REMOVAL OF ORGANIC FILMS FROM SOLID-SURFACES USING AQUEOUS-SOLUTIONS OF NONIONIC SURFACTANTS .1. EXPERIMENTS

An important step in the production of printed wiring assemblies (PWAs ) is the postsolder removal of flux residues from the surface. Traditi onally, this has been accomplished using CFC-113-based solutions, but the Montreal Protocol and the Clean Air Acts have forced the developme nt of alternative cleaners. This is a study of the mechanisms by which aqueous solutions of a nonionic surfactant (pentaethylene glycol mono -n-dodecyl ether (C(12)E(5))) remove films of flux residues (abietic a cid in isopropyl alcohol) from PWA surfaces. Cleaning rates were studi ed in a rotating disk apparatus to control hydrodynamic conditions. Th e cleaning process followed a three-step mechanism. In the first stage , surfactant liquefies the organic by partitioning into the film. In t he second and third stages, shear stresses at the PWA surface remove a ggregates of the surfactant-laden liquefied AA from the bulk AA film a nd the PWA substrate, respectively.