Interfacial fracture strength evaluation of Cu/SiN micro-components: applicability of the linear fracture mechanics criterion under a hydrogen environment

摘要

The strength against fracture initiation from an interface free-edge of bonded copper (Cu) and silicon nitride (SiN) micro-components is studied. Quantitative fracture tests are conducted either in a vacuum environment or in a gaseous hydrogen (H environment. By using two kinds of specimens, Types I and II, having the same free-edge geometry (135/135) but different outer shape, the validity of the linear fracture mechanics criterion is critically evaluated. For specimens tested in vacuum, fracture initiation strength represented by the elastic stress intensity factor of the near-edge normal stress component is found to be the same irrespective of the specimen type, indicating that the fracture mechanics criterion holds. For specimens tested in H gas, the strength of both types is reduced and, interestingly, Type II strength shows greater reduction than Type I. In other words, the fracture mechanics criterion does not hold in H gas. Such a difference may be attributable to the difference of local plasticity in each specimen type.