Cohesive zone modeling of mixed-mode delamination test

Delamination is one of the main problems in electronic packaging due to the relatively weak adhesion strength of interfaces. In order to predict interface delamination the cohesive zone method is a possible tool. However, the correct choice of the cohesive parameters still forms an obstacle for general usage. In order to improve this, the present paper focuses on delamination modeling of delamination of an interface between Molding Compound and Copper lead frame as observed in preceding mixed mode bending tests. The choice of the cohesive zone parameters in relation to the active length of the cohesive zone, the mesh size and the crack propagation speed was first investigated by 2D modeling. Here the plane stress assumption was applied, as the test samples were quite narrow. Afterwards a symmetry half of the specimen was modeled, again combined with cohesive zone elements, to verity the plane stress condition. Simulation results of both the 2D and 3D models agree well with the experimental results.