Characteristic Comparing between Thermosonic Flip Chip Bonding and Reflow Flip Chip

Ultrasonic features in bonding area are of interests for researchers in the field of microelectronics packaging. In this study, the interface characteristics of bonding were detected by using XD7100 X-ray, the velocity of ultrasonic vibration at bonding tool was determined with a PSV-400-M2 high frequency (1.5 MHz) laser Doppler vibrometer, micro- characteristics of the specimens of thermosonic flip chip bonding were inspected by using a high resolution transmission electron microscope. Results show that bubbles at the interfaces of reflow soldering flip chip were observed, however they were not discovered during thermosonic flip chip, the interface characteristics of thermosonic flip chip is better than that of reflow soldering flip chip. The acceleration of the ultrasonic vibration was about 500000 m/s2 for a 62.73 kHz bonding frequency. This strong mechanical effect activates dislocations in the metal crystalline lattice and enhances atomic diffusion across the bonding interfaces, and these differ from melting mechanism of reflow soldering.