Fine pitch copper wire bonding — Why now?

Fine pitch Cu wire bonding is at the cusp of becoming main stream. Many challenges had to be overcome when making the transition from fine pitch Au wire bonding to fine pitch Cu wire bonding in a high volume manufacturing environment. The challenges for Cu wire bonding arise from the inherent properties of Cu: propensity to oxidize, increased hardness, slow intermetallic growth whilst dice are (still) designed for packaging with Au wire bonding i.e. pad metal stack and thickness.