Response Surface Analysis of Process Parameters for Thermocompression Ultrasonic Flip Bonding of Chips

Thermocompression ultrasonic flip bonding has been widely used in semiconductor packaging. In order to better understand the mechanism of bonding interface formation of thermocompression ultrasonic flip bonding. A 3-D dynamics finite element model (FEM) of the chip, gold bumps, and substrate was developed, which considers the softening effect of gold bumps during the bonding process. The effects of pressure application position, pressure magnitude, temperature, and ultrasonic power on the stress and plastic strain in the chip, gold bumps, and substrate were analyzed. The results indicated that the maximum stress and plastic strain occurred at gold bumps and the edge of under-bump metallization (UBM) layers for the global model, while the maximum stress at a single bump appeared in the central region. The pressure application position had a minor effect on reducing stress concentration, but had a significant effect on reducing plastic strain concentration. The pressure under various amplitudes had a major effect on the stress, while temperature had a minor effect. The results may provide some references for thermocompression ultrasonic flip bonding of chips.