Via fatigue failure has been identified4 as a potential failure mechanism in high density interconnects. This failure mechanism is directly influenced by the stress-strain level at the potential points of failure in the structure and the ductility of the via material. This paper looks at the effect of some manufacturing and design process variables on the fatigue life of the vias. The key variables are the trace or conductor thickness (metallization thickness), the layer or layers of the dielectric around the trace and in the via, the via geometry, wall slope, the ductility coefficient of the conductor material and the strain concentration factor. The metallization thickness is found to have the most dramatic effect on the fatigue life of the via compared to the other design variables. Good via ductility and strain concentration factors improve the fatigue life drastically.