Reactions of high lead solders with BIOACT EC-7R semi-aqueous cleaning reagent

Due to environmental concerns, terpene based cleaning fluids have replaced Freon in cleaning baths at several AT&T manufacturing sites. The terpene formulations employed in semi-aqueous processes, typically, are used to deflux circuit boards where most of the interconnections are formed using 60 Sn/40 Pb solder. Recently, the use of terpene cleaning, BIOACT EC-7R, was extended to thin film ceramic substrates where high lead solder (95 Pb/5 Sn) forms the interconnection. In the presence of high lead solder, EC-7R quickly changes from colorless to bright yellow. In addition, the cleaning process deteriorates and residues are found on the circuits. Thus, the use of high lead solder leads to the replacement of the cleaning baths at shorter time intervals (four weeks) than when 60 Sn/40 Pb solder is present (6 months). The goal of the work discussed below is to elucidate the reactions between the circuit metallurgy and the EC-7R chemical composition.