A Viscoplastic-Based Fatigue Reliability Model for the Polyimide Dielectric Thin Film

Abstract

In this study the fatigue characteristics of polyimide thin film used in redistribution interconnects were considered. Cyclic tension tests under various stress-and strain-ranges were performed to investigate the damage accumulation in the thin film. It was observed that, under cyclic strain loading, the deformation of the thin film is mainly governed by viscoelastic stress relaxation behavior, and damage of the thin film is insignificant. On the other hand, the thin film under cyclic stress loading exhibits a viscoplastic ratcheting response. Furthermore, the envelope of the strain response under stress-controlled cycling increases as the fatigue cycle increases. A phenomenological model was developed for characterizing the damage accumulation under cyclic stress condition. The model considers the viscoplastic response by superpositioning a power-law plastic model and a linear viscoelastic model for predicting the growth of the strain envelope. The fatigue prediction model can be applied for predicting the fatigue failure of the polyimide dielectric in the redistribution interconnects.