Related to microelectronics’ reliability, lifetime estimation methods have gained importance, especially for surface-mounted devices. The virtual testing of electronic assemblies necessitates the geometry modeling and finite element analysis of the solder joint. The effect of the simplification of the solder geometry on the predicted lifetime is an open question. Furthermore, there is still not yet straightforward guidance for the choice of the material model and fatigue lifetime model. In this study, the impact of the geometry input method, the material model and the lifetime model choice is investigated on two different surface-mounted capacitors in a simulation-based benchmark analysis under thermal cyclic loading. Four different types of solder geometry modeling approaches are compared, among which one is a physics-based approach. Ten different fatigue models founded on plastic and viscoplastic material models are benchmarked. The results show that the component standoff height and the solder volume have a positive effect on the lifetime, while the capacitor size has a slightly negative effect on the lifetime. The results also suggest that approximate geometries can be used to replace the physics-based model with a restriction for the minimum standoff height.

Thermomechanical fatigue is one of the most common cause of the failure in microelectronic technology in the solder joints. The lifetime prediction for microelectronic components is a very important area in nowadays automotive industry, because the lifetime estimation fatigue models in the literature differ in their results by orders of magnitude. However, developing an accurate lifetime estimation methodology for microelectronic components is not straightforward, because the failure mechanism of the solder joints under cyclic thermomechanical load is not fully understood. In addition, there are numerous tolerances and uncertainties during the designing and manufacturing processes, such as component size, copper pad area, solder material volume or the formed standoff height of the component from the copper pad. These parameters can hugely affect the lifetime of the solder joint. In this paper a benchmark analysis based on finite element method were carried out with four plastic strain-based fatigue models to understand the impact of the standoff height to the estimated lifetimes. Three CAD models were created with identical parameters, except the standoff height of the components. Creating the solder geometries for the 3D models, Surface Evolver software were used. The result shows that the fatigue models give the same tendencies varying the standoff height values. However, changing the standoff height increases the differences between models, even if they are tuned so that the estimated lifetime matches for a certain standoff height.

In the lifetime prediction simulations of microelectronics solder joints, the stand-off height and misalignment parameters are founded on a variety of estimation methods from very simple to complex approaches. However, the stand-off height and misalignment play essential role in the lifetime of solder joints. Thus, a reliable lifetime simulation requires proper solder geometry model. Many researchers calculate the solder geometry with the software called Surface Evolver, which minimizes the total energy, including the surface tension energy. Some of these studies used energy-based methods for the stand-off height prediction. The first hypothesis is that by changing the predefined value of stand-off height in the Surface Evolver simulation, we gain different total energy values and by differentiating the energy with respect to the stand-off height, we can obtain the vertical force and a nonlinear spring characteristic for the molten solder. Similar results can be found in the literature for BGA. Secondly, it is hypothesized that this spring-like behaviour is observable in horizontal direction too, which is related with the misalignment of the component. The presented approach provides a simple model for the prediction of the stand-off height and misalignment.