Reliability of Silver Wire Bonds in Harsh Environments
Dr. Pradeep Lall
Silver wire bonds are being targeted as a cost-effective replacement for gold-wire bonds used for chip-level interconnects. Experimental data on the reliability and failure mechanisms of Silver wire bonds is scarce. In absence of historical data, the correlation of silver wire bond performance in accelerated tests and its correlation with operational life is at best tenuous. Further, silver has long been known as a material, which exhibits resistive shorts. The use of existing decapsulation protocols result in the reduction in the silver wire diameter, thus resulting in destruction of important data sought through the decapsulation process. The proposed project attempts to resolve the shortcomings in the state of art.
Research will focus on the study of the physics of failure mechanisms in Silver wirebonds operating under high current and high voltage bias for the development of acceleration factors to allow for assurance of long-term storage reliability in harsh environments. Correlation of the high-temperature and high-humidity with the operational reliability of silver wirebonds will be established. Damage proxies for the initiation and progression of damage in wirebonds will be developed to allow for identification of pathways for ascertaining the accrued damage in components and assemblies that have been stored for long periods of time. The polarization curves and Tafel parameters will be measured for the silver wirebond system for a number of commonly encountered pH values, and contamination concentrations and storage times. The measurements will be used for development of a multiphysics model for life prediction and assessment of remaining useful life.