6 A Workflow Combining Ansys Sherlock, Icepak, and Mechanical to Evaluate the Reliability of Electronic Systems
10. With fans included in the design, the reliability goal for the PCBA is met with significant margin regardless of the incorporation
of DCIR analysis in the workflow. The fan solution would prevent solder fatigue, but it is possibly over-designed. These results hint
that a compromise may be achieved. Perhaps a heat sink attached to the high power BGA at the center of the board that is driv-
ing peak temperature would reduce temperatures enough to prevent failure risk even without the fans.
For the remainder of this analysis, we will assume we move forward with the forced air solutions. This would prevent thermal
cycling related solder fatigue, but would it fully mitigate failure risk associated with temperature.
11. In order to fully capture the effects of part temperature rise, the Icepak CFD results must be included as an input to the
structural FEA analysis. This is imperative to properly account for constraint effects from the PCBA expanding within its housing
and buckling/warping, temperature gradients resulting in mismatched component/board expansion rates, and temperature-
dependent material properties.
12. To accomplish this, the temperature map with airflow is imported into Ansys Mechanical ahead of a pothole shock simulation.
Figure 10: Mapping of Thermal Gradients from Icepak to Mechanical.
