Wire bonding is the most common process for creating interconnects between an integrated circuit (IC) and its package using fine metal (such as gold or aluminum) wires [1][2]. In wedge bonding, ultrasonic energy, pressure, and heat are applied to form a bond; the process avoids introducing impurities and provides flexibility in material choice. For larger diameter wires, the frequency is often around 50-60 kHz whereas, for finer diameter wires, the frequency is much higher, up to as much as 200 kHz.
The design of the transducer includes examining the natural frequencies associated with its longitudinal motion. Changes in geometry, for example, can influence the vibration and electrical characteristics of the device.
In piezoelectric ceramics, an applied voltage induces strain (displacement) in the material and vice-versa, demonstrating the coupling of the electric and structural fields. Piezoelectric ceramics are very brittle in tension, so a preload is needed to keep the ceramics in a compressive state of stress in operation.
The following figure shows the ultrasonic transducer modeled in this example.
