Analysis and application of vibration behaviour for wirebonding capillary by transmission laser vibrometer

With the application of the proprietary transmission laser vibrometer, we have developed a novel calibration system which enabled the real time acquisition of vibration characteristics of a wirebonding capillary. This system mainly comprises an ultrasonic (US) monitoring unit and the transmission laser vibrometer. Using this calibration system, we could analyze the exact vibration modes of a wirebonding capillary, as well as the correlation between the set parameter for the US oscillator and actual vibration amplitudes of the wirebonding capillary. Therefore, even with the presence of machine to machine differences in vibration characteristics, we could independently obtain appropriate processing parameters for each wirebonder by performing linear calibration of each vibration characteristic against the reference characteristics. Finally, by real time monitoring of US output characteristics, i.e. current, voltage, frequencies, impedance, and phase difference, this system enabled the in-situ detection of abnormal US oscillation. This capability was applied to identify insufficient intermetallic formations during wirebonding and contributed to the reduction of poor bond failures.