	US 12,173,424 B2
	Gold electroplating solution
Koichiro Inoue, Hiratsuka (JP); Junko Tsuyuki, Hiratsuka (JP); Shinji Maeda, Hiratsuka (JP); and Yusa Imanishi, Hiratsuka (JP)
Assigned to EEJA LTD., Tokyo (JP)
Filed by EEJA LTD., Tokyo (JP)
Filed on Sep. 25, 2023, as Appl. No. 18/372,302.
Claims priority of application No. 2022-152878 (JP), filed on Sep. 26, 2022.
Prior Publication US 2024/0102193 A1, Mar. 28, 2024
Int. Cl. C25D 3/48 (2006.01); C25D 3/62 (2006.01)

CPC C25D 3/48 (2013.01) [C25D 3/62 (2013.01)]

8 Claims

1. A cyanide-free gold electroplating solution for forming gold deposits containing bismuth preferentially over thallium and compact-packed via-filling deposit with a U-shaped stacked structure in cross section inside drilled holes, comprising the following basic elements and additional elements,

said basic elements being:

(a) gold (I) sulfite complex (as gold element) 1-30 g/L

(b) sulfurous acid or sulfites 5-200 g/L

and said additional elements being:

(d) bismuth catalyst (as bismuth element) 30-150 mg/L

(e) thallium catalyst (as thallium element) 5-50 mg/L.