STRESS SINGULARITIES IN BI‐MATERIAL WEDGES WITH ADHESION AND DELAMINATION

Abstract

Abstract The order of the stress singularity at corners in bi‐materials is calculated by means of a local approximation of the stresses. This is performed for interfaces with adhesion and for interfaces which show delamination. It is demonstrated that the singular behaviour is less severe in the case of adhesion, i.e. when delamination is prevented. This result provides an explanation for the phenomenon that cracking at comers of bi‐material wedges only occurs in the presence of delamination. This conclusion is confirmed by experiments on micro‐electronic devices using scanning acoustic tomography, Fracture of the plastic encapsulation and failures of the electrical circuits are only observed in areas where the plastic has delaminated from the chip surface.