Measurements of tin-palladium catalyst concentration by an optical method

Abstract

Abstract Electroless plating on plastics is a technology that changes the plastic surfaces to appear like metals for decoration as well as specific applications. The plastic surfaces are commonly treated in a catalysing process by using a tin-palladium catalyst whose concentration is in a specific range. Since the concentration of the tin-palladium catalyst strongly affects the catalysing process as well as the plating quality, its concentration is regularly monitored. We present a study on measurements of the concentration of the tin-palladium catalyst with red-brown color based on an optical method. Its absorption spectrum monotonously decreases when the wavelength of the incident light increases. For a given wavelength, the absorbance increases with the concentration. Five standard concentrations are used to construct several calibration equations between the absorbance and the concentration by linear fits for different wavelengths. The calibration equations are verified by eight tested solutions. The results show that wavelengths in the range of 310 – 500 nm are suitable for the concentration measurements of tin-palladium catalyst since the errors are less than 5%.