The effect of electro-thermal fatigue on the structure of power electronic devices. Micro-structural evolution of the metallization layer

Abstract The fatigue-induced modifications of the structure of power devices on components that underwent extreme electro-thermal fatigue were investigated, with special attention to the behaviour of the Al metallization layer. Electrical cycling induced a moderate grain growth in the metallization layer, except for the regions located beneath the connection wires. There the wire bonding process is associated with severe plastic deformation, leading to a fragmentation of the initial grains and significant grain growth. Grain-boundary grooving is another example of fatigue-induced structural changes: it reveals an intense stress- and temperature-driven grain boundary diffusion process.