Heat sink substrate consisting essentially of copper and molybdenum and method of manufacturing the same

• US 6,271,585 B1
• Filed: 07/07/1998
• Issued: 08/07/2001
• Est. Priority Date: 07/08/1997
• Status: Expired due to Term

• Current Assignee: A.L.M.T. Corp. (Sumitomo Corporation)
• Original Assignee: Tokyo Tungsten Co. Ltd. (Sumitomo Corporation)
• Inventors: Asai, Kiyoshi, Hirayama, Norio, Arikawa, Tadashi, Maesato, Hidetoshi, Osada, Mitsuo, Ichida, Akira
• Primary Examiner(s): CRANE, SARA W
• Application Number:
  US09/110,669
• Time in Patent Office: 1,127 Days
• Field of Search: 257/712, 257/796, 752/46, 752/47
• US Class Current: 257/712
• CPC Class Codes: B22F 1/09 Mixtures of metallic powders
• CPC Class Codes: B22F 2998/10 Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 3/10 Sintering only
• CPC Class Codes: B22F 3/18 by using pressure rollers
• CPC Class Codes: B22F 3/26 Impregnating making ferrous alloys by impregnation C22C33/0242
• CPC Class Codes: C22C 1/0475 Impregnated alloys
• CPC Class Codes: H01L 21/4878 Mechanical treatment, e.g. deforming
• CPC Class Codes: H01L 23/3733 having a heterogeneous or anisotropic structure, e.g. powder or fibres in a matrix, wire mesh, porous structures H01L23/3732, H01L23/3737 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: H05K 1/0306 Inorganic insulating substrates, e.g. ceramic, glass
• CPC Class Codes: H05K 3/102 by bonding of conductive powder, i.e. metallic powder H05K3/12 takes precedence

Abstract

A heat sink substrate comprises a Cu—Mo composite substrate composed of a molybdenum (Mo) green compact with which Copper (Cu) of 20-60 wt % is impregnated. It is preferable that the heat sink substrate is a rolled plate obtained by repeatedly warm rolling or cold rolling the Cu—Mo composite substrate and that the rolled plate does not include any fine void and unevenly impregnated copper, that is, copper and molybdenum are uniformly distributed therein.

Claims

1. A heat sink substrate, consisting essentially of a Cu-Mo composite substrate which is formed by impregnating melted copper (Cu) into a molybdenum (Mo) green compact and which is given in the form of a rolled plate obtained by rolling the Cu—

Mo composite plate in a rolling direction after impregnation, the rolled plate comprising 20-60 wt % of Cu and exhibiting characteristic anisotropy,

said characteristic anisotropy of the rolled plate being specified by a difference between the thermal expansion coefficient in a direction parallel to the rolling direction and that perpendicular to the rolling direction;

the difference between the thermal expansion coefficients being not greater than 8%.

2. A heat sink substrate according to claim 1, consisting essentially of a rolled plate obtained by repeating warm rolling or cold rolling, wherein the rolled plate does not contain any fine void and unevenly impregnated cooper.

3. A heat sink substrate according to claim 2, wherein the rolled plate is stamped to a shape having an excellent accuracy without chipping, cracking and fracture on the end surfaces, sides and front surfaces thereof, the plated layer being in intimate contact with the rolled plate without the occurrence of the swelling, exfoliation and unevenness of the plated layer even if the rolled plate is subjected to heat treatment at 700°

C. or higher after plating is applied to the surface thereof.

4. A heat sink substrate according to claim 1, consisting essentially of a rolled plate obtained by rolling the Cu—

Mo composite plate, wherein the aspect ratio of the molybdenum particle is defined by longest particle size/shortest particle size in the rolled plate and is 2 or less.

5. A heat sink substrate according to claim 4, wherein the rolled plate has a deformed shape with a recessed step, said deformed shape being made by subjecting the rolled plate to a stamping process.

6. A heat sink substrate according to claim 5, wherein said rolled plate has a surface roughness of Ra≦

0.1 mm and a warp≦

0.3 mm.

7. A semiconductor package, comprising the heat sink substrate according to claim 6.

8. A heat sink substrate according to claim 1, wherein the amount of impregnated cooper is 10-40 wt % of the total weight of said heat sink substrate.

9. A heat sink substrate according to claim 8, wherein the heat sink substrate is used to a power semiconductor which is used to an electric automobile and electric railcar, the heat sink substrate mounting a plurality of semiconductor elements.

10. A heat sink substrate according to claim 9, wherein the amount of impregnated copper is 20-30 wt % of the total amount of said heat sink substrate.

11. A heat sink substrate according to claim 10, wherein the heat sink substrate has such characteristics that a thermal expansion coefficient is 7-8.5×

10<sup>−

6</sup>/K, a thermal conductivity is 170-90 W/m·

K, a Young'"'"'s modulus is 220-240 GPa and a density is 10 g/cm² or less and also has high reliability.

12. A heat sink substrate according to claim 9, wherein the amount of impregnated copper is 30-40 wt % of the total weight of said heat sink substrate.

13. A heat sink substrate according to claim 12, wherein said composite substrate is mounted on a large-capacity rectifier of a vehicle or a car.

14. A heat sink substrate according to claim 1, wherein the amount of impregnated copper is 40-60 wt % of the total weight of said heat sink substrate.

15. A heat sink substrate according to claim 14, wherein the heat sink substrate has such characteristics that a thermal expansion coefficient is 8.7-12×

10<sup>−

6</sup>/K, a thermal conductivity is 230-280 W/m·

K, a Young'"'"'s modulus is 170-200 GPa and a density is 10 g/cm² or less.

16. A heat sink substrate according to claim 15, wherein the heat sink substrate is mounted on a microwave semiconductor.

17. A Cu—

Mo composite heat sink substrate, consisting essentially of a Cu—

Mo composite substrate which is formed by impregnating melted copper (Cu) into a molybdenum (Mo) green compact and which is given in the form of a rolled plate obtained by rolling the Cu—

Mo composite plate in a rolling direction after impregnation, the rolled plate comprising 40-60 wt % of Cu and exhibiting characteristic anisotropy,

said characteristic anisotropy of the rolled plate being specified by a difference between the thermal expansion coefficient in a direction parallel to the rolling direction and that perpendicular to the rolling direction;

the difference between the thermal expansion coefficients being not greater than 8%;

the Cu∫

Mo composite substrate being made from the Mo green compact which comprises a mixture of copper powder not greater than 5 wt % and the balance of molybdenum.

18. A heat sink substrate according to claim 17, wherein the heat sink substrate has such characteristics that a thermal expansion coefficient is 8.7-12×

10<sup>−

6</sup>/K, a thermal conductivity is 230-280 W/m·

K, a Young'"'"'s modulus is 170-200 GPa and a density is 10 g/cm² or less.

19. A heat sink substrate according to claim 18, wherein the heat sink substrate is used to mount a microwave semiconductor thereon.

20. A heat sink substrate according to claim 19, consisting essentially of a rolled plate that is obtained by subjecting the Cu-Mo composite substrate to cold rolling or warm rolling, wherein the rolled plate does not contain any fine void and unevenly impregnated copper.

21. A heat sink substrate according to claim 20, wherein the rolled plate is stamped to a shape having an excellent accuracy without chipping, cracking and fracture on the end surfaces or sides thereof, the plated layer being in intimate contact the rolled plate without the occurrence of the swelling, exfoliation and unevenness of the plated layer even if the rolled plate is subjected to heat treatment at 700°

C. or higher after plating is applied to the surface thereof.

22. A heat sink substrate according to claim 20, wherein the rolled plate has a deformed shape with a recessed step which is made by subjecting the rolled plate to a stamping process.

23. A large area heat sink substrate semiconductor device, the heat sink substrate consisting essentially of a single layer composite material composed of copper and molybdenum and having a thermal conductivity of at least 200 W/m·

K and a thermal expansion coefficient of 12×

10<sup>−

6</sup>/K or less within a temperature range of from room temperature to 200°

C.;

the heat sink substrate exhibiting characteristic anisotropy of thermal conductivity and thermal expansion coefficient in a substrate surface direction thereof;

the characteristic anisotropy being specified by a difference of 12% or less between the lengthwise direction and the lateral direction of the thermal conductivity and by another difference of 8% or less between the lengthwise direction and the lateral direction of the thermal expansion coefficient.

24. A heat sink substrate according to claim 23, wherein the heat sink substrate has a thermal conductivity of at least 230 W/m·

K within the temperature region from room temperature to 200°

C.

25. A heat sink substrate according to claim 24, wherein the heat sink substrate has a thermal expansion coefficient of 9×

10<sup>−

6</sup>/K or less.

26. A power semiconductor device, comprising the heat sink substrate claimed in claim 23 and a plurality of power semiconductor elements on the heat sink substrate.

27. A large area heat sink substrate as claimed in claim 23, subjected to a process such that the warp of the heat sink substrate is suppressed to 100 μ

m or less and that residual strain is caused in a relatively less amount so as to mount the power semiconductor device with high reliability.