JP6231031B2 - Thermally conductive particle composition, method for producing thermally conductive particle composition, thermally conductive resin composition, and thermally conductive resin cured body - Google Patents

Description

  The present invention relates to a thermally conductive particle composition, a method for producing a thermally conductive particle composition, a thermally conductive resin composition, and a thermally conductive resin cured body.

  2. Description of the Related Art Conventionally, a method has been used in which a thermal conductive filler is contained in a resin composition or a resin sheet to improve thermal conductivity as compared with a resin alone. In particular, a thermally conductive resin composition in which a matrix resin such as a silicone resin or an epoxy resin is filled with a thermally conductive inorganic filler is used for mounting an insulating layer of a printed wiring board on which a heat generating electronic component is mounted or a heat generating electronic component. Widely used in applications such as an insulating layer between a formed circuit and a heat sink.

  In recent years, along with the high performance and high integration of electronic parts, the heat generation density inside the electronic device is increasing, and a highly heat conductive resin composition and resin sheet are required. In order to achieve high thermal conductivity, it is necessary to highly fill the resin with a highly heat-conductive inorganic filler. However, if the filler is highly filled, poor filler dispersion and agglomeration occur, and it becomes difficult to improve the thermal conductivity of the resin composition. In particular, when a nitride such as boron nitride is used as the thermally conductive filler, the modification of the filler surface is difficult, and the effect of improving the affinity between the resin and the filler is insufficient. There was a problem with dispersibility in the resin.

  Therefore, a method for modifying the filler surface has been studied for the purpose of improving the fluidity of a composition using these thermally conductive particles. For example, boron nitride filler, a method using an amine-based (Patent Document 1) or an epoxy-based (Non-Patent Document 1) silane coupling agent, a zirconate coupling agent, a zirconium aluminate coupling agent, an aluminate coupling A method of surface treatment with an agent (Patent Document 2) is disclosed, but a coupling agent alone is insufficient to obtain sufficient dispersibility.

JP 2013-203770 A JP 2006-257392 A Hiroshima Prefectural Institute of Technology Research Report 49, 2006, p19

  An object of this invention is to provide the heat conductive particle composition excellent in the dispersibility and resin viscosity reduction, and its manufacturing method in view of the said problem and the situation. In addition, it aims at providing the resin composition excellent in the heat conductivity manufactured using this heat conductive particle composition, and a hardening body.

That is, the present invention employs the following method in order to solve the above problems.
(1) Thermally conductive particle composition comprising boron nitride fine powder having a mean particle diameter of 20 to 150 μm and boron nitride fine powder and boron nitride fine powder in the form of scales having an average particle diameter of 1 to 10 μm and an average thickness of 0.001 to 1 μm. .
(2) The thermally conductive particle composition according to (1), wherein the boron nitride fine powder is dispersed with a silane coupling agent.
(3) The thermally conductive particle composition according to (1) or (2), wherein a part of the boron nitride fine powder is attached to the surface of the boron nitride coarse powder.
( 4 ) The heat conduction according to any one of (1) to ( 3 ), wherein the boron nitride fine powder is 0.2 to 10 parts by mass with respect to 90 to 99.8 parts by mass of the boron nitride coarse powder. Particle composition.
( 5 ) A thermally conductive resin composition comprising the thermally conductive particle composition according to any one of (1) to ( 4 ) and a resin.
( 6 ) At least one selected from the group consisting of epoxy resin, silicone resin, liquid crystal polymer, polyester, polyamide, polyimide, polyphthalamide, polyphenylene sulfide, polycarbonate, polyether ether ketone, polyaryl ether ketone, and polyphenylene oxide. The heat conductive resin composition as described in ( 5 ) which is the above resin.
( 7 ) A thermally conductive resin cured product obtained by using an epoxy resin as the resin in the thermally conductive resin composition according to ( 6 ) , and curing the epoxy resin .
( 8 ) A first step of pulverizing boron nitride powder with a high-pressure homogenizer into scaly boron nitride fine powder having an average particle diameter of 1 to 10 μm and an average thickness of 0.01 to 1 μm, and the boron nitride fine powder with a silane coupling agent A method for producing a thermally conductive particle composition, comprising: a second step of dispersion treatment; and a third step of mixing boron nitride fine powder surface-treated with the silane coupling agent with boron nitride coarse powder by dry mixing. .

  As a result of intensive studies, the present inventors have determined that a thermally conductive particle composition using a thermally conductive particle coarse powder and a boron nitride fine powder having a scale shape having an average particle diameter and an average thickness in a specific range is a resin composition. It has been found that it is excellent in dispersibility and viscosity reduction. Furthermore, since the resin composition and cured body using the thermally conductive particle composition of the present invention can be highly filled with the thermally conductive particle composition, it exhibits excellent thermal conductivity.

1 is a scanning electron micrograph of fine boron nitride powder used in Example 1. FIG. FIG. 2 is a scanning electron micrograph showing the thickness of the boron nitride fine powder used in Example 9. FIG. 3 is a scanning electron micrograph of the thermally conductive particle composition of Example 2. FIG. 4 is a scanning electron micrograph in which FIG. 3 is partially enlarged.

<Thermal conductive particle coarse powder>
As the heat conductive particle coarse powder of the present invention, alumina, aluminum nitride, boron nitride, silicon nitride, silicon carbide, silica, surface-treated metal or carbon-based conductive particles can be used. Among these, alumina, aluminum nitride, and boron nitride are preferable because they exhibit high thermal conductivity and high insulation.

  20-150 micrometers is preferable and, as for the average particle diameter of heat conductive particle coarse powder, 20-70 micrometers is more preferable. When the average particle diameter of the heat conductive particle coarse powder is less than 20 μm, the heat conductivity may be lowered. When the average particle diameter exceeds 150 μm, the insulating properties may deteriorate.

<Boron nitride fine powder>
The boron nitride fine powder of the present invention has a scaly shape, and the average particle diameter is 1 to 10 μm, preferably 2 to 8 μm. If it is less than 1 μm, the dispersibility may be lowered, or the viscosity of the resin composition may be increased and the filling property may be lowered. Moreover, when larger than 10 micrometers, favorable fluidity | liquidity and a filling property may not be provided to a heat conductive particle coarse powder.

  The average thickness of the boron nitride fine powder is 0.001 to 1 μm, preferably 0.05 to 0.5 μm. When the average thickness is less than 0.001 μm or exceeds 1 μm, it may be difficult to highly fill the resin composition with the heat conductive particle composition.

  The boron nitride fine powder can be produced using, for example, a high-pressure homogenizer, a bead mill, a fine mill, or a vibration mill that can pulverize the boron nitride powder in a wet manner. In particular, a pulverization process using a mediumless high-pressure homogenizer is preferable in order to avoid contamination with impurities. In addition to the method described above, boron nitride fine powder may be produced using a chemical vapor deposition (CVD) method or a method of irradiating ultrasonic waves in an organic solvent.

  Further, the boron nitride fine powder is preferably subjected to a dispersion treatment for the purpose of improving dispersibility in the resin composition and reducing the viscosity of the resin composition. Examples of the dispersion treatment include a method using an amine or epoxy silane coupling agent, and a method using a zirconate coupling agent, a zirconium aluminate coupling agent, or an aluminate coupling agent. Among these, those dispersed with a silane coupling agent are preferable from the viewpoint of dispersibility.

  A publicly known method can be adopted as a method of distributed processing. For example, when a silane coupling agent is used as the dispersant, a method of removing the alcohol by vacuum drying after mixing boron nitride fine powder with an alcohol solution to which a silane coupling agent is added can be mentioned.

<Heat conductive particle composition>
The heat conductive particle composition of the present invention (hereinafter abbreviated as a particle composition) includes heat conductive particle coarse powder and boron nitride fine powder. It is preferable that a part of the boron nitride fine powder is attached to the surface of the thermally conductive particle coarse powder. The adhesion means a state in which the boron nitride fine powder is physically adhered to the surface of the thermally conductive particle coarse powder by Fade Awarus force. The particle composition is preferably 0.2 to 10 parts by mass of boron nitride fine powder with respect to 90 to 99.8 parts by mass of thermally conductive particle coarse powder, and 95 to 99.5 parts by mass of thermally conductive particle coarse powder. On the other hand, boron nitride fine powder is more preferably 0.5 to 5 parts by mass. When the heat conductive particle coarse powder is less than 90 parts by mass, the viscosity of the heat conductive resin composition described later may increase. Moreover, when it exceeds 99.8 mass parts, a dispersibility may fall.

  The particle composition is prepared by mixing the boron nitride fine powder with the heat conductive particle coarse powder by dry mixing. As a mixing method, a predetermined amount of each component may be uniformly mixed using a Henschel mixer, a rolling fluid mixer, a V-type blender, a raking machine, and a butterfly mixer.

<Thermal conductive resin composition>
The thermally conductive resin composition (hereinafter abbreviated as a resin composition) of the present invention comprises a particle composition and a resin. Examples of the resin include one or more resins selected from epoxy resins, silicone resins, liquid crystal polymers, polyesters, polyamides, polyimides, polyphthalamides, polyphenylene sulfides, polycarbonates, polyether ether ketones, polyaryl ether ketones, and polyphenylene oxides. You can choose. In addition, when resin is a thermosetting resin, a hardening | curing agent, a hardening adjuvant, etc. can be mix | blended.
Among these, epoxy resins are suitable as insulating layers for printed wiring boards because of their excellent heat resistance and adhesiveness to copper foil circuits. Silicone resin is suitable as a thermal interface material because it is excellent in heat resistance, flexibility and adhesion to a heat sink. When the total mass of the resin composition is 10 to 90% by mass, and particularly preferably 20 to 80% by mass is the particle composition, it is possible to improve the thermal conductivity, electrical insulation, and the like of the resin composition.
In addition, in order to promote the dispersibility to a particle composition, it is preferable to add a silane coupling agent to a resin composition.

  The resin composition can be prepared using a mill, a Banbury mixer, a Brabender, a single or twin screw extruder, a continuous mixer, a kneader and the like.

  The resin composition can be applied on a metal substrate having a thickness of 0.1 to 5 mm, superimposed on a metal foil that forms a circuit, and then heated at 150 to 240 ° C. for 5 to 8 hours to obtain a cured product. . The coating can be performed using a method such as a die coater, comma coater, roll coater, bar coater, gravure coater, curtain coater, doctor blade coater, spray coater, and screen printing. Or after apply | coating a resin composition on a metal substrate and making it harden | cure by heating, the method of laminating or hot-pressing with metal foil on the surface of a resin composition is employable. Furthermore, after a resin composition is semi-cured into a sheet, a metal substrate and a metal foil are bonded together to obtain a cured body.

<Hardened body>
The thickness of the cured body is preferably 20 to 150 μm, and more preferably 40 to 125 μm. By setting the thickness to 20 μm or more, the withstand voltage characteristics are improved, and by setting the thickness to 150 μm or less, the thermal resistance is lowered. As the metal substrate, aluminum, iron, copper and alloys thereof, or a clad material thereof is preferable in terms of thermal conductivity. As the metal foil, copper, aluminum, nickel, iron, tin, gold, silver, molybdenum, titanium, stainless steel, or the like can be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to an Example.

Example 1
<Preparation of boron nitride fine powder>
In a 300 ml glass beaker, 5 parts by mass of scale-shaped boron nitride powder (manufactured by Denki Kagaku Kogyo Co., Ltd., product name “SGP”, average particle diameter 18 μm), 47.5 parts by mass of ethanol, and 47.5 parts by mass of water And mixed. This solution was pulverized using a high-pressure homogenizer (wet atomizer “Starburst Mini”) manufactured by Sugino Machine. As a condition, a ball collision type was used for the nozzle shape, and the treatment at a pressure of 200 MPa was performed 10 times to prepare a boron nitride fine powder dispersion solution. The obtained dispersion solution was subjected to suction filtration with a filter paper having an opening of 0.5 μm and separated into solid and liquid, and the residue was vacuum dried at 45 ° C. for 12 hours to obtain fine boron nitride powder.

<Dispersion treatment of boron nitride fine powder>
To 3.4 parts by mass of a methanol solvent, 5 parts by mass of an epoxy silane coupling agent (trade name “KBM403”, 3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.), and pH to 3.3. 1.6 parts by mass of the adjusted aqueous acetic acid solution was added, and the mixture was stirred at room temperature for 1 hour. While dripping this solution to 100 parts by mass of boron nitride fine powder obtained by the above method, mixing with a mixer, air-drying, and leaving to stand in a 45 ° C. vacuum dryer for 12 hours to disperse the boron nitride fine powder Processed.

<Preparation of thermally conductive particle composition>
0.2 parts by mass of boron nitride fine powder dispersed by the above method was pulverized for 10 seconds with a mixer (Iwatani, “IFM-620DG”, impeller diameter: 58 mm, rotation speed: 20000 rpm). Further, 99.8 parts by mass of boron nitride coarse powder (manufactured by Denki Kagaku Kogyo Co., Ltd.) having an average particle diameter of 64.1 μm was added as the heat conductive particle coarse powder, and further mixed for 50 seconds with a mixer. A particle composition comprising 99.8 parts by mass of conductive particle coarse powder and 0.2 parts by mass of boron nitride fine powder was obtained. In addition, from the scanning electron microscope image of the obtained particle composition, it was confirmed that the boron nitride fine powder was in a state of adhering to the surface of the boron nitride coarse powder.

<Preparation of thermal conductive resin composition>
75 parts by mass of the particle composition obtained by the above method, 19 parts by mass of a bisphenol A type liquid epoxy resin (manufactured by DIC, “EPICLON 850CRP”), aromatic amine (manufactured by Nippon Synthetic Chemical Industry, “H-48B” ) 6 parts by mass (manufactured by Dow Corning Toray, “z-6040”) 1.0 part by mass of a silane coupling agent was added to a planetary stirrer (“Shinky Corporation Awatori Nertaro AR-250”, rotation speed 2000 rpm) ) To prepare a resin composition.

  The characteristics of the raw materials used in Example 1, the produced particle composition, and the resin composition were evaluated by the following methods. The results are shown in Table 1.

[Average particle size]
The average particle size of the thermally conductive particle coarse powder or boron nitride fine powder was measured using “Laser Diffraction Particle Size Distribution Measuring Device LS 13 320” manufactured by Beckman Coulter. The sample is a glass beaker with 10 cc of pure water and 1 g of heat conductive particle coarse powder or boron nitride fine powder added, and dispersion treatment is performed for 15 minutes with an ultrasonic cleaner (AUSONE, “US CLEANER”, output 80 W). Went. The dispersion liquid of the thermally conductive particle coarse powder or boron nitride fine powder subjected to the dispersion treatment was added drop by drop to the apparatus with a dropper, and the ultrasonic wave was irradiated again for 90 seconds, and measurement was performed 60 seconds later. In the laser diffraction particle size distribution measuring device, the particle size distribution was calculated from the data of the light intensity distribution of the diffracted / scattered light by the particles detected by the sensor. The average particle size was determined by multiplying the value of the measured particle size by the relative particle amount (difference%) and dividing by the total relative particle amount (100%).

[Average thickness of boron nitride fine powder]
75 parts by mass of boron nitride fine powder, 19 parts by mass of bisphenol A type liquid epoxy resin (DIC Corporation, “EPICLON 850CRP”), 6 parts by mass of aromatic amine (Nippon Synthetic Chemical Industry Co., Ltd., “H-48B”) After kneading with a type stirrer, it was extruded at 60 ° C. with a single screw extruder of 30 mmΦ to obtain a sheet shape in which the major diameter of boron nitride fine powder was oriented in the extrusion direction. The obtained sheet was heated at 200 ° C. for 8 hours to be cured. After collecting the central portion of the cured sheet, the end surface was processed with a microtome to obtain a 10 mm × 10 mm strip. The maximum thickness of 20 arbitrarily selected boron nitride fine powders was measured from the scanning electron microscope image of the cross-sectional view of the obtained strip, and the arithmetic average value was taken as the average thickness.

[Viscosity of thermally conductive resin composition]
The viscosity of the obtained resin composition was measured under the following conditions using a rheometer (“MCR-300” manufactured by Nippon Shibel Hegner).
Plate shape: Circular flat plate 25mmφ
Sample thickness: 1 mm
Temperature: 25 ± 1 ° C
Shear rate: 0.1S ^-1

[Dispersibility of thermally conductive resin composition]
Using a scraper, the resin composition heated to 50 ° C. was applied on a flat plate. A range of 50 mm × 50 mm in the center of the coated surface was selected, and the number of aggregates that could be visually confirmed was evaluated according to the following judgment. For the evaluation, the total number of agglomerates when three samples were used was used.
Excellent: No clumps were observed.
Good: The number of aggregates was 1 or more and less than 3.
Bad: There were 3 or more aggregates.

[Thermal conductivity]
The thermal conductivity was calculated by preparing a sheet of the obtained resin composition and multiplying all of the thermal diffusivity, specific gravity, and specific heat. The thermal diffusivity was determined by a laser flash method after processing the sample into a width of 10 mm × 10 mm × thickness of 1 mm. The measuring device used was a xenon flash analyzer (LFA447 NanoFlash manufactured by NETZSCH). Specific gravity was determined using the Archimedes method. The specific heat was obtained by using a differential scanning calorimeter (“Q Instruments”, “Q2000”) and raising the temperature from room temperature to 400 ° C. at a heating rate of 10 ° C./min in a nitrogen atmosphere. The results are shown in Table 1. The resin sheet was cured at 200 ° C. for 8 hours.

(Example 2)
Evaluation was carried out in the same manner as in Example 1 except that the content was changed to 99 parts by mass of boron nitride coarse powder and 1 part by mass of boron nitride fine powder.

(Example 3)
Evaluation was carried out in the same manner as in Example 1 except that the mass was changed to 90 parts by mass of boron nitride coarse powder and 10 parts by mass of boron nitride fine powder.

( Reference Example 4)
Evaluation was performed in the same manner as in Example 2 except that the heat conductive particle coarse powder was changed to boron nitride (manufactured by Denki Kagaku Kogyo Co., Ltd., “SGP”, average particle diameter: 18 μm).

(Example 5)
Evaluation was carried out in the same manner as in Example 2 except that the heat conductive particle coarse powder was changed to boron nitride (manufactured by Denki Kagaku Kogyo Co., Ltd., average particle size 150 μm).

( Reference Example 6)
Evaluation was carried out in the same manner as in Example 1 except that the thermally conductive particle coarse powder was changed to alumina (manufactured by Denki Kagaku Kogyo Co., Ltd., “DAW-70”, average particle diameter 71 μm).

( Reference Example 7)
Evaluation was carried out in the same manner as in Reference Example 6 except that the mass was changed to 99 parts by mass of thermally conductive particle coarse powder and 1 part by mass of boron nitride fine powder.

( Reference Example 8)
Evaluation was carried out in the same manner as in Reference Example 6 except that the mass was changed to 90 parts by mass of thermally conductive particle coarse powder and 10 parts by mass of boron nitride fine powder.

Example 9
Evaluation was performed in the same manner as in Example 2 except that boron nitride fine powder having an average particle diameter of 1.7 μm and an average thickness of 0.03 μm was used.

(Example 10)
Evaluation was performed in the same manner as in Example 2 except that boron nitride fine powder having an average particle diameter of 9 μm and an average thickness of 0.62 μm was used.

(Comparative Example 1)
Evaluation was performed in the same manner as in Example 2 except that the average particle size of the boron nitride fine powder was changed to 0.5 μm. The results are shown in Table 2.

(Comparative Example 2)
Evaluation was performed in the same manner as in Example 2 except that the average particle size of the boron nitride fine powder was changed to 20 μm.

(Comparative Example 3)
Evaluation was carried out in the same manner as in Example 1 except that only the heat conductive particle coarse powder was used without using boron nitride fine powder.

(Comparative Example 4)
Evaluation was carried out in the same manner as in Example 4 except that the average particle size of the boron nitride fine powder was changed to 0.5 μm.

(Comparative Example 5)
Evaluation was performed in the same manner as in Example 4 except that the average particle size of the boron nitride fine powder was changed to 20 μm.

(Comparative Example 6)
Evaluation was carried out in the same manner as in Example 4 except that only the heat conductive particle coarse powder was used without using boron nitride fine powder.

(Comparative Example 7)
Evaluation was carried out in the same manner as in Example 5 except that the average particle size of the boron nitride fine powder was changed to 0.5 μm. The results are shown in Table 3.

(Comparative Example 8)
Evaluation was carried out in the same manner as in Example 5 except that the average particle size of the boron nitride fine powder was changed to 20 μm.

(Comparative Example 9)
Evaluation was performed in the same manner as in Example 5 except that only the heat conductive particle coarse powder was used without using boron nitride fine powder.

(Comparative Example 10)
Evaluation was carried out in the same manner as in Example 7 except that the average particle size of the boron nitride fine powder was changed to 0.5 μm.

(Comparative Example 11)
Evaluation was carried out in the same manner as in Example 7 except that the average particle size of the boron nitride fine powder was changed to 20 μm.

(Comparative Example 12)
Evaluation was carried out in the same manner as in Example 6 except that only the heat conductive particle coarse powder was used without using boron nitride fine powder.

  The resin composition in which the particle composition of the present invention was blended resulted in a lower viscosity than the resin composition in which no boron nitride fine powder was blended. Moreover, it was confirmed that the resin composition of the present invention also has good dispersibility and thermal conductivity.

  Since the resin composition using the particle composition of the present invention is excellent in thermal conductivity, it can be used for insulating materials such as hybrid integrated circuits that require heat dissipation in addition to insulating materials for metal base circuit boards. .

Claims (8)

A thermally conductive particle composition comprising boron nitride coarse powder having an average particle diameter of 20 to 150 μm, and boron nitride fine powder having a scale-like shape having an average particle diameter of 1 to 10 μm and an average thickness of 0.001 to 1 μm. The thermally conductive particle composition according to claim 1, wherein the boron nitride fine powder is dispersed with a silane coupling agent. The thermally conductive particle composition according to claim 1 or 2, wherein a part of the boron nitride fine powder is attached to the surface of the boron nitride coarse powder. The thermally conductive particle composition according to any one of claims 1 to 3 , wherein the boron nitride fine powder is 0.2 to 10 parts by mass with respect to 90 to 99.8 parts by mass of the boron nitride coarse powder. The heat conductive resin composition containing the heat conductive particle composition and resin as described in any one of Claims 1-4 . The resin is at least one resin selected from epoxy resin, silicone resin, liquid crystal polymer, polyester, polyamide, polyimide, polyphthalamide, polyphenylene sulfide, polycarbonate, polyether ether ketone, polyaryl ether ketone, and polyphenylene oxide. The thermally conductive resin composition according to claim 5 , wherein Thermal conductivity using an epoxy resin as the resin in the resin composition, thermally conductive resin cured product The epoxy resin is cured according to claim 6. A first step of pulverizing boron nitride powder with a high-pressure homogenizer into flaky boron nitride powder having an average particle diameter of 1 to 10 μm and an average thickness of 0.01 to 1 μm, and the boron nitride powder is dispersed with a silane coupling agent. A method for producing a thermally conductive particle composition, comprising a second step and a third step of mixing boron nitride fine powder surface-treated with the silane coupling agent with boron nitride coarse powder by dry mixing.