Analysis of impedance loading in ultrasonic transducer systems

The authors develop an equivalent network model for a piezoelectrically driven acoustic system used in microelectronic wire bonding. The system includes a concentrator horn and flexurally resonant tip piece, which are the most commonly encountered connection structures. Starting from the differential equations of motion, impedance transfer functions are developed for each structure. These are combined to form an aggregate system transfer function relating the electrical input impedance to the mechanical load impedance. The model has been validated for the unloaded case subject to continuous variations in the mechanical dimensions of the system. Experimental data are presented which support the validity of the model