High frequency transducer for ultrasonic bonding

Study of the fabrication, material properties, and resonance characteristics of lead zirconate titanate (PZT)/epoxy 1–3 piezocomposite rings and investigation of the design, fabrication, and evaluation of ultrasonic transducers for high frequency wire bonding in microelectronic packaging based on these composite rings were presented and discussed in this thesis. Original contributions reported in this research included: (1) Hard PZT piezoceramic ring, PKI804, and epoxy, Araldite LY5210/HY2954, were selected as the active and passive phases in the 1–3 structure, respectively. The technique for making composite rings was devised. (2) An existing parallel model was applied to predict the material properties of the composite rings as a function of &phis;. This model was extended to include the prediction of dielectric loss tangent and mechanical quality factor $Qm$. An optimization of composite properties against different values of &phis; for transducer design was discussed. (3) The resonance characteristics of the composite rings were investigated by classifying the resonance modes into two main categories, namely the longitudinal-thickness mode f_H and lateral mode f_L1 and f_L2 resonances of the individual PZT elements inside the rings as well as the radial mode f_R, wall-thickness mode f_W, and stopband f_S1 and f_S2 resonances of the whole rings. A guide of operating f_H in the rings without causing mode coupling was presented to optimize the composite structure for transducer design. (4) Physical models for designing piezoelectric drivers and ultrasonic horns, were consolidated based on the one-dimensional elastic wave theory. These transducers were about 50% shorter than the commercial designs for facilitating high-speed bonding and comprised minimal number of components for assuring good quality of manufacturing. (5) The natural frequencies and vibration mode shapes of both transducers were computed using finite element analysis (FEA). A reliable design procedure was proposed to use the physical models for exploring a design possibility and to apply the FEA for detailed behavior study and/or design optimization. (6) The technique used to build a high quality ultrasonic bonding transducer was disclosed, whereby the design prototypes were fabricated. The process-test results showed that the use of the composite transducer on an ultrasonic wire bonder had widened its operating window, thereby promoting the fine-pitch and high-speed capabilities in terms of higher bonding yield. (Abstract shortened by UMI.)...