Copper wire in automotive: Key challenges and robust validation

Opportunities and challenges of copper wire bonding implementation in the automotive context are presented from two different viewpoints: manufacturability and reliability. Compared to gold, copper offers better thermal and electrical properties, but its higher hardness imposes a tighter process control and a dedicated approach to process setup, optimization and validation. Compatibility with the plastic package direct materials and process flow has to be addressed, too. From a reliability standpoint, intrinsic ageing mechanisms like separation of Cu-Al Inter-Metallic Compounds (IMC), bond thermal fatigue in presence of molding compound delamination, copper or Cu-Al IMC corrosion have to be characterized in terms of lifetime margin versus severe application-specific environmental conditions typical of the automotive field. The key pillars of a robust qualification methodology are proposed, where the dominant failure mechanisms are prevented through a “copper-compatible” design, and their impact on product wear-out verified by extended stress testing in corner conditions.