Interface fracture mechanics evaluation by correlation of experiment and simulation

Interface fracture mechanics is one of the main focuses of electronics reliability research. Determination of fracture mechanical properties of interface cracks is a substantial task for design for reliability concept. Without experimental determined fracture mechanical parameters such as the critical energy release rate a reliability forecast based on simulation results cannot be given. In fracture mechanics testing often a correct measurement of the crack tip location is needed for the calculation of the energy release rate. The authors present a combined simulative and experimental method for crack tip location determination of typical interface specimens. The specimens are loaded in a newly designed testing apparatus, the Mixed Mode Chisel (MMC) setup, and images of the crack tip at the interface are taken at different load states during the testing procedure. Then images are analyzed by image correlation techniques (DAC, deformation analysis by correlation) and crack tip displacement fields are determined. In the next analysis step the displacement fields are compared to fields from finite element analysis of the same specimen geometry with boundary conditions similar to the experimental setup. The point of the best matching of the experimental and simulative field is the actual crack tip location. If finite-element data or analytical solution for the crack tip displacement field is available the method can be applied for a variety of different interface samples.