Formation and study of the properties of finishing coatings of a circuit board with tin–zinc alloy instead of tin–lead alloy coatings

Abstract

A formation technique of electroplating coatings of tin–zinc alloy (50) based on using low-toxicity lactic acid as surfactant, ligand, and buffer addition was developed. The dependences of alloy composition and cathodic yield on the alloy current and the coating quality on the concentration of tin and zinc ions in the solution, the content of lactic acid, the solution acidity (pH), the temperature, and the current cathodic density were investigated. The optimum conditions of the process carrying out were determined. The performance characteristics of obtained coatings were investigated. It was proven that the coating with this alloy meets the requirements of GOST (State Standard) 23752–79 “Circuit Boards. General Technical Specifications” and can be used for the circuit boards of products of the instrument-making industry instead of tin–lead alloy, which will make it possible to reduce the environmental risk of production, as well as increase the efficiency and maintainability of devices and systems.