Ultrasonic Bonding of Ag and Ag-Alloy Ribbon—An Innovative Alternative for High Power IC Packages

With the development of automotive power electronics and high-power integrated circuits, ribbon bonding is currently in the spotlight for its superior properties to those of traditional heavy wire bonding. In this article, innovative ribbon materials made of Ag and Ag-4Pd are introduced. The ultrasonic bonding of Ag and Ag-alloy ribbons on direct bonded copper (DBC) substrates metallized with Ni/Pd/Au films was evaluated as replacements for Al and Cu ribbons. A continuous bonding interface with satisfactory pull strength can be obtained from substrates metallized with Pd and Au films due to their similar metallurgical properties and softer surface conditions. The footprint study of bond residuals after pull tests correlated with the failure codes and bond strengths of the modules. The reliability of Ag and Ag-4Pd ribbons with regard to pull strength after high-temperature storage tests (HTSTs) at 150 °C for 1000 h was slightly increased, and the bond interface remained unchanged. The results showed that Ag and Ag-alloy ribbons made specifically for power electronics are feasible and can be an attractive alternative to aluminum ribbons.