Ultrasonic Cu Wire Bonding on Nano-Twinned Ag-Cu Films Coated SiC Chips Sintering Cladded with Stress-Buffered Cu Foils for Artificial Intelligent (AI) Servers

Through adequate sputtering process, Ag-8.2 Cu alloy nanotwins with very high density of (111)-orientation of 98.1% were sputtered on Ti-precoated SiC chips.The nanotwin enhanced Ag sintered cladding of Cu foils with SiC chips led to low porosity (1.3 to 2.1 %) and high bonding strength (26.1 to 48.3 MPa).The first use of Ag-8.2 Cu alloy nanotwinned film in this study exhibits a higher hardness and strength than those of the conventional pure Ag or Cu nanotwins.Sound shear strengths of 5.8 Kgf and 6.3 Kgf at the interface of Cu wire/SiC chip and Cu wire/DBC substrate, respectively, were achieved and the ultrasonic bonded specimens fractured in the Cu thick wire after shear tests, ensuring satisfactory joints.When a practical and efficient industrial processing is considered, an alternative product of Ag preforms previously coated with nano-twinned Ag films has been developed to replace the Ag sintered Cu folis on a nanotwinned coated SiC.