Coupled Thermal and Mechanical Analysis of Thermal Interface Materials in Electronic Packaging

Abstract

Nowadays, the AI ∖ HPC devices are becoming more advanced; therefore, the demand for larger packages is rising. However, increased package sizes are causing larger warpage levels to occur. As a result of larger warpage levels, the effects of warpage on the thermal performance of thermal interface materials (TIMs) inside the packages become more critical. However, current thermal characterization methodologies (e.g., ASTM D5470) use ideal surface conditions during testing and overlook the effects of chip package interactions, such as temperature- and pressure-dependent warpage during operation. Such conditions could deteriorate the contact or coverage of TIMs with the die and the heat spreader/heat sink elements in the package. In addition, the lack of a fully coupled thermal and mechanical analysis of TIMs inside IC packages increases the risk of selecting improper TIMs, which might cause thermal performance issues. To address these problems, we combine in situ thermal characterization of TIMs using packaged thermal test vehicles (TTVs) and fully coupled thermal and mechanical modeling of the package in realistic application conditions. Fully coupled thermal and mechanical modeling includes the assembly-induced warpage, warpage-induced gaps at the TIM cold plate interface, pressure-dependent TIM coverage, and their overall effects on the thermal performance of both the TIM and the packaging. The results of this study show that warpage of the die can play a crucial role in the thermal performance of the package based on the mechanical properties of the TIMs, bond line thickness (BLT), and pressure. Using the coupled thermal and mechanical modeling, the mechanisms behind the nonuniform temperature distributions measured by packaged TTV are explained, as the temperature difference between the center and the corner of the chip can increase up to a factor of 2, caused by warpage-induced gaps. Outcomes of this work can be used as a guideline for selecting proper TIMs for improved thermal management of IC packaging.