TW202124262A - Boron nitride particles and resin composition - Google Patents

Abstract

One aspect of the present invention provides boron nitride particles having a BET diameter of at least 160 nm but not more than 300 nm, and having a total oxygen content of at least 0.4% by mass but not more than 0.8% by mass.

Description

Boron nitride particles and resin composition

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

In electronic parts such as transistors, thyristors, and CPUs, it is an important issue to effectively dissipate heat generated during use. Therefore, a heat dissipation member with high thermal conductivity will be used together with such electronic parts. On the other hand, because boron nitride particles have high thermal conductivity and high insulation, they are widely used as fillers in heat dissipation members.

For example, Patent Document 1 shows a boron nitride agglomerated particle composition that exhibits high thermal conductivity and is very useful for exothermic sheets necessary for power semiconductor devices, etc., and discloses a boron nitride agglomerated particle composition. The composition of boron nitride aggregate particles with a particle size (D ₅₀ ) of 1 μm to 200 μm is characterized by satisfying predetermined conditions. [Prior Technical Documents] [Patent Documents]

[Patent Document 1] JP 2017-036190 A

[The problem to be solved by the invention]

In recent years, in devices equipped with electronic components, high-speed signal transmission and large-capacity have progressed. Therefore, heat dissipation components are also required to have characteristics that contribute to the above-mentioned needs. Specifically, a heat dissipation member with a low dielectric constant and low dielectric tangent is expected.

Therefore, the object of the present invention is to provide boron nitride particles that can realize a heat dissipation member with low dielectric constant and low dielectric tangent. [Means to solve the problem]

One aspect of the present invention is a boron nitride particle having a BET diameter of 160 nm or more and 300 nm or less, and a total oxygen content of 0.4% by mass or more and 0.8% by mass or less.

The average circularity of the boron nitride particles may be 0.8 or more. The average particle size of the boron nitride particles may be 1 μm or less.

Another aspect of the present invention is a resin composition containing resin and the above-mentioned boron nitride particles. [Effects of Invention]

According to the present invention, it is possible to provide boron nitride particles capable of realizing a heat dissipation member with low dielectric constant and low dielectric tangent.

One embodiment of the present invention is a boron nitride particle having a specific BET diameter and total oxygen content.

Considering the viewpoint that the dielectric constant and dielectric tangent of the heat dissipation member containing boron nitride particles (hereinafter, also simply referred to as "heat dissipation member") is low, the BET diameter of the boron nitride particles is 160nm or more, preferably 170nm or more It can also be 180nm or more, or 190nm or more. Considering the viewpoint that the dielectric constant and the dielectric tangent of the heat dissipation member are low, the BET diameter of the boron nitride particles is 300 nm or less, preferably 290 nm or less, or may be 280 nm or less, 270 nm or less, or 260 nm or less.

The BET diameter of the boron nitride particles is a value calculated according to the following formula. BET diameter = the diameter when 1g of boron nitride is one particle of a real ball/(BET specific surface area/the surface area when 1g of boron nitride is assumed to be one particle of a real ball) Here, ･assume 1g of boron nitride Diameter when it is 1 particle of a real sphere = (6/(density of boron nitride particles×π)) ^1/3 (However, 2.26g/cm ^{3 is} used as the density of boron nitride particles) ･Assuming 1g of nitride The surface area when boron is 1 particle of a real sphere=π×(Assuming that 1g of boron nitride is the diameter of 1 particle of a real sphere) ² ･BET specific surface area complies with JIS Z 8803:2013 and uses nitrogen as determined by the BET one-point method The measured BET specific surface area of the boron nitride particles.

Considering the viewpoint that the dielectric rate and dielectric tangent of the heat dissipation member are low, the total oxygen content of the boron nitride particles is 0.4% by mass or more, preferably 0.45% by mass or more, or 0.5% by mass or more, 0.55% by mass or more , Or more than 0.6% by mass. Considering the viewpoint that the dielectric constant and the dielectric tangent of the heat dissipation member are low, the total oxygen content of the boron nitride particles is 0.8% by mass or less, preferably 0.75% by mass or less, or may be 0.7% by mass or less. The total oxygen content of boron nitride particles is the mass ratio of oxygen in the boron nitride particles. It is a value measured using an oxygen-nitrogen analyzer (for example, manufactured by Horiba Manufacturing Co., Ltd., trade name: EMGA-620W/C) .

Considering that the filling of the boron nitride particles when fabricating the heat dissipating member is better, and the properties of the heat dissipating member (thermal conductivity, dielectric rate, etc.) are isotropic, the boron nitride particles have a spherical shape or close to a spherical shape. The shape of the shape is ideal. Considering the same point of view, the average circularity of the boron nitride particles is preferably 0.8 or more, 0.82 or more, 0.84 or more, 0.86 or more, or may be 0.88 or more.

The average circularity of the boron nitride particles is determined by the following procedure. For the image of boron nitride particles (magnification: 10,000 times, image resolution: 1280×1024 pixels) taken by using a scanning electron microscope (SEM), by using image analysis software (for example, manufactured by Mountech Corporation, product Name: MacView) image analysis to calculate the projected area (S) and perimeter (L) of the boron nitride particles. Using the projected area (S) and perimeter (L), follow the formula: circularity = 4πS/L ² to find the circularity. The average circularity obtained for 100 boron nitride particles selected arbitrarily is defined as the average circularity.

In consideration of the viewpoint that the viscosity increase when the boron nitride particles are mixed with the resin can be suppressed, the average particle size of the boron nitride particles is preferably 0.01 μm or more, and can be 0.05 μm or more, 0.1 μm or more, 0.2 μm or more, 0.3 μm Above, or above 0.4μm. From the viewpoint of improving the insulation failure characteristics of the heat dissipation member, the average particle size of the boron nitride particles is 1 μm or less, or may be 0.9 μm or less, 0.8 μm or less, or 0.7 μm or less.

The average particle size of the boron nitride particles is measured by the following procedure. Distilled water was used as a dispersion medium for dispersing boron nitride particles, and sodium hexametaphosphate was used as a dispersant to prepare a 0.125% by mass sodium hexametaphosphate aqueous solution. Add boron nitride particles to the aqueous solution at a ratio of 0.1g/80mL, and use an ultrasonic homogenizer (for example, manufactured by Nippon Seiki Seisakusho, trade name: US-300E), and perform once under the condition of AMPLITUDE (amplitude) 80% Ultrasonic dispersion for 1 minute and 30 seconds to prepare a dispersion of boron nitride particles. Separate and sample the dispersion while stirring at 60 rpm, and measure the volume standard with a laser diffraction scattering method particle size distribution measuring device (for example, Beckman Coulter, trade name: LS-13 320). Particle size distribution. At this time, 1.33 was used as the refractive index of water, and 1.7 was used as the refractive index of the boron nitride particles. From the measurement results, the average particle diameter is calculated on the particle diameter (median particle diameter, d50) of 50% of the cumulative value of the cumulative particle size distribution.

The boron nitride particles described above are obtained by a manufacturing method with the following steps: the first step is to react borate and ammonia at 750 to 1400°C to obtain the first precursor; and the second step , The first precursor is heated at 1000-1600°C to obtain the second precursor; the third step is to heat the second precursor at 1000-1600°C to obtain the third precursor; In 4 steps, the third precursor is heated at 1800-2200°C to obtain the fourth precursor.

Furthermore, in this manufacturing method, after the second step is completed and before the third step is started, the temperature of the environment in which the second precursor is placed is temporarily lowered to room temperature (10-30°C). In this way, by heating at 1000 to 1600°C, returning to normal temperature, and heating again at 1000 to 1600°C, boron nitride particles having the above-mentioned characteristics can be obtained. On the other hand, in the conventional manufacturing method, for example, the manufacturing method including the above-mentioned first step, second step, and fourth step is known. However, in the manufacturing method of this embodiment, as described above, except for the first step In addition to the second step, the third step is performed, and the ambient temperature is temporarily lowered to normal temperature between the second step and the third step, thereby obtaining boron nitride particles having characteristics that have not been available until now.

In the first step, for example, a reaction tube (for example, a quartz tube) installed in a resistance heating furnace is heated, and the temperature is increased to 750 to 1500°C. On the other hand, the passive gas is passed through the liquid borate and then introduced into the reaction tube, thereby introducing the borate into the reaction tube. On the other hand, the ammonia gas is directly introduced into the reaction tube. As for the passive gas, rare gases such as helium, neon, and argon, and nitrogen can be cited. The borate may be, for example, an alkyl borate, preferably trimethyl borate.

The molar ratio of the introduction amount of ammonia to the introduction amount of borate (ammonia/borate) may be, for example, 1 or more and 10 or less.

The introduced borate and ammonia react in the heated reaction tube to produce the first precursor (white powder). Although a part of the first precursor produced will adhere to the reaction tube, most of the first precursor will be sent to the recovery container installed at the front end of the reaction tube by inactive gas or unreacted ammonia gas for recovery. The time (reaction time) for reacting the borate and ammonia is preferably within 30 seconds. The reaction time is the time that borate and ammonia stay in the part (heating part) heated to 750 to 1400°C in the reaction tube. It can be determined by the gas flow rate when the borate and ammonia are introduced and the resistance set in it. The length of the reaction tube in the heating furnace (the length of the heating part of the reaction tube) is adjusted.

In the second step, the first precursor obtained in the first step is charged into another reaction tube (for example, an alumina tube) installed in a resistance heating furnace, and nitrogen and ammonia gas are respectively introduced into the reaction tube. The gas introduced at this time can also be only ammonia gas. The flow rate of nitrogen gas and ammonia gas may be adjusted appropriately so that the reaction time can be a desired value. For example, the larger the flow rate of ammonia gas, the shorter the reaction time. As a result, the BET diameter of the boron nitride particles finally obtained tends to decrease, and the total oxygen content tends to decrease.

Then, the reaction tube is heated to 1000 to 1600°C. The heating time may be, for example, 1 hour or more, and may be 10 hours or less. In this way, the second precursor can be obtained.

After the second step, cut off the power of the resistance heating furnace, stop the introduction of nitrogen and ammonia, and after the temperature in the reaction tube has dropped to room temperature (10～30℃), remove the second precursor It is allowed to stand, and the standing time may be, for example, 0.5 hours or more, or 96 hours or less.

In the third step, nitrogen and ammonia are introduced into the reaction tube again, and the reaction tube is heated to 1000 to 1600°C again. Examples of the flow rates of nitrogen and ammonia and the heating time can be the same as those described in the second step. The conditions of the second step and the third step may be the same or different from each other. In this way, a third precursor can be obtained.

In the fourth step, the third precursor obtained in the third step is put into a boron nitride crucible and heated to 1800-2200°C in a nitrogen atmosphere in an induction heating furnace. The heating time can be, for example, 0.5 hours or more and 10 hours or less. Thereby, boron nitride particles having the above-mentioned characteristics can be obtained.

The boron nitride particles described above can be ideally used for heat dissipation members, for example. By using the above-mentioned boron nitride particles, a heat dissipation member with low dielectric constant and low dielectric tangent can be obtained. When the boron nitride particles are used in a heat dissipation member, for example, they can be used in the form of a resin composition formed by mixing with resin. That is, another embodiment of the present invention is a resin composition containing a resin and the above-mentioned boron nitride particles.

Considering that the thermal conductivity of the resin composition is better, and excellent heat dissipation performance can be easily obtained, the content of the above-mentioned boron nitride particles is preferably 30% by volume or more based on the total volume of the resin composition, 40% by volume The above is more ideal, and 50% by volume or more is even more desirable. Considering that it can suppress the generation of voids during molding, and can suppress the reduction of insulation and mechanical strength, it is ideal that 85% by volume or less, and 80% by volume or less is more ideal. , 70% by volume or less is more ideal.

As for the resin, for example, epoxy resin, silicone resin, silicone rubber, acrylic resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyolefin (polyethylene, etc.) , Polyimide, polyimide imine, polyether imide, polybutylene terephthalate, polyethylene terephthalate, polyphenylene ether, polyphenylene sulfide, fully aromatic poly Ester, poly, liquid crystal polymer, polyether, polycarbonate, maleimide modified resin, ABS (acrylonitrile-butadiene-styrene) resin, AAS (acrylonitrile-acrylic rubber, styrene) ) Resin, and AES (acrylonitrile, ethylene, propylene, diene rubber-styrene) resin.

The content of the resin is 15 vol% or more, 20 vol% or more, or 30 vol% or more, 70 vol% or less, 60 vol% or less, or 50 vol% or less based on the total volume of the resin composition.

The resin composition may further contain a hardener to harden the resin. The hardener can be appropriately selected according to the type of resin. For example, in the case of a resin-based epoxy resin, the curing agent includes, for example, phenol novolac compounds, acid anhydrides, amino compounds, and imidazole compounds. The content of the hardener relative to 100 parts by mass of the resin 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.

The resin composition may further contain boron nitride particles other than the above-mentioned boron nitride particles (for example, well-known boron nitride particles such as bulk boron nitride particles formed by agglomeration of scaly primary particles). [Example]

Hereinafter, the present invention will be described in more detail with examples. However, the present invention is not limited by the following examples.

[Examples 1 to 3] By the following procedure, boron nitride particles are produced. First, in the first step, the reaction tube (quartz tube) installed in the resistance heating furnace is heated to the temperature shown in Table 1. On the other hand, the nitrogen gas is introduced into the reaction tube after passing through the trimethyl borate, thereby introducing the trimethyl borate into the reaction tube. On the other hand, the ammonia gas is directly introduced into the reaction tube. The molar ratio of the introduction amount of ammonia to the introduction amount of trimethyl borate (ammonia/trimethyl borate) was set to 4.5. In this way, trimethyl borate and ammonia are reacted to obtain a first precursor (white powder). In addition, the reaction time is shown in Table 1.

Then, in the second step, the first precursor obtained in the first step was put into other reaction tubes (alumina tubes) installed in the resistance heating furnace, and the nitrogen and ammonia were respectively as shown in Table 1. The flow rate is introduced into the reaction tube. Then, the reaction tube was heated at the temperature and time shown in Table 1. In this way, the second precursor is obtained.

Then, the power of the resistance heating furnace was cut off, the introduction of nitrogen and ammonia was stopped, and the second precursor was allowed to stand for 2 hours while the temperature in the reaction tube was lowered to 25°C.

Then, in the third step, nitrogen and ammonia were introduced into the reaction tube again at the flow rates shown in Table 1, and the reaction tube was heated again at the temperature and time shown in Table 1. In this way, the third precursor was obtained.

Then, in the fourth step, the third precursor obtained in the third step is placed in a boron nitride crucible, and heated in an induction heating furnace at the temperature and time shown in Table 1 under a nitrogen atmosphere . In this way, boron nitride particles are obtained.

[Comparative Example 1] Except that the third step was not performed, the same method as in Example 1 was used to obtain boron nitride particles.

For each obtained boron nitride particle, the BET diameter, total oxygen content, average circularity, and average particle diameter were measured by the following methods. The results are shown in Table 1.

(BET diameter) The BET diameter is calculated according to the following formula. BET diameter = the diameter when 1g of boron nitride is one particle of a real ball/(BET specific surface area/the surface area when 1g of boron nitride is assumed to be one particle of a real ball) Here, ･assume 1g of boron nitride Diameter when it is 1 particle of a real sphere = (6/(density of boron nitride particles×π)) ^1/3 (However, 2.26g/cm ^{3 is} used as the density of boron nitride particles) ･Assuming 1g of nitride The surface area when boron is 1 particle of a real sphere=π×(Assuming that 1g of boron nitride is the diameter of 1 particle of a real sphere) ² ･BET specific surface area complies with JIS Z 8803:2013 and uses nitrogen as determined by the BET one-point method The measured BET specific surface area of the boron nitride particles.

(Total Oxygen) The total oxygen content was measured using an oxygen and nitrogen analyzer (manufactured by Horiba Manufacturing Co., Ltd., trade name: EMGA-620W/C).

(Average circularity) First, the image of boron nitride particles (magnification: 10,000 times, image resolution: 1280×1024 pixels) taken by using a scanning electron microscope (SEM) is analyzed by using image analysis Image analysis of software (for example, manufactured by Mountech, trade name: MacView), calculates the projected area (S) and perimeter (L) of the boron nitride particles. Then use the projected area (S) and perimeter (L) to obtain the circularity ^{according to the following formula: circularity = 4πS/L 2.} The average circularity obtained for 100 boron nitride particles selected arbitrarily is calculated as the average circularity.

(The average particle size) Distilled water was used as a dispersion medium for dispersing boron nitride particles, and sodium hexametaphosphate was used as a dispersant to prepare a 0.125% by mass sodium hexametaphosphate aqueous solution. Add boron nitride particles to the aqueous solution at a ratio of 0.1g/80mL, and use an ultrasonic homogenizer (for example, manufactured by Nippon Seiki Seisakusho, trade name: US-300E), and perform once under the condition of AMPLITUDE (amplitude) 80% Ultrasonic dispersion for 1 minute and 30 seconds to prepare a dispersion of boron nitride particles. Separate and sample the dispersion while stirring at 60 rpm, and measure the volume standard with a laser diffraction scattering method particle size distribution measuring device (for example, Beckman Coulter, trade name: LS-13　320) Particle size distribution. At this time, 1.33 was used as the refractive index of water, and 1.7 was used as the refractive index of the boron nitride particles. From the measurement results, the average particle diameter is calculated on the particle diameter (median particle diameter, d50) of 50% of the cumulative value of the cumulative particle size distribution.

The dielectric constant and dielectric tangent when each obtained boron nitride particle was used were measured by the following method. The results are shown in Table 1. The boron nitride particles are kneaded with polyethylene (manufactured by Nippon Polyethylene Co., Ltd., trade name "NOVATECHY540") so that the boron nitride particles are 20% by volume, and the sheet is formed to obtain a sheet with a thickness of 0.2 mm material. Kneading and sheet forming are performed using a two-axis extruder at a temperature of 180°C. Using a measuring device of the cavity resonator method, the obtained sheet was measured under the conditions of a frequency of 36 GHz and a temperature of 25° C., and the dielectric constant and the dielectric tangent of the sheet were determined.

[Table 1] Example 1 Example 2 Example 3 Comparative example 1 Step 1 Temperature (°C) 1150 1150 1150 1150 Time (seconds) 10 10 10 10 Step 2 Temperature (°C) 1500 1500 1600 1500 Time (hour) 2.5 2.5 2.5 2.5 N ₂ flow (L/min) 10 10 10 10 NH ₃ flow (L/min) 15 17 15 15 Step 3 Temperature (°C) 1500 1500 1600 - Time (hour) 2.5 2.5 2.5 - N ₂ flow (L/min) 10 10 10 - NH ₃ flow (L/min) 15 17 15 - Step 4 Temperature (°C) 2000 2000 2000 2000 Time (hour) 5 5 5 5 Evaluation BET diameter (nm) 259 204 171 236 Total oxygen (mass%) 0.72 0.42 0.47 1.92 Average circularity 0.89 0.88 0.89 0.82 Average particle size (nm) 514 679 547 950 Dielectric rate 2.58 2.56 2.58 3.47 Dielectric Tangent 0.00034 0.00035 0.00035 0.00125

Claims (4)

A boron nitride particle having a BET diameter of 160 nm or more and 300 nm or less, and a total oxygen content of 0.4% by mass or more and 0.8% by mass or less. For example, the boron nitride particles of claim 1 have an average circularity of 0.8 or more. For example, the boron nitride particles of claim 1 or 2 have an average particle diameter of 1 μm or less. A resin composition containing resin and boron nitride particles according to any one of claims 1 to 3.