Abstract: Demand for high-performance power devices continues to grow with the continuous development of power electronics and high-end field applications. Although packaging materials based on epoxy resins and silica gels have been widely developed, higher operating temperatures and operating voltages are still critical to the performance of power devices. Here, a composite film containing functionalized mesoporous hollow silica particles (MH-SiO₂) and polyimide (PI) was prepared by a template method and layer-by-layer coating strategy to address the current bottlenecks in packaging material development. The electrical breakdown strength of the prepared PI/SiO₂ composite film was 323.41 kV/mm, while the mass fraction of MH-SiO₂ was only 5 %. This indicates that the mesoporous structure can effectively inhibit electron collisions with nano-restricted domains. The simulation results also indicate that the size variation of inorganic fillers and the interaction of organic/inorganic heterogeneous interfaces are the main reasons affecting the performance of the composites. Meanwhile, the PI/SiO₂ composite films achieved other properties required for practical applications, such as matched coefficient of thermal expansion (CTE) (23.5 ppm/°C), excellent thermal stability (T_{5 %} = 559.0 °C) and low dielectric constant (2.27@1 M Hz). These results highlight the great potential of inorganic phase-specific structural designs for the preparation of high-performance power device packaging materials.

Key words: Mesoporous hollow silica, Polyimide, Coefficient of thermal expansion, Dielectric properties, Breakdown strength