A sensor integrated in a smart ultrasonic transducer was used to monitor the bonding quality during wire-bonding process. The sensor was a lead zirconate titanate (PZT) ring located in the middle of the Langevin sandwich driver of a wire-bonding transducer, where the electrode of the sensor was sub-divided into several regions. The specially designed electrode pattern can increase the bandwidth of the sensor, while the signal patterns for different bonding conditions, such as wire missing, good bond, peeled off bond and non-stick bond, were identified. The bonding quality has been experimentally correlated with the area under the normalized sensor signal. Hence, the sensor in the smart transducer provides a useful tool for in situ bonding monitoring of an automatic wire-bonding system. (C) 2002 Elsevier Science B.V. All rights reserved.