Fatigue life evaluation accuracy of power devices using finite element method

Fatigue life evaluation of power devices is closely related to the temperature distribution on the solder layer. During thermal cycling, the solder layer reaches a uniform temperature. In case the power cycle becomes short, this state is different from the real active state of the power device. Because the real temperature distribution on the solder layer is non-uniform. Therefore, there is a difference between a fatigue life evaluation that uses power cycling and one that uses temperature cycling.To accurately predict the fatigue properties of power devices, evaluation techniques based on a coupled electrical-thermal–mechanical analysis are proposed. This method is based on the finite element method. Therefore, the calculation accuracy of the fatigue life evaluation depends on the mesh resolution. The accuracy of the prediction is expected to indicate the accuracy of the numerical solution procedure, or modeling techniques (the accuracy of the physics captured, the electro-thermal-structure coupling and plasticity law etc.). To verify the calculation accuracy of this fatigue life evaluation method for a power device, we investigate how the mesh resolution affects the fatigue life evaluation.

Fatigue life evaluation of power devices is closely related to the temperature distribution on the solder layer. During thermal cycling, the solder layer reaches a uniform temperature. In case the power cycle becomes short, this state is different from the real active state of the power device. Because the real temperature distribution on the solder layer is non-uniform. Therefore, there is a difference between a fatigue life evaluation that uses power cycling and one that uses temperature cycling. To accurately predict the fatigue properties of power devices, evaluation techniques based on a coupled electrical-thermal–mechanical analysis are proposed. This method is based on the finite element method. Therefore, the calculation accuracy of the fatigue life evaluation depends on the mesh resolution. The accuracy of the prediction is expected to indicate the accuracy of the numerical solution procedure, or modeling techniques (the accuracy of the physics captured, the electro-thermal-structure coupling and plasticity law etc.). To verify the calculation accuracy of this fatigue life evaluation method for a power device, we investigate how the mesh resolution affects the fatigue life evaluation.Figure optionsDownload as PowerPoint slideHighlights
► To develop a reliable power device, a fatigue life evaluation based on a simulation is developed.
► The simulation consists of an electrical analysis, a thermal analysis and a mechanical analysis.
► Using the simulation, both heat dissipation and internal stress absorption also can be calculated.
► The calculation accuracy for the fatigue life cycle depends on the mesh resolution.
► The life cycle prediction accuracy can be improved by selecting an adequate mesh based on knowledge.