Thermal fatigue life evaluation of substrate with Cu through-hole considering the mechanical properties of Cu thin film and glass fiber cloths structure

Abstract

In this study, the thermal fatigue life of substrate with Cu through-hole is evaluated by considering the mechanical properties of Cu thin film and glass fiber cloths structure. We first conducted tensile tests of Cu thin film and found that the rate-dependence of inelastic property varies abruptly with temperature. An inelastic constitutive model for Cu thin film is then proposed by combining both rate-independent and rate-dependent models. The proposed inelastic constitutive model is introduced in a Finite Element Method based analysis of glass epoxy substrate with Cu through-hole. Moreover, low cycle tests of Cu thin film are carried out by using repeated 4-point bending to evaluate its isothermal fatigue properties. Through our analysis we verified the capability of the proposed model to predict thermal fatigue life of Cu through-hole using the isothermal fatigue properties. The results show that the glass fiber cloths structure of the substrate needs to be considered in order to successfully predict the thermal fatigue life of the Cu through-hole.