Corrosion engineering in the packaging of electronic, magnetic and optical devices

Corrosion processes affecting electronic, magnetic and optical devices are chemical and electrochemical in nature. Ionic contaminants, applied voltages, and relative humidity accelerate failure of integrated circuits. Packaging materials often reduce the corrosion rate although understanding of the basic processes taking place at the coating/metallic circuitry interface is incomplete. In this paper the role played by oxygen, water and ionic contaminants on packaged metallic materials are considered. Transport properties of polyimides (currently used as packaging and dielectric in microelectronics) and corrosion behaviour of polyimide/iron and polyimide/aluminium systems were investigated. Experimental findings reported in this paper indicate that metallic failure can be ascribed to the transport of ionic contaminant across the packaging material. A relationship between the resistivity of the insulator and the time of failure is also presented and discussed in the light of trend towards device densification. (A