Diffusion on Two Interfaces of Ultrasonic Flip Chip Bonding

Cross-section features in a flip-chip bonding area were inspected by using a high resolution transmission electron microscope (HRTEM). For the better flip chip bonding variables, depth of atom diffusion at Au/Al interface of ultrasonic flip chip (FC) bonding was about 500 nm by using a line scanning of HRTEM, and depth of atom diffusion at Au/Ag interface of ultrasonic FC bonding was about 200 nm. If Au/Ag interface received ultrasonic energy first by changing the process of ultrasonic FC, depth of Au/Ag atomic diffusion was about 450 nm, and depth of Au/Al atomic diffusion was about 250 nm. An ultrasonic energy conversion law was discovered that the ratio of first interface to next interface along ultrasonic energy transmitting path in ultrasonic FC bonding was about 2.28:1, which indicated an optimizing process of ultrasonic FC bonding, and a new way of FC bonding was designed for the first interface along the path of ultrasonic energy transmitting.