Design and Experiment of a Dual-Frequency Ultrasonic Transducer for Aluminum Wedge Bonding

Abstract

Ultrasonic transducer (UT) plays a critical role in the aluminum wedge bonding of insulated gate bipolar transistors (IGBTs). Compared with the conventional single longitudinal transducer, we propose a dual-frequency UT that can effectively bond aluminum wires ranging from 100 to $500~\mu $ m. The configuration of the transducer is designed by finite element method (FEM). A grooved annular flange is developed to obtain the transducer with the common nodal flanges of the two disparate frequencies. The effect of pretightening torques on the performances of the transducer is investigated, and the optimum torque with 55 kg cm is obtained. The impedance measurement proves that the dual frequency of the developed transducer is 61.3 and 86.5 kHz, respectively. Vibration tests indicate that the amplitudes of the capillary at low and high frequencies are 24.4 and $6.4~\mu $ m, which can satisfy the bonding specification. Finally, the bonding of 100– $500~\mu $ m aluminum wires is successfully realized, with the tensile strength exceeding standard strength.