Cu wire stitch bond reliability study under high temperature storage

Copper wire bond has been applied in industry for years and its package reliability is certainly an important subject for researchers and manufacturers. The mechanism of wire bond formation is complicated and a consensus hasn´t been reached. Combination of a few theories to hypothesize the whole process of copper wire stitch bond formation on silver plating surface is elaborated in this paper. The key factors determine high temperature aging reliability of a system consists of copper, silver and epoxy mold compound is discussed. Lastly, a case of stitch bond open failure under high temperature storage with copper wire bonded on silver plated copper leadframe package is discussed. Failure analysis is conducted and root cause is identified.