Sensors for automatic process control of wire bonding

PZT sensors were installed on an ultrasonic transducer used for wire bonding in order to record ultrasonic amplitude and bonding time during the bonding process. To find an appropriate location for the sensor placement, the vibration displacement distributions of the transducer were measured using a high frequency heterodyne interferometer. The non-linear signal detected by the PZT sensor was processed and the signatures of the higher frequency harmonics were recorded and related to the bonding quality. The change in harmonic contents and its relation with bond quality will be used to develop a real-time automatic process control system for wire bonding