| abstract |
When using an immersion tin plating solution, contaminants accumulate in the solution, which reduces the plating speed and quality of the plated deposit. One major contaminant that accumulates in the plating solution in use is hydrogen sulfide, H 2 S. When the gas is bubbled or blown through the solution, contaminants, especially hydrogen sulfide, can be effectively removed from the solution, resulting in high plating rates and plating quality being restored or maintained. In this regard, any gas may be used, but other than stripping off contaminants, it is preferred to use a gas that will not adversely interact with the solution. Nitrogen is particularly preferred for this purpose because it is effective in stripping off contaminants, including hydrogen sulfide, and does not induce oxidation of the tin ions from the divalent state to the harmful tetravalent state. |