Acid tin-silver alloy electroplating bath and method for electroplating tin-silver alloy

摘要

The invention relates to an acid tin-silver alloy plating bath which comprises tin ions, silver ions, one compound selected from the group consisting of aromatic thiol compounds and aromatic sulfide compounds, substantially non-cyanide and a balance of water, the pH of the bath being not higher than 2. According to this acid bath, tin and silver can be kept dissolved in the bath in a stable state for a long period of time even at a high temperature and a predetermined plating capacity is kept for a long period of time even though the bath is free from cyanide.