The Design And Realization Of Ultrasonic Generator

Thermo-sonic wire bonding is a vital technology in semiconductor packaging industry. Nowadays, a welding spot is completed in about 20 ms, and high consistency of all welding spots is demanded by semiconductor packaging industry. Traditional ultrasonic wire bonding devices only have harmonic frequency tracing function, so its amplitude of ultrasonic vibration rises slowly and unstable. This kind of ultrasonic bonding devices cannot keep up with the development of semiconductor packaging industry.By analyzing the equivalent electrical model of ultrasonic transducer, this thesis proved that the vibration amplitude of ultrasonic transducer is proportional to drive current and the better matching inductor matches ultrasonic transducer, the bigger the ratio is. Based on the conclusion mentioned above, an experimental method was proposed to find optimum matching inductor. Furthermore, equivalent electrical model of transformer was analyzed to get equivalent inductance of transformer winding. Optimum matching inductor and equivalent inductance of transformer winding make it possible to get optimum impedance matching network.Based on the proportional relationship between the vibration amplitude of transducer and drive current, an advanced ultrasonic generator with current closed-loop control was designed and realized by this dissertation. It also prevents ultrasonic generator from failing to trace harmonic frequency and eliminates the mutual influence between PLL and current closed-loop. In contrast to traditional ultrasonic generator, the rise time of drive current is shortened from 4 ms to 2 ms.