Reliability Assessment of Flip-Chip Assembly of Al Bumps

This article reports on a flip-chip bonding technology using an Al bump at high temperatures, such as for SiC semiconductors. In recent years, double-sided mounting structures have been proposed for purposes of miniaturization and low inductance. The surface-mounting method requires durability against high temperatures. We propose a new technique for the flip-chip bonding of an Al bump made from bonding wire. The recrystallization temperature of Al is under 250°C. As a result, there is an expectation of mitigating mechanical stress between the chip and the bonded substrate. We conducted a high-temperature aging test at 250°C for 3,000 h and a thermal shock test between −40°C and 250°C for 3,000 cycles. Results indicate that the shear strength of the Al bump meets the requirements specified in the IEC60749-19 guideline up to 2,000 cycles at room temperature.