Poly(ionic liquid)s: A Promising Matrix for Thermal Interface Materials

The swift progression of high-density chiplet packaging, propelled by the artificial intelligence revolution, has precipitated a critical need for high-performance chip-scale thermal interface materials (TIMs). The elevated thermal resistance, limited interfacial adhesion, and mechanical flexibility intrinsic to silicone systems present a substantial challenge in meeting reliability standards amidst chip warpage. This particular matter underscores a significant performance bottleneck within existing high-end TIMs. In this study, we present poly(ionic liquid)s (PILs) as an innovative matrix for TIMs. Our findings highlight the unique properties of PILs, showcasing a low elastic modulus (60 kPa), exceptional flexibility and stretchability (>3800%), high adhesion to diverse substrates (up to 4.10 MPa), favorable filler compatibility, remarkable thermal stability, and prompt self-healing capabilities coupled with recyclability. The collective findings suggest that the PIL serves as an ideal matrix for heat transfer. As a proof of concept, PIL blended with liquid metal was straightforwardly combined to produce a TIM, exhibiting exceptional performance within practical encapsulated structures. The PIL-based TIM demonstrates substantial elongation at break (>350%), coupled with sustained high adhesion strength (up to 1.70 MPa), and exhibits favorable thermal conductivity in package testing. This study presents an innovative TIM matrix with the potential to enhance existing TIM systems, delivering significant performance benefits compared to silicones. Besides elucidating their multifaceted characteristics, this study forecasts an expanded range of applications for PILs, along with laying the groundwork for advancing next-generation TIMs.