Influence of Technological Parameters on the Behavior during Aging at High Temperature of Various Packages, in the Automotive Environment

The failure mechanism related to Kirkendall voids is a consequence of the intermetallic thickness growth (Au- Al). It impacts the wires bonding reliability at high temperature. Temperature accelerates the intermetallic thickness growth as the diffusion between gold and aluminium is accelerated. Moreover, the role of the package geometry was identified, and experimental results were confirmed by both simple analytical model and FEM simulations. This study confirms a good choice for the automotive environment at high thermal aging (150degC). Finally, the WP and BS tests of the thermal behavior do not allow a continuous monitoring of the degradation, and are time and sample consuming. So we are developing a measurement procedure coupled to a theoretical study of the resistance variation of the wire bond, aimed to produce an early failure indicator of the ball bonds.