Optimizing thermal conductivity and stability of silicone grease using branched PDMS-modified AlN/Al2O3 hybrid fillers

This study tackles thermal management challenges in high-power electronics by developing trimethoxy-terminated polydimethylsiloxane (PDMS) with tailored branched architectures (TTMOS series) as surface treatment agents (STAs) for AlN/Al 2 O 3 hybrid fillers. We systematically optimized filler size distribution, STA structure, and matrix viscosity to enhance thermal interface material (TIM) performance. Critical findings reveal that a hybrid filler mass ratio of 120 μm AlN: 3 μm Al 2 O 3 : 0.5 μm Al 2 O 3 = 8:4:2 (87 vol% loading) delivers exceptional thermal conductivity ( λ = 9.74 W m −1 K −1 ), low thermal resistance ( θ = 2.86 K cm 2 W −1 ), balanced penetrability (54.6/0.1 mm), and oil resistance ( R 16h = 1.50). Branched STAs, such as TTMOS-T1, significantly outperform linear analogues by enhancing interfacial compatibility, suppressing particle agglomeration (validated via SEM/XPS), and reducing oil seepage ( R 16h = 1.45 vs. 1.77 for TTMOS-I), while maintaining a high thermal conductivity ( λ = 9.79 W m −1 K −1 ). A 100 mPa s Me-PDMS matrix further ensures post-thermal cycling stability, with λ increasing from 9.13 to 9.26 W m −1 K −1 . Practical validation demonstrates that TTMOS-T1-modified grease reduces the surface temperature of a 30 W HB-LED chip by 10 °C versus commercial TIMs, highlighting its real-world efficacy. • Novel branched PDMS STAs enhance filler compatibility via Si–O–Al bonding, reducing agglomeration in AlN/Al 2 O 3 composites. • Optimal AlN/Al 2 O 3 hybrid filler ratio (87 vol%) achieves λ = 9.74 W·m −1 ·K −1 and θ = 2.86 K·cm 2 ·W −1 . • Moderately branched PDMS STA balances thermal conductivity (9.79 W·m −1 ·K −1 ) and oil resistance, outperforming linear types. • Silicone paste with AlN/Al₂O₃ fillers reaches λ = 10.02 W·m −1 ·K −1 and 56.3 (0.1 mm) cone penetration.