Sensors for ultrasonic bonding process control

Abstract

The main objective of this project is to develop a sensor system that can be used to monitor important parameters in ultrasonic wire bonding, namely, ultrasonic amplitude, impact force and bonding time. These parameters can be used to distinguish the bond quality and to provide real-time feedback signals for in-process control. Chapter one gives background information relating to ultrasonic wire bonding and highlights the importance of measuring different bonding parameters. Chapter two presents a review of the working principle and describes the characteristics of ultrasonic wedge transducer used in the present study. Chapter three describes an innovative way of placing a polyvinylidene fluoride (PVDF) polymer sensor between the piezoelectric driver and the concentrator horn. Different electrode patterns are evaluated for use in detecting the ultrasonic amplitude and the impact force. The most suitable electrode configuration is being evaluated further in Chapter four. Chapter five describes how the sensor is calibrated and Chapter six relates the bond quality to the sensor output. A short conclusion and suggestions for future work are given in Chapter seven. The placement and calibration of sensor for bond quality monitoring described in this thesis is an original work with practical application that has not been reported before. We have filed a United State Patent based on the present work.