Compressible vertically-oriented high-thermal-conductivity graphene thermal interface material and preparation method thereof

Abstract

The invention provides a compressible vertically-oriented high-thermal-conductivity graphene thermal interface material and a preparation method thereof, and belongs to the technical field of heat dissipation materials. The preparation method comprises the following steps: blade-coating a microporous filter membrane with a graphene oxide aqueous solution, heating and drying the filter membrane to obtain a graphene oxide film, graphitizing the graphene oxide film at a high temperature to obtain a graphene film, sputtering a layer of metal nickel at two ends of the graphene film, and cutting the graphene film into micron-sized strips by using a laser cutting machine to obtain the graphene film. And finally, inducing the vertical orientation of the graphene microribbons by using a magnetic field, and encapsulating by using an elastomer. According to the graphene thermal interface material, the thermal conductivity of the thermal interface material in the vertical direction is improved through magnetic field vertical orientation arrangement, a brand new heat dissipation technology is brought to the field of integrated circuits, and the heat dissipation efficiency of the integrated circuits is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat dissipation materials, and particularly relates to a compressible vertically oriented high thermal conductivity graphene thermal interface material and a preparation method thereof. Background Art

[0002] The miniaturization and integration of modern electronic devices cause a large amount of heat to be generated when the electronic devices are working. In electronic components, when the temperature rises by 10-15 °C, the service life and system reliability of the electronic components will be reduced by 50%. Therefore, an efficient heat dissipation material is the key to solving this problem. Graphene has an extremely high intrinsic thermal conductivity (5300 W·m -1 ·K -1 ), so many studies are devoted to developing high-performance graphene thermal interface materials to solve the problem of interfacial heat transfer. However, the heat of high-power density electronic devices is usually generated in the vertical direction and needs to be quickly exported, while the weak intermolecular force in the vertical direction of the graphene film results in a low thermal conductivity. Therefore, it is necessary to achieve a high thermal conductivity in the vertical direction of the graphene thermal interface material through reasonable design.

[0003] Currently, by directly introducing a three-dimensional template material and further depositing a heat-conducting filler on the surface of the template to construct a three-dimensional heat-conducting network is a relatively common method. However, since the three-dimensional template material is usually a polymer, the thermal conductivity of the composite material is comparable to that of commercial thermal conductive silicone pads (<10 W·m -1 ·K -1 ). In addition, the 3D printing method can construct a complex and multifunctional network structure at a low cost. Graphene can be used as an ink to prepare a heat-conducting composite material. However, the high-density network structure makes the processing technology too complex, and the liquid polymer in the ink reduces the thermal conductivity of the overall material. Therefore, there is an urgent need for a compressible vertically oriented high thermal conductivity graphene thermal interface material to effectively control the temperature of modern electronic devices. Summary of the Invention

[0004] The purpose of the present invention is to provide a compressible vertically oriented high thermal conductivity graphene thermal interface material and a preparation method thereof, which are used to solve the technical problem that the existing graphene heat-conducting material has a weak intermolecular force in the vertical direction, resulting in a low thermal conductivity.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of a compressible vertically oriented high thermal conductivity graphene thermal interface material, including the following steps:

[0007] 1) Scraping and coating a graphene oxide dispersion liquid on a microporous filter membrane, and obtaining a graphene oxide film after heating and drying;

[0008] 2) Anneal the graphene oxide film to obtain a graphene film;

[0009] 3) Sputter a strip-shaped nickel metal layer on both ends of the graphene film, and cut the graphene film along the width direction of the strip-shaped nickel metal layer to obtain graphene microbands;

[0010] 4) Use a magnetic field to induce the perpendicular orientation of the graphene microbands, and encapsulate and cure the graphene microbands with an organic solution of an elastomer to obtain a compressible and vertically oriented high-thermal-conductivity graphene thermal interface material.

[0011] Furthermore, the concentration of the graphene oxide dispersion is 5 - 30 mg / mL, and the thickness of the graphene oxide film is 5 - 300 μm.

[0012] Furthermore, the microporous filter membrane includes one of a mixed cellulose filter membrane, a polytetrafluoroethylene filter membrane, a nylon filter membrane, a polyvinylidene fluoride filter membrane, a polyethersulfone filter membrane, and a polypropylene filter membrane, and the pore size of the microporous filter membrane is 0.45 - 3 μm.

[0013] Furthermore, in step 1), the temperature for heating and drying is 30 - 60 °C, and the time for heating and drying is 0.5 - 3 h;

[0014] In step 2), the annealing temperature is 2000 - 3000 °C, and the annealing time is 1 - 3 h.

[0015] Furthermore, the thickness of the nickel metal layer is 0.05 - 5 μm, the width of the graphene microbands is 0.1 - 5 mm, and the thickness of the graphene microbands is 20 - 200 μm.

[0016] Furthermore, the magnetic field strength of the magnetic field is 500 - 5000 Gs.

[0017] Furthermore, the elastomer in the organic solution of the elastomer includes one or several of silicone, epoxy resin, polyurethane, and acrylic acid, and the volume fraction of the elastomer in the organic solution is 5 - 50%.

[0018] Furthermore, the curing temperature is 70 - 90 °C, and the curing time is 5 - 8 h.

[0019] The present invention also provides a compressible and vertically oriented high-thermal-conductivity graphene thermal interface material.

[0020] The beneficial effects of the present invention:

[0021] The present invention utilizes magnetic field-induced orientation to enhance the thermal conductivity in the vertical direction of graphene thermal interface materials. A layer of metallic nickel is sputtered on both ends of the graphene microbelts, and the graphene microbelts are induced to be vertically oriented by a magnetic field and encapsulated with an elastomer. The compressible vertically oriented high-thermal-conductivity graphene thermal interface material can rapidly conduct the heat of high-power chips to the heat sink, greatly improving the heat dissipation efficiency of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the preparation flow chart of the graphene thermal interface material of the present invention;

[0023] Figure 2 is the thermal conductivity graph of the graphene film prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention provides a method for preparing a compressible vertically oriented high-thermal-conductivity graphene thermal interface material, comprising the following steps:

[0025] 1) Scraping and coating a graphene oxide dispersion liquid on a microporous filter membrane, and heating and drying to obtain a graphene oxide film;

[0026] 2) Annealing the graphene oxide film to obtain a graphene film;

[0027] 3) Sputtering a strip-shaped metallic nickel layer on both ends of the graphene film respectively, and cutting the graphene film along the width direction of the strip-shaped metallic nickel layer to obtain graphene microbelts;

[0028] 4) Inducing the graphene microbelts to be vertically oriented by a magnetic field, and encapsulating and curing the graphene microbelts with an organic solution of an elastomer, thus obtaining the compressible vertically oriented high-thermal-conductivity graphene thermal interface material.

[0029] In the present invention, the concentration of the graphene oxide dispersion liquid is 5-30 mg / mL, preferably 10-20 mg / mL, and more preferably 12-18 mg / mL; the thickness of the graphene oxide film is 5-300 μm, preferably 10-200 μm, and more preferably 20-100 μm.

[0030] In the present invention, the graphene dispersion liquid is obtained by dispersing graphene in water, and the dispersion is preferably carried out under stirring, the rotation speed of the stirring is 800-2000 r / min, preferably 1000-1500 r / min, and the stirring time is 4-10 h, preferably 5-8 h. The shear force generated by stirring can fully disperse the graphene oxide. The present invention has no special requirements for the dosage of the graphene oxide dispersion liquid, and it can be determined according to the thickness and size of the target graphene oxide film.

[0031] In the present invention, the microporous membrane comprises one of a mixed cellulose membrane, a polytetrafluoroethylene membrane, a nylon membrane, a polyvinylidene fluoride membrane, a polyethersulfone membrane, and a polypropylene membrane, preferably a mixed cellulose membrane; the pore size of the microporous membrane is 0.45 to 3 μm, preferably 0.5 to 2 μm, and more preferably 0.8 to 1.2 μm. There is no special limitation on the size of the filter film in the present invention, and it can be determined according to the size of the target graphene oxide film.

[0032] In the present invention, in step 1), the temperature for heating and drying is 30 to 60 °C, preferably 40 to 50 °C; the time for heating and drying is 0.5 to 3 h, preferably 1 to 2 h.

[0033] In the present invention, in step 2), the annealing temperature is 2000 to 3000 °C, preferably 3000 °C; the annealing time is 1 to 3 h, preferably 2 h. In the present invention, in a high-temperature environment, the oxygen-containing functional groups of graphene oxide are removed and reduced to graphene, and the structure of graphene is also repaired, improving the thermal properties of graphene.

[0034] In the present invention, the thickness of the nickel metal layer is 0.05 to 5 μm, preferably 0.1 to 4 μm, and more preferably 0.2 to 3 μm; the width of the graphene micro-ribbon is 0.1 to 5 mm, preferably 0.2 to 2 mm; the thickness of the graphene micro-ribbon is 20 to 200 μm, preferably 50 to 100 μm.

[0035] In the present invention, the magnetic field strength of the magnetic field is 500 to 5000 Gs, preferably 2000 to 4000 Gs.

[0036] In the present invention, in the organic solution of the elastomer, the elastomer comprises one or more of silicone, epoxy resin, polyurethane, and acrylic acid, preferably polyurethane; the volume fraction of the elastomer in the organic solution is 5 to 50%, preferably 20 to 40%.

[0037] In the present invention, the curing temperature is 70 to 90 °C, preferably 80 °C; the curing time is 5 to 8 h, preferably 6 h.

[0038] The present invention also provides a compressible and vertically oriented high-thermal-conductivity graphene thermal interface material.

[0039] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0040] Example 1

[0041] The 15 mg / mL graphene oxide aqueous dispersion was blade-coated on a microporous membrane with a pore size of 0.8 μm. Subsequently, the film was dried at 40 °C for 2 h. After drying, the graphene oxide film was peeled off from the membrane. The graphene oxide film was annealed at 3000 °C for 2 h to obtain a graphene film with a thickness of 20 μm. At this time, the thermal conductivity of the graphene film refers to Figure 2 , and its in-plane thermal conductivity is 1460 W·m -1 ·K -1 , and the through-plane thermal conductivity is 5.8 W·m -1 ·K -1 . A 1-μm-thick nickel metal layer was sputtered on both ends of the graphene film. The laser power of the ultraviolet laser cutting machine was set to 50 W, and the cutting speed was set to 20 mm / s. The graphene film was cut into graphene micro-ribbons with a width of 0.2 mm. The graphene micro-ribbons were placed in a mold with a magnetic field strength of 4000 Gs to induce the perpendicular orientation of the graphene micro-ribbons. 10 vol% of polyurethane powder was dissolved in dimethylformamide solution, and then poured into the mold to encapsulate the graphene micro-ribbons and cured at 80 °C for 6 h. After curing, the magnetic field was removed, and the graphene thermal interface material was taken out and the nickel-plated graphene micro-ribbons at both ends were cut off. The graphene thermal interface material was cut into sheets with a thickness of 0.5 mm for performance testing. The through-plane thermal conductivity of the graphene thermal interface material is 311.7 W·m -1 ·K -1 . The thermal resistance is less than 0.02 Kcm 2 / W, and the residual stress under 50% compression is less than 280 kPa.

[0042] Example 2

[0043] Referring to Example 1, the difference is that the graphene film with a thickness of 50 μm was cut into graphene micro-ribbons with a width of 0.5 mm. The applied orientation magnetic field strength was 2000 Gs. The through-plane thermal conductivity of the prepared graphene thermal interface material is 403.5 W·m -1 ·K -1 . The thermal resistance is less than 0.06 Kcm 2 / W, and the residual stress under 50% compression is less than 410 kPa.

[0044] Example 3

[0045] Referring to Example 1, the difference is that the graphene film with a thickness of 100 μm was cut into graphene micro-ribbons with a width of 1 mm. The applied orientation magnetic field strength was 1000 Gs. The through-plane thermal conductivity of the prepared graphene thermal interface material is 590.8 W·m -1 ·K -1 . The thermal resistance is less than 0.09 Kcm 2 / W, and the residual stress under 50% compression is less than 780 kPa.

[0046] Example 4

[0047] Referring to Example 1, the difference is that the applied orientation magnetic field strength is 3000 Gs. The vertical thermal conductivity of the prepared graphene thermal interface material is 326.1 W·m -1 ·K -1 . The thermal resistance is less than 0.03 Kcm 2 / W, and the residual stress under 50% compression is less than 320 kPa.

[0048] Example 5

[0049] Referring to Example 1, the difference is that the graphene film with a thickness of 100 μm is cut into graphene microbelts with a width of 1 mm. The vertical thermal conductivity of the prepared graphene thermal interface material is 601.2 W·m -1 ·K -1 . The thermal resistance is less than 0.08 Kcm 2 / W, and the residual stress under 50% compression is less than 810 kPa.

[0050] Comparative Example 1

[0051] Referring to Example 1, the difference is that the applied orientation magnetic field strength is 300 Gs. The vertical thermal conductivity of the prepared graphene thermal interface material is 89.2 W·m -1 ·K -1 . The thermal resistance is less than 0.16 Kcm 2 / W, and the residual stress under 50% compression is less than 190 kPa.

[0052] Comparative Example 2

[0053] Referring to Example 1, the difference is that the applied orientation magnetic field strength is 6000 Gs. The vertical thermal conductivity of the prepared graphene thermal interface material is 410.5 W·m -1 ·K -1 . The thermal resistance is less than 0.01 Kcm 2 / W, and the residual stress under 50% compression is less than 344 kPa.

[0054] As can be seen from the above examples, the present invention provides a compressible vertically oriented high - thermal - conductivity graphene thermal interface material and its preparation method. The present invention uses magnetic - field - induced orientation to improve the vertical thermal conductivity of the graphene thermal interface material. A layer of nickel metal is sputtered on both ends of the graphene microbelt, and the graphene microbelt is induced to be vertically oriented by a magnetic field and encapsulated with an elastomer. The compressible vertically oriented high - thermal - conductivity graphene thermal interface material can quickly conduct the heat of high - power chips to the heat sink, greatly improving the heat dissipation efficiency of the device.

[0055] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a compressible vertically oriented high thermal conductivity graphene thermal interface material, characterized in that: The following steps are involved: 1) applying a graphene oxide dispersion onto a microporous filter membrane, and heating and drying to obtain a graphene oxide film; 2) annealing the graphene oxide film to obtain a graphene film; 3) sputtering a strip-shaped metal nickel layer at both ends of the graphene film, and cutting the graphene film along the width direction of the strip-shaped metal nickel layer to obtain graphene micro-ribbons; 4) Using a magnetic field to induce vertical orientation of the graphene microbelts, and using an organic solution of an elastomer to encapsulate and solidify the graphene microbelts, thereby obtaining a compressible vertically oriented high thermal conductivity graphene thermal interface material.

2. The preparation method according to claim 1, characterized in that: The concentration of the graphene oxide dispersion is 5 to 30 mg / mL, and the thickness of the graphene oxide film is 5 to 300 μm.

3. The preparation method according to claim 1 or 2, characterized in that: The microporous filter membrane comprises one of a mixed cellulose filter membrane, a polytetrafluoroethylene filter membrane, a nylon filter membrane, a polyvinylidene fluoride filter membrane, a polyethersulfone filter membrane and a polypropylene filter membrane, and the pore size of the microporous filter membrane is 0.45 to 3 μm.

4. The preparation method according to claim 3, characterized in that: In the step 1), the heating and drying temperature is 30 to 60° C., and the heating and drying time is 0.5 to 3 hours; In the step 2), the annealing temperature is 2000-3000° C., and the annealing time is 1-3 hours.

5. The preparation method according to claim 1, 2 or 4, characterized in that: The thickness of the metal nickel layer is 0.05-5 μm, the width of the graphene micro-ribbon is 0.1-5 mm, and the thickness of the graphene micro-ribbon is 20-200 μm.

6. The preparation method according to claim 5, characterized in that: The magnetic field strength of the magnetic field is 500-5000 Gs.

7. The preparation method according to claim 1 or 6, characterized in that: The elastomer in the organic solution of the elastomer comprises one or more of organic silicon, epoxy resin, polyurethane and acrylic acid, and the volume fraction of the elastomer in the organic solution is 5-50%.

8. The preparation method according to claim 7, characterized in that: The curing temperature is 70-90° C. and the curing time is 5-8 hours.

9. A compressible vertically oriented high thermal conductivity graphene thermal interface material prepared by the preparation method according to any one of claims 1 to 8.

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