JP2019085446A - Boron nitride-containing resin composition - Google Patents

Abstract

To provide a resin composition excellent in insulating characteristics.SOLUTION: A resin composition contains scaly boron nitride particles having an average particle size of 3 μm or more and 40 μm or less and spherical boron nitride particles having an average particle size of 0.05 μm or more and 1 μm or less, has an orientation index calculated by X-ray diffraction of the scaly boron nitride of 15 or more and 70 or less, has a content of the scaly boron nitride particles with respect to the whole resin composition of 3 vol% or more and 75 vol% or less, a content of the spherical boron nitride particles with respect to the whole resin composition of 0.3 vol% or more and 30 vol% or less, and a ratio of the spherical boron nitride particles with a particle size of 2 μm or more with respect to the spherical boron nitride particles of 1% or less.SELECTED DRAWING: None

Description

  The present invention relates to a thermally conductive resin composition containing scaly boron nitride particles and spherical boron nitride particles excellent in insulating properties.

  In recent years, with regard to electronic members, miniaturization has been demanded, and along with that, the heat dissipation and insulation properties of the members have become more important. As insulation characteristics, dielectric breakdown characteristics and long-term insulation reliability characteristics (partial discharge characteristics) are particularly important.

  The filler used in the electronic component is often used in combination with a coarse powder of several μm to several tens of μm and a fine powder of submicron to several μm. The role of fine powder is important.

  Although silica, alumina or the like is often used as the insulating filler, a boron nitride powder having a low dielectric constant and high heat dissipation characteristics is attracting attention.

  Boron nitride is generally obtained by reacting a boron source (boric acid, borax, etc.) with a nitrogen source (urea, melamine, ammonia, etc.) at a high temperature (solid phase method), usually in the form of flakes Several tens of μm boron nitride particles are obtained (Patent Document 1).

  On the other hand, in the vapor phase synthesis method, a method of obtaining spherical boron nitride fine powder has been reported (Patent Document 2, Patent Document 3, Patent Document 4).

  Patent Document 5 discloses a thermally conductive silicone composition which can use granular boron nitride having an average particle diameter of 0.1 to 50 μm and plate-like boron nitride having an average particle diameter of 0.1 to 30 μm as a thermally conductive filler. There is.

JP, 2014-40341, A Japanese Patent Laid-Open No. 2000-327312 Unexamined-Japanese-Patent No. 2004-182572 International Publication 2015 1222379 JP 2016-534161 gazette

  However, even if it used the boron nitride powder based on the prior art described in the patent documents 1-4 mentioned above as a filler, the problem that sufficient insulation characteristics were not obtained could not be solved until now. Further, the thermally conductive silicone composition of Patent Document 5, for example, heat containing 4.4% by mass of boron nitride having an average particle diameter of 20 μm described in the example and 8.8% by mass of boron nitride having an average particle diameter of 0.8 μm In the conductive silicone resin composition, sufficient long-term insulation reliability characteristics (partial discharge characteristics) could not be obtained.

  The present inventors have mixed scaly boron nitride powder having an average particle diameter of a specific micron order and spherical boron nitride powder having an average particle diameter of a specific nano to submicron region in a predetermined ratio. In addition, the ratio of spherical boron nitride particles having a particle diameter of 2 μm or more is suppressed to a low level, and the orientation and dispersibility thereof are controlled to be used as a filler, thereby improving the insulation properties to a level not conventionally found in resin compositions. The present invention has been completed.

  That is, the present invention can provide the following.

(1)
Scaly boron nitride particles having an average particle diameter of 3 μm to 40 μm,
Spherical boron nitride particles having an average particle diameter of 0.05 μm or more and 1 μm or less
A resin composition containing
The orientation index calculated from X-ray diffraction of scaly boron nitride is 15 or more and 70 or less,
The content of scaly boron nitride particles with respect to the entire resin composition is 3% by volume or more and 75% by volume or less,
The resin composition has a content of spherical boron nitride particles of 0.3% to 30% by volume with respect to the entire resin composition, and a ratio of spherical boron nitride particles having a particle diameter of 2 μm or more to the entire spherical boron nitride particles is 1% or less object.

(2)
The insulation member using the resin composition as described in (1).

(3)
The resin composition according to (1) or the insulating member according to (2), wherein the dielectric breakdown strength is 65 kV / mm or more.

  By using the present invention, a resin composition having excellent insulation properties can be provided.

  The scaly boron nitride powder that can be used to prepare the resin composition according to the embodiment of the present invention is prepared by a method commonly used in the art such as the solid phase method described in Patent Document 1 above, or is commercially available. The scaly boron nitride powder may be used (for example, GP grade manufactured by Denka Co., Ltd.).

  In addition, the method for producing spherical boron nitride powder that can be used for preparation of the resin composition according to the embodiment of the present invention is not a solid phase method which is a conventional method for producing hexagonal boron nitride, but a tubular in inert gas flow. After using the furnace to perform so-called gas phase synthesis using boric acid alkoxide volatilized and ammonia as raw materials (firing condition 1), next, firing in a resistance heating furnace (firing condition 2) and finally Preferably, the fired product is put in a crucible made of boron nitride and fired in an induction heating furnace to form a boron nitride powder (firing condition 3). In addition, it is desirable to control the dispersibility of the spherical boron nitride particles in the resin composition in order to improve the insulating properties.

  In the preferred method for producing spherical boron nitride powder, as described above, there are three stages of firing conditions. Among these, the firing condition 1 is preferably a temperature of 750 ° C. or more and 2,200 ° C. or less. If the temperature is less than 750 ° C., gas phase synthesis does not occur, which is not preferable. Further, if the temperature exceeds 2,200 ° C., a large amount of electricity is used for firing, which is costly and not preferable in production. Further, the reaction time under the firing condition 1 is preferably within 30 seconds, and more preferably within 20 seconds.

  It is preferable that the temperature of the baking condition 2 sets it as 1,000 degreeC or more and 1,600 degreeC or less, and the temperature of the baking condition 3 sets it as 1,800 degreeC to 2,200 degreeC. The reaction time under firing condition 2 is preferably 1 hour or more, more preferably in the range of 1 to 10 hours, and still more preferably in the range of 1 to 6 hours. If the reaction time is less than 1 hour, sometimes sufficiently spherical boron nitride particles can not be obtained. In addition, for firing conditions 1 and 2, an electric furnace of resistance heating type can be used as a tubular furnace, and for firing condition 3, an electric furnace of induction heating type can be used as a tubular furnace.

  Moreover, in order to obtain high purity and high crystallinity, it is more preferable to bake at a temperature of 1,800 ° C. to 2,200 ° C. in a nitrogen atmosphere under baking condition 3. The reaction time under firing condition 3 is preferably 0.5 hours or more, more preferably 0.5 to 8 hours, and still more preferably 0.5 to 6 hours. If the reaction time is less than 0.5 hours, the purity of the obtained boron nitride powder may be lowered.

  3 micrometers-40 micrometers are preferable, and, as for the average particle diameter of scale-like boron nitride powder which can be used by embodiment of this invention, 4-30 micrometers is more preferable. If the average particle size is less than 3 μm, the dielectric breakdown voltage is not improved, which is not preferable. Further, in order to obtain scale-like particles having an average particle size of more than 40 μm, it is necessary to raise the temperature of firing and further to extend the firing time, which is not preferable because the production cost becomes large. In the present specification, the average particle diameter of the scaly boron nitride powder is defined as the average particle diameter obtained by subjecting the scaly boron nitride powder to the laser diffraction scattering method as described later.

  The content of the scaly boron nitride particles is preferably 3% by volume to 75% by volume, and more preferably 4% by volume to 70% by volume, with respect to the total volume of the resin composition according to the embodiment of the present invention. If the content is less than 3% by volume, no improvement in the dielectric breakdown voltage is observed, and if it exceeds 75% by volume, the filling of the resin becomes difficult. The dielectric breakdown strength is preferably 65 kV / mm or more, more preferably 70 kV / mm or more, and still more preferably 75 kV / mm or more.

  The orientation index of the scaly boron nitride particles contained in the resin composition according to the embodiment of the present invention is preferably 15 to 70. If the orientation index is less than 15, the orientation is insufficient, and the improvement of the dielectric breakdown voltage is not observed, which is not preferable. When the orientation index exceeds 70, it is disadvantageous in terms of thermal conductivity, which is also not preferable.

  The average particle diameter of the spherical boron nitride powder of the present invention is preferably 0.05 μm to 1.0 μm. If the thickness is less than 0.05 μm, aggregation tends to easily occur when kneading with a resin, and both the dielectric breakdown characteristics and the partial discharge characteristics are apt to deteriorate. On the other hand, if it exceeds 1.0 μm, the effect on the partial discharge characteristics is reduced, which is not preferable.

  The content of the spherical boron nitride particles is preferably 0.3% by volume to 30% by volume, more preferably 0.4% by volume to 28% by volume, with respect to the total volume of the resin composition according to the embodiment of the present invention -25 vol% is more preferred. If the content is less than 0.3% by volume, the partial discharge characteristics are not sufficiently improved, while if it exceeds 30% by volume, the filling of the resin becomes difficult.

  The ratio of spherical boron nitride particles having a particle diameter of 2 μm or more to the whole spherical boron nitride particles contained in the resin composition is preferably 1% or less, more preferably 0.9% or less, and further preferably May be 0.7% or less, particularly preferably 0.5% or less. When the ratio exceeds 1%, there arises a problem that the partial discharge characteristics are inferior. In addition, it is considered that spherical boron nitride particles that are typically 2 μm or more in particle diameter are aggregated particles.

  Whether the form of the boron nitride powder is spherical or scaly can be determined by electron microscopic observation. In the present specification, a primary particle having an average circularity of 0.8 or more is defined as a spherical boron nitride powder, and one having an average circularity of less than 0.8 is defined as a scaly boron nitride powder. More preferably, those having an average particle diameter of 1 μm or less and an average circularity of 0.8 or more can be considered as spherical boron nitride powder.

  The resin used for the resin composition according to the embodiment of the present invention is preferably a heat conductive resin in consideration of use for applications requiring heat dissipation. As the heat conductive resin, for example, epoxy resin, silicone resin, silicone rubber, acrylic resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluorine resin, polyamide (for example, polyimide, polyamide imide, polyether imide etc.), Polyester (eg, polybutylene terephthalate, polyethylene terephthalate etc.), polyphenylene ether, polyphenylene sulfide, wholly aromatic polyester, polysulfone, liquid crystal polymer, polyether sulfone, polycarbonate, maleimide modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber styrene) ) Resin, AES (acrylonitrile ethylene propylene diene rubber-styrene) resin, etc. can be used.

<Measurement method>
The scaly boron nitride powder and the spherical boron nitride powder were analyzed by the measurement method described below.

(1) Average particle size: For measurement, a particle size distribution measuring apparatus by laser diffraction scattering method “LS-13 320” manufactured by Beckman Coulter, Inc. was used. The average particle size obtained is an average value by volumetric statistics. When the average particle size was less than 100 nm, a dynamic light scattering measurement apparatus "Zetasizer Nano ZS" manufactured by MALVERN was used.

(2) Orientation index: Measurement of the orientation index is carried out using an X-ray diffractometer ("Ultima IV" manufactured by RIGAKU CO., LTD.) In the range of 2θ = 10 ° to 70 °, around 2θ = 27 ° (( The intensity I ₀₀₂ of the diffraction line of the ( ₀₀₂ ) plane) and the intensity I ₁₀₀ of the diffraction line near 2θ = 41 ° ((100) plane) were determined. The orientation index is determined by the peak intensity ratio of boron nitride X-ray diffraction:
Orientation index = I ₀₀₂ / I ₁₀₀
Calculated as Although two types of diffraction lines of scaly boron nitride and spherical boron nitride may be confirmed near 2θ = 27 °, sharp diffraction on the high angle side corresponding to scaly boron nitride is made in the present specification. Calculations were made using lines.

(3) Amount of spherical BN particles having a particle diameter of 2 μm or more: The amount of spherical BN particles having a particle diameter of 2 μm or more was measured by the following method. That is, the prepared resin composition was processed by a CP (cross section polisher) method to expose a cross section, and after fixing on a sample table, osmium coating was performed. Thereafter, the cross section was observed using a scanning electron microscope (for example, "JSM-6010LA" manufactured by Nippon Denshi Co., Ltd.) at an observation magnification of 2,000 times to 10,000 times to obtain an image. From the obtained image, 1,000 spherical boron nitride particles are extracted, and among them, spherical boron nitride particles having aggregated particles of 2 μm or more are present as spherical BN particles having a particle diameter of 2 μm or more. Was calculated and evaluated. In addition, "A image kun" (made by Asahi Kasei Engineering Co., Ltd.) and "Mac-View Ver. For example, the number of pixels of the image analysis can be set to, for example, 15.1 million pixels by 1000 times.

(4) Evaluation of dielectric breakdown strength: The dielectric breakdown strength was measured by the following method. That is, the prepared resin composition sample is placed in an IP-55D insulating oil tester manufactured by Musashi Intech Co., Ltd., fixed between spherical electrodes in a fluorine-based liquid ("Fluorinert (trademark)" manufactured by 3M Japan), and initial voltage The pressure was increased at 3 kV / sec up to 12 kV, ((voltage value at which dielectric breakdown occurred)-1) kV was taken as the dielectric breakdown value, and the value divided by the thickness of the sample was taken as the dielectric breakdown strength (kV / mm). As dielectric breakdown strength, 65 kV / mm or more was taken as the pass value, and the case where it was 70 kV / mm or more was recognized as preferable when it was 75 kV / mm or more as preferable.

(5) Partial discharge erosion volume evaluation: The partial discharge erosion volume was measured by the following method. That is, the produced resin composition sample is fixed to a hemispherical electrode having a diameter of 10 mm and a flat electrode having a diameter of 25 mm, and a low frequency transmitter ("AG-204D" manufactured by KENWOOD Co., Ltd.) and a high-pressure amplifier for AC / DC dual use (manufactured by TREK Co.) A voltage was applied for 24 hours under the conditions of a frequency of 1 kHz and a voltage of 5 kV _{rms in} the atmosphere using 20/20 C-HS "). The surface roughness of the sample after the test was evaluated using a one-shot 3D shape measuring machine ("VR-3000" manufactured by Keyence Corporation) to obtain a 3D image, and the erosion volume (mm ³ ) was evaluated. As partial discharge erosion volume, 1.3 mm ³ or less was taken as the pass value.

  Hereinafter, the present invention will be described in detail by way of Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1
The resin composition of Example 1 was produced as follows.

<Flaky Boron Nitride Powder>
As scale-like boron nitride powder, GP grade (average particle diameter 7 μm) manufactured by Denka Co., Ltd. was used.

<Spherical boron nitride powder>
Spherical boron nitride powder was synthesized using the following process.

(Firing condition 1)
The core tube was placed in a resistance heating furnace and heated to a temperature of 1,000 ° C. Trimethyl borate (“TMB-R” manufactured by Tama Chemical Co., Ltd.) is introduced into the core pipe through the introduction pipe by nitrogen bubbling, while ammonia gas (purity 99.9% or more) is also introduced into the core pipe via the introduction pipe did. The trimethyl borate and ammonia introduced had a molar ratio of 1: 1.2. A gas phase reaction was carried out in a furnace, and a white powder was produced by synthesizing at a reaction time of 10 seconds. The resulting white powder was collected.

(Firing condition 2)
The white powder recovered under firing condition 1 is filled in a crucible made of boron nitride and set in a resistance heating furnace, then heated at 1,350 ° C. for 5 hours in a mixed atmosphere of nitrogen and ammonia, cooled after completion of firing. The fired product was recovered.

(Firing condition 3)
The fired product obtained under firing condition 2 was put into a boron nitride crucible, and fired at 2,000 ° C. for 4 hours in a nitrogen atmosphere in an induction heating furnace to obtain a boron nitride powder.

  The boron nitride powder obtained above was observed with an electron microscope, and it was confirmed that it was spherical boron nitride powder and that its average particle size was 0.5 μm.

<Resin composition preparation conditions>
An epoxy main agent and a curing agent were used as the resin, EP816A manufactured by Mitsubishi Chemical Corp. was used as the epoxy main agent, and EK113 manufactured by Mitsubishi Chemical Corp. was used as the curing agent at a ratio of 30% by mass to the main agent. To this resin, 10% by volume of the above scaly boron nitride powder and 1% by volume of spherical boron nitride powder are added, and mixed for 20 minutes at 2,000 rpm in the air using an autorotation revolution type high-speed rotary mixer (ARV310 manufactured by Shinky Co., Ltd.) The hardener was added and mixed in vacuum at 1,500 rpm for 5 minutes. The mixed slurry was poured into a 0.5 mm-thick mold and molded. After 30 minutes after pouring the slurry, the curing operation was started, and after degassing in vacuum at a temperature of 70 ° C. for 15 minutes, the primary curing was performed at 70 ° C. for 3 hours and the secondary curing at 120 ° C. for 3 hours. The resin composition according to The ratio of spherical boron nitride particles having a particle diameter of 2.0 μm or more contained in the obtained resin composition was measured by the above-described method to be 0.1%.

Example 2
Example 2 produced the resin composition on the conditions similar to Example 1 except having changed content of scale-like boron nitride and spherical boron nitride into 4.5 volume% and 0.5 volume%, respectively.

[Example 3]
Example 3 produced the resin composition on the conditions similar to Example 1 except content of scaly boron nitride having been 65 volume%.

Example 4
Example 4 produced the resin composition on the conditions similar to Example 1 except having made content of spherical boron nitride 25 volume%.

[Example 5]
Example 5 produced the resin composition on the conditions similar to Example 1 except having replaced scaly-like boron nitride by Denka Co., Ltd. HGP (average particle diameter 4 micrometers).

[Example 6]
Example 6 was produced under the same conditions as in Example 1 except that scaly boron nitride was changed to XGP (average particle diameter 30 μm) manufactured by Denka Co., Ltd., to produce a resin composition.

[Example 7]
Example 7 produced the resin composition on the conditions similar to Example 1 except having set the introduction ratio of trimethyl borate and ammonia to 1: 9 molar ratio regarding baking condition 1 in manufacture of spherical boron nitride powder. . The average particle diameter of the spherical boron nitride powder was 0.1 μm.

[Example 8]
Example 8 manufactured the resin composition on the conditions similar to Example 1 except the heating temperature having been 820 degreeC regarding baking conditions 1 in manufacture of spherical boron nitride powder. The average particle diameter of the spherical boron nitride powder was 0.9 μm.

[Example 9]
Example 9 was produced in the same manner as Example 1 except that the curing operation was started 10 minutes after pouring the slurry at the time of production of the resin composition.

[Example 10]
Example 10 was prepared in the same manner as Example 1 except that the curing operation was started 60 minutes after the slurry was poured into the resin composition.

[Example 11]
Example 11 was mixed at 1,000 rpm in the air for 10 minutes using a rotation-revolution type high-speed rotational mixer (ARV 310 manufactured by Shinky) at the time of resin composition preparation, and a curing agent was added and mixed for 5 minutes in 1,000 rpm. It was prepared in the same manner as Example 1.

Comparative Example 1
The comparative example 1 hardened | cured and produced the resin composition on the conditions similar to Example 1 except having used only resin without using boron nitride.

Comparative Example 2
Comparative Example 2 is an example except that mixing was performed for 5 minutes in air at 300 rpm using a rotation-revolution type high-speed rotational mixer (ARV 310 manufactured by Shinky) at the time of resin composition preparation, and a curing agent was added and mixed for 5 minutes in vacuum at 300 rpm. It produced similarly to 1.

Comparative Example 3
In Comparative Example 3, a resin composition was produced under the same conditions as Example 1, except that the scaly boron nitride powder was replaced with SP3-7 (average particle diameter: 2 μm) manufactured by Denka Co., Ltd.

Comparative Example 4
The comparative example 4 produced the resin composition on the conditions similar to Example 1 except content of scale-like boron nitride having been 2.5 volume%.

Comparative Example 5
The comparative example 5 produced the resin composition on the conditions similar to Example 1 except having made content of spherical boron nitride 0.1 volume%.

Comparative Example 6
Comparative Example 6 was carried out under the same conditions as Example 1 except that the content of scaly boron nitride was changed to 80% by volume, but a resin composition worthy of evaluation because the content of boron nitride was too large was produced could not.

Comparative Example 7
Comparative Example 7 was carried out under the same conditions as Example 1 except that the content of spherical boron nitride was 35% by volume, but a resin composition worthy of evaluation was produced because the content of boron nitride was too large. could not.

Comparative Example 8
Comparative Example 8 was produced in the same manner as Example 1 except that the curing operation was started immediately after pouring the slurry produced at the time of production of the resin composition.

Comparative Example 9
Comparative Example 9 was produced in the same manner as Example 1 except that alumina powder (ASFP-20 manufactured by Denka Co., average particle diameter 0.5 μm) was used instead of spherical boron nitride powder.

Comparative Example 10
Comparative Example 10 was prepared in the same manner as Example 1 except that silica powder (SFP-20M manufactured by Denka Co., average particle diameter 0.5 μm) was used instead of spherical boron nitride powder.

  The above conditions, measurement and evaluation results are summarized in the following table.

  Since the resin composition according to the embodiment of the present invention is excellent in insulation, it can be widely used for insulation members and the like.

Claims (3)

Scaly boron nitride particles having an average particle diameter of 3 μm to 40 μm,
A resin composition comprising spherical boron nitride particles having an average particle diameter of 0.05 μm or more and 1 μm or less,
The orientation index calculated from X-ray diffraction of scaly boron nitride is 15 or more and 70 or less,
The content of scaly boron nitride particles with respect to the entire resin composition is 3% by volume or more and 75% by volume or less,
A resin composition in which the content of spherical boron nitride particles is 0.3% to 30% by volume based on the whole resin composition, and the ratio of spherical boron nitride particles having a particle diameter of 2 μm or more to the whole spherical boron nitride particles is 1% or less object.   An insulating member using the resin composition according to claim 1.   The resin composition according to claim 1 or the insulating member according to claim 2, wherein the dielectric breakdown strength is 65 kV / mm or more.