Characterizing the Aging-Driven Degradation Rate of Electrical Contact Resistance and Mechanical Integrity of Plastic-Encapsulated Au/Al Wire Bonds
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Abstract
Gold-aluminum interconnect is an integral part of conventional chip packaging. The gold-aluminum interface deteriorates during the operation of a device due to the formation of gold-aluminum intermetallic compounds. Spatial changes during intermetallic formation cause voids, which separate the interface, resulting in the catastrophic failure of the bond, and hence the device. This phenomenon is driven by temperature and time. With increasing device densities and overall package miniaturization, device heat dissipation densities are increasing, necessitating adequate understanding of the phenomena to assure appropriate device life for the intended application. Intermetallic formation is governed by diffusion rules, but the observed failure rates reported in the literature many times diverge from Fickian pattern. This conflict is resolved in this dissertation. Various failure rates are considered to show that a digression from Fickian pattern is possible. An effort is undertaken to improve the understanding of failure modeling. Failure mechanism is analyzed and a solution is presented.