Scaling and universality in electrical failure of thin films

We describe the electrical failure of thin films as a percolation in two-di mensional random resistor networks. We show that the resistance evolution f ollows a sealing relation expressed as R similar to epsilon(-mu) where epsi lon = (1 - t/tau). tau is the time of electrical failure of the film, and m u is the same critical exponent appearing in the scaling relation between R and the defect concentration. For uniform degradation the value of mu is u niversal. The validity of this scaling relation in the case of nonuniform d egradation is proved by discussing the case in which the failure is due to a filamentary defect growth. The existence of tills relation allows predict ions of failure times from early time measurements of the resistance.