Evaluation of interfacial fracture toughness of Al/sapphire joints fabricated by SAB process.

The bonded area is largely affected by the surface morphology and mechanical properties of materials by surface activated bonding (SAB) process, because the room temperature bonding process is carried out under a low temperature and low pressure for short time. Accordingly, interfacial defects cause fatally harmful problems in many cases. For an application of this technique, it is important to know the effect of interfacial defects on fracture behavior. The fracture mechanism and its criterion for the growth of interfacial defects were investigated using the Al/sapphire joint. It became clear that the growth of interfacial defects is the dominant factor for crack propagation. An estimation of stress intensity factor for the growth of interfacial defects was tried in two ways, stress criterion and energy criterion. A critical stress intensity factor for the growth of interfacial defects was estimated as 0.3–0.5 MPa m[sup 1/2] by the analysis of FEM calculation and experimental observation. [ABSTRACT FROM AUTHOR]