INVESTIGATION OF STRESS SINGULARITY FIELDS AND STRESS INTENSITY FACTORS FOR CRACKS

The reliability of semiconductor devices and packages used in microele ctronics is compromised by interfacial delamination and homogenous cra cking that is initiated at the edge of the interface between dissimila r materials during processing and stress tests. These failures have ce rtain characteristics in that they begin at the stress singularity poi nt. The knowledge of interfacial fracture mechanics is very important to the design for reliability of these devices and packages. In this p aper, a model of stress singularity is proposed and applications of th e model for the characterization of interfaces are subsequently presen ted. Examples are integrated circuit (IC) device interfaces and plasti c package interfaces. These interfaces were mainly characterized with the order of stress singularity. Furthermore, this study demonstrates applications of the stress intensity factors for the stress singularit y fields. The stress intensity factors were obtained from a r-theta co ordinate system, the order of stress singularity, the Dunders' paramet ers, and the extrapolation as a function of distance. The relationship between the stress intensity factors and the fracture toughness stren gth of molding compound as a function of mode mixed was also investiga ted for cracking at the edge of the interface. The proposed numerical scheme was verified by the experiments on the lead-on-chip (LOC) packa ge crack under temperature cyclic loads. (C) 1998 Elsevier Science B.V . All rights reserved.