THERMALLY CONDUCTIVE COMPOSITION AND CURED PRODUCT THEREOF

A heat conducting composition comprising a curable silicone resin (A) and a thermally conductive powder (B), whereinthe thermally conductive powder (B) has a content of 70 to 98% by mass based on the total amount of the heat conducting composition,the thermally conductive powder (B) contains, based on the total amount of the thermally conductive powder (B), 30 to 75% by mass of aluminum nitride particles (B-1) having a cumulative volume-based 50% particle size of 50 µm or more and 150 µm or less, 10 to 30% by mass of aluminum nitride particles (B-2) having a cumulative volume-based 50% particle size of 15 µm or more and less than 50 µm, 5 to 15% by mass of a metal oxide (B-3) other than zinc oxide having a cumulative volume-based 50% particle size of 1 µm or more and less than 20 µm, and 10 to 40% by mass of zinc oxide (B-4) having a cumulative volume-based 50% particle size of 0.1 µm or more and less than 1 µm and a BET specific surface area of less than 9.0 m2/g, andthe metal oxide (B-3) other than zinc oxide and the zinc oxide (B-4) are both surface treated with at least one surface treatment agent selected from the group consisting of a silane coupling agent having an alkyl group having 10 to 22 carbon atoms and α-butyl-ω-(2-trimethoxysilylethyl)polydimethylsiloxane.