JP2010159176A - Method of manufacturing heat dissipating sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a heat dissipating sheet effectively improving heat conductivity. <P>SOLUTION: A polyimide sheet 11 is prepared. An intermediate is formed by preliminarily calcinating the polyimide sheet 11 in an atmosphere containing a gallium gas. The intermediate is calcinated at a temperature higher than that in a process for forming the intermediate. In the process for forming the intermediate, preliminary calcination is preferably carried out at a temperature not lower than 1,000°C and lower than 2,000°C, and in the process for calcinating the intermediate, calcination is preferably carried out at a temperature not lower than 2,000°C and not higher than 3,000°C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a heat dissipation sheet, and more particularly to a heat dissipation sheet having a high thermal conductivity.

  As personal computers and mobile electronic devices become more sophisticated, the amount of heat generated by heat sources such as CPUs (Central Processing Units) has increased dramatically, improving the performance of heat dissipation devices. Is required. A typical heat dissipation method is a method of dissipating heat by interposing a heat dissipation sheet or an adhesive between a heat pipe made of Cu (copper) having a high heat transport capability and a heat generation source. In recent years, instead of a heavy heat pipe, a thin and lightweight heat transport sheet having an extremely high thermal conductivity in the in-plane direction such as a graphite sheet is often used. The graphite sheet is a heat dissipation sheet in which graphite c-axes are arranged in a direction perpendicular to the surface. For this reason, a graphite sheet can be used instead of a heat pipe.

  Such a method for producing a graphite sheet is disclosed, for example, in JP-A-7-109171 (Patent Document 1). Patent Document 1 discloses a method for producing a graphite sheet by pre-treating polypyromellitimide at 1000 ° C. and further heat-treating at 2900 ° C. to 3000 ° C.

JP-A-7-109171

  It is disclosed that the graphite sheet of Patent Document 1 subjected to heat treatment at 2900 ° C. to 3000 ° C. has a thermal conductivity of 750 (W / m · K) to 800 (W / m · K). In the said patent document 1, although this heat processing was performed at high temperature, this inventor revealed for the first time that the thermal conductivity of a graphite sheet has not fully improved.

  Moreover, in the said patent document 1, since the temperature of the heat processing required in order to manufacture the graphite sheet which has the heat conductivity of the said range is high, this inventor revealed for the first time that energy input amount becomes large. In this case, the cost required for producing the graphite sheet increases.

  Therefore, an object of the present invention is to solve the above-described problems, and to provide a method of manufacturing a heat dissipation sheet that efficiently improves thermal conductivity.

  As a result of intensive research on a method for manufacturing a heat dissipation sheet that efficiently improves thermal conductivity, the present inventor has made gallium (Ga) gas to produce a precursor (intermediate) mainly made of carbon produced in an intermediate process. It has been found that a graphite sheet having higher orientation than that of the prior art can be produced by carrying out in a gas containing.

  Then, the manufacturing method of the thermal radiation sheet | seat of this invention is equipped with the following processes. Prepare a polyimide sheet. The intermediate is formed by pre-baking the polyimide sheet in an atmosphere containing Ga gas. The intermediate is fired at a temperature higher than the temperature in the step of forming the intermediate.

  According to the method for manufacturing a heat dissipation sheet of the present invention, since the polyimide sheet is pre-fired in an atmosphere containing Ga gas, the polyimide sheet can be brought into contact with Ga vapor (Ga gas). The present inventor has found that the orientation of the carbon six-membered ring of the polyimide sheet is promoted by bringing it into contact with Ga gas during the production of the intermediate. For this reason, the intermediate body which improved the orientation can be formed. Therefore, when the intermediate with improved orientation is baked, a heat dissipation sheet with further improved orientation can be produced. If the orientation can be improved, the thermal conductivity can be improved. As mentioned above, when baking at the temperature comparable as a prior art, the heat conductivity of a thermal radiation sheet can be improved. Moreover, when manufacturing the thermal radiation sheet | seat which has a thermal conductivity comparable as a prior art, the temperature of baking can be lowered | hung. Therefore, the heat-radiation sheet which improves a thermal conductivity efficiently can be manufactured.

  Preferably, in the method of manufacturing the heat dissipation sheet, in the step of forming the intermediate, preliminary baking is performed at a temperature of 1000 ° C. or higher and lower than 2000 ° C., and in the step of baking the intermediate, the temperature is 2000 ° C. or higher and 3000 ° C. or lower. Bake.

  Thereby, since the orientation of an intermediate body can be improved more, the orientation of a thermal radiation sheet can be improved more. For this reason, the thermal radiation sheet which improves thermal conductivity more efficiently can be manufactured.

  Preferably, in the method of manufacturing the heat dissipation sheet, in the step of forming the intermediate, an intermediate containing B element and N element is introduced by introducing a gas containing boron (B) element and nitrogen (N) element. Form.

  By introducing a gas containing B and N, B and N can be reacted. Therefore, a BN (boron nitride) sheet having a structure similar to that of a graphite sheet and an insulator can be easily manufactured.

  Preferably in the manufacturing method of the said heat radiating sheet, in the process of forming the said intermediate body, it pre-bakes with the pressure of 0.05 Mpa or less.

  Thereby, even the inside of an intermediate body can be made to contact with Ga gas uniformly. For this reason, since graphitization inside the intermediate can be promoted, the orientation of the intermediate can be improved. Therefore, it is possible to manufacture a heat radiating sheet with improved conductivity.

  Preferably, the method for manufacturing a heat dissipation sheet further includes a step of performing a rolling process after the step of firing the intermediate.

  Thereby, since the orientation of a heat radiating sheet can be further advanced, the heat radiating sheet having higher thermal conductivity can be manufactured.

  Preferably, in the method for manufacturing the heat dissipation sheet, an aromatic polyimide sheet is prepared in the step of preparing the polyimide sheet.

  Since the aromatic polyimide sheet has a high orientation in the sheet plane of the aromatic six-membered ring, it has a property of being easily oriented when contacted with Ga gas. For this reason, the thermal radiation sheet which improved thermal conductivity more by improving orientation can be manufactured.

  Preferably, in the method for manufacturing the heat dissipation sheet, in the step of preparing the polyimide sheet, a polyimide sheet having a thickness of 5 μm to 100 μm is prepared.

  When the thickness is 5 μm or more, handling is easy. In the case of 100 μm or less, since the orientation of the carbon six-membered ring is very high, the thermal conductivity of the heat dissipation sheet can be further improved.

  Preferably, in the method for manufacturing a heat dissipation sheet, the step of preparing the polyimide sheet includes a step of preparing a plurality of polyimide sheets and a step of integrating the plurality of polyimide sheets by applying pressure.

  After integrating a plurality of polyimide sheets, the step of forming the intermediate and the step of firing the intermediate improve the thermal conductivity by improving the orientation, and the heat dissipation sheet with a dense structure Can be manufactured.

  Preferably, in the method for manufacturing a heat dissipation sheet, in the step of preparing the polyimide sheet, a polyimide sheet having an average pore diameter of 0.01 μm or more and 5 μm is prepared. Preferably, in the method for producing the heat dissipation sheet, in the step of preparing the polyimide sheet, a polyimide sheet having an average pore diameter of 0.1 μm or more and 2 μm or less is prepared.

  When the thickness is 0.01 μm or more, diffusion of gas such as Ga gas easily occurs. For this reason, the heat-radiation sheet which improved thermal conductivity more by improving orientation can be manufactured. On the other hand, in the case of 5 μm or less, a dense heat dissipation sheet can be produced. In the case of 2 μm or less, it is possible to produce a heat dissipation sheet with a denser structure.

  According to the method for manufacturing a heat dissipation sheet of the present invention, since the polyimide sheet is pre-fired in an atmosphere containing Ga gas, the orientation of the intermediate can be improved. Therefore, it is possible to manufacture a heat dissipation sheet that efficiently improves thermal conductivity.

It is sectional drawing which shows schematically the heat dissipation sheet in embodiment of this invention. It is sectional drawing which shows schematically the manufacturing apparatus of the thermal radiation sheet in embodiment of this invention. It is a flowchart which shows the manufacturing method of the thermal radiation sheet in embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

  FIG. 1 is a cross-sectional view schematically showing a heat dissipation sheet according to an embodiment of the present invention. With reference to FIG. 1, the thermal radiation sheet | seat 10 in this Embodiment is demonstrated.

  The heat dissipation sheet 10 is, for example, a graphite sheet or a BN sheet. When the heat dissipation sheet 10 is a graphite sheet, for example, it has a thermal conductivity in the in-plane direction of 1354 (W / mK) to 1580 (W / mK). Moreover, when the thermal radiation sheet | seat 10 is a BN sheet | seat, it has the heat conductivity of 611 (W / mK) or more and 652 (W / mK) or less, for example. Moreover, the heat dissipation sheet 10 may be a single sheet, or a plurality of sheets may be laminated.

  Then, with reference to FIG. 2 and FIG. 3, the manufacturing method of the thermal radiation sheet in this Embodiment is demonstrated. FIG. 2 is a cross-sectional view schematically showing an apparatus for manufacturing a heat dissipation sheet in the present embodiment. FIG. 3 is a flowchart showing a method for manufacturing a heat dissipation sheet in the present embodiment.

  Here, with reference to FIG. 2, the manufacturing apparatus 100 of the thermal radiation sheet in this Embodiment is demonstrated.

As shown in FIG. 2, the manufacturing apparatus 100 mainly includes a chamber 101, a carbon plate 102, crucibles 103 and 104, and a heater 105. Two rows of carbon plates 102 are stacked inside the chamber 101, and the carbon plate 102 divides the space into three. A gap is formed in the carbon plate 102. A polyimide sheet 11 is disposed on the upper carbon plate 102. Below the lower carbon plate 102, a crucible 103 filled with liquid Ga is disposed. On the lower carbon plate 102, a crucible 104 filled with powder B ₂ O ₃ is disposed. The heater 105 is disposed outside the chamber 101 and heats the inside of the chamber 101.

  The manufacturing apparatus 100 may include various elements other than those described above, but illustration and description of these elements are omitted for convenience of description.

  First, as shown in FIGS. 2 and 3, a polyimide sheet is prepared (step S1). In the present embodiment, the prepared polyimide sheet 11 is disposed on the upper carbon plate 102.

  Although the polyimide sheet prepared in step S1 is not particularly limited, it is preferable to prepare an aromatic polyimide sheet from the viewpoint of high orientation in the sheet plane of the aromatic six-membered ring. As such an aromatic polyimide, for example, a product name Kapton (R) manufactured by Dupont, Novax manufactured by Mitsubishi Kasei, PPT manufactured by Toho Rayon, etc., polyimide such as Upilex manufactured by Ube Industries may be used. From the viewpoint of easy orientation when in contact with Ga gas, Kapton (R) is preferably used.

  In step S1, it is preferable to prepare a polyimide sheet having a thickness of 5 μm to 100 μm, and it is more preferable to prepare a polyimide sheet of 25 μm to 100 μm. The smaller the thickness of the polyimide sheet, the higher the orientation of the carbon six-membered ring, and the higher the thermal conductivity of the heat dissipation sheet. In addition, in Step S2 for pre-baking, which will be described later, the smaller the thickness of the polyimide sheet, the easier it is to make the Ga gas evenly contact the inside of the polyimide sheet, so the thermal conductivity of the heat dissipation sheet increases. When the thickness is 100 μm or less, the thermal conductivity of the heat dissipation sheet is significantly increased. On the other hand, when the thickness is 5 μm or more, handling is easy. In the case of 25 μm or more, handling is easier.

  In step S1, it is preferable to use porous polyimide as the polyimide sheet. By using the porous polyimide sheet, regardless of the thickness of the sheet, Ga gas can be uniformly contacted to the inside in the pre-baking step S2 described later. For this reason, even when a thick polyimide sheet is prepared, the orientation can be enhanced.

  In step S1, a polyimide sheet having an average pore diameter of preferably 0.01 μm to 5 μm, more preferably 0.1 μm to 2 μm is prepared. In the case of 0.01 μm or more, a gas such as Ga gas easily diffuses into the polyimide sheet. For this reason, the orientation of an intermediate body and a heat-radiation sheet can be improved more. On the other hand, in the case of 5 μm or less, a dense heat dissipation sheet can be produced. In the case of 2 μm or less, it is possible to produce a heat dissipation sheet with a denser structure.

  The “average pore diameter” is a value measured by a mercury intrusion method, a gas adsorption method, or the like.

  The porosity of the polyimide sheet is not particularly limited, but is preferably 25% or more and 55% or less. A polyimide sheet in this range can be easily produced. If it is 25% or more, a gas such as Ga gas diffuses easily into the interior. In the case of 55% or less, a dense heat dissipation sheet can be produced.

  In step S1, one polyimide sheet or a plurality of polyimide sheets may be prepared. When preparing a plurality of polyimide sheets, it is preferable to integrate the plurality of polyimide sheets by pressurizing them. The method of pressurizing is not particularly limited, and a generally known method can be adopted.

  Next, an intermediate is formed by pre-baking the polyimide sheet in an atmosphere containing Ga gas (step S2).

  When the manufacturing apparatus 100 shown in FIG. 2 is used, the liquid Ga12 is filled into the crucible 103. Thereafter, the interior of the chamber 101 is heated by the heater 105 to evaporate the liquid Ga12 to generate Ga gas. The evaporated Ga gas is supplied to the polyimide sheet 11 through the gap of the carbon plate 102. For this reason, it can be fired while contacting the Ga gas with the polyimide sheet 11. Thereby, the polyimide sheet is thermally decomposed, and an intermediate body from which N, O (oxygen), and H (hydrogen) are removed can be generated. The intermediate includes an elemental carbon and is amorphous.

  In step S2, the pre-baking temperature is preferably 1000 ° C. or higher and lower than 2000 ° C., and more preferably around 1575 ° C. In the case of 1000 ° C. or higher, an intermediate with improved orientation can be produced. When the temperature is lower than 2000 ° C., an amorphous intermediate can be easily generated. In the case of around 1575 ° C., an amorphous intermediate with higher orientation can be easily generated.

The temperature when the vapor pressure of Ga becomes 1 × 10 ⁻² (Torr) is about 1093 ° C. Therefore, when the manufacturing apparatus 100 shown in FIG. 2 is used, when the interior of the chamber 101 is heated to a temperature higher than that with the liquid Ga12 disposed in the chamber 101, the liquid Ga12 evaporates and the Ga gas is generated. Can be generated. Therefore, the higher the temperature, the higher the vapor pressure of Ga, which is preferable. However, from the viewpoint of generating an intermediate, the upper limit is, for example, less than 2000 ° C.

  In step S2, the inside of the chamber 101 is preferably decompressed, for example, pre-baked at a pressure of 0.05 MPa or less, more preferably 0.25 MPa or less. When the pressure is reduced in a state where the liquid Ga12 in the chamber 101 is disposed, the liquid Ga12 is easily gasified. In the case of 0.05 MPa or less, Ga gas can be generated more easily. Moreover, since the production | generation of Ga gas is accelerated | stimulated in the case of 0.05 Mpa or less, it can contact uniformly to the inside of a polyimide sheet. As a result, the orientation of the intermediate can be improved. In the case of producing a graphite sheet, when the pressure is 0.05 MPa or less, the graphitization inside the polyimide sheet proceeds to improve the orientation, and finally the thermal conductivity is increased. In the case of 0.025 MPa or less, the orientation of the intermediate can be further improved. As described above, the lower the pressure, the more preferable it is because the liquid Ga12 can be generated at a lower temperature. However, the lower limit is, for example, 0.013 MPa or more from the viewpoint of easily reducing the pressure.

The material for generating Ga gas is not particularly limited to liquid Ga as long as it contains a Ga element, and a hydrocarbon-based material such as trimethylgallium ((CH ₃ ) ₃ Ga) may be used.

In step S2, it can be performed in at least one inert gas such as Ar (argon), He (helium), N ₂ or the like.

When manufacturing a graphite sheet as a heat dissipation sheet, the above materials are mainly used. When a BN sheet is manufactured as a heat dissipation sheet, a BN sheet having a structure similar to that of a graphite sheet can be produced by introducing a gas containing B element and N element together with Ga gas. As a method for forming the intermediate of the BN sheet, a method of reacting a gas containing B element and N element with the polyimide sheet may be simple. As a reaction method, for example, boron oxide such as B ₂ O ₃ and nitrogen gas are chemically reacted at a high temperature. B ₂ O ₃ decomposes at a high temperature to generate a gas such as B ₂ O ₃ gas, B ₂ O ₂ gas, or BO ₂ gas, reaches the surface of the polyimide sheet, undergoes reduction by carbon (C), and N To produce BN.

The B source may be another substance as long as it is a substance that generates boron by heating. As the B source, for example, organic boric acid compounds such as diborane (B ₂ H ₆ ), boric acid and melamine borate, solids of substances such as a mixture of boric acid and an organic substance, liquid, gas containing boron and oxygen, etc. Can be used. The N source may be a neutral or reducing gas containing nitrogen, and is easy to use as it is or after being mixed or diluted, and therefore nitrogen gas (N ₂ ), ammonia (NH ₃ ), etc. are preferable. Used. N ₂ gas is most preferred because it is inexpensive and safe.

  When a BN sheet is manufactured, BN is generated thermodynamically at 1200 ° C. or higher. For this reason, when manufacturing a BN sheet, the pre-baking temperature in step S2 is preferably 1200 ° C. or higher and lower than 2000 ° C., and particularly preferably 1300 ° C. or higher and 1800 ° C. or lower.

  If this step S2 is implemented, a polyimide sheet can be made to contact Ga vapor | steam. Thereby, Ga gas works as a kind of catalyst, and the orientation of the carbon six-membered ring of the polyimide sheet is promoted. For this reason, the intermediate body which improved the orientation can be formed.

  Next, the intermediate is fired at a temperature higher than the temperature in step S2 for forming the intermediate (step S3). In step S3, the temperature of the heater 105 may be further increased using the manufacturing apparatus 100 in FIG. 2, or another high temperature furnace may be used.

  In this step S3, the temperature for firing the intermediate is preferably 2000 ° C. or higher and 3000 ° C. or lower, more preferably 2500 ° C. or higher and 2700 ° C. or lower. In the case of 2000 degreeC or more, it can manufacture to the heat-radiation sheet which improved the crystallinity of the amorphous intermediate body and improved the orientation. In the case of 2500 degreeC or more, the heat-radiation sheet which further improved crystallinity and orientation can be manufactured. On the other hand, when it is 3000 ° C. or lower, it does not become too high, and can be easily manufactured. When the temperature is 2700 ° C. or lower, the amount of energy input can be reduced, thereby reducing the cost.

  In step S3, Ga vapor may be contained as in step S2. In step S3, the crystallinity is improved, but even if it contacts with Ga vapor, the progress of orientation is not hindered, and in some cases, the orientation may be promoted. That is, in the case where the alignment has not sufficiently progressed in step S2, the progress of the alignment is facilitated if it is brought into contact with Ga vapor in step S3.

  Note that the firing time in steps S2 and S3 is appropriately determined according to the firing temperature and the like.

  In this step S3, since the intermediate whose orientation has been improved by step S2 is baked, a heat dissipation sheet with improved orientation can be produced. If the orientation can be improved, the thermal conductivity can be improved. Therefore, the heat-radiation sheet which improved the thermal conductivity of the surface direction can be manufactured.

  Next, after step S3 for firing the intermediate, a rolling process is performed (step S4). The method for rolling the heat radiating sheet after step S3 is not particularly limited. For example, the heat radiating sheet is passed through a roller.

  In particular, when preparing a porous polyimide in step S1, the heat dissipating sheet such as a graphite sheet and a BN sheet has a porous structure at the time when step S3 for firing the intermediate is completed, and thus the orientation is not perfect. Therefore, in step S4 in which the rolling process is performed, orientation can be further advanced, high thermal conductivity can be obtained, and densification of the structure can proceed. This step S4 may be omitted.

  The heat dissipation sheet 10 shown in FIG. 1 can be manufactured by performing the above steps S1 to S4.

  As described above, in the method for manufacturing a heat dissipation sheet in the present embodiment, the polyimide sheet is pre-fired in an atmosphere containing Ga gas (step S2). Thereby, a polyimide sheet can be made to contact Ga vapor | steam. The present inventor has found that the orientation of the carbon six-membered ring of the polyimide sheet is promoted by bringing it into contact with Ga gas during the production of the intermediate. For this reason, the orientation of the intermediate can be improved by step S2. Therefore, when the intermediate with improved orientation is fired, a heat dissipation sheet with improved orientation can be produced. As it is oriented, the thermal conductivity of the surface on which the six-membered rings of the polyimide sheet are arranged increases.

  From this, when baking at the same temperature as a prior art, the heat conductivity of a thermal radiation sheet can be improved. That is, when the temperatures of steps S2 and S3 are the same, the heat dissipation sheet of the present embodiment brought into contact with Ga gas is more oriented than the conventional heat dissipation sheet (in the case of producing a graphite sheet, the orientation of graphitization). Degree) becomes higher. Moreover, when manufacturing the thermal radiation sheet | seat which has a thermal conductivity comparable as a prior art, the temperature to bake can be reduced. That is, in the case of manufacturing a heat radiating sheet having the same orientation (the degree of orientation of graphitization in the case of manufacturing a graphite sheet), it can be manufactured at a lower temperature by being brought into contact with Ga gas. When the heat radiation sheet can be manufactured at a low temperature, the amount of energy input can be reduced, and a furnace (device) having a special structure is not necessary, so that the manufacturing cost can be reduced. Therefore, the heat-radiation sheet 10 which improves a thermal conductivity efficiently can be manufactured.

  In this example, the effect of providing a step of forming an intermediate by pre-baking a polyimide sheet in an atmosphere containing Ga gas was examined.

(Invention Examples 1 to 5)
Invention Examples 1 to 5 each produced a heat radiating sheet using the production apparatus 100 shown in FIG. 2 according to the method for producing a heat radiating sheet in the above-described embodiment.

Specifically, the manufacturing apparatus 100 used an external heating type CVD (Chemical Vapor Deposition) furnace. As the chamber 101, a carbon furnace core tube having an inner diameter of 200 mm was used. The crucibles 103 and 104 had an inner diameter of 2 cm and a depth of 2 cm, and were made of graphite. In this manufacturing apparatus 100, 5 g of liquid Ga12 was filled in the crucible 103. Moreover, when producing the heat radiating sheets of Invention Examples 3 and 5, 3 g of B ₂ O ₃ powder was filled in the crucible 104.

  In step S1 of preparing a polyimide sheet, Kapton (R) manufactured by Dupont was prepared. The number, thickness, porosity, and average fine diameter of the prepared polyimide sheets were as shown in Table 1 below. In Invention Example 4, three polyimide sheets were integrated by compression molding. This polyimide sheet 11 was placed on the carbon plate 102 located in the uppermost layer.

Next, the intermediate body was formed by pre-baking the polyimide sheet 11 in the atmosphere containing Ga gas on the conditions shown in following Table 2 (step S2). Specifically, the temperature was increased from room temperature to 1200 ° C. at a rate of temperature increase of 3 ° C./min in an atmosphere containing Ar gas, and held for 3 hours when the temperature reached 1300 ° C. Then, it was heated to 1575 ° C. at a rate of temperature increase of 3 ° C./min while maintaining Ar gas or switching to N ₂ gas so that the atmosphere described in Table 2 below was obtained. At this stage, the pressure in the chamber 101 was reduced to the pressure described in Table 2 below. In this atmosphere, each was fired for 2 hours. The Ar gas or N ₂ gas was introduced into the chamber 101 as a gas G1 in FIG. Further, the exhaust gas was discharged to the outside of the chamber 101 as G2. As a result, the polyimide was thermally decomposed, and nitrogen, oxygen, and hydrogen escaped, and an intermediate of a structure mainly composed of amorphous carbon or amorphous BN was generated. Thereafter, the inside of the chamber 101 was naturally cooled.

  Next, the intermediate was baked at a temperature higher than the temperature in step S2 for forming the intermediate (step S3). Specifically, each intermediate was transferred to an ultra high temperature furnace. In an atmosphere containing Ar gas at 1 atm, the temperature was raised to 1000 ° C. at a rate of 10 ° C./min, and then raised to 2200 ° C. at a rate of 5 ° C./min. When it reached 2200 ° C., it was held for 1 hour. Then, it heated up to the main calcination temperature of Table 2 below with the temperature increase rate of 5 degree-C / min, and the holding time in this calcination temperature was 3 hours. Thereafter, the temperature was lowered to 2200 ° C. at a rate of 5 ° C./min, then lowered to 1300 ° C. at a rate of 10 ° C./min, and further lowered to room temperature at a rate of 20 ° C./min.

  Next, with respect to Inventive Examples 4 and 5, rolling treatment was further performed. From the above, the heat dissipation sheets of Invention Examples 1 to 5 were manufactured.

(Comparative Examples 1-5)
The heat-radiation sheet manufacturing methods of Comparative Examples 1 to 5 were basically provided with the same configuration as the heat-radiation sheet manufacturing methods of Invention Examples 1 to 5, respectively, but differed in that they were not filled with liquid Ga12. It was. That is, in Comparative Examples 1 to 5, the intermediate was formed in an atmosphere not containing Ga gas.

(Measuring method)
About the thermal radiation sheet | seat of this invention example 1, 2, and 4, the cross-sectional structure was observed with the scanning electron microscope (SEM). Moreover, the X-ray diffraction analysis was performed about the thermal radiation sheet | seat of this invention example 1-5. Furthermore, the thickness and thermal conductivity of the heat dissipation sheets of Invention Examples 1 to 5 and Comparative Examples 1 to 5 were measured. The thermal conductivity was measured using a periodic heating method. The results are shown in Table 3 below.

(Measurement result)
As a result of observing the cross-sectional structure of the heat-dissipating sheets of Invention Examples 1, 2, and 4 with an SEM, it was found to have a laminated graphite structure similar to the graphene layer.

  In addition, as a result of X-ray diffraction analysis of the heat-dissipating sheets of Invention Examples 1 to 5, it was found to be a highly oriented graphite sheet or hBN sheet in which the c-axis was oriented perpendicular to the sheet surface.

  Moreover, as shown in Table 3, it turned out that the thermal radiation sheet | seat of this invention example 1-5 can improve thermal conductivity compared with the thermal radiation sheet | seat of the comparative examples 1-5 pre-baked and baked at the same temperature. .

  As described above, according to this example, it is possible to confirm that an intermediate with improved orientation can be formed by pre-baking a polyimide sheet in an atmosphere containing Ga gas, and as a result, a sheet with high heat dissipation can be manufactured. It was. Therefore, it was confirmed that a heat dissipation sheet that efficiently improves the thermal conductivity can be manufactured by pre-baking the polyimide sheet in an atmosphere containing Ga gas.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the above-described embodiment but by the scope of claims for patent, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims for patent.

10 heat dissipation sheet, 11 polyimide sheet, 12 a liquid _{Ga, 13 B 2 O 3,} 100 manufacturing apparatus, 101 a chamber, 102 a carbon plate, 103 a crucible, 105 a heater.

Claims (10)

Preparing a polyimide sheet;
A step of forming the intermediate by pre-baking the polyimide sheet in an atmosphere containing gallium gas;
And a step of firing the intermediate at a temperature higher than the temperature in the step of forming the intermediate. In the step of forming the intermediate, pre-baking is performed at a temperature of 1000 ° C. or more and less than 2000 ° C.,
The method for producing a heat dissipation sheet according to claim 1, wherein in the step of firing the intermediate, firing is performed at a temperature of 2000 ° C. to 3000 ° C.   The method for producing a heat-radiating sheet according to claim 1 or 2, wherein, in the step of forming the intermediate, an intermediate containing a boron element and a nitrogen element is formed by introducing a gas containing a boron element and a nitrogen element. .   The method for manufacturing a heat dissipation sheet according to any one of claims 1 to 3, wherein in the step of forming the intermediate, preliminary baking is performed at a pressure of 0.05 MPa or less.   The manufacturing method of the thermal radiation sheet of any one of Claims 1-4 further equipped with the process of performing a rolling process after the process of baking the said intermediate body.   In the process of preparing the said polyimide sheet, the manufacturing method of the thermal radiation sheet of any one of Claims 1-5 which prepares an aromatic polyimide sheet.   The method for producing a heat dissipation sheet according to any one of claims 1 to 6, wherein in the step of preparing the polyimide sheet, the polyimide sheet having a thickness of 5 µm to 100 µm is prepared. The step of preparing the polyimide sheet includes:
Preparing a plurality of polyimide sheets;
The manufacturing method of the heat-radiation sheet of any one of Claims 1-7 including the process integrated by pressurizing the said several polyimide sheet.   The method for manufacturing a heat dissipation sheet according to any one of claims 1 to 8, wherein in the step of preparing the polyimide sheet, the polyimide sheet having an average pore diameter of 0.01 µm or more and 5 µm is prepared.   The method for producing a heat-radiating sheet according to claim 9, wherein in the step of preparing the polyimide sheet, the polyimide sheet having an average pore diameter of 0.1 μm to 2 μm is prepared.

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