Testing and simulation of lifetime for wire bond interconnections with varying bond foot angle

Ensuring sufficient reliability is one key aspect in the design process of a power electronic module. The wire bond interconnection to the semiconductor chip is often limiting the power cycling lifetime of the module. Increased packaging density as well as integration of additional components on module level can limit the available space for the wire bond layout. To enable proper "design for reliability" measures the layout parameters affecting the lifetime of the module have to be identified. In this paper, the rotation of the bond foot relative to the bond loop is identified as a significant factor that decreases lifetime. The resulting bond foot angle is evaluated for different power semiconductor chips by means of accelerated lifetime testing isolated from other design parameters as well as with application relevant designs, compounding multiple parameters relevant for the lifetime of the module. In order to further facilitate "design for reliability" by reducing the number of necessary design iterations a multiphysics simulation is set up. An applicable evaluation method for bond layout changes is identified and good correlation of the computed equivalent plastic strain to lifetime testing data is established. Additionally, the impact of operation conditions of the module based on the load current applied to the bond wires is evaluated numerically.