Abstract: A cyanide-free gold electroplating solution for forming gold deposits contains bismuth and compact-packed via-filling deposit with a U-shaped stacked structure in cross section inside drilled holes. A gold electroplating solution includes 15 g/L of gold (I) sodium sulfite (as gold element), 15 g/L of sodium sulfate, 50 g/L of sodium sulfite, 10 mg/L of thallium formate (as thallium element), 50 mg/L of bismuth nitrate (as bismuth element) and 1 g/L of sodium phosphate.

Abstract: The present invention provides a non-cyanogen type electrolytic gold plating solution, which can form a plating film capable of maintaining a high hardness even when the plating film is subjected to a heat treatment. A non-cyanogen type electrolytic gold plating solution of the present invention includes: a gold source including an alkaline salt of gold sulfite or ammonium of gold sulfite; and a conductive salt including sulfite and sulfate. The non-cyanogen type electrolytic gold plating solution includes a salt of at least one of iridium, ruthenium, and rhodium in a metal concentration of 1 to 3000 mg/L. Further, the non-cyanogen type electrolytic gold plating solution preferably includes a crystal adjuster. The crystal adjuster is particularly preferably thallium.