Simulation of the lifetime of wire bonds modified through wedge trenches for higher reliability

A new lifetime model for aluminum wire bonds, which is capable of describing the physical influence of material properties, thermal loading condition and geometry, has been used to investigate the reliability of modified wire bonds. The model is based on finite element simulation and the description of crack propagation in the region near the Al-Si inter-face (wedge crack) through a modified Paris law. To improve the lifetime of wire bonds, the mechanical stiffness of the wedge can be reduced through geometric alteration; this can be done e.g. through laser cutting. The impact of the modified geometry on crack propagation rate and thus on wire bond lifetime is calculated using the new modelling technique.