The Reliability Modeling Analysis And Life Prediction Of An Automotive Power Module

With the wildly use of the Automotive Power Module, its reliability becomes more and more important. During thermal cycling test, the coefficient of thermal expansion mismatch (CTE) between chip and solder joints or wires may cause alternating thermal stress and strain, which will induce the interconnect layer failure because of crack initiation and propagation. In this paper, the finite element simulation software ANSYS(?) is used to analysis the reliability of an Automotive Power Module, the main works and conclusions are summarized as follows:First, a3D finite element model of an automotive power module is built with ANSYS, both the energy-based method and the effective creep-strain-based method are investigated and discussed through numerical analysis. The differences are compared and analyzed. The characteristic life of solder joints are predicted through different life prediction models. The research result showed that, for a complex structure of a power module, the characteristic fatigue life predicted in energy method is closer to experimental values.Second, the solder joint fatigue life of a low-temperature sintered Nano-silver material is simulated by using both the energy-based method and the creep-strain-based method. Compared to the traditional material of solder joint, the low-temperature sintered Nano-silver has small equivalent stress, strain, the larger tensile strength and the stronger ability to resist the thermal fatigue failure. So, the characteristic fatigue life of low-temperature sintered Nano-silver is far greater than traditional solder joints, and fully illustrated the importance of low-temperature sintered Nano-silver in microelectronic power package.Third, various solder die attachments and6MOSFETS with different thicknesses are studied and their fatigue lives were further predicted by energy method and effective strain method. The result showed that, the trends of solder joints’fatigue life are different from different life prediction methods.At last, a3D finite element model with wire bonding structure is developed, and the characteristic life of key wire is analyzed by using sub-model technique. At the same time, a parameter study for radius of bonding wire, the length of lead connector in different diameters is examined in two different working conditions. And the material property and mesh density of the bonding wire are studied for its impact on the characteristic life.