HEAT-DISSIPATING SHEET HAVING HIGH THERMAL CONDUCTIVITY AND ITS PRODUCTION METHOD

• US 20150257251A1
• Filed: 11/12/2014
• Published: 09/10/2015
• Est. Priority Date: 03/05/2014
• Status: Abandoned Application

• Current Assignee: Seiji Kagawa
• Original Assignee: Seiji Kagawa
• Inventors: KAGAWA, Seiji
• Application Number:
  US14/539,595
• Publication Number:
  US 20150257251A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B05D 1/02 performed by spraying
• CPC Class Codes: B05D 1/36 Successively applying liquids or other fluent materials, e.g. without intermediate treatment
• CPC Class Codes: B05D 2401/10 Organic solvent B05D2401/21 takes precedence
• CPC Class Codes: B05D 2502/00 Acrylic polymers
• CPC Class Codes: B05D 2507/005 modified
• CPC Class Codes: B05D 2508/00 Polyesters
• CPC Class Codes: B05D 3/007 After-treatment
• CPC Class Codes: B05D 3/02 by baking B05D3/04 takes precedence
• CPC Class Codes: B05D 3/0254 After-treatment
• CPC Class Codes: B05D 3/0272 with ovens
• CPC Class Codes: B05D 5/00 Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
• CPC Class Codes: B05D 7/52 Two layers
• CPC Class Codes: C09K 5/14 Solid materials, e.g. powdery or granular
• CPC Class Codes: H01L 23/373 Cooling facilitated by selection of materials for the device or materials for thermal expansion adaptation, e.g. carbon
• CPC Class Codes: H01L 23/3737 Organic materials with or without a thermoconductive filler
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H05K 1/0203 Cooling of mounted components H05K1/0272 takes precedence
• CPC Class Codes: Y10T 428/30 Self-sustaining carbon mass or layer with impregnant or other layer

Abstract

A heat-dissipating sheet having a density of 1.9 g/cm³ or more and an in-plane thermal conductivity of 570 W/mK or more, which comprises carbon black uniformly dispersed among fine graphite particles, a mass ratio of fine graphite particles to carbon black being 75/25 to 95/5, is obtained by repeating plural times a cycle of applying a dispersion of fine graphite particles, carbon black and an organic binder in an organic solvent to a surface of a support plate, and then drying it, to form a resin-containing composite sheet; burning the resin-containing composite sheet to remove the organic binder; and pressing the resultant composite sheet of fine graphite particles and carbon black for densification.

Claims

1. A heat-dissipating sheet having a structure in which carbon black is uniformly dispersed among fine graphite particles, a mass ratio of fine graphite particles to carbon black being 75/25 to 95/5;

and said heat-dissipating sheet being obtained by burning and pressing a composite sheet of fine graphite particles, carbon black and an organic binder, so that it has a density of 1.9 g/cm³ or more and an in-plane thermal conductivity of 570 W/mK or more.

2. The heat-dissipating sheet according to claim 1, which has thickness of 25-150 μ

m.

3. The heat-dissipating sheet according to claim 1, wherein said fine graphite particles have an average diameter of 3-150 μ

m and average thickness of 200 nm or more.

4. The heat-dissipating sheet according to claim 1, which is coated with insulating resin layers or insulating plastic films.

5. A method for producing the heat-dissipating sheet according to claim 1, comprising the steps of (1) preparing a dispersion comprising 5-25% by mass in total of fine graphite particles and carbon black, and 0.05-2.5% by mass of an organic binder, in an organic solvent, a mass ratio of said fine graphite particles to said carbon black being 75/25 to 95/5;

(2) repeating plural times a cycle of applying said dispersion to a surface of a support plate and then drying it, to form a resin-containing composite sheet comprising said fine graphite particles, said carbon black and said organic binder;

(3) burning said resin-containing composite sheet to remove said organic binder; and

(4) pressing the resultant composite sheet of fine graphite particles and carbon black for densification.

6. The method for producing a heat-dissipating sheet according to claim 5, wherein a mass ratio of said organic binder to the total amount of said fine graphite particles and said carbon black is 0.01-0.5.

7. The method for producing a heat-dissipating sheet according to claim 5, wherein the amount of said dispersion applied by one operation is 5-15 g/m² (expressed by the total weight of fine graphite particles and carbon black per 1 m²).

8. The method for producing a heat-dissipating sheet according to claim 5, wherein said organic binder is an acrylic resin, a polystyrene resin or polyvinyl alcohol.

9. The method for producing a heat-dissipating sheet according to claim 5, wherein said organic solvent is at least one selected from the group consisting of ketones, aromatic hydrocarbons and alcohols.

10. The method for producing a heat-dissipating sheet according to claim 5, wherein said dispersion is applied by a spraying method.

11. The method for producing a heat-dissipating sheet according to claim 5, wherein said burning step is conducted at a temperature of 550-700°

C.

12. The method for producing a heat-dissipating sheet according to claim 5, wherein cooling after burning is gradually conducted to room temperature over 1 hour or more.

13. The method for producing a heat-dissipating sheet according to claim 5, wherein said pressing step is conducted at pressure of 20 MPa or more.

14. The method for producing a heat-dissipating sheet according to claim 5, wherein said resin-containing composite sheet is pressed in a state sandwiched by a pair of planar die plates in a die plate apparatus.

15. The method for producing a heat-dissipating sheet according to claim 14, wherein said die plate apparatus comprises a lower die plate and an upper die plate;

and wherein using said lower die plate as said support plate, said resin-containing composite sheet is formed in a cavity of said lower die plate, burned without being peeled from said lower die plate, and then pressed with said lower die plate combined with said upper die plate.

16. The method for producing a heat-dissipating sheet according to claim 5, wherein said composite sheet of fine graphite particles and carbon black is cooled to a temperature equal to or lower than the freezing point of water, and then pressed.

17. The method for producing a heat-dissipating sheet according to claim 5, wherein said pressing step is conducted at a temperature of room temperature to 200°

C.