Improvement of Silver-Sintered Die Bonding of SiC/DBC Power Modules Through Backside Metallization With High-Density (111) Orientation Ag Nanotwinned Films

Silver paste sintering is a promising die attachment technology for power electronic devices due to its high thermal and electrical conductivities, as well as superior mechanical properties. This study presents the silver-sintered die bonding of SiC/DBC power modules with traditional Ti/Ni/Ag backside metallization and Ti/Ag nanotwinned metallization with a high-density (111) orientation. Cross-sectional analyses of the sintered die bonding joints of Ti/Ag nanotwinned metallized SiC chip with direct bonded copper (DBC) substrate indicate minimal porosity at the interface, leading to increased shear strength. In addition, fractographic analysis highlights the effective bonding between the silver sintering paste and the nanotwinned film. An innovative “Green channel model” is proposed that the interface between the silver-sintered layer and nanotwinned thin film with (111) orientation provides a rapid path for the silver atoms supplied by the silver-sintered particles to be transported to the gaps of Ag powders, leading to the effective reduction of sintering porosity and increase of die bonding strength. The high diffusivity of nanotwins effectively promotes silver-sintered die bonding, particularly at lower temperatures, indicating the potential of applications in electronic packaging of power modules.