Dynamic and Equilibrium Phase Behavior in the C12E5–Abietic Acid–H2O System

Abstract Previous research has investigated the removal of representative flux residues (abietic acid (AA) in isopropyl alcohol (IPA)) from printed wiring assemblies using aqueous solutions of a nonionic surfactant (pentaethylene glycol mono- n -dodecyl ether (C 12 E 5 )). To optimize cleaning with this surfactant, greater understanding of the equilibrium and dynamic phase behavior in the AA-C 12 E 5 -H 2 O system is required. In this research, partial ternary phase diagrams were developed at 60 and 45°C (above the binary cloud point). Increasing the AA content of the system caused isotropic surfactant (L2) and lamellar liquid crystalline (La) phases to form at lower temperatures than in the binary C 12 E 5 –H 2 O system. As the temperature increased, the solubility of AA in the L2 phase increased considerably, while the AA content of the La phase was not affected as strongly. The dynamic phase behavior resulting from contact of micellar C 12 E 5 solutions with AA or AA/IPA particles at 24°C (below the binary cloud point) and 45°C was also observed. When AA or AA/IPA particles were contacted with 4.1 × 10 −3 M C 12 E 5 solutions, the surfactant and water penetrated into the particles to create isotropic liquid aggregates. When particles were contacted with more concentrated micellar C 12 E 5 solutions (0.25 M ), a new concentrated surfactant phase surrounded the particles and solubilized the AA.