Thermosonic bonding for ultrasound transducers: Low-temperature metallurgical bonding

A low-temperature bonding process for ultrasound transducers is presented: compatible with poling requirements, manufacturability and reliability. In this work, we demonstrate that a thermosonic bonding process can provide a reliable, metallurgical bond at moderate temperatures, even down to room temperature, with bonding times in the order of seconds. Bonding parameters (temperature, compression force, ultrasonic energy) were optimized by evaluating shear strength on Au stud bump bonded Si chips. Model systems have been bonded, mimicking a complete Electro-Acoustic Module (EAM), including a stack of IC emulator / flex interconnection / interface part of the ultrasound transducer.