Thermomechanical Modeling of High-Temperature Bonded Interface Materials

In an automotive power electronics package, bonded interface materials play a critical role in providing a smooth heat dissipation path from the device to the coolant. However, these materials are susceptible to failure when the package gets exposed to repeated changes in its thermal environment and internal temperature variations. Under these thermal conditions, the coefficient of thermal expansion mismatch between the different component layers results in thermally induced stresses and consequently the delamination of the material from its adjoining surfaces or crack initiation and propagation within the material. Thermomechanical modeling offers a path to study the complex nature of these bonded materials, guides their design and selection, and, in conjunction with experimental results, plays an important role in predicting their lifetime. In this chapter, two modeling strategies - similar in approach and implementation but different in the underlying theory - are discussed in the context of high-temperature bonded materials. In addition, a short review of sintered silver is provided, as it is widely seen as a potentially promising and reliable bonded material for high-temperature applications.