Electromagnetic wave absorbing heat conductive sheet, method for producing electromagnetic wave absorbing heat conductive sheet, and semiconductor device

1. An electromagnetic wave absorbing heat conductive sheet, comprising:

a polymer matrix component;

a magnetic metal powder; and

fibrous heat conductive fillers,

wherein 90% or more of the fibrous heat conductive fillers are oriented in one direction,

an angle of an orientation direction of the oriented fillers relative to an extending direction of a sheet surface is in the range of more than 60° to 90°,

and

the electromagnetic wave absorbing heat conductive sheet satisfies condition of (a), (b) or (c):

(a) a heat conductivity in thickness direction of 5 W/(m·K) or more and a transmission absorption rate of the electromagnetic wave at 1 GHz of 3.6% or more,

(b) a heat conductivity in thickness direction of 5 W/(m·K) or more and a transmission absorption rate of the electromagnetic wave at 3 GHz of 30% or more,

(c) a heat conductivity in thickness direction of 5 W/(m·K) or more and a transmission absorption rate of the electromagnetic wave at 6 GHz of 70% or more.

2. The electromagnetic wave absorbing heat conductive sheet according to claim 1 , wherein the electromagnetic wave absorbing heat conductive sheet comprises 4% to 40% by volume of the fibrous heat conductive fillers and 35% to 75% by volume of the magnetic metal powder.

3. The electromagnetic wave absorbing heat conductive sheet according to claim 2 , wherein the electromagnetic wave absorbing heat conductive sheet comprises 5% to 30% by volume of the oriented fillers and 40% to 65% by volume of the magnetic metal powder.

4. The electromagnetic wave absorbing heat conductive sheet according to claim 1 , wherein the fibrous heat conductive fillers are carbon fiber.

5. The electromagnetic wave absorbing heat conductive sheet according to claim 1 , further comprising an inorganic filler.

6. A method for producing the electromagnetic wave absorbing heat conductive sheet according to claim 1 , the method comprising:

preparing a sheet composition which comprises the polymer matrix component, the fibrous heat conductive fillers, and the magnetic metal powder;

orientating 90% or more of the fibrous heat conductive fillers in one direction;

producing a molded article for sheet by curing the polymer matrix component while keeping the fibrous heat conductive fillers oriented; and

producing an electromagnetic wave absorbing heat conductive sheet by cutting the molded article for sheet at an angle of more than 60° to 90° relative to a longitudinal axis of the fibrous heat conductive fillers oriented.

7. A semiconductor device, comprising:

a heat source;

a heat dissipation member; and

the electromagnetic wave absorbing heat conductive sheet according to claim 1 , the electromagnetic wave absorbing heat conductive sheet being held between the heat source and the heat dissipation member.

8. The electromagnetic wave absorbing heat conductive sheet according to claim 4 , wherein the carbon fiber has an average fiber length of 50 μm to 300 μm.

9. The electromagnetic wave absorbing heat conductive sheet according to claim 4 , wherein the carbon fiber has an aspect ratio of 7 to 30.

10. An electromagnetic wave absorbing heat conductive sheet, comprising:

a polymer matrix component;

a magnetic metal powder; and

fibrous heat conductive fillers,

wherein 90% or more of the fibrous heat conductive fillers are oriented in one direction,

an angle of an orientation direction of the oriented fillers relative to an extending direction of a sheet surface is in the range of more than 30° to 60°,

and

the electromagnetic wave absorbing heat conductive sheet satisfies condition of (a), (b) or (c):

(a) a heat conductivity in thickness direction of 2.7 W/(m·K) or more and a transmission absorption rate of the electromagnetic wave at 1 GHz of 3.8% or more,

(b) a heat conductivity in thickness direction of 2.7 W/(m·K) or more and a transmission absorption rate of the electromagnetic wave at 3 GHz of 39% or more,

(c) a heat conductivity in thickness direction of 2.7 W/(m·K) or more and a transmission absorption rate of the electromagnetic wave at 6 GHz of 70% or more.

11. A method for producing the electromagnetic wave absorbing heat conductive sheet according to claim 10 comprising:

preparing a sheet composition which comprises the polymer matrix component, the fibrous heat conductive fillers, and the magnetic metal powder;

orientating 90% or more of the fibrous heat conductive fillers in one direction;

producing a molded article for sheet by curing the polymer matrix component while keeping the fibrous heat conductive fillers oriented; and

producing an electromagnetic wave absorbing heat conductive sheet by cutting the molded article for sheet at an angle of more than 30° to 60° relative to a longitudinal axis of the fibrous heat conductive fillers oriented.

12. A semiconductor device, comprising:

a heat source;

a heat dissipation member; and

an electromagnetic wave absorbing heat conductive sheet held between the heat source and the heat dissipation member,

wherein the electromagnetic wave absorbing heat conductive sheet is the electromagnetic wave absorbing heat conductive sheet according to claim 10 .

13. An electromagnetic wave absorbing heat conductive sheet, comprising:

a polymer matrix component;

a magnetic metal powder; and

fibrous heat conductive fillers,

wherein 90% or more of the fibrous heat conductive fillers are oriented in one direction,

an angle of an orientation direction of the oriented fillers relative to an extending direction of a sheet surface is in the range of 0° to 30°, and

the electromagnetic wave absorbing heat conductive sheet satisfies condition of (a), (b) or (c):

(a) a heat conductivity in thickness direction of 1.5 W/(m·K) or more and a transmission absorption rate of the electromagnetic wave at 1 GHz of 4.8% or more,

(b) a heat conductivity in thickness direction of 1.5 W/(m·K) or more and a transmission absorption rate of the electromagnetic wave at 3 GHz of 68% or more,

(c) a heat conductivity in thickness direction of 1.5 W/(m·K) or more and a transmission absorption rate of the electromagnetic wave at 6 GHz of 70% or more.

14. A method for producing the electromagnetic wave absorbing heat conductive sheet according to claim 13 comprising:

preparing a sheet composition which comprises the polymer matrix component, the fibrous heat conductive fillers, and the magnetic metal powder;

orientating 90% or more of the fibrous heat conductive fillers in one direction;

producing a molded article for sheet by curing the polymer matrix component while keeping the fibrous heat conductive fillers oriented; and

producing an electromagnetic wave absorbing heat conductive sheet by cutting the molded article for sheet at an angle of 0° to 30° relative to a longitudinal axis of the fibrous heat conductive fillers oriented.

15. A semiconductor device, comprising:

a heat source;

a heat dissipation member; and

an electromagnetic wave absorbing heat conductive sheet held between the heat source and the heat dissipation member,

wherein the electromagnetic wave absorbing heat conductive sheet is the electromagnetic wave absorbing heat conductive sheet according to claim 13 .