CHARACTERIZATION OF NITROGEN-BLANKETED WAVE SOLDERING REACTIONS USINGTHERMAL-ANALYSIS

Thermal analysis techniques have been employed to elucidate the mechan ism of low solids soldering flux activation. Metal oxides (SnO, PbO an d PbO2) are converted to carboxylate salts, which are displaced in the solder wave, rendering a solderable metal surface. Neither of the act ivators tested, namely succinic acid and adipic acid, react with SnO2 at soldering wave temperatures and therefore cannot yield a solderable surface when SnO2 is present. Further, adipic acid reacts with SnO to form a salt that can decompose to cyclopentanone, so the preheating o f the printed circuit board must be carefully controlled to yield a so lderable surface.