Case Study

Ansys Sherlock for Predicting Thermal Stress Fatigue in Solder Balls

The use of electronics is ever increasing in automotive applications. Automotive designers however must still adhere the same size and packaging constraints to ensure vehicle size and weight does not increase. Because of this, there has been a push to make electronic components and packages smaller, while increasing performance. Continental Automotive has seen increased use of Ball Grid Array (BGA) components and High Density Interconnect (HDI) FR4 boards in their Printed Circuit Board Assemblies (PBCA). These changes have not been without their issues and Continental has noticed additional reliability issues in solder joints due to solder fatigue. Therefore the capability to predict these failures is critical, allowing Continental to avoid these failures with design changes.

Currently the ability to predict high cycle fatigue (vibration) solder and copper leads can be accomplished using Miner’s Rule. However the ability to predict low cycle fatigue due to thermal cycle is required. Continental chose to overcome this obstacle by employing Ansys Sherlock to model their board and components. Sherlock’s key advantage for this project was its ability to model and run multiple iterations quickly, minimize thermal cycle and shock validation tests, determine the largest contributor to stress/strain and allow for changes to layout.