Ansys Sherlock for Evaluating Thermal Cycling

March 28, 2023 Adam LeMay

Ansys Sherlock is a powerful physics-based electronics reliability design tool that enables engineers to predict the life of printed circuit boards (PCBs) and electronic assemblies accurately and quickly using multi-physics simulation. Whether you are in the early stages of design or are trying to identify issues within a more mature product, Sherlock’s capability to create meshed circuit card models with realistic component properties based on its extensive library of component models can be asset to any design team. The software’s intuitive interface also encourages collaboration between engineers of different disciplines, allowing them to generate fully meshed FEA models that can be exported and analyzed using Mechanical, IcePack, and LS-DYNA, depending on the specific project needs.

In this example, we will use Ansys Sherlock to evaluate the solder joint reliability of an open-source game controller called PhobGCC. The PhobGCC project aims to recreate the Gamecube controller from the early 2000s with more modern, wear-resistant components. Like all consumer electronics, these kinds of products can be abused more than you might think.

Figure 1: PhobGCC PCB

To begin, we will import the PCB design data into Sherlock. Ansys Sherlock supports various file types, including ODB++ and Gerber libraries, which can be imported and assembled into a layered PCB model. Once we have imported the data, we can update the parts list using the extensive Sherlock library, which includes component models and data from numerous manufacturers.

Figure 2: Layer Viewer in Ansys Sherlock

Figure 3: Fully Mesh FEA Model of the PCB

Next, we will define the thermal cycling profile. In this case, let’s say the manufacturer was interested in how many times the controller could be cycled between room temperature and the temperature of a hot car before 3% of the production lot would fail. Of course, you could set up a physical test with a large sample size and equipment to check the performance of each board, but Sherlock allows you model this quickly without needing to manage testing efforts.

Figure 4: Thermal Cycle

To predict solder joint fatigue of the PhobGCC controller, Sherlock utilizes the FEA model we’ve generated to determine the strain on each joint caused by CTE differences between the CCA and the component. Sherlock uses accepted models for the accumulation of strain in a solder joint under repeated loading and a Weibull distribution based on characteristic life to generate a life curve for each component and for the system. After subjecting the CCA model to the virtual testing environment where the above thermal cycle is applied 24 hours a day, Sherlock generates the following life cycle curve for the product.

Based on these results, around day 650, 3% of units will have failed under the temperature cycling profile. The designer can evaluate this data and decide if the failure rate is acceptable. If not, the individual life curves of each component can be used to pinpoint the weakest links in the reliability chain and make necessary changes. This workflow eliminates costly testing efforts and allows design teams to optimize product reliability prior to first build.

In conclusion, while this example may seem like a bit of fun, it showcases the power of Ansys Sherlock in simulating the effects of thermal cycling on electronics assemblies. By accurately predicting the probability of failure under specific conditions, Sherlock can help design teams optimize product reliability while eliminating costly testing efforts. Whether you are designing video game controllers or aerospace electronics, Ansys Sherlock is a valuable tool for predicting the life of electronics assemblies and optimizing their reliability.

This post includes references to PhobGCC, an open-source project aimed at recreating the Gamecube controller. PhobGCC is licensed under the Creative Commons Attribution-ShareAlike 4.0 International License. As such, this post acknowledges the copyright claims of PhobGCC and respects the terms of the license. The inclusion of references to PhobGCC in this post constitutes fair use of the copyrighted material for the purpose of commentary and analysis, and does not imply any endorsement or affiliation with the project.

License: Creative Commons — Attribution-ShareAlike 4.0 International — CC BY-SA 4.0

About the Author

Adam LeMay

FEA Consulting Engineer

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