Alkanolamines as activators in no-clean flux systems: investigation of humidity robustness and solderability

This paper systematically investigates the humidity robustness and solderability of five alkanolamines used as activators in flux systems, and their effect was assessed along with the influence of soldering temperature. Electrochemical impedance spectroscopy and chronoamperometry techniques were used to obtain a better understanding of water adsorption, absorption, and protonation tendencies of alkanolamine candidates. Potentiodynamic polarization, hot plate spreading test, and wetting balance test were adapted for the etching ability and solderability evaluation. Thermal degradation of alkanolamine compounds was analyzed using thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FT-IR). The combined results indicate a strong water absorption and protonation of diethanolamine (DEA), triethanolamine (TEA), and triisopropanolamine (TIPA), rendering them not reliable and not feasible as activators. Poor solderability of alkanolamine-based fluxes was inferred based on their thermal degradation behavior and poor oxide removal ability under the soldering conditions.