The influence of boric acid and dissolved oxygen on the morphology of electroless palladium films

Abstract

The effects of boric acid and dissolved oxygen on the morphology of palladium films deposited from the ethylenediaminetetraacetic acid (EDTA) and triethyleneamine (TEA) baths were studied. Striking morphological differences in the palladium films after the addition of boric acid were observed by scanning electron microscopy. The addition of boric acid in the EDTA bath enhances the deposition rate, while in the TEA bath it has the effect of producing lower coverage films and changing the particle shape from agglomerated nodules to round and smooth particles. The function of boric acid in the electroless bath is not only to act as a buffer but also to affect the nucleation and growth behavior of deposits, depending on the bath composition. The effect of dissolved oxygen on the electroless palladium films was investigated by growing films from EDTA and TEA baths that had had the dissolved oxygen concentration reduced by bubbling nitrogen through the baths for 10 min prior to electroless deposition. The palladium films deposited from the bath with dissolved oxygen are typically loosely packed discontinous films. The EDTA bath seems to be more sensitive to the dissolved oxygen, resulting in palladium deposits which are fewer than those from the nitrogen-bubbled bath. A possible mechanism of the dissolved oxygen effect in the electroless metal bath is proposed.