Thermally conductive silicone grease composition and method for producing the same

A thermally conductive silicone grease composition that is non-curable, comprising:

• A. 100 parts by mass of a non-curable silicone oil with a kinematic viscosity of 50 to 10000 mm2/s at 40° C.;
• and
• B. 105 to 500 parts by mass of thermally conductive particles with respect to 100 parts by mass of the component A,
• wherein the thermally conductive particles contain the following:
• B1. 50 to 300 parts by mass of pretreated irregularly-shaped alumina with a median particle size of 0.1 to 1 μm, in which a part or all of the alumina previously was surface treated, before mixing of the irregularly-shaped alumina with the silicone oil, with an alkoxysilane compound expressed by RaSi(OR′)4-a, where R represents a substituted or unsubstituted alkyl group having 8 to 12 carbon atoms, R′ represents an alkyl group having 1 to 4 carbon atoms, and a represents 0 or 1, or a partial hydrolysate of the alkoxysilane compound;
• B2. 5 to 50 parts by mass of plate-like boron nitride with a median particle size of 0.1 to 1 μm;
• and
• B3. 50 to 150 parts by mass of aggregated boron nitride with a median particle size of 20 to 70 μm,
• wherein a blending ratio of the component B3 to the component B2 is 2 to 20,
• wherein the thermally conductive silicone grease composition has a specific gravity of 1.0 or more and 2.0 or less and a thermal conductivity of 2.0 W/m·K or more and 8.0 W/m·K or less, and an absolute viscosity of 1000 to 7000 Pas at 23° C., as measured with a B-type viscometer using a T-E spindle at a rotational speed of 5 rpm.