| abstract |
Upon use of an immersion tin plating solution, contaminants build in the solution, which cause the plating rate and the quality of the plated deposit to decrease. One primary contaminant, which builds in the plating solution upon use, is hydrogen sulfide, H 2 S. If a gas is bubbled or blown through the solution, contaminants, especially hydrogen sulfide, can be effectively removed from the solution and, as a result, the high plating rate and plate quality can be restored or maintained. In this regard, any gas can be used, however, it is preferable to use a gas that will not detrimentally interact with the solution, other than to strip out contaminants. Nitrogen is particularly preferred for this purpose because it is efficient at stripping out contaminants, including hydrogen sulfide, but does not induce the oxidation of the tin ions from their divalent state to the tetravalent state, which is detrimental. |