Roadmap and Challenges on the Next Generation of Thermal Interface Material for High Warpage Heterogonies Package

Abstract

With the constant increases of power density in silicon year after year, there is a constant strive to provide better thermal management innovation to improve thermal design solutions for the high-power density. The Thermal Interface Material (TIM) is a first-order solution for thermal management of high-power density silicon. This TIM plays a crucial role in defining the solution, both thermally and mechanically. This study addresses the challenges of the next generation of thermal Interface material for high warpage heterogonies package. There is no question that Thermal Interface Materials (TIMs) materials have been helpful in coupling the IC packages thermally and mechanically to the thermal management solution and have addressed the issue of thermal contact optimally by displacing the air that is present between the irregular surfaces of the silicon and the heat spreader at the micro-level thereby decreasing the thermal contact resistance It also bridges the CTE (coefficient of thermal expansion) gap between two dissimilar materials. This work points out challenges that the TIM material has to overcome to maintain its thermal performance without degradation over time which depends on its intrinsic characteristics defined by the elongation, adhesion, thermal conductivity, and bond line thickness (BLT). As the power density and the sizes of the packages increase when these are surface mounted on the board, they exhibit warpage during its operation. The die side of the package can be warped by 10% to 30% in the operating range of 50°C to 100°C as compared to the warpage of standalone silicon die at 20°C, which was observed by analyzing a baseline FCBGA package using Digital Image Correlation (DIC) approach. This warpage also created the need for the higher BLT of the TIM to cover the entire die surface, and this will also induce high stresses and may also cause TIM delamination during the lifetime of the device. Hence there is a surface interaction between the die and the TIM that occurs due to the thermal and mechanical behavior of the package, which dictates the device lifetime and performance degradation. This study is given the roadmap of the first level of system-level interaction with the next generation of packages. Also, it reports the new finding on the impact of warpage and adhesion on the thermal interface resistance.