Feasibility of lead-free piezoceramic based power ultrasonic transducers

Lead-based piezoceramics are currently the most widely used transduction material in power ultrasonic applications. Directives such as the Restriction of Hazardous Substances (RoHS and RoHS2) regulate the sale of electrical and electronic equipment containing hazardous substances, such as lead, entering the European marketplace. However, lead-based piezoceramics have been exempt due to the lack of a genuine lead-free equivalent. Lead-free piezoceramics were first developed in the 1950s, however their relatively poor properties when compared to PZT left them largely neglected until the implementation of the European directive. This study investigates the incorporation of a modern lead-free piezoceramic, a variant of bismuth sodium titanate (BNT), into a commercial power ultrasonic transducer used in semiconductor wire bonding. It is reported that a device containing BNT was capable of forming wire bonds, and that the lead-free transducer exhibited properties that could make them suitable in other power ultrasonic applications.