Reliability Assessment of Cu-Al WB under Automotive Temperatures in Presence of Ionic Contamination and Voltage Bias

Abstract

A deeper understanding of the acceleration factors under operating stresses is required for high-reliability harsh environment applications. Copper wire is now being used for first-level interconnects in automotive electronics. Palladium coated copper and gold-flash palladium coated copper are two copper wire compositions that have emerged. The corrosion resistance of copper wire bonds in high-temperature environments is still unknown. The EMC used to encapsulate chips and interconnects can vary widely in formulation, including pH, porosity, diffusion rate, composition of contaminants and contaminant concentration. A predictive model that can account for ambient factors, operational circumstances, and EMC exposure is required to accurately reflect projected wirebond dependability. Different EMCs were investigated in this work in a high-temperature-current environment with temperatures ranging from 60°C to 100°C and currents ranging from 0.2A to 1A. To build a Multiphysics model, diffusion kinetics based on the Nernst-Planck Equation for chlorine ion migration were combined with the Butler-Volmer equation for corrosion kinetics. Polarization curves for copper, aluminum, and intermetallics have been measured at various pH levels and chlorine-ion concentrations.Measurements of polarization curves were used to extract Tafel parameters.