| abstract |
When using an immersion tin plating solution, contaminants build up in the solution, which results in a reduction in plating rate and quality of the plating deposit. One major contaminant that builds up in the bath during use is hydrogen sulfide, H2S. If gas is bubbled or blown through the solution, contaminants, especially hydrogen sulfide, can be effectively removed from the solution, and thus high plating rates and plating quality can be restored or maintained. In this regard, any gas can be used, however, it is preferred to use a gas that will not adversely interact with the solution rather than removing contaminants. For this purpose, nitrogen gas is particularly preferred because it is effective in removing contaminants including hydrogen sulfide, but does not cause oxidation of tin ions from its divalent to tetravalent state, which is disadvantageous. |