Cu Ribbon Ultrasonic Bonding on Die-Top Nanotwinned Cu Films Evaporated on SiC Chips for Power Modules

Résumé fourni par la source

Cu ribbons were manufactured through continuous casting to 6 mm thick wire, drawing to 0.51 mm fine wire and rolling to 200 μm thickness and 1000 μm ribbons. Annealing treatments with applying an electrical current of 34 Amp led to an average breaking load of 4.2 Kgf, elongation of 38.0% and hardness of 76.2 Hv. Nanotwinned Cu films were sputtered on SiC dies as stress buffer layer to prevent the chip cratering during the ultrasonic bonding using Cu ribbons. The results indicated that satisfactory joints were obtained with shear strengths of 6.3 Kgf and 7.5 Kgf at the interface of Cu ribbon/SiC chip and Cu ribbon/DBC substrate, respectively. The joints after shear tests fractured in the Cu ribbon, rather than along the bonding interfaces, displaying a tight interconnection for the power modules.

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