Comprehensive Characterization of All Inorganic and Organic Components in Neutral Tin Plating Bath for Electronics Applications

Abstract

Tin plating at neutral and near-neutral pH is the preferable process in the application of electronic components such as capacitors and resistors, where the chemically sensitive ceramic and glass portions can be damaged by highly acidic solutions (often used in semiconductor packaging processes). Stannous ions are not as stable at elevated pH due to oxidation and hydrolysis, and plating demands the use of a large number of additives making the process control very challenging. Various analytical techniques are developed for automatic and comprehensive characterization of all inorganic and organic bath components including simultaneous detection of conductive salt, anti-whisker and chelator by near-infrared (NIR) spectroscopy, brightener by potentiometric titration, stannous ions by electrochemical method, and the breakdown stannic ions by spectro-titration.