Analysis of Cu(I) Complexes in Copper Sulfate Electroplating Solution by Using Reaction Kinetics with a Chelate Reagent

摘要

Cu(I) in electroplating solutions was analyzed by absorption of a chelate of Cu(I) with balhocuproinedisulfonic acid, disodium salt (BCS). The absorbance of the color reaction of Cu(I) increased quickly in a few minutes after mixing with BCS and subsequently continued to increase slowly. Cu(I)-PEG (polyethylene glycol) complexes with different chain lengths were detected using MALDI-MS. Results show that Cu(I) ions exist not only as small complexes but also as large complexes with PEG. We divided Cu(I) complexes into two groups, small and large complexes, and assumed the color reaction is a first order reaction with a specific reaction rate constant and simulated the absorption curve with a good correlation and obtained the concentrations and the time constants, inverse of rate constants, of small and large complexes. These are important parameters to control plating solutions. Using this analysis, we monitored the variation of Cu(I) concentrations in production lines for one month.