Advanced Mixed-Mode Bending Test: Influence of the Surface Topography on the Fracture Behavior of an EMC to Copper Lead Frame Bi-Material Interface

Abstract

In this paper, a hypothesis is further investigated which states the dependence of fracture toughness on the orientation of the crack opening to the topography of the surface of the lead frame which forms the interface with the EMC. Additionally, the size effect of the specimen width is investigated as well.A test series using the Advanced Mixed Mode Bending method was performed using eight samples. The samples are bi-material beams which are extracted from a mold map. The sample width was varied as well as the orientation of the beam according to the topography of the lead frame. The samples are destructively tested and the measured sensor and image data are then used in a finite element analysis. A new algorithm is introduced which utilizes a digital image correlation software to extract the displacement fields from the recorded images of the beam flank. The simulation results in form of the critical energy release rate $G_{c}$ versus the corresponding mode mixity $\psi$ of the eight samples are than analyzed to test the hypothesis of the orientation and the effect of the sample width as alias of the size effect.