Study on the Chip and Tool Tip Vibration of Thermosonic Flip Chip Bonding

The vibration of flip chip and tool tip during thermosonic flip chip (TSFC) bonding were observed and the effect of bonding force on the chip vibration was studied. Firstly, the vibration velocity of tool tip and chip on TSFC bonding was monitored with a laser Doppler vibration measure system (LDV), and the "stall" phenomena was observed by the virtual value curve of vibration velocity, i.e., after the TSFC bonding started a fever milliseconds, the chip velocity decreases suddenly, while the tool tip velocity still increases. Stall indicated that the bump/pad interface has formed initial bonding strength. And then the frequency characters of the vibration velocity signals were studied. It is found that the 3rd harmonic of chip vibration velocity indicates the stall phenomena, i.e., when the 3rd harmonic appeared, the stall happens. Finally, effect of bonding force on vibration harmonics of chip were studied, and the experiment results show that the 3rd harmonic is appeared early when the bonding force is little, which indicated that the little bonding force is good for the initial bonding force formation.