フーリエ変換赤外全反射 (FTIR ATR) 法による無電解ニッケル-リン合金めっき浴の In Situ モニタリング

概要

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In situ monitoring of electroless nickel plating baths using sodium hypophosphite as a reducing agent was investigated by FTIR ATR spectrometry.Basic bath composition was NiSO4·6H2O 0.1mol/L, C6H5O7Na3 0.2mol/L, NaH2PO2·H2O 0.2mol/L and Na2HPO3·5H2O 0.2mol/L (pH 8).Linear relationships were obtained between the absorbance of the characteristic absorption bands and the concentrations of hypophosphite, phosphite, citrate and sulfate. In continuously used baths with large accumulations of phosphite and sulfate, the ATR spectra of hypophosphite, phosphite and sulfate overlapped, but even in these cases compositions could be determined with sufficient accuracy by curve fitting.This constitutes a simple, rapid procedure that requires no dilution, separation or other pre-treatment, and was applied to the in situ monitoring of electroless plating baths with satisfactory analytical results.