High thermal conductivity/low coefficient of thermal expansion composites
View Patent ↗A high thermal conductivity/low coefficient of thermal expansion thermally conductive composite material for heat sinks and an electronic apparatus comprising a heat sink formed from such composites. The thermally conductive composite comprises a high thermal conductivity layer disposed between two substrates having a low coefficient of thermal expansion. The substrates have a low coefficient of thermal expansion and a relatively high modulus of elasticity, and the composite exhibits high thermal conductivity and low coefficient of thermal expansion even for composites with high loadings of the thermally conductive material.
1. A thermally conductive composite comprising:
a first metal substrate;
a second metal substrate; and
a layer of thermal pyrolytic graphite disposed between the first and second metal substrates, wherein the thermal pyrolytic graphite comprises a plurality of layered planes and the graphite is disposed in the composite such that the layered planes are oriented in a direction vertical to the plane of the first and second metal substrates; the first and second metal substrates bonded to the graphite layer and comprising a metal having a modulus of elasticity of about 200 GPa or greater, the composite having an in-plane coefficient of thermal expansion of about 13 ppm/° C. or less and a thermal conductivity of about 200 W/m-K or greater.
2. The thermally conductive composite of claim 1 , wherein the first and second metal substrate independently comprises a metal chosen from tungsten, molybdenum, tungsten alloys, molybdenum alloys, or combinations of two or more thereof.
3. The thermally conductive composite of claim 1 , wherein the first and second substrates independently comprise a metal chosen from a tungsten-copper alloy, a molybdenum-copper alloy, or a combination of two or more thereof.
4. The thermally conductive composite of claim 1 , wherein the first and second metal substrate each have a coefficient of thermal expansion of about 4 to about 13 ppm/° C.
5. The thermally conductive composite of claim 1 , comprising from about 20 to about 90% by volume of thermal pyrolytic graphite.
6. The thermally conductive composite of claim 1 , comprising from about 40 to about 80% by volume of thermal pyrolytic graphite.
7. The thermally conductive composite of claim 1 , comprising from about 55 to about 87% by volume of thermal pyrolytic graphite.
8. The thermally conductive composite of claim 1 , wherein the substrates have a modulus of elasticity of about 300 GPa or greater.
9. The thermally conductive composite of claim 1 , wherein the substrates have a modulus of elasticity of about 400 GPa or greater.
10. The thermally conductive composite of claim 1 , wherein the composite has a coefficient of thermal expansion of about 4 to about 9 ppm/° C.
11. The thermally conductive composite of claim 1 , wherein the composite has a coefficient of thermal expansion of about 4 to about 7 ppm/° C.
12. An electronic structure comprising:
an electronic device; and
a heat sink assembly in thermal contact with the electronic device, the heat sink assembly comprising a rigid thermally conductive composite comprising a piece of thermal pyrolytic graphite disposed between first and second metal substrates, wherein the thermal pyrolytic graphite comprises a plurality of layered planes and the graphite is disposed in the composite such that the layered planes are oriented in a direction vertical to the plane of the first and second metal substrates; the first and second metal substrates bonded to the graphite and comprising a metal independently having a modulus of elasticity of about 200 GPa or greater, and the composite having a coefficient of thermal expansion of about 13 ppm/° C. or less and a thermal conductivity of about 200 W/m-K or greater.
13. The electronic device of claim 12 , wherein the first and second metal substrate independently comprises a metal chosen from tungsten, molybdenum, tungsten alloys, molybdenum alloys, or combinations of two or more thereof.
14. The electronic device of claim 12 , wherein the first and second metal substrate each have a modulus of elasticity of about 300 GPa or greater.
15. The electronic device of claim 12 , comprising from about 20 to about 90% by volume of thermal pyrolytic graphite.
16. The electronic device of claim 12 , comprising from about 40 to about 80% by volume of thermal pyrolytic graphite.
17. A composite sheet comprising:
a first metal substrate chosen from at least one of tungsten, molybdenum, tungsten-alloys, and molybdenum-alloys;
a second metal substrate chosen from at least one of tungsten, molybdenum, tungsten-alloys, and molybdenum alloys; and
a thermal pyrolytic graphite sheet disposed between the first and second metal substrates, the thermal pyrolytic graphite sheet comprising a plurality of layered planes and the graphite is disposed in the composite such that the layered planes are oriented in a direction vertical to the plane of the first and second metal substrates, the first and second metal substrates having a modulus of elasticity of about 200 GPa or greater, the composite sheet having a coefficient of thermal expansion of about 13 ppm/° C. or less and a thermal conductivity of about 200 W/m-K or greater.
18. The composite sheet of claim 17 , comprising from about 20 to about 90% by volume of thermal pyrolytic graphite.
19. The composite sheet of claim 17 , comprising from about 55 to about 87% by volume of thermal pyrolytic graphite.
20. The composite sheet of claim 17 having a thermal conductivity of about 300 to about 1000 W/m-K.
21. The composite sheet of claim 17 , wherein the substrates are bonded to the graphite sheet.