Ni Micro-Plating and Ni nano-particle bonding were applied for high temperature resistant chip interconnections of power device packaging. During the evaluation of the reliability of interconnections annealed at up to 300°C, we observed no significant changes in mechanical or electrical properties. Die attach connection was carried out by sintering Ni nano-particles at a low temperature below 300°C. It was also revealed in a bonding experiment using a SiC chip with a deposited Al layer that direct bonding to an Al electrode was possible by using Ni nano-particles. A stress-relaxation structure using a metal film was presented as a new structure for resolving the problem of deteriorating bonding reliability due to thermal stress arising from differences in the coefficient of thermal expansion (CTE) between the chip and the substrate. A SiC device was assembled using the new bonding methods and an operating test was performed to verify normal operation in a high-temperature environment of approximately 300°C and higher.