Kinetics of flux residue formation in a humid environment

Abstract

Flux residue has been a manufacturing concern for many decades, as these potentially conductive residues increase the possibility of circuit failure. To avoid this, printed wire assemblies were cleaned with chloroflourocarbon (CFC) solvents. However, CFC's are very detrimental to the environment, contributing to the destruction of the ozone layer. While it is possible to identify an environmentally friendly cleaner, eliminating residue formation, and thus the need for any cleaning is also desirable. A series of studies conducted at Rensselaer demonstrated that residue forms as a result of a reaction between either the retained flux or the by-product of the fluxing reaction, and water vapor. This study evaluates the growth of residue and residue precursor (flux or by-product) in order to determine the chemical kinetics of residue formation and the relation to the soldering flux.