Comparative study of tripropylamine and naphthylamine as additives in wave solder flux: investigation of solderability and corrosion effects

Dicarboxylic acid flux activators are used in no-clean wave solder flux formulation for activating the solder surfaces on Printed Board Assembly (PBA) during the soldering process. However, flux residues containing dicarboxylic acid chemistry on PBA can cause adverse corrosion issues under humid conditions due to its hygroscopic and acidic nature. This paper systematically investigated tripropylamine and naphthylamine as additives together with dicarboxylic acid activators on the solderability performance and humidity robustness. Evaluation of the solderability was assessed using hot plate spreading test and wetting balance methods, while thermal degradation was investigated using Fourier-transform infrared spectroscopy. The moisture interaction behavior of activator chemistry was investigated using electrochemical impedance spectroscopy and chronoamperometry techniques. Results showed improvement of wetting ability using tripropylamine additive in succinic acid based fluxes, while tripropylamine additive increased the maximum wetting force for adipic acid based flux activators. Significant reduction of leakage current value was obtained using tripropylamine and naphthylamine additives in succinic acid based fluxes under 98% RH/40 °C.