Thermal, Mechanical, and Electrical Properties of AlN /Polyamide‐Imide and AlN –Ag/Polyamide‐Imide Composite Films Fabricated by Solution Casting

Balanced optimization of thermal, mechanical, and electrical properties at low filler loading remains challenging for thermally conductive polymer composites. Polyamide‐imide (PAI) was used as the matrix, and aluminum nitride (AlN) particles as the thermally conductive filler. AlN/PAI composite films with 1–15 wt% AlN (below the percolation threshold) were fabricated by solution casting. To further enhance thermal conductivity, silver nanoparticles (AgNPs) were anchored onto the modified AlN surface via in situ reduction to prepare AlN–Ag/PAI composite films. The thermal conductivity of pure PAI (0.093 W/(m·K)) was enhanced by approximately 5.5 times after AlN incorporation. Owing to the local bridging effect of AgNPs, the thermal conductivity of the 15 wt% AlN–Ag/PAI composite film reached 0.605 W/(m·K), 18.2% higher than the corresponding AlN/PAI film. Both AlN and AlN–Ag fillers improved the thermal stability of the composite films and increased the calculated LOI values derived from the TGA char residue. Mechanical properties gradually decreased with rising filler fraction; nevertheless, AgNP decoration partially alleviated the tensile strength deterioration. Electrical characterization revealed that the volume resistivity of the composite films remained above 10 14 Ω·cm even at 15 wt% filler loading, indicating satisfactory electrical insulation for electronic packaging.