Manufacturing and Characterization of Piezoelectric Force Sensor Arrays for Investigation of Ultrasonic Wire Bonding

Abstract:
Ultrasonic (US) wire bonding is a very complex process. Different mechanisms occur at different locations of the bonding interface in a very short time making a spatially resolved investigation of the process extremely difficult. As a result the local mechanisms stay unclear. Therefore, a novel 3x4 force sensor array has been developed for the in-situ investigations of the ultrasonic wire bonding process. The array is based on the piezoelectric ceramic lead zirconate titanate (PZT), which is first divided into individual sensor columns via precision dicing and then filled with a polymer. Each of these columns acts as a single sensor of the array with a sensing area of 360x160 µm². The array was used to measure the local tangential forces, which occur at the contact region between the wire and the substrate during the bonding process. To be able to detect the local effects even more precisely a sensor array with smaller elements has been developed recently. Building on the existing design, the new version of the array now features 4x12 sensors with a sensing area of 100x100 µm² while maintaining the same total size of around 1600x500 µm² as before. This work presents the manufacturing and characterization of the new sensor array, which promises in-situ measurements of the bonding process with enhanced resolution.