Discussions on the Failure Mode and Criterion of Passivation Cracks

Passivation cracks are studied with experimental observation and finite element simulation. Corner cracks are first initiated, and then edge cracks are subsequently initiated along the edge from the corner to the center. The cracks show a good symmetric pattern over both symmetric axes. Simulation results show that the maximum Von Mises stress is located at die corner, which correlates to the first crack initiation from experimental observation, and the direction of first principal stress matches exactly with the cracking direction (principal stress direction is vertical to the crack surface). Failure criterion for the passivation crack is then discussed.