NOVELTY - An insulating thermally-conductive filler dispersion composition comprises high heat-resistant resin (A), insulating thermally-conductive filler (B), and solvent (C). The resin (A) is polyamidoimide, solvent soluble polyimide, polyether imide, or imide-modified elastomer. The filler (B) contains boron nitride, and has specific surface area of 15-25 m2/g. The amount of filler (B) contained in the composition is 35-70 volume%. A uniform dispersion of particles having volume average particle diameter of 4.5-10 mu m is carried out in the filler (B).    USE - Insulating thermally-conductive filler dispersion composition is used for manufacture of insulating thermally-conductive resin composition used for insulation film for metal heat sink and metal base circuit board (all claimed) of power converter devices e.g. inverter. Uses include but are not limited to hybrid motor vehicle, fuel cell electric vehicle, motor components, light-emitting diode, mobile telephone, portable terminal, personal computer or server, base station apparatus of communication system, and semiconductor manufacturing apparatus.    ADVANTAGE - The insulating thermally-conductive filler dispersion composition provides the metal heat sink and metal base circuit board with excellent thermal conductivity and insulation property, and high dielectric breakdown voltage.    DETAILED DESCRIPTION - An insulating thermally-conductive filler dispersion composition comprises high heat-resistant resin (A), insulating thermally-conductive filler (B), and solvent (C). The resin (A) is polyamidoimide, solvent soluble polyimide, polyether imide, or imide-modified elastomer. The filler (B) contains boron nitride, and has specific surface area of 15-25 m2/g. The amount of filler (B) contained in the composition is 35-70 volume%. A uniform dispersion of particles having volume average particle diameter of 4.5-10 mu m is carried out in the filler (B), such that particle diameter (d10) is maintained at 0.3 mu m or more and particle diameter (d90) is maintained at 15 mu m or less. INDEPENDENT CLAIMS are included for the following:    (1) manufacture of insulating thermally-conductive resin composition, which involves coating the insulating thermally-conductive filler dispersion composition, and heat-processing;    (2) insulation film, which contains the insulating thermally-conductive resin composition;    (3) metal heat sink, which consists of a metal plate and an insulating layer containing the thermally-conductive resin composition; and    (4) metal base circuit board, which consists of a metal foil for circuits and the insulating layer.