Corrosion Engineering in Device Packaging

Abstract

ABSTRACTCorrosion processes affecting electronic devices are chemical and electrochemical in nature. Ionic contaminants, applied voltages, and relative humidity accelerate failure of integrated circuits. Although packaging materials often reduce the corrosion rate of the underlying circuitry, a complete understanding of the mechanism for the basic processes taking place at the coating/metallic circuitry interface is missing.In this paper the role played by water and ionic contaminants on coated metallic substrates is considered. Transport properties of free standing polyimide membranes have been examined. The corrosion behavior of polyimide/Fe and polyimide/Al systems has been investigated using electrochemical polarization, and a.c. impedance measurements. For the AI/PI system underfilm degradation has been examined using x-ray photoelectron spectroscopy (XPS). Results indicate that the flux of ions is very small compared to that of oxygen and water and yet metallic failure can be ascribed mainly to the transport of ions across the packaging material. XPS showed that considerable degradation takes place at the metal/polyimide interface prior to visible corrosion or delamination.