New techniques for the design of advanced ultrasonic transducers for wire bonding

A new high-frequency ultrasonic transducer, in particular for the application wire-bonding, has been conceived, designed, prototyped, and tested. In the design phase an advanced approach was used and established. The method is based on the two basic principles of modularity and iteration. The transducer is decomposed in its elementary components. For each component an initial draft is obtained with finite-elements-method simulations (FEM). The simulated ultrasonic modules are then built and characterized experimentally through laser-interferometry measurements and electrical resonance spectra. The comparison of simulation results with experimental data allows the parameters of FEM models to be iteratively adjusted and optimized. The achieved FEM simulations exhibit a remarkably high predictive potential and allow full control on the vibration behavior of the ultrasonic modules and of the whole transducer. The new transducer is fixed on the welding device with a flange whose special geometry was calculated by means of FEM simulations. This flange allows the converter to be attached on the welding device not only in longitudinal nodes but also in radial nodes of the ultrasonic field excited in the horn. This leads to a total decoupling of the transducer to the welding device, which has so far been unheard of. The new approach to mount ultrasonic transducers on a welding-device is of major importance not only for wire-bonding but also for all high-power ultrasound applications.