JP7273587B2 - Boron nitride powder and resin composition - Google Patents

Description

The present invention relates to boron nitride powders and resin compositions.

Electronic components such as power devices, transistors, thyristors, and CPUs face the challenge of efficiently dissipating heat generated during use. In order to solve this problem, conventionally, the insulating layer of a printed wiring board on which electronic components are mounted has a high thermal conductivity, or the electronic components or printed wiring board is attached to a heat sink via an electrically insulating thermal interface material. things have been done. Ceramic powder with high thermal conductivity is used for such insulating layers and thermal interface materials.

Boron nitride powder, which has properties such as high thermal conductivity, high insulation, and low relative dielectric constant, has attracted attention as a ceramic powder. For example, in Patent Document 1, the shape of the aggregate is made more spherical to improve the packing property, and the strength of the powder is improved. As a hexagonal boron nitride powder that achieves improved and stabilized withstand voltage, the ratio of the major diameter and thickness of primary particles is on average 5 to 10, and the size of aggregates of primary particles is 2 μm in average particle diameter (D50). A hexagonal boron nitride powder characterized by having a particle size of 200 μm or less and a bulk density of 0.5 to 1.0 g/cm ³ is disclosed.

JP 2011-98882 A

However, conventional boron nitride powder still has room for improvement in terms of withstand voltage. Accordingly, an object of the present invention is to improve the voltage resistance of boron nitride powder.

The inventors of the present invention have studied to improve the voltage resistance, and found that it is effective to use a boron nitride powder having a relatively small particle size and a boron nitride powder having a relatively large particle size in combination. rice field.

One aspect of the present invention is a boron nitride powder having a volume-based particle size distribution having a peak A existing in a region of 5 μm or more and less than 30 μm and a peak B existing in a region of 50 μm or more and less than 100 μm.

The ratio I (002) / I (100) of the peak intensity I (002) of the (002) plane to the peak intensity I (100) of the (100) plane in the powder X-ray diffraction method of the boron nitride powder is 9.0 or less. can be

The maximum frequency at peak B may be greater than the maximum frequency at peak A.

Another aspect of the present invention is a resin composition containing a resin and the above boron nitride powder.

In another aspect of the present invention, the primary particles of boron nitride are aggregated, and the boron nitride powder A having a mode diameter in the region of 5 μm or more and less than 30 μm in the volume-based particle size distribution, and the primary particles of boron nitride A method for producing a boron nitride powder comprising a step of mixing boron nitride powder B which is agglomerated and has a mode diameter in the region of 50 μm or more and less than 100 μm in a volume-based particle size distribution.

In the above process, the boron nitride powder A and the boron nitride powder B may be mixed so that the volume ratio of the boron nitride powder B is larger than the volume ratio of the boron nitride powder A.

Another aspect of the present invention is a boron nitride powder A having a resin and primary particles of boron nitride aggregated and having a mode diameter in the region of 5 μm or more and less than 30 μm in the volume-based particle size distribution, and boron nitride. A method for producing a resin composition, comprising a step of mixing boron nitride powder B formed by agglomeration of primary particles and having a mode diameter in the region of 50 µm or more and less than 100 µm in a volume-based particle size distribution.

In the above step, the resin, the boron nitride powder A, and the boron nitride powder B may be mixed so that the volume ratio of the boron nitride powder B is greater than the volume ratio of the boron nitride powder A.

ADVANTAGE OF THE INVENTION According to this invention, the withstand voltage property of boron nitride powder can be improved.

(a) is a graph showing the particle size distribution of boron nitride powder A used in Examples, and (b) is a graph showing the particle size distribution of boron nitride powder B used in Examples. 1 is a graph showing the particle size distribution of boron nitride powder of Example 1. FIG. 4 is a graph showing the particle size distribution of the boron nitride powder of Example 2. FIG. 4 is a graph showing the particle size distribution of the boron nitride powder of Reference Example 1. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail.

The boron nitride powder according to one embodiment is a boron nitride powder (massive boron nitride powder) formed by agglomeration of primary particles of boron nitride. The primary particles of boron nitride may be, for example, scale-like hexagonal boron nitride particles. In this case, the longitudinal length of the primary particles of boron nitride may be, for example, 1 μm or more and 10 μm or less.

The boron nitride powder obtained by aggregating such primary particles of boron nitride has a volume-based particle size distribution (hereinafter also simply referred to as “particle size distribution”), in which peak A exists in a region of 5 μm or more and less than 30 μm, and 50 μm and a peak B existing in a region of more than 100 μm and less than 100 μm. The particle size distribution of boron nitride powder means a volume-based particle size distribution measured by a laser diffraction scattering method. Specific measurement conditions may be the measurement conditions described in Examples. The presence of a peak in a region of 5 μm or more and less than 30 μm means that a diameter with a maximum frequency (% by volume) (a diameter at which the slope of the particle size distribution changes from positive to negative) exists in a region of 5 μm or more and less than 30 μm. means. Similarly, the presence of a peak in the region of 50 μm or more and less than 100 μm means that the diameter (the diameter at which the slope of the particle size distribution changes from positive to negative) at which the frequency (% by volume) is maximum is present in the region of 50 μm or more and less than 100 μm. means to

The lower limit of the region (diameter of boron nitride powder) where peak A exists may be 8 μm or more, 10 μm or more, 12 μm or more, 14 μm or more, 16 μm or more, or 18 μm or more. The upper limit of the region (diameter of boron nitride powder) where peak A exists may be 28 μm or less, 26 μm or less, 24 μm or less, 22 μm or less, or 20 μm or less.

The lower limit of the region where peak B exists (boron nitride powder diameter) may be 55 μm or more, 60 μm or more, 65 μm or more, 70 μm or more, 80 μm or more, or 85 μm or more. The upper limit of the region where peak B exists (boron nitride powder diameter) may be 98 μm or less, 96 μm or less, 94 μm or less, 92 μm or less, or 90 μm or less.

In one embodiment, the frequency of maxima F _B (% by volume) at peak B is greater than the frequency of maxima F _A (% by volume) at peak A. The ratio ( _FB / _FA ) of the maximum frequency _FB (% by volume) at the peak _B to the maximum frequency FB (% by volume) at the peak A is preferably 3 from the viewpoint of improving the thermal conductivity of the boron nitride powder. 10 or more, 20 or more, or 30 or more, and more preferably 40 or more, 60 or more, 80 or more, 100 or more, 120 or more, 140 or more, 160 or more, or 180 or more. From the viewpoint of further improving the voltage resistance of the boron nitride powder, the ratio (F _B /F _A ) is preferably 220 or less, more preferably 200 or less, 180 or less, 160 or less, 140 or less, 120 or less, 100 80 or less, 60 or less, or 40 or less, more preferably 30 or less, 20 or less, or 10 or less.

The maximum frequency F _A (% by volume) at peak A may be, for example, 0.01% by volume or more and 5% by volume or less. The local maximum frequency F _B (% by volume) at peak B may be, for example, 10% by volume or more and 20% by volume or less.

The boron nitride powder may or may not have other peaks in regions other than the region where peak A exists and the region where peak B exists. When the boron nitride powder further has other peaks, the boron nitride powder, for example, further has other peaks only in a region of 30 μm or more and less than 50 μm, and has other peaks in a region of less than 5 μm and a region of more than 100 μm. You don't have to.

The ratio I(002)/I(100) of the peak intensity I(002) of the (002) plane to the peak intensity I(100) of the (100) plane in the powder X-ray diffraction method of the boron nitride powder is preferably 9. It is 0 or less, more preferably 8.0 or less, and still more preferably 7.0 or less. It means that the smaller the ratio I(002)/I(100), the more aggregated the primary particles of boron nitride. The ratio I (002) / I (100) is the peak intensity of the (002) plane and the peak of the (100) plane of the boron nitride powder measured using an X-ray diffractometer (eg, Rigaku ULTIMA-IV) Calculated from intensity. In the X-ray diffraction measurement, after the boron nitride powder is press-molded as a pretreatment, X-rays are irradiated so as to be symmetrical with respect to the normal to the plane in the in-plane direction of the molded body.

The boron nitride powder as described above is, for example, a boron nitride powder A having a mode diameter in the region of 5 μm or more and less than 30 μm in the volume-based particle size distribution, and a volume-based particle size distribution in the region of 50 μm or more and less than 100 μm. It is obtained by a manufacturing method comprising a step (mixing step) of mixing boron nitride powder B having a diameter.

Boron nitride powder A and boron nitride powder B are each formed by agglomeration of primary particles of boron nitride. The mode diameter of each of the boron nitride powder A and the boron nitride powder B means the diameter at which the frequency (% by volume) in the particle size distribution of each of the boron nitride powder A and the boron nitride powder B is maximum. The particle size distributions of the boron nitride powder A and the boron nitride powder B are measured in the same manner as the particle size distribution of the boron nitride powder described above.

The lower limit of the region where the boron nitride powder A has a mode diameter (diameter of the boron nitride powder) may be 8 μm or more, 10 μm or more, 12 μm or more, 14 μm or more, 16 μm or more, or 18 μm or more. The upper limit of the region where the mode diameter of the boron nitride powder A exists (the diameter of the boron nitride powder) may be 28 μm or less, 26 μm or less, 24 μm or less, 22 μm or less, or 20 μm or less.

The lower limit of the region where the mode diameter of the boron nitride powder B exists (the diameter of the boron nitride powder) may be 55 μm or more, 60 μm or more, 65 μm or more, 70 μm or more, 80 μm or more, or 85 μm or more. The upper limit of the region where the mode diameter of the boron nitride powder B exists (the diameter of the boron nitride powder) may be 98 μm or less, 96 μm or less, 94 μm or less, 92 μm or less, or 90 μm or less.

In one embodiment, in the mixing step, the boron nitride powder A and the boron nitride powder B may be mixed such that the volume ratio of the boron nitride powder B is greater than the volume ratio of the boron nitride powder A. From the viewpoint of improving the thermal conductivity of the boron nitride powder, the volume ratio of the boron nitride powder B is preferably 60 parts by volume or more, more preferably 100 parts by volume in total of the boron nitride powder A and the boron nitride powder B. , 65 parts by volume or more, 70 parts by volume or more, 75 parts by volume or more, 80 parts by volume or more, 85 parts by volume or more, or 90 parts by volume or more, more preferably 91 parts by volume or more, 93 parts by volume or more, or 95 parts by volume More preferably, it is 96 volume parts or more, or 98 volume parts or more. From the viewpoint of further improving the voltage resistance of the boron nitride powder, the volume ratio of the boron nitride powder B is preferably 99 parts by volume or less, 97 parts by volume or less, or 95 parts by volume or less, more preferably 90 parts by volume or less. , 85 parts by volume or less, 80 parts by volume or less, 75 parts by volume or less, 70 parts by volume or less, or 65 parts by volume or less.

For each of the boron nitride powder A and the boron nitride powder B, for example, a pulverizing step of pulverizing bulk boron carbide, a nitriding step of nitriding the pulverized boron carbide to obtain boron carbonitride, and decarburizing the boron carbonitride. It can be produced by a production method comprising a decarburization step.

In the pulverization step, lumped carbon boron (boron carbide lumps) is pulverized using a general pulverizer or pulverizer. At this time, for example, by adjusting the pulverization time and the charged amount of the boron carbide lumps, boron carbide powder having a desired mode diameter is obtained. The mode diameter of the boron carbide powder is measured in the same manner as the mode diameter of the boron nitride powder described above. By adjusting the mode diameter of the boron carbide powder so as to approach the desired mode diameter of the boron nitride powder, the boron nitride powder A and the boron nitride powder B having the above-described mode diameter can be obtained.

Subsequently, in the nitriding step, boron carbonitride is obtained by sintering the boron carbide powder under an atmosphere and pressurized conditions in which the nitriding reaction proceeds.

The atmosphere in the nitriding step is an atmosphere that promotes the nitriding reaction, and may be, for example, nitrogen gas, ammonia gas, or the like, and may be one of these or a combination of two or more of them. The atmosphere is preferably nitrogen gas from the viewpoint of ease of nitriding and cost. The content of nitrogen gas in the atmosphere is preferably 95% by volume or more, more preferably 99.9% by volume or more.

The pressure in the nitriding step is preferably 0.6 MPa or higher, more preferably 0.7 MPa or higher, and preferably 1.0 MPa or lower, more preferably 0.9 MPa or lower. The pressure is more preferably 0.7-1.0 MPa. The firing temperature in the nitriding step is preferably 1800° C. or higher, more preferably 1900° C. or higher, and preferably 2400° C. or lower, more preferably 2200° C. or lower. The firing temperature is more preferably 1800-2200°C. The pressure conditions and sintering temperature are preferably 1800° C. or higher and 0.7 to 1.0 MPa because they are industrially suitable conditions that promote the nitridation of boron carbide more favorably.

The firing time in the nitriding step is appropriately selected within a range in which nitriding proceeds sufficiently, and is preferably 6 hours or longer, more preferably 8 hours or longer, and preferably 30 hours or shorter, more preferably 20 hours or shorter.

In the decarburization step, the boron carbonitride obtained in the nitridation step is subjected to heat treatment in an atmosphere of normal pressure or higher at a predetermined holding temperature for a certain period of time. This makes it possible to obtain boron nitride particles in which decarburized and crystallized primary particles of boron nitride (primary particles are scale-like hexagonal boron nitride) are aggregated.

The atmosphere in the decarburization step is a normal pressure (atmospheric pressure) atmosphere or a pressurized atmosphere. In the case of a pressurized atmosphere, the pressure may for example be 0.5 MPa or less, preferably 0.3 MPa or less.

In the decarburization step, for example, the temperature is first raised to a predetermined temperature (the temperature at which decarburization can be started), and then the temperature is further raised to the holding temperature at the predetermined temperature. The predetermined temperature (the temperature at which decarburization can be started) can be set according to the system, and may be, for example, 1000° C. or higher, 1500° C. or lower, and preferably 1200° C. or lower. The rate of temperature increase from a predetermined temperature (the temperature at which decarburization can be started) to the holding temperature may be, for example, 5°C/min or less, preferably 4°C/min or less, 3°C/min or less, or 2°C. / minute or less.

The holding temperature is preferably 1,800° C. or higher, more preferably 2,000° C. or higher, from the viewpoints that grain growth tends to occur favorably and the thermal conductivity of the obtained boron nitride powder can be further improved. The holding temperature may preferably be 2200° C. or lower, more preferably 2100° C. or lower.

The holding time at the holding temperature is appropriately selected within a range in which crystallization sufficiently progresses. 3 hours or more, more preferably 5 hours or more, and particularly preferably 10 hours or more. The holding time at the holding temperature may be, for example, less than 40 hours, and it is possible to reduce the decrease in particle strength due to excessive grain growth, and from the viewpoint of reducing industrial disadvantages, it is preferably 30 hours or less. More preferably, it is 20 hours or less.

In the decarburization step, a boron source may be mixed as a raw material in addition to the boron carbonitride obtained in the nitridation step for decarburization and crystallization. Boron sources include boric acid, boron oxide, or mixtures thereof. In this case, if necessary, other additives used in the technical field may be used.

A mixing ratio of the boron carbonitride and the boron source is appropriately selected. When boric acid or boron oxide is used as the boron source, the proportion of boric acid or boron oxide may be, for example, 100 parts by mass or more, preferably 150 parts by mass or more, with respect to 100 parts by mass of boron carbonitride. Also, for example, it may be 300 parts by mass or less, preferably 250 parts by mass or less.

A step of classifying the boron nitride powder obtained as described above with a sieve so as to obtain a boron nitride powder having a desired particle size distribution (classifying step) may be carried out. Thereby, the boron nitride powder A and the boron nitride powder B having desired mode diameters can be obtained more preferably.

The boron nitride powder described above is suitably used for, for example, a heat radiating member. Boron nitride powder is used, for example, as a resin composition mixed with a resin when it is used for a heat radiating member. That is, another embodiment of the present invention is a resin composition containing a resin and the above boron nitride powder.

Examples of resins include epoxy resins, silicone resins, silicone rubbers, acrylic resins, phenol resins, melamine resins, urea resins, unsaturated polyesters, fluororesins, polyimides, polyamideimides, polyetherimides, polybutylene terephthalate, polyethylene terephthalate, Polyphenylene ether, polyphenylene sulfide, wholly aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide modified resin, ABS (acrylonitrile-butadiene-styrene) resin, AAS (acrylonitrile-acrylic rubber/styrene) resin, AES (acrylonitrile)・Ethylene/propylene/diene rubber-styrene) resin, etc. can be used.

When the resin composition is used for the insulating layer of a printed wiring board, the resin is preferably an epoxy resin, more preferably a bisphenol A type epoxy resin or a naphthalene type, from the viewpoint of excellent heat resistance and adhesive strength to a circuit. Epoxy resin. When the resin composition is used as the thermal interface material, the resin is preferably a silicone resin from the viewpoint of excellent heat resistance, flexibility, and adhesion to a heat sink or the like.

The resin composition may further contain a curing agent that cures the resin. A curing agent is appropriately selected depending on the type of resin. For example, curing agents used together with epoxy resins include phenol novolak compounds, acid anhydrides, amino compounds, imidazole compounds and the like, and imidazole compounds are preferably used. The content of the curing agent may be, for example, 0.5 parts by mass or more or 1.0 parts by mass or more, and may be 15 parts by mass or less or 10 parts by mass or less with respect to 100 parts by mass of the resin.

The content of the boron nitride powder, based on the total volume of the resin composition, is preferably 30% by volume or more, more preferably from the viewpoint of improving the thermal conductivity of the resin composition and easily obtaining excellent heat dissipation performance. It is 40% by volume or more, preferably 85% by volume or less, more preferably 80% by volume or less, from the viewpoint of suppressing the formation of voids during molding and the deterioration of insulation and mechanical strength.

The resin composition as described above can be obtained, for example, by a manufacturing method including a step (mixing step) of mixing the resin, the boron nitride powder A described above, and the boron nitride powder B described above.

In one embodiment, in the mixing step, the boron nitride powder A and the boron nitride powder B may be mixed such that the volume ratio of the boron nitride powder B is greater than the volume ratio of the boron nitride powder A. The volume ratio of the boron nitride powder B is the same as that described in the mixing step in the method for producing the boron nitride powder described above.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

(Example 1)
5 parts by volume of boron nitride powder A (mode diameter: 19.8 μm) having a particle size distribution shown in FIG. .9 μm) was mixed with 95 parts by volume to obtain a boron nitride powder. The particle size distribution of the boron nitride powders A and B was measured using a Beckman Coulter laser diffraction scattering method particle size distribution measuring device (LS-13 320), which is a measurement condition that can be set with this device, from 0.04 to 2000 μm. It is a volume-based particle size distribution measured under the condition that the particle size range is divided into 116 (width of log (μm)=0.04).

(Example 2)
A boron nitride powder was obtained in the same manner as in Example 1, except that the boron nitride powder A was changed to 35 parts by volume and the boron nitride powder B was changed to 65 parts by volume.

(Reference example 1)
A boron nitride powder was obtained in the same manner as in Example 1, except that only the boron nitride powder B was used.

[Measurement of particle size distribution]
For each of the obtained boron nitride powders, the volume-based particle size distribution was measured in the same manner as for the boron nitride powders A and B. The particle size distributions of the boron nitride powders of Examples 1 and 2 are shown in FIGS. 2(a) and 3(a), respectively, and the particle size distribution of the boron nitride powder of Reference Example 1 is shown in FIG. 4(a). FIGS. 2(b), 3(b), and 4(b) show enlarged graphs of the particle size distribution in the 5 to 30 μm region of each boron nitride powder. As can be seen from FIGS. 2 to 4, in the boron nitride powders of Examples 1 and 2, peak A exists at a position corresponding to the mode diameter (19.8 μm) of boron nitride powder A, and the mode of boron nitride powder B A peak B exists at a position corresponding to the diameter (87.9 μm). On the other hand, as can be seen from FIG. 4, in Reference Example 1, peak B exists at a position corresponding to the mode diameter (87.9 μm) of boron nitride powder B, but peak A does not exist.

Further, for each of the boron nitride powders of Examples 1 and 2, the ratio ( _FB / _FA ) of the maximum frequency F _B (% by volume) at peak B to the maximum frequency F _A (% by volume) at peak A was calculated. , Example 1: 38.7, Example 2: 3.8.

[Measurement of I (002) / I (100)]
Using an X-ray diffractometer ("ULTIMA-IV" manufactured by Rigaku), the ratio of the peak intensity I (002) of the (002) plane to the peak intensity I (100) of the (100) plane in the powder X-ray diffraction method of boron nitride powder When I(002)/I(100) was calculated, it was Example 1: 6.2 and Example 2: 6.5. In the X-ray diffraction measurement, after the boron nitride powder was press-molded as a pretreatment, X-rays were irradiated so as to be symmetrical with respect to the normal to the plane in the in-plane direction of the molded body.

[Measurement of withstand voltage]
A mixture of 100 parts by mass of a naphthalene type epoxy resin (manufactured by DIC, HP4032) and 10 parts by mass of imidazoles (manufactured by Shikoku Kasei Co., Ltd., 2E4MZ-CN) as a curing agent is mixed with 50% by volume of the resulting boron nitride powder. A resin composition was obtained by mixing so that This resin composition was applied on a PET film to a thickness of 0.2 mm, and then dried by heating at 100° C. for 40 minutes to prepare a B-stage sheet.
The obtained sheet was peeled off from the PET film, placed on a copper plate with a thickness of 2.0 mm, and further a copper plate with a thickness of 0.5 mm was placed thereon to obtain a laminate. This laminate was heat-cured at 180° C. for 300 minutes while applying a surface pressure of 160 kgf/cm ² with a press to obtain an evaluation sample. The withstand voltage of the obtained evaluation sample was measured based on JIS C 6481 using "TOS 8650" manufactured by KIKUSUI. Table 1 shows the results.

[Measurement of thermal conductivity]
The thermal conductivity of the boron nitride powders of Examples 1 and 2 was also measured by the following procedure.
Boron nitride powder of Examples 1 and 2 was added to a mixture of 100 parts by mass of naphthalene type epoxy resin (HP4032, manufactured by DIC) and 10 parts by mass of imidazoles (2E4MZ-CN, manufactured by Shikoku Kasei Co., Ltd.) as a curing agent. A resin composition was obtained by mixing so as to be 50% by volume. This resin composition was applied to a PET sheet so as to have a thickness of 1.0 mm, and then degassed under reduced pressure of 500 Pa for 10 minutes. After that, press heating and pressing was performed for 60 minutes at a temperature of 150° C. and a pressure of 160 kg/cm ² to produce a sheet of 0.5 mm.
A measurement sample with a size of 10 mm × 10 mm was cut out from the obtained sheet, and the thermal diffusivity A (m ² /sec) of the measurement sample was measured by a laser flash method using a xenon flash analyzer (LFA447NanoFlash, manufactured by NETZSCH). was measured. Also, the specific gravity B (kg/m ³ ) of the measurement sample was measured by the Archimedes method. Further, the specific heat capacity C (J/(kg·K)) of the measurement sample was measured using a differential scanning calorimeter (DSC; ThermoPlus EvoDSC8230 manufactured by Rigaku Corporation). Using these physical property values, the thermal conductivity H (W/(m·K)) was obtained from the formula H=A×B×C. Table 1 shows the results.

Claims (3)

A boron nitride powder formed by agglomeration of primary particles of boron nitride,
In the volume-based particle size distribution, it has a peak A existing in a region of 5 μm or more and 26 μm or less and a peak B existing in a region of 50 μm or more and less than 100 μm ,
A boron nitride powder , wherein the ratio ( _FB / _FA ) of the maximum frequency F _B (% by volume) at the peak B to the maximum frequency F A ₍ % by volume ) at the peak A is 20 or more . The ratio I (002) / I (100) of the peak intensity I (002) of the (002) plane to the peak intensity I (100) of the (100) plane in the powder X-ray diffraction method of the boron nitride powder is 9.0 or less. The boron nitride powder according to claim 1, wherein A resin composition containing a resin and the boron nitride powder according to claim 1 or 2 .

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