Influence of the Bond Foot Angle on Active Power Cycling Lifetime of Wire Bonds

The wire bond interconnection on a semiconductor chip is one of the key failure points for standard power electronic modules. Miniaturization efforts as well as additional module components can limit the design options regarding the geometry of the bond loop and the positioning of the bond feet. It can be necessary to deviate from the standard layout with all bond feet positioned along one axis, which results in an angle between the bond foot and the bond loop. The impact of this design parameter was evaluated by means of a power cycling study. It was found that an increase in the bond foot angle resulted in a significant reduction in lifetime for bonds on power semiconductors. For a better understanding of this effect, the strain distribution at the bond interface was evaluated using a multiphysics simulation. An adapted analysis routine for the simulation results was established, which was able to confirm the impact of the bond foot angle and provided a good correlation of the strain at the interface to the tested lifetime of the interconnection.