications of electroplating addictives[M]. China: National Defense Industry Press, 2006.

[22] Shaw C F. Gold-based therapeutic agents[J]. Chem. Rev., 1999, 99(9): 2589-2600.

[23] Huang S S, Liu C, Jin L, Yang F Z, Tian Z Q. Complex coordination silver electrocrystallization mechanism on glassy carbon electrode surface[J]. J. Electrochem., 2018, 24(04): 344-350.

[24] Budevski E, Staikov G, Lorenz W J. Electrocrystallization nucleation and growth phenomena[J]. Electrochim. Acta, 2000, 45(15-16): 2559-2574.

[25] Scharifker B, Hills G. Theoretical and experimental studies of multiple nucleation[J]. Electrochim. Acta, 1983, 28(7): 879-889.