JP5343478B2 - Graphite composite - Google Patents

Description

  The present invention relates to a graphite complex for conducting and dissipating heat generated by a heating element.

  In recent years, with the demand for higher performance, smaller size, and thinner electronic devices, as represented by mobile phones and personal computers, the amount of heat generated by electronic devices such as semiconductor elements has become higher. Increasing and suppressing the temperature rise of electronic devices has become an important issue.

  As a heat countermeasure, a graphite sheet with good thermal conductivity, thin film, and light weight and flexibility is used, and the heat of the heating element of the electronic component is transferred to the heat sink such as a heat sink or housing through the graphite sheet. Or quickly diffuse the heat of the heating element to lower the temperature of the heat spot.

  As a graphite sheet used for this, a pyrolytic graphite sheet obtained by pyrolyzing a polymer film at a high temperature and a graphite sheet using expanded graphite are known.

As prior art document information relating to the invention of this application, for example, the one shown in Patent Document 1 is known.
JP 2006-203018 A

  Since electronic devices are becoming smaller and thinner, and semiconductor devices have higher performance and higher density, it is required to increase the heat transport capacity of graphite sheets and further improve heat transport performance. . The heat transport amount of the graphite sheet can be increased by increasing the thermal conductivity in the surface direction and the sheet thickness when conducting heat in the sheet surface direction.

  However, in the case of the conventional pyrolytic graphite sheet, the thermal conductivity is very large, but if the polymer film of the raw material is made thick, the gas generated from the inside of the film during pyrolysis will become brittle and powdery, and the sheet may be thickened. There was a problem that could not be done.

  In the case of a graphite sheet, the sheet can be made thicker than a pyrolytic graphite sheet, but as the sheet becomes thicker, delamination tends to occur and it is difficult to make it thicker. Since it is relatively lower than the decomposed graphite sheet, there is a problem that the heat transport amount cannot be increased at a predetermined sheet thickness and the heat transport performance is insufficient.

  An object of the present invention is to solve such a conventional problem and to provide a graphite composite having high heat transport performance at a predetermined sheet thickness.

  In order to achieve the above object, the present invention provides a graphite composite comprising a pyrolytic graphite sheet and a graphite sheet laminated on both principal surfaces of the pyrolytic graphite sheet, wherein the pyrolytic graphite sheet is provided. Is produced by firing a polymer film, and the graphite sheet contains graphite powder, and the graphite sheet is bonded to each other at least at a part of the outer periphery of the pyrolytic graphite sheet. A graphite composite composite provided at a position opposed to at least the center of gravity of the pyrolytic graphite sheet, and the opposed joints provided at one-fourth or more of the outer circumference. Is the body.

  As described above, according to the graphite composite of the present invention, the joining portion of the graphite sheet is provided at a position facing at least the center of gravity of the pyrolytic graphite sheet, and this facing joining portion is provided on the outer periphery of the pyrolytic graphite sheet. By providing each one or more parts, a flexible graphite sheet can be directly adhered and laminated on the pyrolytic graphite sheet.

  Therefore, it is possible to suppress a decrease in heat conduction at the principal surface interface between the pyrolytic graphite sheet and the graphite sheet, and to increase the sheet thickness without reducing the synthetic thermal conductivity obtained by stacking the graphite sheet and the pyrolytic graphite sheet. In addition, since a pyrolytic graphite sheet having a thermal conductivity larger than that of the graphite sheet is laminated between graphite sheets having a large thermal conductivity, the synthetic thermal conductivity can be increased, and the heat transport performance is high at a predetermined sheet thickness. A graphite complex can be obtained.

  The graphite composite may have a through hole in the main surface of the pyrolytic graphite sheet, and the graphite sheets may be bonded to each other through the graphite powder filled in the through hole. Adhesion at the main surface interface with the sheet can be increased and the gap can be further reduced, and a decrease in heat conduction at the main surface interface can be suppressed to prevent a decrease in the synthetic thermal conductivity, thereby further improving the heat transport performance.

  The graphite composite may be one in which the bulk density of the graphite sheet on which the graphite sheet is on the through hole is smaller than the bulk density of the graphite sheet on the main surface of the portion without the through hole. Generation and expansion of delamination can be prevented, and the bending resistance of the graphite composite can be improved.

(Embodiment 1)
A graphite composite according to Embodiment 1 of the present invention as set forth in claim 1 will be described.

  FIG. 1 is a side cross-sectional view of a graphite composite according to Embodiment 1 of the present invention, FIG. 2 is a plan view thereof, and FIG. 1 is a cross-sectional view taken along line AA in FIG.

  As shown in FIGS. 1 and 2, the graphite composite includes a pyrolytic graphite sheet 12 and a graphite sheet 11 that sandwiches the pyrolytic graphite sheet 12.

  The pyrolytic graphite sheet 12 has a rectangular main surface 14 on both sides, and has an outer periphery 15 on an outer peripheral end surface of the main surface 14.

  The graphite sheet 11 is laminated in contact with both main surfaces 14 of the pyrolytic graphite sheet 12, and the graphite sheet 11 on both main surfaces 14 has a joint portion 17 that extends outward from the main surface 14 and is coupled to each other. doing.

  The coupling portion 17 is provided in contact with at least a part of the outer periphery 15 of the pyrolytic graphite sheet 12, and is provided at a position opposed to at least the center of gravity 16 of the pyrolytic graphite sheet 12. Further, the opposing coupling portion 17 has an outer periphery. It is provided in more than 1/4 of 15.

  In FIG. 2, the center of gravity 16 of the pyrolytic graphite sheet 12 is provided at the center of the main surface 14 because the pyrolytic graphite sheet 12 is uniform with a constant sheet thickness.

  By providing the coupling portion 17 in this manner, the flexible graphite sheet 11 can be securely adhered and laminated on the pyrolytic graphite sheet 12. Therefore, a decrease in heat conduction at the interface of the main surface 14 where the graphite sheet 11 and the pyrolytic graphite sheet 12 are in contact with each other is suppressed, and heat conduction is dispersed between the graphite sheet 11 and the pyrolytic graphite sheet 12 to efficiently perform the main surface. The heat can be conducted in 18 directions. And the graphite composite sheet 11 and the pyrolytic graphite sheet 12 in contact with each other can be made thick without increasing the synthetic thermal conductivity, and the graphite composite sheet can be increased in thickness, thereby improving the heat transport performance of the graphite composite. be able to.

  On the other hand, when the opposing coupling portion 17 is provided smaller than a quarter of the outer circumference 15, the graphite sheet 11 on the main surface 14 cannot be prevented from being deformed, and the graphite sheet 11 and the pyrolytic graphite sheet 12 are mainly used. It becomes difficult to make it adhere on the surface 14.

  In FIG. 2, the connecting portion 17 of the graphite composite is provided along the outer periphery 15 over the entire opposing long sides on both sides of the outer periphery 15, and is not provided on the short side of the outer periphery 15. The graphite sheet 11 is brought into close contact with the main surface 14 of the pyrolytic graphite sheet 12 by the coupling portion 17, and the pyrolytic graphite sheet 12 is sandwiched between the graphite sheets 11.

  The graphite composite is more preferably one in which the joint portion 17 is provided over the entire outer periphery 15 of the pyrolytic graphite sheet 12 and the entire pyrolytic graphite sheet 12 is embedded between the graphite sheets 11. And the adhesion strength between the pyrolytic graphite sheet 12 can be further increased.

  The graphite sheet 11 of the graphite composite contains scale-like graphite powder, and the graphite powder is deposited so as to be oriented along the main surface 18 of the graphite composite.

  The graphite powder is preferably expanded graphite. The expanded graphite is obtained by crushing natural graphite, adding a solution of concentrated sulfuric acid and concentrated nitric acid between the graphite layers, acid-treating, and then heating to foam the natural graphite. Scale graphite powder is formed. Since expanded graphite is plastic, it can be pressure-molded without using a resin binder, and a graphite sheet 11 having high thermal conductivity can be obtained.

  The graphite powder may be scale-like or spherical pyrolytic graphite.

  The graphite sheet 11 has a thermal conductivity in the direction of the main surface 18 of 100 W / mK to 350 W / mK. By increasing the thickness of the graphite sheet 11 on the main surface 14, the graphite sheet 11 can be compared with a single pyrolytic graphite sheet. The sheet thickness can be increased and the heat transport performance in the direction of the principal surface 18 of the graphite composite can be enhanced.

  The pyrolytic graphite sheet 12 of the graphite composite is produced by firing a raw material polymer film having a constant thickness at a temperature of 2500 ° C. to 3100 ° C., and graphite having large layered crystals extends in the direction of the main surface 14. Are oriented and stacked.

  Moreover, as the pyrolytic graphite sheet 12, it is preferable to use a sheet obtained by further rolling the pyrolytic graphite sheet after firing, and the thermal conductivity can be improved.

  The polymer film preferably uses a heat-resistant aromatic polymer such as polyimide, polyamide, polyamideimide, etc., and the pyrolytic graphite sheet 12 can have a much higher thermal conductivity than the graphite sheet 11, The thermal conductivity in the direction of the main surface 14 of the pyrolytic graphite sheet 12 can be 400 W / mK to 1800 W / mK.

  Thus, since the thermal conductivity of the pyrolytic graphite sheet 12 is larger than that of the graphite sheet 11, the thermal conductivity in the direction of the main surface 18 of the graphite composite can be set to a larger value than the thermal conductivity of the single graphite sheet. In addition, a graphite composite having higher heat transport performance than a single graphite sheet having the same sheet thickness can be obtained.

  Next, in the method for producing the graphite composite of Embodiment 1, first, graphite powder is roll-formed to form a graphite sheet, and the main surface of the graphite sheet is provided larger than the area of the main surface of the pyrolytic graphite sheet. The pyrolytic graphite sheet is directly contacted between the graphite sheets and overlapped.

  Next, a rigid plate having a flat surface in contact with the graphite sheet is used, the rigid plate is pressed against the graphite sheet, and the graphite sheet is pressed and compressed.

  By this pressurization, the portions projecting outward from the outer periphery of the pyrolytic graphite sheet in the graphite sheets on both sides are pressure-bonded to each other to form a joint portion 17 to form a sheet-like graphite composite.

  Further, the graphite composite has a high thermal conductivity in the sheet thickness direction because the pyrolytic graphite sheet 12 and the graphite sheet 11 are laminated in direct contact with each other without using a low thermal conductivity material such as a resin adhesive. can do.

  As described above, the graphite composite of the first embodiment can be laminated by adhering the graphite sheet 11 onto the main surface 14 of the pyrolytic graphite sheet 12, and has high heat transport performance at a predetermined sheet thickness. A graphite complex can be obtained.

  In addition, the graphite complex may be coated with a resin film or a metal film, and can protect the graphite complex or improve handling.

(Embodiment 2)
Next, the graphite composite according to Embodiment 2 of the present invention as set forth in claims 2 and 3 will be described.

  FIG. 3 is a side cross-sectional view of the graphite composite according to Embodiment 2 of the present invention, and FIG. 4 is a plan view thereof.

  In the graphite composite of the second embodiment, the pyrolytic graphite sheet 22 is the same except that the through-hole 31 is provided in the pyrolytic graphite sheet 12 of the first embodiment, and the graphite sheet 21 is the same as that of the first embodiment. The graphite sheet 11 on the main surface 24 is the same except that the configuration is different, and the same configuration is given the same number and the description is omitted.

  As shown in FIGS. 3 and 4, the graphite composite is provided with at least one through hole 31 in the main surface 24 of the pyrolytic graphite sheet 22, and in contact with both main surfaces 24 of the pyrolytic graphite sheet 22. Sheets 21 are laminated.

  The through hole 31 of the pyrolytic graphite sheet 22 penetrates in a direction substantially perpendicular to the main surface 24 and is provided symmetrically with respect to the center of the main surface 24, and the center of gravity 26 of the pyrolytic graphite sheet 22 is at the center of the main surface 24. Is provided.

  The graphite sheets 21 extend outward through the graphite sheets 21 on both main surfaces 24 and are coupled to each other at the coupling portion 17. Further, the graphite sheets 21 on both main surfaces 24 are passed through the graphite powder filled in the through holes 31. Are combined.

  Thus, the graphite sheet 21 is fixed to the pyrolytic graphite sheet 22 in the region of the graphite sheet 21 provided on the main surface 24 by bonding the graphite sheet 21 through the graphite powder filled in the through holes 31. Therefore, the deformation of the graphite sheet 21 provided on the main surface 24 can be further reduced. As a result, the adhesion between the graphite sheet 21 and the pyrolytic graphite sheet 22 at the interface of the main surface 24 can be improved, heat conduction can be improved, and heat transport performance can be improved.

  The method for producing a graphite composite according to the second embodiment is a pyrolytic graphite sheet in which through-holes are formed by punching the pyrolytic graphite sheet according to the first embodiment instead of the pyrolytic graphite sheet used in the first embodiment. The process is the same as in the first embodiment except that is used.

  First, a pyrolytic graphite sheet having a through-hole is directly contacted between and superimposed on a graphite sheet formed by roll forming, and then the graphite sheet is pressed and compressed. By this pressurization, a part of the graphite powder of the graphite sheet disposed on both main surfaces of the pyrolytic graphite sheet is pushed into the through holes 31.

  Next, the pressed graphite powders are combined with each other inside the through holes 31 to fill the through holes 31 with the graphite powder, and the graphite sheets on both main surfaces 24 are interposed between the graphite powders filled in the through holes 31. Join. Further, the graphite sheets on both main surfaces 24 are pressure-bonded to each other at the outer periphery 15 of the pyrolytic graphite sheet 22 to form a joint portion 17 to form a sheet-like graphite composite.

  The graphite sheet 21 on the main surface 24 is composed of a region 32 of the graphite sheet 21 on the through hole 31 and a region 33 of the graphite sheet 21 on the main surface 24 in a portion without the through hole 31, and the region 32 is a region. 33 is provided.

  In the positive pressurization, a part of the graphite powder of the graphite sheet disposed on the through hole 31 is filled in the through hole 31, the amount of the graphite powder in the region 32 is smaller than that in the region 33, and the main surface 24. Since the main surface 28 of the upper graphite sheet 21 is formed flat and the thickness of the region 32 and the region 33 is the same, the region 32 of the graphite sheet 21 is formed with a smaller bulk density than the region 33.

  In this way, by providing the graphite sheet 21 on the main surface 24 with the region 32 having a lower bulk density than the region 33, the region 32 of the graphite sheet 21 has a lower bulk density and therefore the flexibility is improved. The occurrence of delamination can be reduced, and even if delamination occurs, the expansion in the region 32 can be prevented. Therefore, the adhesion of the graphite composite 21 to the main surface 24 interface between the graphite sheet 21 and the pyrolytic graphite sheet 22 can be improved. Flexibility can be improved and bending resistance can be improved.

  The graphite composite of the present invention has an effect of improving heat transport performance at a predetermined sheet thickness, and is useful as a graphite composite for conducting and dissipating heat generated by a heating element.

Side surface sectional drawing of the graphite complex in Embodiment 1 of this invention The top view of the graphite complex in Embodiment 1 of this invention Side surface sectional drawing of the graphite complex in Embodiment 2 of this invention Plan view of graphite composite in Embodiment 2 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Graphite sheet 12 Pyrolytic graphite sheet 14 Main surface 15 Outer periphery 16 Center of gravity 17 Joint part 18 Main surface 21 Graphite sheet 22 Pyrolytic graphite sheet 24 Main surface 26 Center of gravity 28 Main surface 31 Through-hole

Claims (3)

A graphite composite comprising a pyrolytic graphite sheet and a graphite sheet laminated on both principal surfaces of the pyrolytic graphite sheet,
The pyrolytic graphite sheet is produced by firing a polymer film, the graphite sheet contains graphite powder, and the graphite sheet is formed on at least a part of the outer periphery of the pyrolytic graphite sheet. Sheets have joints joined together, and the joints are provided at positions facing each other at least across the center of gravity of the pyrolytic graphite sheet, and the joints facing each other are at least a quarter of the outer circumference. The pyrolytic graphite sheet, the graphite sheet, and the graphite composite that are directly laminated without using a material having low thermal conductivity . The graphite composite according to claim 1, wherein the main surface of the pyrolytic graphite sheet is provided with a through hole, and the graphite sheets are bonded to each other through graphite powder filled in the through hole. 3. The graphite composite according to claim 2, wherein the graphite sheet is provided with a bulk density of the graphite sheet on the through hole smaller than a bulk density of the graphite sheet on the main surface of the portion without the through hole.

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