Multiway Softness Polyurethane Elastomeric Composite with Enhanced Thermal Conductivity and Application as Thermal Interface Materials

Abstract The ever‐increasing computing power in modern electronics comes with significant heat waste that can't be ignored. For microchips to dissipate heat efficiently, thermal interface materials (TIMs) are the most critical components in semiconductor packaging. Soft elastomer composites are often used as TIMs due to their large‐strain reversible deformability with a small external force. For TIMs to cushion between the microchip and heat spreader, they must have high thermal conductivity and temperature‐tunable softness to reduce thermal resistance and relieve the warpage failure caused by thermal stress. However, thermal conductivity and softness are interrelated and restrict each other. To address this challenge, a radical strategy of introducing dynamic covalent bonds in the polyurethane/aluminum composite is used. The reversible and low energy of dynamic imine bonds along with the lengthening of the Khun segment in the crosslinking network imbues the material with temperature‐tunable softness function while maintaining high thermal conductivity. The resulting polyurethane elastomer (PUE) composite exhibits remarkable thermal conductivity (6.90 W m⁻¹ K⁻¹), low thermal resistance (0.13 K cm² W⁻¹), and excellent softness (elastic modulus 759.50 kPa, and stretchability 140.30%). This work provides a practical method to design thermally conductive and temperature‐tunable soft elastomer composites as TIMs in semiconductor packaging.