Method for producing ceramic for heat-radiating members, ceramic for heat-radiating members, and solar cell module and LED light-emitting module using said ceramic

• US 9,108,887 B2
• Filed: 05/30/2011
• Issued: 08/18/2015
• Est. Priority Date: 05/31/2010
• Status: Active Grant

• Current Assignee: Nishimura Porcelain Co., Ltd.
• Original Assignee: Nishimura Porcelain Co., Ltd.
• Inventors: Nishimura, Takeo, Ishida, Nobuyuki
• Primary Examiner(s): SAMPLE, DAVID R
• Application Number:
  US13/393,802
• Publication Number:
  US 20130065067A1
• Time in Patent Office: 1,541 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: C04B 2235/3201 Alkali metal oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3267 MnO2
• CPC Class Codes: C04B 2235/327 Iron group oxides, their mixed metal oxides, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3272 Iron oxides or oxide forming salts thereof, e.g. hematite, magnetite
• CPC Class Codes: C04B 2235/3281 Copper oxides, cuprates or oxide-forming salts thereof, e.g. CuO or Cu2O
• CPC Class Codes: C04B 2235/3418 Silicon oxide, silicic acids or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint
• CPC Class Codes: C04B 2235/5409 expressed by specific surface values
• CPC Class Codes: C04B 2235/5427 millimeter or submillimeter sized, i.e. larger than 0,1 mm
• CPC Class Codes: C04B 2235/5445 submicron sized, i.e. from 0,1 to 1 micron
• CPC Class Codes: C04B 2235/656 characterised by specific heating conditions during heat treatment
• CPC Class Codes: C04B 2235/6562 Heating rate
• CPC Class Codes: C04B 2235/6565 Cooling rate
• CPC Class Codes: C04B 2235/6567 Treatment time
• CPC Class Codes: C04B 2235/72 Products characterised by the absence or the low content of specific components, e.g. alkali metal free alumina ceramics
• CPC Class Codes: C04B 2235/77 Density
• CPC Class Codes: C04B 2235/786 Micrometer sized grains, i.e. from 1 to 100 micron
• CPC Class Codes: C04B 2235/96 Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
• CPC Class Codes: C04B 2235/9607 Thermal properties, e.g. thermal expansion coefficient
• CPC Class Codes: C04B 35/111 Fine ceramics
• CPC Class Codes: C04B 35/265 Compositions containing one or more ferrites of the group comprising manganese or zinc and one or more ferrites of the group comprising nickel, copper or cobalt
• CPC Class Codes: C04B 35/62695 : Granulation or pelletising devices for shaping artificial aggregates from ceramic mixtures B28B1/004
• CPC Class Codes: C04B 35/645 : Pressure sintering
• CPC Class Codes: C04B 35/6455 : Hot isostatic pressing
• CPC Class Codes: H01L 23/3731 : Ceramic materials or glass H01L23/3732, H01L23/3733, H01L23/3735, H01L23/3737, H01L23/3738 take precedence
• 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: H01L 31/052 : Cooling means directly associated or integrated with the PV cell, e.g. integrated Peltier elements for active cooling or heat sinks directly associated with the PV cells cooling means in combination with the PV module H02S40/42
• CPC Class Codes: H01L 33/641 : characterized by the materials
• CPC Class Codes: Y02E 10/50 : Photovoltaic [PV] energy

Abstract

Provided is a process for producing a ceramic for a heat-radiating member. The process includes providing as a raw material an alumina powder having an alumina (Al₂O₃) content of at least 99.5 mass % and an average particle size of from 0.2 to 1 μm, and granulating the powder into a granular form ranging from 50 to 100 μm, pressing the raw material which has been obtained in the granulation step and which includes granular alumina, and heating a green compact in an air atmosphere at a firing temperature of from 1,480 to 1,600° C. to obtain a sintered body. Also provided is a process for producing a ceramic for a heat-radiating member, the ceramic being a sintered alumina body which has high thermal conductivity, efficient heat dissipation, excellent mechanical strength and thermal shock resistance and which is usable for cooling applications at heat generating areas of electronic devices and equipment.

Claims

1. A process for producing a ceramic for a heat-radiating member, comprising:

providing as raw materials, an alumina powder having an alumina (Al₂O₃) content of at least 99.5 mass % and an average particle size of from 0.2 to 1 μ

m, and a silica (SiO₂) content of at most 0.1 mass %;

granulating the powder into a form of granules ranging from 50 to 100 μ

m;

pressing the raw material which has been obtained during the granulating and which includes granular alumina so as to form a green compact;

heating the green compact in an air atmosphere at a firing temperature of from 1,480 to 1,600°

C. so as to obtain a sintered alumina body; and

forming a coating of a far-red radiation coating composition on at least a part of a surface of the sintered alumina body obtained by the heating, and baking the coating so as to form a far-infrared radiation film,

wherein the sintered alumina body has crystal grain sizes from 1 to 10 μ

m, contains crystal grains in a range from 30 to 55 and from 126 to 145 grains in an area of 30×

20 μ

m, and has a thermal conductivity of at least 33 W/m·

K.

2. The process according to claim 1, wherein the firing temperature is from 1,500 to 1,592°

C.

3. The process according to claim 1, wherein the green compact is obtained with a density of at least 2.40 g/cm³.

4. The process according to claim 1, further comprising quenching the green compact, after the heating, at a rate from 1.3 to 2.0 times a heating rate of the green compact during heating to the firing temperature, so as to obtain the sintered alumina body.

5. The process according to claim 1, wherein the heating is conducted in an air-circulating batch furnace.

6. The process according to claim 1, wherein the far-infrared radiation coating composition comprises a heat-resistant inorganic bonding agent and a calcined, fine powder mixture, which has been obtained by mixing at least two kinds of transition element oxides and calcining the resulting mixture at a temperature from 700 to 1,300°

C., at a mass ratio from 97;

3 to 20;

80.

7. A ceramic for a heat-radiating member, comprising:

a sintered alumina body having an alumina (Al₂O₃) content of at least 99.5 mass % and

a silica (SiO₂) content of at most 0.1 mass %; and

a far-infrared radiation film formed on at least a part of a surface of the sintered alumina body,

wherein the sintered alumina body has crystal grain sizes from 1 to 10 μ

m, contains crystal grains in a range from 30 to 55 and from 126 to 145 grains in an area of 30×

20 μ

m, and has a thermal conductivity of at least 33 W/m·

K.

8. The ceramic according to claim 7, wherein the sintered alumina body has a density of at least 3.8 g/cm³.

9. The ceramic according to claim 8, wherein the sintered alumina body has a density of at least 3.93 g/cm³.

10. The ceramic according to claim 7, wherein in the sintered alumina body, the alumina (Al₂O₃) content is at least 99.8 mass %, and the silica (SiO₂) content is at most 0.05 mass %.

11. The ceramic according to claim 7, wherein the far-infrared radiation film comprises:

a baked coating of a far-infrared radiation coating composition comprising a heat-resistant inorganic bonding agent and a calcined fine powder mixture, which has been obtained by mixing at least two transition element oxides and calcining the resulting mixture at a temperature from 700 to 1,300°

C., at a mass ratio from 97;

3 to 20;

80.

12. The ceramic according to claim 11, wherein the at least two transition metal oxides are selected from the group consisting of MnO₂ in an amount from 10 to 80 mass %, Fe₂O₃ in an amount from 5 to 80 mass %, CoO in an amount from 5 to 50 mass %, CuO in an amount from 10 to 80 mass % and Cr₂O₃ in an amount from 2 to 30 mass %.

13. The ceramic according to claim 7, the sintered alumina body further comprising at least one material selected from the group consisting of magnesia in an amount from 0.07 to 0.15 mass %, Na₂O in an amount from 0.03 to 0.05 mass %, and Fe₂O₃ in an amount from 0.01 to 0.02 mass %.

14. The ceramic according to claim 13, wherein the sintered alumina body comprises no other impurities.

15. The ceramic according to claim 7, wherein the sintered alumina body has no segregation of silica at interfaces of the crystal grains.

16. The ceramic according to claim 15, wherein the sintered alumina body has the thermal conductivity of at least 36 W/m·

K.

17. The ceramic according to claim 7, wherein the sintered alumina body has a flexural strength from 400 to 520 MPa.

18. A solar cell module comprising power generation cells and a ceramic for a heat-radiating member arranged on back sides of the power generation cells,

wherein the ceramic comprises a sintered alumina body having an alumina (Al₂O₃) content of at least 99.5 mass % and a silica (SiO₂) content of at most 0.1 mass %, and

the sintered alumina body has crystal grain sizes from 1 to 10 μ

m, contains crystal grains in a range from 30 to 55 and from 126 to 145 grains in an area of 30×

20 μ

m, and has a thermal conductivity of at least 33 W/m·

K.

19. The solar cell according to claim 18, wherein the sintered alumina body has a density of at least 3.8 g/cm³.

20. An LED light-emitting module comprising:

a substrate;

a circuit formed on a surface of the substrate; and

LED devices arranged on the circuit,

wherein the substrate is a ceramic for a heat-radiating member,

the ceramic comprises a sintered alumina body having an alumina (Al₂O₃) content of at least 99.5 mass % and a silica (SiO₂) content of at most 0.1 mass %, and

the sintered alumina body has crystal grain sizes from 1 to 10 μ

m, contains crystal grains in a range from 30 to 55 and from 126 to 145 grains in an area of 30×

20 μ

m, and has a thermal conductivity of at least 33 W/m·

K.

21. The LED light-emitting module according to claim 20, wherein the sintered alumina body has a density of at least 3.8 g/cm³.