Study of stepped horn transducer for ultrasonic wire bonding

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Study of stepped horn transducer for ultrasonic wire bonding

 

Author: Liou, Chi-wa
Title: Study of stepped horn transducer for ultrasonic wire bonding
Degree: M.Sc.
Year: 1998
Subject: Wire bonding (Electronic packaging)
Transducers
Ultrasonic welding
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Applied Physics
Pages: xxi, 145 leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1436968
URI: http://theses.lib.polyu.edu.hk/handle/200/389
Abstract: A throughout study of the stepped horn transducer for ultrasonic wire bonding is carried out. The theory of piezoelectric sandwich driver and a design chart is developed which is used for designing the sandwich driver (Chapter 3). The theory of the stepped horn has also been studied. Various vibration modes such as the longitudinal, torsional and flexural modes are being studied and design charts for the these vibration modes are given (Chapter 4). A stepped horn is fabricated according to the theory and longitudinal mode of vibration is being measured by using a laser interferometer (Chapter 5). The measurement helps to determine the position of the wedge tool. Finally, a discussion and suggestion for future work is provided (Chapter 6). Topics discussed in this thesis are as follows: I. A brief introduction and importance about ultrasonic wire bonding are given. The wire bonding mechanism and testing method of the wire bonding is also reviewed. Various kinds of horns are being introduced including the stepped horn (Chapter 1). II. The measurement of the ultrasonic vibration by using laser interferometer is given. A study of the principle of operation, electronic configuration and calibration of the laser interferometer measurement is shown (Chapter 2). III. Basic principle of piezoelectricity is developed which leads to the theory of the piezoelectric driver. By using the Mason equivalent circuit, a design chart is drawn which helps to design a sandwich transducer (Chapter 3). IV. A detail study of various vibration mode of cylindrical rod is developed. Thus, leads to the development of the theory of the stepped horn. The various vibration modes include longitudinal, torsional and flexural modes are being studied. With this development, various design charts are drawn. From these design charts, the position of the step and resonance frequency with maximum amplification can be determined (Chapter 4). V. Stepped horns are being fabricated with two type of aluminium alloy. The stepped horns are finely polished to facilitate the laser interferometer measurement. With the experimental setup in Chapter 2, the longitudinal mode of vibration is measured. The impedance/gain phase analyzer is used to measure the electrical impedance of the stepped horn. From the measurement result of the laser interferometer, the position of the wedge tool is determined. After mounting the wedge tool onto the stepped horn, a laser interferometer is used to measure the flexural mode of vibration of the wedge tool. All the detail experimental results are given (Chapter 5). VI. An explanation for the measurement results in the previous chapter is given. Finally, a suggestion for the future development is also presented (Chapter 6).

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