Improved Thermal Conductivity and Reliability Through Graphene Reinforced Nanopaste for Power Devices in New Energy Vehicles

Ag nanopaste is one of the most promising die-attach materials in power devices. In this work, robust sintered SiC devices are achieved by using graphene reinforced Ag nanopaste to improve the heat dissipation and shear strength. Microstructure, mechanical, and electrical properties of the sintered joints are investigated. The addition graphene can bring exciting performance improvements, and graphene (< 0.25 wt%) is found to be enough to bridge voids among Ag particles. The decomposition temperature of nanopaste exhibits an increasing trend with the increase of graphene content. The sintered layer forms metallurgical interfaces between chip and substrate, while excellent metallurgical combination ensures the mechanical, electrical, and thermal properties of die attachments. The joint strength is significantly improved after adding graphene compared with pristine Ag nanopaste, especially when sintered at a lower temperature of 230 °C, the joint strength is increased by 3~4 times. Good interconnection can be achieved at a sintering temperature of 190 °C. Low temperature interconnection, fast sintering (sintering time:
$\ge 1$
min), and lower thermal resistance and junction temperature will provide an effective way to enhance the quality of the sintered Ag joints, which is promising for the attachment of power devices in new energy vehicles.