Thermally conductive grease composition

Abstract

A non-curable thermally conductive grease composition includes: A. 100 parts by mass of an ethylene-α-olefin copolymer with a kinematic viscosity of 10000 mm/s or less at 40° C.; and B. 115 to 580 parts by mass of thermally conductive particles with respect to 100 parts by mass of the component A. The thermally conductive particles contain the following: B1. 55 to 350 parts by mass of irregularly-shaped alumina with a median particle size of 0.1 to 1 μm, in which a part or all of the alumina is surface treated with a specific alkoxysilane compound or its partial hydrolysate; B2. 5 to 60 parts by mass of plate-shaped boron nitride with a median particle size of 0.1 to 10 μm; and B3. 55 to 170 parts by mass of aggregated boron nitride with a median particle size of 20 to 70 μm. The B3/B2 mass ratio is 2 to 20. Thus, the thermally conductive grease composition is less likely to generate low molecular siloxane and has high drop resistance and a low specific gravity.