The ultrasonic wirebond failure mechanism associated with interfacial changes in a thin-film device was studied. The thin-film device was fabricated on a ferrite substrate and composed of a gold layer on top with titanium, nickel-iron and aluminum oxide underneath. The chemical changes at the nickel-iron/aluminum oxide interface, induced by the transfer of ultrasonic energy through the gold and the titanium layers were investigated by Auger electron spectroscopy. The applied ultrasonic energy promoted preferential migration of iron to the interface resulting in weakening of the bond between the nickel-iron and its adjacent aluminum oxide layer.