Electrical matching of low power piezoelectric ultrasonic transducers for microelectronic bonding

• The electrical matching of low power piezoelectric transducers for microelectronic bonding is studied.
• A frequency ratio function has been introduced to decide whether or not an electric matching is necessary.
• The frequency ratio function is analyzed and electrical matching is discussed.
• Results show that it is not necessary to operate electrical matching when the frequency ratio function is small

The electrical matching of low power piezoelectric ultrasonic transducers for microelectronic bonding is studied in this paper. The admittance characteristics of the transducers are described through admittance circle diagrams and the electrical matching analysis for the transducers is presented. The frequency ratio function has been introduced and analyzed. The result shows that the frequency ratio function increases with the static capacitance, dynamic capacitance and dynamic resistance, and decreases with the dynamic inductance. When the static capacitance, dynamic capacitance, dynamic resistance and dynamic inductance are small, there are little differences between the resonance frequency and the series resonance frequency, and it is not necessary to operate electrical matching when the frequency ratio function is less than 0.001. A typical low power piezoelectric transducer used in microelectronic bonding has been adopted to verify the results of electrical matching analysis. The analysis and experimental results show that the transducer can work well at its vibration frequency without electrical matching.