Numerical analysis of interfacial delamination in thin array plastic package

It is well-known that high thermal stresses induced interfacial delamination is a typical failure mode in multi-layered micro-electronic components. Therefore, it is a key factor in package design to minimize interfacial stresses to enhance package reliability. In this paper, two designs of TAPP with different die attach pastes were manufactured. It was found that some test vehicles had cracks near the lead-frame paddle/mold compound side interface after 1000 temperature cycles (-65 degC to 150 degC) although the electrical test passed. The failed units were analyzed and the physical location and shape of the failure was determined. Meanwhile finite element analysis was performed to find the locations of highest stress, and the expected modes of failure. A quarter three-dimensional (3-D) FEM model was constructed using commercial software ANSYS 11.0. The distribution of thermal stresses in the package was calculated and mapped, which were used to predict the most possible delamination origin and to describe the entire failure history of the package subjected to different thermal histories. It also identified material properties of the as the primary factors in this failure mechanism.