Boron nitride aggregated powder, resin composition, heat dissipation sheet, and semiconductor device

Abstract

To provide a boron nitride aggregated powder capable of improving heat dissipation characteristics of a heat dissipation sheet, a resin composition and a heat dissipation sheet comprising the boron nitride aggregated powder, and a semiconductor device using the heat dissipation sheet.SOLUTION: A boron nitride aggregated powder according to one aspect of the present invention comprises hexagonal boron nitride aggregated particles, has an average particle diameter (D50) of 10 μm or more and 100 μm or less, has a tap density of 0.5 g / cc or more and 1.0 g / cc or less, and has a DBP absorption amount [ml / 100 g] measured and calculated in accordance with JIS-K-6217-4 that satisfies the relational expression: A≥DBP absorption amount≥B (where A is a numerical value obtained by substituting the average particle diameter (D50) into the relational expression A=-1.2×D50+180, B is a numerical value obtained by substituting the average particle diameter (D50) into the relational expression B=-0.6×D50+110, and D50 is 10 μm or more and 100 μm or less).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a boron nitride agglomerated powder suitably used for a heat dissipation sheet for semiconductor devices, a resin composition and a heat dissipation sheet containing the boron nitride agglomerated powder, and a semiconductor device using the heat dissipation sheet.

Background Art

[0002] Boron nitride (BN) is an insulating ceramic, and various crystal forms such as c-BN having a diamond structure, h-BN having a graphite structure, α-BN having a turbostratic structure, and β-BN are known. Among these, h-BN has the same layered structure as graphite, and is relatively easy to synthesize and has characteristics of excellent thermal conductivity, solid lubricity, chemical stability, and heat resistance. Therefore, it is widely used in the field of electric and electronic materials.

[0003] In recent years, especially in the field of electric and electronics, heat generation associated with the high density of integrated circuits has become a major problem, and heat dissipation has become an urgent issue. Despite being insulating, h-BN has attracted attention as a thermal conductivity filler for such heat dissipation members by taking advantage of its high thermal conductivity. However, it is known that h-BN particles have thermal conductivity anisotropy in the crystal axis direction. In order to suppress the anisotropy of properties due to orientation, studies have been made to obtain a heat dissipation member having higher breakdown voltage characteristics and thermal conductivity by using agglomerated particles that satisfy specific conditions for agglomerating h-BN.

[0004] Patent Document 1 proposes a hexagonal boron nitride powder having a predetermined maximum torque value measured in accordance with JIS-K-6217-4, a DBP absorption amount calculated from the measured value, and a tap density. Patent Document 2 proposes a hexagonal boron nitride powder having a predetermined oil absorption amount and specific surface area measured based on JIS K 5101-13-1.

Prior Art Documents

Patent Documents

[0005] Patent Document 1 Japanese Patent No. 6979034 Patent Document 2 Japanese Patent No. 6516509 Summary of the Invention Problems to be Solved by the Invention

[0006] In the case where the hexagonal boron nitride powder of Patent Document 1 contains a large amount of fine powder due to crushing caused by the shearing force applied to the agglomerated particles during kneading with a resin, there is a concern about a decrease in thermal conductivity. In addition, there is also a concern about an increase in viscosity and an increase in the maximum torque value due to the generation of crushed powder. In Patent Document 2, when the specific surface area becomes high due to a decrease in the agglomerated particle diameter or a decrease in the primary particle diameter constituting the agglomerated particles, there is a concern about an increase in the DBP absorption amount and a decrease in thermal conductivity due to the generation of a large amount of crushed powder caused by the shearing force applied to the agglomerated particles during kneading with a resin.

[0007] An object of the present invention is to provide a boron nitride agglomerated powder capable of improving the thermal conduction characteristics of a heat dissipation sheet, a resin composition and a heat dissipation sheet containing the boron nitride agglomerated powder, and a semiconductor device using the heat dissipation sheet. Means for Solving the Problems

[0008] As a result of intensive studies to solve the above problems, the inventors of the present invention have found that when the average particle diameter (D50), tap density of the boron nitride agglomerated powder are in a specific range, and the relationship between the DBP absorption amount calculated by measuring in accordance with JIS-K-6217-4 and the average particle diameter (D50) is in a specific range, high thermal conduction characteristics are imparted when the boron nitride agglomerated powder and a resin are compounded. In addition, as a result of intensive studies to solve the above problems, the inventors of the present invention have found that when boron nitride agglomerated powder has a DBP absorption amount, a maximum torque value, and an average particle diameter (D50) calculated by measurement in accordance with JIS-K-6217-4 within specific ranges, and the value obtained by dividing the DBP absorption amount by the maximum torque value and the average particle diameter (D50) is within a specific range, high thermal conductivity characteristics are imparted when the boron nitride agglomerated powder and a resin are compounded. That is, the gist of the present invention is as follows.

[0009] [1] A boron nitride agglomerated powder containing hexagonal boron nitride agglomerated particles, having an average particle diameter (D50) of 10 μm or more and 100 μm or less, a tap density of 0.5 g / cc or more and 1.0 g / cc or less, and a DBP absorption amount [ml / 100 g] calculated by measurement in accordance with JIS-K-6217-4 satisfying the following relational expression.

[0010] Relational expression: A ≧ DBP absorption amount ≧ B A: A numerical value obtained by substituting the average particle diameter (D50) into the relational expression of A = -1.2 × D50 + 180 B: A numerical value obtained by substituting the average particle diameter (D50) into the relational expression of B = -0.6 × D50 + 110 However, D50 is 10 μm or more and 100 μm or less.

[0011] [2] A boron nitride agglomerated powder containing hexagonal boron nitride agglomerated particles, having a DBP absorption amount calculated by measurement in accordance with JIS-K-6217-4 of 50 ml / 100 g or more and less than 170 ml / 100 g, a maximum torque value calculated by measurement in accordance with JIS-K-6217-4 of 0.010 Nm or more and 1.000 Nm or less, an average particle diameter (D50) of 10 μm or more and 100 μm or less, and a value (DBP absorption amount / maximum torque value / D50) obtained by dividing the DBP absorption amount by the maximum torque value and the average particle diameter (D50) of 11.0 [ml / (100 g·Nm·μm)] or more and 100 [ml / (100 g·Nm·μm)] or less.

[0012] [3] The boron nitride agglomerated powder according to [1] or [2] above, wherein the hexagonal boron nitride agglomerated particles have a card house structure. [4] The boron nitride agglomerated powder according to any one of [1] to [3] above, wherein the boron nitride purity measured by XPS is 97.0 wt% or more and 99.0 wt% or less, and the boron nitride purity measured by XRF is 95.0 wt% or more. [5] A resin composition containing the boron nitride agglomerated powder according to any one of [1] to [4] above. [6] A heat dissipation sheet made of the resin composition according to [5] above. [7] A semiconductor device including the heat dissipation sheet according to [6] above.

Advantages of the Invention

[0013] The boron nitride agglomerated powder of the present invention is less likely to generate crushed pieces in the kneading process with a resin, so that a decrease in thermal conductivity can be suppressed. A heat dissipation sheet using this boron nitride agglomerated powder can obtain a high thermal conductivity particularly on the small particle size side.

Brief Description of the Drawings

[0014]

Figure 1

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist.

[0016] 〔Boron Nitride Agglomerated Powder〕 In the present invention, the boron nitride agglomerated powder (hereinafter, may be simply referred to as "BN agglomerated powder") represents a powder that is an aggregate of boron nitride agglomerated particles (hereinafter, may be simply referred to as "BN agglomerated particles"). When there is no mention of the first aspect and the second aspect described later, the present invention refers to both the first aspect and the second aspect.

[0017] The BN agglomerated powder in the first aspect of the present invention contains hexagonal boron nitride agglomerated particles, has an average particle size (D50) of 10 μm or more and 100 μm or less, a tap density of 0.5 g / cc or more and 1.0 g / cc or less, and a DBP absorption amount [ml / 100 g] measured and calculated in accordance with JIS-K-6217-4 satisfies the following relational expression. Relational expression: A ≥ DBP absorption amount ≥ B A: A numerical value obtained by substituting the average particle size (D50) into the relational expression of A = -1.2 × D50 + 180 B: A numerical value obtained by substituting the average particle size (D50) into the relational expression of B = -0.6 × D50 + 110 However, D50 is 10 μm or more and 100 μm or less.

[0018] [Mechanism] The mechanism for obtaining a heat dissipation sheet excellent in thermal conductivity by using the BN agglomerated powder in the first aspect of the present invention, particularly an agglomerated powder with a small particle size, is estimated as follows. Although it is known that there is a close relationship between the DBP absorption amount and the tap density of the BN agglomerated powder (Patent Document 1), the range of the relationship between the average particle size (D50) of the BN agglomerated powder for realizing high thermal conductivity characteristics and the DBP absorption amount and the average particle size (D50) is not known.

[0019] For example, regarding the average particle size (D50), if the average particle size (D50) is too small, the thermal conductivity of the particles themselves decreases. If the average particle size (D50) is too large, the surface smoothness of the heat dissipation sheet decreases when formed, and the contact between the heat dissipation sheet and the base material deteriorates, resulting in a decrease in thermal conductivity. In addition, when the relationship between the DBP absorption and the average particle diameter (D50) exceeds A in the relational expression: A ≥ DBP absorption ≥ B, as described in Patent Documents 1 and 2, a diluting solvent is required during kneading with the resin, and voids and bubbles generated during the drying process of the solvent are likely to remain, resulting in a decrease in thermal conductivity. When the relationship between the DBP absorption and the average particle diameter (D50) is below B in the relational expression: A ≥ DBP absorption ≥ B, crushing occurs due to the shear force applied to the agglomerated particles during kneading, and the agglomerated structure is destroyed. As a result, appropriate contact between the particles due to deformation of the agglomerated particles cannot be obtained inside the sheet, and since it contains a large amount of crushed powder, the thermal conductivity is considered to decrease. Furthermore, if the tap density is too low, the contact between the particles inside the sheet deteriorates, and voids are likely to occur between the particles, resulting in a decrease in thermal conductivity. On the other hand, if the tap density is too high, there are few pores inside the particles and the particle strength is too high. Therefore, particle deformation does not occur inside the sheet, and the contact area between the particles decreases, so the heat dissipation characteristics do not improve. Therefore, it is considered that the BN agglomerated powder in the first aspect of the present invention has a predetermined average particle diameter (D50) and tap density, and the relationship between the DBP absorption and the average particle diameter (D50) is within an appropriate range, so that high heat dissipation characteristics can be obtained by adding the BN agglomerated powder to the resin.

[0020] The BN agglomerated powder in the second aspect of the present invention contains hexagonal boron nitride agglomerated particles, the DBP absorption calculated by measurement in accordance with JIS-K-6217-4 is 50 ml / 100 g or more and less than 170 ml / 100 g, the maximum torque value calculated by measurement in accordance with JIS-K-6217-4 is 0.010 Nm or more and 1.000 Nm or less, the average particle diameter (D50) is 10 μm or more and 100 μm or less, and the value obtained by dividing the DBP absorption by the maximum torque value and the average particle diameter (D50) (DBP absorption / maximum torque value / D50) is 11.0 [ml / (100 g·Nm·μm)] or more and 100 [ml / (100 g·Nm·μm)] or less.

[0021] [Mechanism] As described above, when crushing occurs due to the shearing force applied to the agglomerated particles during kneading with the resin and a large amount of fine powder is contained, a decrease in thermal conductivity is a concern. Here, the presence or absence of crushing during kneading with the resin was determined by the magnitude of the value obtained by dividing the DBP absorption amount measured and calculated in accordance with JIS-K-6217-4 of the BN agglomerated powder by the maximum torque value and the average particle diameter (D50). The smaller this value, the easier it is for crushing to occur. Generally, the smaller the average particle diameter, the larger the specific surface area, the larger the maximum torque value, and the lower the tap density, so the DBP absorption amount increases. When the agglomerated powder is crushed during kneading, the specific surface area increases, so the maximum torque value increases, but the tap density increases and the DBP absorption amount decreases because the pores inside the particles disappear and the particle gaps are filled with crushed powder. Therefore, the value obtained by dividing the DBP absorption amount by the maximum torque value decreases as the amount of crushed powder increases. The value normalized by dividing this by the average particle diameter (D50) is considered to be an index of the presence or absence of crushing during kneading. Therefore, it is considered that the BN agglomerated powder in the second aspect of the present invention has a predetermined DBP absorption amount, maximum torque value, and average particle diameter (D50), and by adding the BN agglomerated powder to the resin when the value obtained by dividing the DBP absorption amount by the maximum torque value and the average particle diameter (D50) is within an appropriate range, high heat dissipation characteristics can be obtained.

[0022] The value obtained by dividing the DBP absorption amount measured and calculated in accordance with JIS-K-6217-4 by the maximum torque value and the average particle diameter (D50) measured and calculated in accordance with JIS-K-6217-4 (DBP absorption amount / maximum torque value / D50) is 11.0 [ml / (100g·Nm·μm)] or more, preferably 11.5 [ml / (100g·Nm·μm)] or more, more preferably 12.0 [ml / (100g·Nm·μm)] or more. Also, considering that when the relationship between the DBP absorption amount and the average particle diameter (D50) exceeds A in the relational expression: A ≧ DBP absorption amount ≧ B, the thermal conductivity decreases, the DBP absorption amount / maximum torque value / D50 is 100.0 [ml / (100g·Nm·μm)] or less, preferably 80.0 [ml / (100g·Nm·μm)] or less, more preferably 60.0 [ml / (100g·Nm·μm)] or less, and still more preferably 40.0 [ml / (100g·Nm·μm)] or less.

[0023] The BN agglomerated powder of the present invention contains hexagonal boron nitride agglomerated particles, has an average particle size (D50) of 10 μm or more and 100 μm or less, a tap density of 0.5 g / cc or more and 1.0 g / cc or less, and a maximum torque value calculated by measurement in accordance with JIS-K-6217-4 is 0.010 Nm or more and 1.000 Nm or less, and the DBP absorption amount [ml / 100 g] calculated by measurement in accordance with JIS-K-6217-4 satisfies the following relational expression, and the DBP absorption amount calculated by measurement in accordance with JIS-K-6217-4 is 50 ml / 100 g or more and less than 170 ml / 100 g, and the maximum torque value calculated by measurement in accordance with JIS-K-6217-4 is 0.010 Nm or more and 1.000 Nm or less, and the value obtained by dividing the DBP absorption amount by the maximum torque value and the average particle size (D50) (DBP absorption amount / maximum torque value / D50) may be 11.0 [ml / (100 g·Nm·μm)] or more and 100 [ml / (100 g·Nm·μm)] or less. Relational expression: A ≥ DBP absorption amount ≥ B A: The numerical value obtained by substituting the average particle size (D50) into the relational expression of A = -1.2 × D50 + 180 B: The numerical value obtained by substituting the average particle size (D50) into the relational expression of B = -0.6 × D50 + 110 However, D50 is 10 μm or more and 100 μm or less.

[0024] [BN agglomerated particles] The BN agglomerated particles according to the present invention are formed by agglomerating BN primary particles, preferably h-BN primary particles, and may contain components other than h-BN primary particles as long as the effects of the present invention are not impaired. Examples of components other than h-BN primary particles include binders, surfactants, and components derived from solvents that may be added to the slurry, as described in the [Method for producing BN agglomerated powder] described later.

[0025] <Shape of BN agglomerated particles in BN agglomerated powder> The shape of the BN agglomerated particles in the BN agglomerated powder of the present invention is not particularly limited. For example, it may be agglomerated particles of any shape that can be produced by aggregating BN primary particles, such as spherical, ellipsoidal, columnar, hexagonal columnar, etc. In particular, in order to obtain high thermal conductivity, it is preferably card house type BN agglomerated particles having a card house structure. The card house structure is described, for example, in Ceramics 43 NO.2 (published by The Ceramic Society of Japan in 2008), and is a structure in which plate-like particles are laminated complexly without orientation. More specifically, the BN agglomerated particles having a card house structure are an aggregate of BN primary particles, and are BN agglomerated particles having a structure in which the planar part and the end face part of the BN primary particles are in contact, and are preferably spherical. Further, the card house structure is preferably the same structure also inside the particles. The aggregation form and internal structure of these BN agglomerated particles can be confirmed by a scanning electron microscope (SEM).

[0026] Note that the BN agglomerated particles according to the present invention preferably have a card house structure and are formed by aggregating BN primary particles, preferably h-BN primary particles, but components other than h-BN primary particles (binder, surfactant, components derived from the solvent that may be added to the slurry) may be included as long as the effects of the present invention are not impaired. That is, the BN agglomerated powder of the present invention preferably is an aggregate of BN agglomerated particles including BN agglomerated particles having a card house structure, and more preferably is an aggregate of BN agglomerated particles that are BN agglomerated particles having a card house structure.

[0027] <Physical properties of BN agglomerated powder> (Average particle diameter (D50)) The average particle size (D50) of the BN agglomerated powder of the present invention is not particularly limited, but is 10 μm or more, preferably 15 μm or more, more preferably 17 μm or more. On the other hand, D50 of the BN agglomerated powder is 100 μm or less, preferably 95 μm or less, more preferably 90 μm or less, and particularly preferably 80 μm or less. When D50 of the BN agglomerated powder is at or above the above lower limit value, the thermal conductivity of the BN agglomerated powder itself increases. Further, when it is at or below the above upper limit value, the surface smoothness is improved when a heat dissipation sheet is formed, the contact between the heat dissipation sheet and the base material becomes good, and the thermal conductivity is improved.

[0028] Here, the average particle size (D50) of the BN agglomerated powder means the particle size at which the cumulative volume is exactly 50% when a cumulative curve is drawn with the volume of the BN agglomerated powder used for measurement as 100%. As a method for measuring the particle size, as a wet measurement method, for a sample in which BN agglomerated particles are dispersed in a pure water medium containing sodium hexametaphosphate or a naphthalenesulfonate-formalin condensate as a dispersion stabilizer, a method of measuring using a laser diffraction / scattering type particle size distribution measuring device or the like can be mentioned. As a dry measurement method, a method of measuring using "MORPHOLOGI" manufactured by MALVERN can be mentioned.

[0029] (Tap density) The tap density of the BN agglomerated powder in the first aspect of the present invention is not particularly limited, but is 0.5 g / ml or more, preferably 0.53 g / ml or more, more preferably 0.56 g / ml or more, and is 1.0 g / ml or less, preferably 0.9 g / ml or less, more preferably 0.8 g / ml or less, and still more preferably 0.78 g / ml or less. When it is within the above range, the thermal conductivity and the withstand voltage characteristics are further improved. The preferable range of the tap density of the BN agglomerated powder in the second aspect of the present invention is the same as the range of the tap density of the BN agglomerated powder in the first aspect.

[0030] (DBP absorption) The DBP absorption of the BN agglomerated powder in the first aspect of the present invention is not particularly limited as long as it satisfies the relational expression: A ≥ DBP absorption ≥ B. The preferable range of the DBP absorption of the BN agglomerated powder in the first aspect is the same as the range of the DBP absorption of the BN agglomerated powder in the second aspect. The DBP absorption of the BN agglomerated powder in the second aspect of the present invention is 50 ml / 100 g or more, preferably 55 ml / 100 g or more, and more preferably 60 ml / 100 g or more. Also, it is less than 170 ml / 100 g, preferably 160 ml / 100 g or less, and more preferably 150 ml / 100 g or less. By being within the above range, the thermal conductivity characteristics are further improved.

[0031] (Maximum torque value) The preferable range of the maximum torque value of the BN agglomerated powder in the first aspect of the present invention is the same as the range of the maximum torque value of the BN agglomerated powder in the second aspect. The maximum torque value of the BN agglomerated powder in the second aspect of the present invention is not particularly limited, but it is 0.010 Nm or more, preferably 0.025 Nm or more, and more preferably 0.050 Nm or more. Also, it is 1.000 Nm or less, preferably 0.800 Nm or less, more preferably 0.600 Nm or less, and still more preferably 0.400 Nm or less. By being within the above range, the thermal conductivity characteristics are further improved.

[0032] (Boron nitride purity) The purity of boron nitride measured by XPS of the BN agglomerated powder of the present invention is not particularly limited, but is preferably 97.0 wt% or more, more preferably 97.2 wt% or more, and still more preferably 97.4 wt% or more. Also, it is preferably 99.0 wt% or less, more preferably 98.5 wt% or less, and still more preferably 98.0 wt% or less. If the purity of boron nitride measured by XPS is too high, the wettability with resins and organic solvents deteriorates, the torque value during kneading increases, and crushing is likely to occur, resulting in a decrease in thermal conductivity. If the purity of boron nitride measured by XPS is too low, the thermal conductivity of the boron nitride primary particles themselves is low, and impurities are likely to exist at the contact interfaces between the boron nitride flakes, resulting in a thermal resistance, so it is considered that the thermal conductivity decreases. By being within the above range, the thermal conduction characteristics are further improved. In the present invention, the value measured by the method described in the examples is defined as the "purity of boron nitride measured by XPS".

[0033] Also, the purity of boron nitride measured by XRF of the BN agglomerated powder of the present invention is not particularly limited, but is preferably 95.0 wt% or more, more preferably 95.1 wt% or more, and still more preferably 95.3 wt% or more. Also, it is preferably 99.9 wt% or less, more preferably 99.0 wt% or less. If the purity of boron nitride measured by XRF is too low, it is considered that the thermal conductivity of the boron nitride primary particles themselves decreases, resulting in a decrease in thermal conduction characteristics. In the present invention, the value measured by the method described in the examples is defined as the "purity of boron nitride measured by XRF".

[0034] It is particularly preferable that the BN agglomerated powder of the present invention has a boron nitride purity measured by XPS of 97.0 wt% or more and 99.0 wt% or less, and a boron nitride purity measured by XRF of 95.0 wt% or more.

[0035] [Manufacturing method of BN agglomerated powder] There is no limitation on the method for manufacturing the BN agglomerated powder of the present invention. In particular, after boron nitride as a raw material (hereinafter, this may be referred to as "raw material BN powder" together with the pulverized one) is pulverized in a pulverization step, it is preferably granulated by agglomerating in a granulation step and further subjected to a heat treatment step of heat treatment. More specifically, after the raw material BN powder is once dispersed in a medium to form a slurry of the raw material BN powder (hereinafter, this may be referred to as "BN slurry"), a dispersion treatment is performed, and then the obtained slurry is used to granulate into spherical particles, and it is preferable to perform heat treatment to crystallize the granulated BN agglomerated granulated particles.

[0036] <raw material BN powder> As the raw material BN powder, commercially available h-BN, commercially available α-BN and β-BN, BN produced by the reduction nitridation method of a boron compound and ammonia, BN synthesized from a boron compound and a nitrogen-containing compound such as melamine, etc. can all be used without limitation, but in particular, h-BN is preferable in terms of more effectively exerting the effects of the present invention.

[0037] As the form of the raw material BN powder, powdery BN particles with a wide half-value width of the peak obtained by powder X-ray diffraction measurement and low crystallinity are suitable. That is, it is also possible to use plate-like h-BN as a raw material, but non-plate-like nanoparticles can also be preferably used. As a criterion for crystallinity, the peak half-value width of the (002) plane obtained from powder X-ray diffraction measurement is usually 0.4° or more, preferably 0.45° or more, more preferably 0.5° or more at an angle of 2θ. Also, it is usually 2.0° or less, preferably 1.5° or less, more preferably 1° or less. When the peak half-value width of the (002) plane is below the above upper limit value, crystal growth is likely to be controlled and productivity tends to improve. When the peak half-value width of the (002) plane is above the above lower limit, it becomes easy to control the primary particle size within an appropriate range, so it becomes easy to control the tap density, DBP absorption amount, and maximum torque value of the BN agglomerated particles within a desired range. Also, the dispersion stability during slurry preparation tends to improve.

[0038] From the perspective of BN crystal growth, it is preferable that a certain amount of oxygen atoms exist in the raw material BN powder. In the present invention, the total oxygen concentration in the raw material BN powder is preferably 1 wt% or more, more preferably 2 wt% or more, still more preferably 3 wt% or more, and particularly preferably 4 wt% or more, and preferably 10 wt% or less, more preferably 9 wt% or less. By the total oxygen concentration being below the above upper limit value, crystal growth does not become excessive, and the tap density, DBP absorption amount, and maximum torque value of the BN agglomerated particles can be controlled within an appropriate range. By the total oxygen concentration being above the above lower limit value, the remaining of oxygen after heat treatment is suppressed, and the effect of improving thermal conductivity becomes higher.

[0039] As a method for adjusting the total oxygen concentration of the raw material BN powder to the above range, for example, a method of performing the synthesis at a low temperature of 1500 °C or lower during BN synthesis, a method of heat-treating the raw material BN powder in a low-temperature oxidation atmosphere of 500 °C to 900 °C, etc. can be mentioned. The total oxygen concentration of the raw material BN powder can be measured by the inert gas fusion-infrared absorption method using an oxygen-nitrogen analyzer manufactured by Horiba, Ltd.

[0040] The total pore volume of the raw material BN powder is preferably 1.5 cm 3 / g or less, but more preferably 0.3 cm 3 / g or more and 1.5 cm 3 / g or less, still more preferably 0.5 cm 3 / g or more and 1.5 cm 3 / g or less. By the total pore volume being 1.5 cm 3 / g or less, since the raw material BN powder is dense, granulation with a high sphericity becomes possible.

[0041] The specific surface area of the raw material BN powder is preferably 50 m 2 / g or more, but more preferably 60 m 2 / g or more, and still more preferably 70 m 2 / g or more. On the other hand, it is preferably 1000 m 2 / g or less, but more preferably 500 m 2 / g or less, and still more preferably 300 m 2 / g or less. When the specific surface area of the raw material BN powder is 50 m 2 / g or more, it is preferable because the dispersed particle size in the BN slurry used for spheroidization by granulation can be reduced. Further, when it is 1000 m 2 / g or less, it is preferable because an increase in the slurry viscosity can be suppressed. The total pore volume of the raw material BN powder can be measured by the nitrogen adsorption method and the mercury intrusion method, and the specific surface area can be measured by the BET one-point method (adsorbing gas: nitrogen).

[0042] <Medium> There is no particular limitation on the medium used for preparing the BN slurry, and water and / or various organic solvents can be used. However, from the viewpoints of ease of spray drying and simplification of the apparatus, it is preferable to use water, and pure water is more preferable. It is preferable to add the medium used for preparing the BN slurry in an amount such that the viscosity of the BN slurry becomes 200 to 5000 mPa·s.

[0043] Specifically, the amount of the medium used for preparing the BN slurry is preferably 10 wt% or more, more preferably 20 wt% or more, still more preferably 30 wt% or more, preferably 70 wt% or less, more preferably 65 wt% or less, still more preferably 60 wt% or less, based on the BN slurry. When the amount of the medium used is below the above upper limit value, the slurry viscosity does not become too low, so sedimentation and the like are suppressed, and the uniformity of the BN slurry tends to be obtained. Therefore, the tap density of the obtained BN agglomerated powder tends to be within a desired range. When the amount of the medium used is above the above lower limit value, the slurry viscosity does not become excessively high, and granulation tends to be easy.

[0044] <Surfactant> Various surfactants may be added to the BN slurry from the viewpoints of adjusting the viscosity of the slurry and the dispersion stability (aggregation suppression) of the raw material BN powder in the slurry. As the surfactant, anionic surfactants, cationic surfactants, nonionic surfactants, etc. can be used, and these may be used alone or in combination of two or more.

[0045] <Binder> The BN slurry may contain a binder in order to effectively granulate the raw material BN powder into particles. The binder acts to firmly bind the BN primary particles and stabilize the granulated particles. As the binder used in the BN slurry, any binder can be used as long as it can enhance the adhesiveness between BN particles. However, in the present invention, since the granulated particles are heat-treated after granulation, those having heat resistance under the high-temperature conditions in this heat-treatment step are preferable.

[0046] As such a binder, metal oxides such as aluminum oxide, magnesium oxide, yttrium oxide, calcium oxide, silicon oxide, boron oxide, cerium oxide, zirconium oxide, titanium oxide, etc. are preferably used. Among these, aluminum oxide and yttrium oxide are preferable from the viewpoints of thermal conductivity and heat resistance as oxides, and the binding force for binding BN particles to each other. Note that a liquid binder such as alumina sol may be used as the binder, or it may react during the heat treatment and be converted into other inorganic components. These binders may be used alone or in combination of two or more.

[0047] The usage amount of the binder (in the case of a liquid binder, the usage amount as a solid content) is preferably 0 wt% or more and 30 wt% or less, more preferably 0 wt% or more and 20 wt% or less, and still more preferably 0 wt% or more and 15 wt% or less, based on the raw material BN powder in the BN slurry. When the usage amount of the binder is below the above upper limit value, crystal growth can be obtained, and there is a tendency to obtain an effect of improving thermal conductivity when used as a filler for thermal conductivity.

[0048] <BN Slurry Preparation Method> The method for preparing the BN slurry is not particularly limited as long as the raw material BN powder, the medium, and, if necessary, the binder and the surfactant are uniformly dispersed and adjusted to a desired viscosity range. However, when using the raw material BN powder, the medium, and, if necessary, the binder and the surfactant, it is preferably prepared as follows.

[0049] Weigh a predetermined amount of the raw material BN powder into a resin bottle, and then add a predetermined amount of the binder. Further, after adding a predetermined amount of the surfactant as needed, add zirconia ceramic balls and stir on a pot mill turntable for about 0.5 to 5 hours until the desired viscosity is reached. The order of addition is not particularly limited. However, when slurrying a large amount of the raw material BN powder, aggregates such as lumps are likely to form. Therefore, after preparing an aqueous solution by adding the surfactant and the binder to water, add a predetermined amount of the raw material BN powder little by little, add zirconia ceramic balls thereto, and disperse and slurry on a pot mill turntable.

[0050] Also, for dispersion, in addition to a pot mill, a dispersion device such as a bead mill or a planetary mixer may be used. When slurrying, the temperature of the slurry is preferably carried out at 10°C or higher and 60°C or lower. When the slurry temperature is at or above the lower limit value, the increase in slurry viscosity can be suppressed, and when it is at or below the upper limit value, the decomposition of the raw material BN powder into ammonia in the slurry can be suppressed. The temperature of the slurry is more preferably 15°C or higher and 50°C or lower, still more preferably 15°C or higher and 40°C or lower, and particularly preferably 15°C or higher and 35°C or lower.

[0051] <Granulation> To obtain granulated particles from the BN slurry, general granulation methods such as the spray drying method, the rolling method, the fluidized bed method, and the stirring method can be used. Among these, the spray drying method is preferred. In the spray drying method, it is possible to produce granulated particles of a desired size and obtain spherical granulated particles by adjusting the concentration of the slurry as the raw material, the liquid feeding rate per unit time introduced into the apparatus, the compressed air pressure and the amount of compressed air when spraying the fed slurry. There is no limitation on the spray drying apparatus to be used, but for obtaining larger spherical granulated particles, the one using a rotary disk is most suitable. Examples of such apparatuses include the spray dryer F series manufactured by Okawara Chemical Machinery Co., Ltd., the spray dryer "MDL-050M" manufactured by Fujisaki Electric Co., Ltd., and the spray dryer "P260" manufactured by Pris Co., Ltd.

[0052] When the range of the volume-based average particle diameter (D50) of the BN agglomerated powder of the present invention is 10 μm or more and 100 μm or less, it is preferable that the average particle diameter (D50) of the granulated particles obtained by granulation is 10 μm or more and 100 μm or less in terms of the volume-based average particle diameter (D50). Here, the volume-based average particle diameter (D50) of the granulated particles can be measured by "Morphorogi" manufactured by Malvern Co., Ltd.

[0053] <Heat treatment> The above-mentioned BN granulated powder can be further heat-treated in a non-oxidizing gas atmosphere to produce a BN agglomerated powder. Here, the non-oxidizing gas atmosphere is an atmosphere such as nitrogen gas, helium gas, argon gas, ammonia gas, hydrogen gas, methane gas, propane gas, carbon monoxide gas, etc. The crystallization rate of the BN agglomerated particles varies depending on the type of the atmosphere gas used here. In order to perform crystallization in a short time, nitrogen gas or a mixed gas of nitrogen gas and another gas is preferably used.

[0054] The heat treatment temperature is preferably 1400 °C or higher and 2300 °C or lower, more preferably 1500 °C or higher and 2000 °C or lower, and still more preferably 1600 °C or higher and 2000 °C or lower. When the heat treatment temperature is at or above the above lower limit value, sufficient growth of BN primary particles can be obtained, and the thermal conductivity of the BN agglomerated powder tends to increase. When the heat treatment temperature is at or below the above upper limit value, decomposition of the BN agglomerated powder and the like tend to be suppressed.

[0055] The heat treatment time is preferably 1 hour or more and 20 hours or less, more preferably 2 hours or more and 15 hours or less. When the heat treatment time is at or above the above lower limit value, sufficient growth of BN primary particles can be obtained, and when it is at or below the above upper limit value, decomposition of BN can be suppressed. In order to perform the heat treatment in a non-oxidizing gas atmosphere, preferably, usually, after evacuating the inside of the firing furnace with a vacuum pump, while introducing a non-oxidizing gas, it is heated to a desired temperature for temperature rise. When the inside of the firing furnace can be sufficiently replaced with a non-oxidizing gas, it may be heated and temperature-rise while introducing a non-oxidizing gas under normal pressure. Examples of the firing furnace include batch furnaces such as muffle furnaces, tubular furnaces, and atmosphere furnaces, and continuous furnaces such as rotary kilns, screw conveyor furnaces, tunnel furnaces, belt furnaces, pusher furnaces, and vertical continuous furnaces, which are used appropriately according to the purpose.

[0056] Usually, the BN agglomerated granulated powder to be heat-treated is put into a crucible with a graphite lid and heated and fired in order to reduce the compositional non-uniformity during firing. At this time, in addition to reducing the compositional non-uniformity, a graphite partition may be inserted for the purpose of suppressing sintering between BN agglomerated particles due to firing. The number of divisions by the partition is not particularly limited as long as sintering can be suppressed, but is usually 2 or more and 16 or less. By setting the number of divisions to be at or below the above upper limit value and at or above the above lower limit value, sintering is suppressed and the growth of h-BN primary particles can be controlled. Therefore, the tap density, DBP absorption amount, and maximum torque value of the BN agglomerated particles can be controlled within a desired range.

[0057] <Classification> The BN agglomerated powder after the above heat treatment is preferably classified in order to reduce the particle size distribution and suppress the increase in viscosity when blended into a resin composition containing the BN agglomerated powder. This classification is usually performed after the heat treatment, but may be performed on the granulated particles before the heat treatment and then subjected to the heat treatment.

[0058] The classification may be either wet or dry, but from the viewpoint of suppressing the decomposition of BN, dry classification is preferred. In particular, when the binder is water-soluble, dry classification is preferably used. For dry classification, in addition to classification by a sieve, there is also air classification that classifies by the difference between centrifugal force and fluid resistance, etc., but it can also be carried out using a classifier such as a cyclone air classifier, a forced vortex centrifugal classifier, or a semi-free vortex centrifugal classifier. Among these, a cyclone air classifier is used to classify small fine particles in the submicron to single micron region, and a semi-free vortex centrifugal classifier, etc., is used to classify relatively larger particles. They can be appropriately selected according to the particle size of the particles to be classified.

[0059] [Resin composition containing BN agglomerated powder] To produce the heat dissipation sheet of the present invention containing the BN agglomerated powder of the present invention, usually, a resin composition (hereinafter, may be referred to as "the resin composition containing the BN agglomerated powder of the present invention" or "the composition of the present invention") containing at least the BN agglomerated powder of the present invention as an inorganic filler and a resin is prepared, and the prepared composition of the present invention is sheet-molded to obtain the heat dissipation sheet of the present invention. Hereinafter, the resin composition containing the BN agglomerated powder of the present invention will be described.

[0060] The resin composition containing the BN agglomerated powder of the present invention generally consists of a resin component, preferably a thermosetting resin component, an inorganic filler containing the BN agglomerated powder of the present invention, a curing agent, a curing catalyst, other components used as required, a solvent for forming a coating slurry, etc. Further, when forming a composite body described later, from the viewpoint of improving the adhesion to a metal, the composition of the present invention preferably contains a compound having a heterocyclic structure containing a nitrogen atom.

[0061] [Components other than BN agglomerated powder] [Thermosetting resin component] ​The thermosetting resin contained in the composition of the present invention may be any resin that cures in the presence of a curing agent or a curing catalyst and is not particularly limited. Specific examples of the thermosetting resin include epoxy resins, phenol resins, polycarbonate resins, unsaturated polyester resins, urethane resins, melamine resins, urea resins, and the like. Among these, epoxy resins are preferred from the viewpoints of viscosity, heat resistance, hygroscopicity, and handleability. Examples of the epoxy resin include silicon compounds containing epoxy groups, aliphatic epoxy resins, bisphenol A or F type epoxy resins, novolak type epoxy resins, alicyclic epoxy resins, glycidyl ester type epoxy resins, polyfunctional epoxy resins, and high molecular weight epoxy resins.

[0062] (Epoxy resin) An epoxy resin is a general term for compounds having one or more oxirane rings (epoxy groups) in the molecule. The oxirane ring (epoxy group) contained in the epoxy resin may be either an alicyclic epoxy group or a glycidyl group, but from the viewpoints of reaction rate or heat resistance, a glycidyl group is more preferred.

[0063] The epoxy resin used in the present invention may be a compound containing an aromatic oxirane ring (epoxy group). Specific examples thereof include bisphenol type epoxy resins obtained by glycidylating bisphenols such as bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethyl bisphenol A, tetramethyl bisphenol F, tetramethyl bisphenol AD, tetramethyl bisphenol S, and tetrafluorobisphenol A; biphenyl type epoxy resins; epoxy resins obtained by glycidylating divalent phenols such as dihydroxynaphthalene and 9,9-bis(4-hydroxyphenyl)fluorene; epoxy resins obtained by glycidylating trisphenols such as 1,1,1-tris(4-hydroxyphenyl)methane; epoxy resins obtained by glycidylating tetrakisphenols such as 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane; and novolak type epoxy resins obtained by glycidylating novolaks such as phenol novolak, cresol novolak, bisphenol A, novolak, and brominated bisphenol A novolak.

[0064] Hereinafter, an epoxy resin suitable as the epoxy resin used in the present invention (hereinafter, may be referred to as "specific epoxy resin") and a polyfunctional epoxy resin preferably used in combination with this specific epoxy resin will be described. In the following, the "organic group" includes any group as long as it contains a carbon atom. Specific examples include an alkyl group, an alkenyl group, an aryl group, etc., and they may be substituted with a halogen atom, a group having a hetero atom, or another hydrocarbon group.

[0065] (Specific Epoxy Resin) Examples of the specific epoxy resin include an epoxy resin having at least one structure selected from the structure represented by the following structural formula (1) (hereinafter, may be referred to as "structure (1)") and the structure represented by the following structural formula (2) (hereinafter, may be referred to as "structure (2)").

[0066]

Chemical Formula

[0067] (In Structure (1), R 1 and R 2 each represent an organic group, and at least one of them is an organic group having a molecular weight of 16 or more. In Structure (2), R 3 represents a divalent cyclic organic group.) Further, examples of the specific epoxy resin include an epoxy resin having a structure represented by the following structural formula (3) (hereinafter, may be referred to as "Structure (3)").

[0068] [Chemical formula]

[0069] (In Structure (3), R 4 , R 5 , R 6 , R 7 each represent an organic group having a molecular weight of 15 or more.)

[0070] In the above Structure (1), at least one of R 1 and R 2 represents an organic group having a molecular weight of 16 or more, preferably an organic group having a molecular weight of 16 to 1000. For example, alkyl groups such as ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, etc., and aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, fluorenyl group, etc. can be mentioned. R 1 and R 2 may both be organic groups having a molecular weight of 16 or more, or one may be an organic group having a molecular weight of 16 or more and the other may be an organic group having a molecular weight of 15 or less or a hydrogen atom. Preferably, one is an organic group having a molecular weight of 16 or more and the other is an organic group having a molecular weight of 15 or less. In particular, it is preferable that either one is a methyl group and the other is a phenyl group from the viewpoint of easy control of handleability such as resin viscosity and strength of the cured product.

[0071] In Structure (2), R 3is a divalent cyclic organic group, which may be an aromatic ring structure such as a benzene ring structure, a naphthalene ring structure, or a fluorene ring structure, or an aliphatic ring structure such as cyclobutane, cyclopentane, or cyclohexane. Further, they may independently have a hydrocarbon group or a substituent such as a halogen atom. The divalent bonding portion may be a divalent group at a single carbon atom or a divalent group at different carbon atoms. Preferably, examples include a divalent aromatic group having 6 to 100 carbon atoms and a group derived from a cycloalkane having 2 to 100 carbon atoms such as cyclopropane or cyclohexane. In particular, the 3,3,5-trimethyl-1,1-cyclohexylene group represented by the following structural formula (4) is preferable from the viewpoints of controlling handleability such as resin viscosity and strength of the cured product.

[0072]

Chemical formula

[0073] In structure (3), R 4 , R 5 , R 6 , R 7 are each an organic group having a molecular weight of 15 or more, preferably an alkyl group having a molecular weight of 15 to 1000. In particular, it is preferable that all of R 4 , R 5 , R 6 , R 7 are methyl groups from the viewpoints of controlling handleability such as resin viscosity and strength of the cured product.

[0074] The specific epoxy resin is preferably an epoxy resin containing either one of structure (1) and structure (2) and structure (3) from the viewpoint of achieving both reduction in moisture absorption and retention of strength of the heat dissipation sheet as the cured product obtained. Such a specific epoxy resin contains a large amount of hydrophobic hydrocarbons and aromatic structures compared with general epoxy resins having a bisphenol A or bisphenol F skeleton. Therefore, by blending the specific epoxy resin, the moisture absorption amount of the heat dissipation sheet as the cured product obtained can be reduced.

[0075] Also, from the viewpoint of reducing the moisture absorption amount, it is preferable that the specific epoxy resin contains many structures (1), (2), and (3) having a hydrophobic structure. Specifically, it is preferably an epoxy resin having a weight average molecular weight of 10,000 or more, more preferably an epoxy resin having a weight average molecular weight of 20,000 or more, and even more preferably an epoxy resin having a weight average molecular weight of 30,000 or more, for example, 30,000 to 40,000.

[0076] Also, it is preferable that the specific epoxy resin is more hydrophobic. Specifically, the epoxy equivalent of the specific epoxy resin is preferably larger, preferably 5,000 g / equivalent or more, more preferably 7,000 g / equivalent or more, for example, 8,000 to 15,000 g / equivalent. Here, the weight average molecular weight of the epoxy resin is a value in terms of polystyrene measured by gel permeation chromatography. Also, the epoxy equivalent is defined as "the weight of an epoxy resin containing 1 equivalent of epoxy groups" and can be measured according to JIS K7236. Such a specific epoxy resin may be used alone or in combination of two or more.

[0077] (Polyfunctional epoxy resin) A polyfunctional epoxy resin is an epoxy resin having three or more oxirane rings (epoxy groups) per molecule. From the viewpoint of increasing the storage modulus of the cured product after heat curing, particularly increasing the storage modulus at high temperatures which is important when there is a large amount of heat generation such as in semiconductor devices, an epoxy resin having two or more oxirane rings (epoxy groups) in the molecule is preferable, an epoxy resin having three or more oxirane rings (epoxy groups) in the molecule is more preferable, and an epoxy resin having four or more glycidyl groups in the molecule is even more preferable. By having a plurality of oxirane rings (epoxy groups), particularly glycidyl groups, in the molecule, the crosslink density of the cured product is improved, and the heat dissipation sheet as the resulting cured product becomes stronger. Thereby, when internal stress is generated in the heat dissipation sheet during the moisture absorption reflow test, the heat dissipation sheet can suppress the generation of voids such as voids in the heat dissipation sheet by maintaining its form without deforming or breaking.

[0078] Also, from the viewpoint of increasing the storage modulus of the heat dissipation sheet after heat curing, the molecular weight of the polyfunctional epoxy resin is preferably 1,000 or less, particularly preferably 100 to 800. In addition, by adding a polyfunctional epoxy resin, it is possible to introduce highly polar oxirane rings (epoxy groups) at a high density, thereby increasing the effects of physical interactions such as van der Waals forces and hydrogen bonds, and improving the adhesion between the metal and the heat dissipation sheet of the present invention which is a resin cured product in the composite body described later. Also, by adding a polyfunctional epoxy resin, the storage modulus of the heat dissipation sheet after heat curing can be increased, and thereby, after the cured product of the thermosetting resin composition enters the unevenness of the metal which is the adherend, a strong anchor effect is exhibited, and the adhesion between the metal and the heat dissipation sheet can be improved.

[0079] On the other hand, by introducing a polyfunctional epoxy resin, the hygroscopicity of the thermosetting resin composition tends to increase, but by improving the reactivity of the oxirane ring (epoxy group), the amount of hydroxyl groups during the reaction can be reduced, and the increase in hygroscopicity can be suppressed. Also, by manufacturing a thermosetting resin composition by combining the specific epoxy resin and the polyfunctional epoxy resin described above, it becomes possible to achieve both high elasticization and low moisture absorption of the resulting heat dissipation sheet.

[0080] As the polyfunctional epoxy resin, specifically, an epoxy resin having three or more epoxy groups is preferable. For example, EX321L, DLC301, DLC402, etc. manufactured by Nagase ChemteX Corporation can be used. These polyfunctional epoxy resins may be used alone or in combination of two or more.

[0081] (Content) The composition of the present invention preferably contains the thermosetting resin component in an amount of 5 to 99 wt%, particularly 50 to 98 wt% in 100 wt% of the composition of the present invention excluding the solvent and the inorganic filler. When the content of the thermosetting resin component is at least the above lower limit, the moldability becomes good, and when it is at most the above upper limit, the content of other components can be ensured and the thermal conductivity can be increased. Further, the composition of the present invention preferably contains 20 to 100 wt%, particularly 45 to 100 wt% of an epoxy resin in the thermosetting resin component.

[0082] Further, the composition of the present invention preferably contains a specific epoxy resin, which is the above-described preferable epoxy resin, in an amount of 50 wt% or less, for example, 5 to 50 wt%, particularly 10 to 40 wt% in all the epoxy resins. When the content of the specific epoxy resin is at least the above lower limit, the above-described effects due to the inclusion of the specific epoxy resin can be effectively obtained. On the other hand, if there is too much specific epoxy resin, the crosslinking density decreases and the cured product becomes brittle. By setting the content of the specific epoxy resin to be at most the above upper limit, the hygroscopicity of the cured product can be suppressed, and the strength performance of the cured product can be made excellent, and it becomes possible to achieve both of these performances.

[0083] In addition, the composition of the present invention preferably contains a polyfunctional epoxy resin, which is the aforementioned preferred epoxy resin, in an amount of 5 to 50 wt%, particularly 10 to 40 wt% in the total epoxy resin. When the content of the polyfunctional epoxy resin is not less than the above lower limit, the aforementioned effects obtained by containing the polyfunctional epoxy resin can be effectively obtained. On the other hand, when the content of the polyfunctional epoxy resin is not more than the above upper limit, the hygroscopicity of the cured product can be suppressed, and the strength performance of the cured product can be made excellent, and it is possible to achieve both of these performances.

[0084] In particular, for the composition of the present invention, as the epoxy resin, it is preferable to contain both a specific epoxy resin and a polyfunctional epoxy resin in order to achieve both high elasticization and low moisture absorption of the obtained cured product. In that case, the content ratio of the specific epoxy resin to the polyfunctional epoxy resin is preferably specific epoxy resin: polyfunctional epoxy resin = 10 to 90: 90 to 10, particularly 20 to 80: 80 to 20 (mass ratio).

[0085] In addition, the epoxy resin other than the specific epoxy resin and the polyfunctional epoxy resin contained in the composition of the present invention is not particularly limited. For example, various bisphenol type epoxy resins obtained by glycidylating bisphenols such as bisphenol A type epoxy resin and bisphenol F type epoxy resin, various biphenyl type epoxy resins obtained by glycidylating biphenyls, and aromatic compounds having two hydroxyl groups such as dihydroxynaphthalene and 9,9-bis(4-hydroxyphenyl)fluorene are glycidylated epoxy resins, epoxy resins obtained by glycidylating trisphenols such as 1,1,1-tris(4-hydroxyphenyl)methane, epoxy resins obtained by glycidylating tetrakisphenols such as 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, novolak type epoxy resins obtained by glycidylating novolaks such as phenol novolak, cresol novolak, bisphenol A novolak, and brominated bisphenol A novolak, and one or more selected from silicone-containing epoxy resins are preferred.

[0086] <Compound having a heterocyclic structure containing a nitrogen atom> A compound having a heterocyclic structure containing a nitrogen atom (hereinafter sometimes referred to as a "nitrogen-containing heterocyclic compound") has an effect of improving the adhesion between the cured product of the composition of the present invention and a metal. That is, when the nitrogen-containing heterocyclic compound is combined with the composition of the present invention and the metal, it is located at their interface, thereby improving the adhesion between the composition of the present invention and the metal. From this viewpoint, in order to make it easier for the nitrogen-containing heterocyclic compound to stay at the interface between the composition of the present invention and the metal, it is more preferably of low molecular weight, and the molecular weight of the nitrogen-containing heterocyclic compound is preferably 1,000 or less, and more preferably 500 or less.

[0087] Examples of the heterocyclic structure of the nitrogen-containing heterocyclic compound include structures derived from imidazole, triazine, triazole, pyrimidine, pyrazine, pyridine, and azole. From the viewpoint of improving the insulation properties and adhesion to metals of the thermosetting resin composition, imidazole-based compounds and triazine-based compounds are preferred. Examples of preferred imidazole-based compounds and triazine-based compounds include 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-s-triazine, 2,4-diamino-6-methacryloyloxyethyl-s-triazine isocyanuric acid adduct, and the like.

[0088] Among these, those having high resin compatibility and a high reaction activation temperature can easily adjust the curing rate and physical properties after curing. As a result, it is possible to improve the storage stability of the composition of the present invention and further improve the adhesive strength after heat molding. Therefore, those having a structure derived from imidazole and those having a structure derived from triazine are particularly preferred, and those having a structure derived from triazine are particularly preferred. As the heterocyclic structure of the nitrogen-containing heterocyclic compound, a structure derived from 1,3,5-triazine is particularly preferred. Moreover, those having a plurality of these exemplified structural parts may be used.

[0089] Note that depending on the structure, the nitrogen-containing heterocyclic compound may contain a curing catalyst described later. Therefore, the composition of the present invention can contain a nitrogen-containing heterocyclic compound as a curing catalyst. Only one kind of nitrogen-containing heterocyclic compound may be used, or two or more kinds may be used in combination. Also, a molecule may have a plurality of heterocyclic structures at the same time.

[0090] The nitrogen-containing heterocyclic compound is preferably contained in an amount of 0.001 to 10 wt%, particularly 0.1 to 5 wt%, based on 100 wt% of the composition of the present invention excluding the solvent and the inorganic filler. When the curing catalyst described later is contained in the nitrogen-containing heterocyclic compound in terms of its molecular structure, the total amount including their contents is preferably within the above range. When the content of the nitrogen-containing heterocyclic compound is not less than the above lower limit, the above effects due to the inclusion of this compound can be sufficiently obtained. When it is not more than the above upper limit, the reaction can proceed effectively, the crosslink density can be improved, the strength can be increased, and the storage stability is further improved.

[0091] <Hardener> The hardener is not particularly limited, but preferred hardeners are phenolic resins, acid anhydrides having an aromatic skeleton or an alicyclic skeleton, or hydrates or modified products of the acid anhydrides. By using these preferred hardeners, a resin cured product excellent in the balance of heat resistance, moisture resistance, and electrical properties can be obtained. Only one type of hardener may be used, or two or more types may be used in combination.

[0092] The phenolic resin is not particularly limited. Specific examples of the phenolic resin include phenol novolac, o-cresol novolac, p-cresol novolac, t-butylphenol novolac, dicyclopentadiene cresol, polyparavinylphenol, bisphenol A type novolac, xylylene-modified novolac, decalin-modified novolac, poly(di-o-hydroxyphenyl)methane, poly(di-m-hydroxyphenyl)methane, or poly(di-p-hydroxyphenyl)methane, etc. Among them, for further improving the flexibility and flame retardancy of the thermosetting resin composition and the mechanical properties and heat resistance of the resin cured product, novolac type phenolic resins having a rigid main chain skeleton or phenolic resins having a triazine skeleton are preferred. Also, for improving the flexibility of the uncured thermosetting resin composition and the toughness of the resin cured product, phenolic resins having an allyl group are preferred.

[0093] Commercially available products of phenolic resins include MEH-8005, MEH-8000H, and NEH-8015 (all manufactured by Meiwa Kasei Co., Ltd.), YLH903 (manufactured by Mitsubishi Chemical Corporation), LA-7052, LA-7054, LA-7751, LA-1356, and LA-3018-50P (all manufactured by Dainippon Ink and Chemicals, Incorporated), and PSM6200, PS6313, and PS6492 (manufactured by Gunei Chemical Industry Co., Ltd.), etc.

[0094] The acid anhydride having an aromatic skeleton, the adduct of the acid anhydride with water, or the modified product of the acid anhydride is not particularly limited. Specific examples include SMA resin EF30 and SMA resin EF60 (both manufactured by Sartomer Japan Co., Ltd.), ODPA-M and PEPA (both manufactured by Mannak Co., Ltd.), Likazit MTA-10, Likazit TMTA, Likazit TMEG-200, Likazit TMEG-500, Likazit TMEG-S, Likazit TH, Likazit MH-700, Likazit MT-500, Likazit DSDA, and Likazit TDA-100 (all manufactured by Shin Nippon Rika Co., Ltd.), EPICLON B4400, and EPICLON B570 (both manufactured by Dainippon Ink and Chemicals, Inc.), etc.

[0095] The acid anhydride having an alicyclic skeleton, the adduct of the acid anhydride with water, or the modified product of the acid anhydride is preferably an acid anhydride having a polyalicyclic skeleton, the adduct of the acid anhydride with water or the modified product of the acid anhydride, or an acid anhydride having an alicyclic skeleton obtained by the addition reaction of a terpene compound and maleic anhydride, the adduct of the acid anhydride with water, or the modified product of the acid anhydride. Specific examples include Likazit HNA and Likazit HNA-100 (both manufactured by Shin Nippon Rika Co., Ltd.), and Epicure YH306 and Epicure YH309 (both manufactured by Mitsubishi Chemical Corporation), etc.

[0096] The curing agent is preferably contained in an amount of 0 to 70 wt%, particularly 0 to 55 wt%, in 100 wt% of the composition of the present invention excluding the solvent and the inorganic filler. When the content of the curing agent is not less than the above lower limit, sufficient curing performance can be obtained. When it is not more than the above upper limit, the reaction can proceed effectively, the crosslink density can be improved, the strength can be increased, and the film-forming property can be further improved.

[0097] <Curing catalyst> The composition of the present invention preferably contains a curing catalyst together with the above curing agent in order to adjust the curing rate, physical properties of the cured product, etc. The curing catalyst is not particularly limited and is appropriately selected according to the type of thermosetting resin component and curing agent used. Specific examples of the curing catalyst include chain or cyclic tertiary amines, organic phosphorus compounds, diazabicycloalkenes such as quaternary phosphonium salts or organic acid salts, and the like. In addition, organometallic compounds, quaternary ammonium salts, metal halides, etc. can also be used. Examples of the above organometallic compounds include zinc octylate, tin octylate, or aluminum acetylacetone complex.

[0098] These may be used alone or in combination of two or more. The curing catalyst is preferably contained in an amount of 0.1 to 10 wt%, particularly 0.1 to 5 wt%, based on 100 wt% of the composition of the present invention excluding the solvent and inorganic filler. When the content of the curing catalyst is at least the above lower limit, the progress of the curing reaction can be sufficiently promoted to achieve good curing. When it is at most the above upper limit, the curing rate is not too fast, and thus the storage stability of the composition of the present invention can be made good.

[0099] <Other components> In the composition of the present invention, other components other than the above may be included as components other than the inorganic filler within a range that does not impair the effects of the present invention. Examples of other components include surface treatment agents such as silane coupling agents that improve the interfacial adhesion strength between the inorganic filler and the resin component, insulating carbon components such as reducing agents, viscosity modifiers, dispersants, thixotropy-imparting agents, flame retardants, colorants, organic fillers, organic solvents, and thermoplastic resins when producing a resin cured product using the composition of the present invention.

[0100] Among these, when a dispersant is included, it may be possible to form a uniform resin cured product and improve the thermal conductivity and dielectric breakdown characteristics of the resulting resin cured product. In addition, when an organic filler or a thermoplastic resin is included, it may be possible to impart appropriate extensibility to the composition, relieve the generated stress, and suppress the occurrence of cracks in the temperature cycle test.

[0101] The dispersant preferably has a functional group containing a hydrogen atom having hydrogen bonding properties. By the dispersant having a functional group containing a hydrogen atom having hydrogen bonding properties, the thermal conductivity and dielectric breakdown properties of the heat dissipation sheet, which is the cured product obtained, can be further enhanced. Examples of the functional group containing a hydrogen atom having hydrogen bonding properties include a carboxyl group (pKa = 4), a phosphoric acid group (pKa = 7), or a phenol group (pKa = 10), etc.

[0102] The pKa of the functional group containing a hydrogen atom having hydrogen bonding properties is preferably in the range of 2 to 10, and more preferably in the range of 3 to 9. When the pKa is 2 or more, the acidity of the dispersant becomes an appropriate range, and the reaction of the epoxy resin in the thermosetting resin component may be easily suppressed. Therefore, when the uncured molded product is stored, the storage stability tends to improve. When the pKa is 10 or less, the function as a dispersant is sufficiently fulfilled, and the thermal conductivity and dielectric breakdown properties of the heat dissipation sheet, which is the cured product obtained, tend to be sufficiently enhanced.

[0103] The functional group containing a hydrogen atom having hydrogen bonding properties is preferably a carboxyl group or a phosphoric acid group. In this case, the thermal conductivity and dielectric breakdown properties of the heat dissipation sheet can be further enhanced. Specific examples of the dispersant include polyester-based carboxylic acid, polyether-based carboxylic acid, polyacrylic-based carboxylic acid, aliphatic carboxylic acid, polysiloxane-based carboxylic acid, polyester-based phosphoric acid, polyether-based phosphoric acid, polyacrylic-based phosphoric acid, aliphatic phosphoric acid, polysiloxane-based phosphoric acid, polyester-based phenol, polyether-based phenol, polyacrylic-based phenol, or polysiloxane-based phenol, etc. Only one type of dispersant may be used, or two or more types may be used in combination.

[0104] As the thermoplastic resin, any generally known thermoplastic resin can be used. Specifically, for example, vinyl polymers such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, (meth)acrylic resin, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polylactic acid resin, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides such as nylon and polyamideamine, polyvinyl acetal resins such as polyvinyl acetoacetal, polyvinyl benzal, and polyvinyl butyral resin, ionomer resin, polyphenylene ether, polyphenylene sulfide, polycarbonate, polyether ether ketone, polyacetal, ABS resin, LCP (liquid crystal polymer), fluororesin, urethane resin, silicone resin, various elastomers, or modified products of these resins may be used.

[0105] These thermoplastic resins may be uniform in the resin phase of the heat dissipation sheet, or may be phase-separated and have a recognizable shape. When they are phase-separated, the shape of the thermoplastic resin in the heat dissipation sheet may be particulate or fibrous. Thus, when the shape of the thermoplastic resin is recognized in the heat dissipation sheet, the thermoplastic resin may be recognized as an organic filler. However, in the present invention, the organic filler refers to natural products such as wood powder, cellulose which may be modified, starch, various organic pigments, etc., and the thermoplastic resin is not included in the organic filler.

[0106] When the composition contains a thermoplastic resin and an organic filler, it may impart appropriate stretchability to the composition, relieve the generated stress, and suppress the occurrence of cracks in the temperature cycle test. When the thermoplastic resin and the organic filler are insoluble in the thermosetting resin, it is possible to prevent the viscosity of the composition of the present invention from increasing, and for example, when molding into a sheet as described later, the smoothness of the sheet surface can be improved. In this case, by mixing a thermoplastic resin and an organic filler insoluble in the thermosetting resin simultaneously with a large amount of inorganic filler, a component phase that is thermoplastic and has good elongation can be efficiently dispersed in the cured product, and the stress can be easily relaxed. Therefore, it is possible to suppress the occurrence of cracks in the cured product without lowering the elastic modulus of the cured product. For these reasons, as the thermoplastic resin, polyamide resins such as nylon, cellulose resins, etc. are preferable, and polyamide resins such as nylon are particularly preferable.

[0107] When the shape of the thermoplastic resin that can be observed in the heat dissipation sheet which is a cured product is particulate, the upper limit of its average particle diameter is preferably 100 μm or less, more preferably 50 μm or less, and still more preferably 30 μm or less. By setting the average particle diameter to be equal to or less than the above upper limit value, sheet-like cured products of various thicknesses can be produced without fear of a decrease in thermal conductivity. The average particle diameter of the particulate thermoplastic resin is determined by observing the cross section of the cured product and taking the average value of the longest diameters of any 20 particles.

[0108] The composition of the present invention may contain an organic solvent, for example, for improving the coatability when molding a sheet-like cured product through a coating process. Examples of the organic solvent that the composition of the present invention can contain include methyl ethyl ketone, cyclohexanone, propylene glycol monomethyl ether acetate, butyl acetate, isobutyl acetate, propylene glycol monomethyl ether, etc. These organic solvents may be used alone or in combination of two or more.

[0109] When the composition of the present invention contains an organic solvent, its content is appropriately determined according to the handleability during the production of the heat dissipation sheet, etc. Usually, it is preferable to use the organic solvent so that the solid content (total of components other than the solvent) concentration in the composition of the present invention is 10 to 90 wt%, particularly 40 to 80 wt%.

[0110] [Inorganic filler] The composition of the present invention contains at least the BN agglomerated powder of the present invention as an inorganic filler. The composition of the present invention may contain an inorganic filler other than the BN agglomerated powder of the present invention. In that case, preferred examples of the inorganic filler other than the BN agglomerated powder of the present invention include spherical fillers.

[0111] The spherical filler used together with the BN agglomerated powder of the present invention preferably has a thermal conductivity of 10 W / m·K or more, more preferably 15 W / m·K or more, and still more preferably 20 W / m·K or more. Also, the new Mohs hardness is preferably 3.1 or more, more preferably 5 or more. In particular, those having a thermal conductivity of 20 to 30 W / m·K and a new Mohs hardness of 5 to 10 are preferred. By using such a spherical filler in combination with the BN agglomerated powder of the present invention, the adhesion of the obtained heat dissipation sheet to the metal and the heat dissipation performance can be enhanced.

[0112] Here, "spherical" means anything that is generally recognized as spherical. For example, the average circularity of 0.4 or more may be regarded as spherical, and 0.6 or more may be regarded as spherical. Usually, the upper limit of the average circularity is 1. The circularity can be measured by image processing of its projection image, and can be measured, for example, with the FPIA series of Sysmex Corporation. The spherical filler is preferably at least one selected from the group consisting of alumina, synthetic magnesite, crystalline silica, aluminum nitride, silicon nitride, silicon carbide, zinc oxide, and magnesium oxide. By using these preferred spherical fillers, the heat dissipation performance of the obtained heat dissipation sheet can be further enhanced.

[0113] The average particle diameter (D50) of the spherical filler is preferably in the range of 0.5 μm or more and 40 μm or less. When the average particle diameter (D50) is 0.5 μm or more, the resin and the filler can easily flow during heat molding, and it is considered that the interfacial adhesive force in the heat dissipation sheet can be increased. Further, when the average particle diameter (D50) is 40 μm or less, it becomes easier to maintain the dielectric breakdown characteristics of the heat dissipation sheet.

[0114] As other inorganic fillers, those having electrical insulation properties can be used, and examples include at least one kind of particles selected from the group consisting of carbon, metal carbides, metal oxides, and metal nitrides. Examples of carbon include diamond. Examples of metal carbides include silicon carbide, titanium carbide, tungsten carbide, etc. Examples of metal oxides include magnesium oxide, aluminum oxide, silicon oxide, calcium oxide, zinc oxide, yttrium oxide, zirconium oxide, cerium oxide, ytterbium oxide, sialon (ceramics composed of silicon, aluminum, oxygen, and nitrogen), etc. Examples of metal nitrides include boron nitride, aluminum nitride, silicon nitride, etc., other than the BN aggregated particles of the present invention.

[0115] There is no limitation on the shape of other inorganic fillers, and they may be particulate, whisker-like, fibrous, plate-like, or aggregates thereof. These inorganic fillers may be surface-treated with a surface treatment agent. As the surface treatment agent, a known surface treatment agent can be used. These inorganic fillers may be used alone, or two or more kinds may be mixed and used in any combination and ratio.

[0116] The content of the inorganic filler in the composition of the present invention is preferably 30 wt% or more, more preferably 40 wt% or more, and still more preferably 50 wt% or more in 100 wt% of the composition of the present invention excluding the solvent. Further, it is preferably 99 wt% or less, more preferably 90 wt% or less, and still more preferably 80 wt% or less. When the content of the inorganic filler is equal to or higher than the above lower limit value, the effect of improving the thermal conductivity and the effect of controlling the linear expansion coefficient by containing the inorganic filler can be sufficiently obtained. Further, when it is equal to or lower than the above upper limit value, the moldability of the cured product and the interfacial adhesiveness in the composite body described later tend to be obtained.

[0117] When the BN agglomerated powder of the present invention and a spherical filler such as alumina are used in combination as the inorganic filler, the content ratio of the BN agglomerated powder of the present invention and the spherical filler in the composition of the present invention is not particularly limited, but the mass ratio is preferably 90:10 to 10:90, and more preferably 80:20 to 20:80. In order to effectively obtain the effect of using the BN agglomerated powder of the present invention, it is preferable that 30 wt% or more, particularly 40 wt% or more of the inorganic filler used is the BN agglomerated powder of the present invention. In the present invention, as the inorganic filler, it is preferable to use only the BN agglomerated powder of the present invention or only the BN agglomerated powder of the present invention and the above spherical filler.

[0118] <Manufacturing method of the composition of the present invention> The composition of the present invention can be obtained by uniformly mixing an inorganic filler containing the BN agglomerated powder of the present invention, a resin component such as a thermosetting resin, and other components added as necessary by stirring or kneading. For mixing, for example, general kneading apparatuses such as mixers, kneaders, single-screw or twin-screw kneaders can be used, and heating may be performed as necessary during mixing.

[0119] The mixing order of each compounding component is also arbitrary as long as there are no particular problems such as reactions or precipitates occurring. For example, a thermosetting resin component is mixed and dissolved in an organic solvent (for example, methyl ethyl ketone) to prepare a resin solution, and a mixture obtained by sufficiently mixing an inorganic filler and other components is added to the obtained resin solution and mixed. Then, after further adding an organic solvent for viscosity adjustment and mixing, further, a method of adding additives such as a curing agent, a curing accelerator, or a dispersant and mixing is mentioned.

[0120] 〔Heat dissipation sheet〕 A method for manufacturing the heat dissipation sheet of the present invention as a sheet-like cured product using the composition of the present invention will be described below. The sheet-like cured product can be manufactured by a commonly used method. For example, it can be obtained by forming the composition of the present invention into a sheet shape and curing it.

[0121] As the method for forming the composition of the present invention into a sheet shape, generally used methods can be used. For example, when the composition of the present invention has plasticity or fluidity, it can be formed by curing the composition in a desired shape, for example, in a state of being accommodated in a mold. In this case, injection molding, injection compression molding, extrusion molding, compression molding, and vacuum compression molding can be utilized.

[0122] The solvent in the composition of the present invention can be removed by known heating methods such as a hot plate, a hot air furnace, an IR heating furnace, a vacuum dryer, and a high-frequency heater. In addition, the sheet-like cured product can also be obtained by cutting out the cured product of the composition of the present invention into a desired shape. The sheet-like cured product can also be obtained by forming the slurry of the composition of the present invention (hereinafter sometimes referred to as "sheet slurry") into a sheet shape by a method such as a doctor blade method, a solvent casting method, or an extrusion coating method. An example of a method for manufacturing a sheet-like cured product using this sheet slurry will be described below.

[0123] <Coating step> First, a coating film is formed on the surface of the substrate with the sheet slurry. That is, using the sheet slurry, a coating film is formed on the substrate by a dipping method, a spin coating method, a spray coating method, a blade method, or any other method. For coating the sheet slurry, coating devices such as a spin coater, a slit coater, a die coater, and a blade coater can be used, and thereby, a coating film with a predetermined film thickness can be uniformly formed on the substrate. As the base material, copper foil or polyethylene terephthalate (PET) film described below is generally used, but it is not limited in any way.

[0124] <Drying process> The coating film formed by applying the slurry for the sheet is dried at a temperature of usually 10 to 150°C, preferably 25 to 120°C, more preferably 30 to 110°C, in order to remove the solvent and low molecular components. When the drying temperature is below the above upper limit value, the curing of the thermosetting resin in the slurry is suppressed, and the resin tends to flow in the subsequent pressing process, making it easier to remove voids. When the drying temperature is above the above lower limit value, the solvent can be effectively removed. The drying time is usually 5 minutes to 10 days, preferably 10 minutes to 3 days, more preferably 20 minutes to 1 day, and particularly preferably 30 minutes to 4 hours. When the drying time is above the above lower limit, the solvent can be sufficiently removed, and the residual solvent can be suppressed from becoming voids in the sheet-like cured product. When the drying time is below the above upper limit, the productivity tends to improve and the manufacturing cost can be suppressed.

[0125] <Pressing process> After the drying process, it is desirable to perform a pressing process for the purpose of joining inorganic fillers to form a heat path, eliminating voids and gaps in the sheet, and improving the adhesion to the base material. The pressing process applies a load of 10 kgf / cm or more to the dried film on the base material. 2 It is desirable to perform the pressing with a load of 20 kgf / cm or more. The load is preferably 20 kgf / cm or more, more preferably 50 kgf / cm or more. Also, it is preferably 2000 kgf / cm or less, more preferably 1000 kgf / cm, and even more preferably 800 kgf / cm. 2 2 2 2 2 ​​​​The following is the case. By setting the load during this pressurization to be equal to or less than the above upper limit, it is possible to obtain a sheet having high thermal conductivity without voids or the like in the sheet without breaking the secondary particles of the inorganic filler. Further, by setting the load to be equal to or greater than the above lower limit, the contact between the inorganic fillers becomes good and it becomes easier to form a heat conduction path, so that a sheet having high thermal conductivity can be obtained.

[0126] In the pressurization step, it is desirable to heat the dry film on the substrate at 25°C or higher. This heating temperature is preferably 40°C or higher, more preferably 50°C or higher, still more preferably 60°C or higher. Further, it is desirable to heat at 300°C or lower, preferably 250°C or lower, more preferably 200°C or lower, still more preferably 180°C or lower. By performing the pressurization step within this temperature range, the melt viscosity of the resin in the coating film can be reduced, and voids and gaps in the sheet can be eliminated. By being equal to or lower than the upper limit value of this temperature range, there is a risk that the organic components may decompose or the residual solvent may become vapor and form voids.

[0127] The time of the pressurization step is usually 30 seconds or longer, preferably 1 minute or longer, more preferably 3 minutes or longer, still more preferably 5 minutes or longer. Further, it is preferably 4 hours or shorter, more preferably 2 hours or shorter, still more preferably 1 hour or shorter, particularly preferably 45 minutes or shorter. By the pressurization time being equal to or lower than the above upper limit, the production time of the sheet-like cured product can be suppressed, and the production cost tends to be reduced. On the other hand, by being equal to or higher than the above lower limit, voids and gaps in the sheet-like cured product can be sufficiently removed, and the heat transfer performance and withstand voltage characteristics tend to be improved.

[0128] <Curing step> The curing step for completely performing the curing reaction may be performed under pressure or without pressure. However, when pressurizing, for the same reason as above, it is desirable to perform it under the same conditions as the above pressurization step. Note that the pressurization step and the curing step may be performed simultaneously. Particularly in the sheet forming step through the pressurization step and the curing step, it is preferable to apply a load within the above range and perform pressurization and curing.

[0129] There is no particular limitation on the thickness of the heat dissipation sheet of the present invention, which is a sheet-like cured product formed in this way, but it is preferably 50 μm or more, more preferably 100 μm or more. Also, it is preferably 400 μm or less, more preferably 300 μm or less. When the thickness of the heat dissipation sheet is equal to or greater than the above lower limit, withstand voltage characteristics can be obtained, and the breakdown voltage tends to improve. Also, when it is equal to or less than the above upper limit, miniaturization and thinning of the device can be achieved, and the thermal resistance of the obtained heat dissipation sheet tends to be suppressed.

[0130] 〔Composite molded body〕 The heat dissipation sheet of the present invention can be used as a composite molded body in which the heat dissipation sheet of the present invention and a metal part are laminated and integrated. In this case, the metal part may be provided on only one surface of the heat dissipation sheet of the present invention, or may be provided on two or more surfaces. For example, it may have a metal part on only one surface of the heat dissipation sheet of the present invention, or may have metal parts on both surfaces. Also, the metal part may be patterned.

[0131] Such a composite molded body can be manufactured by using the metal part as the above-mentioned base material and forming a sheet-like cured product composed of the composition of the present invention on this base material according to the above method. Also, it can be manufactured by peeling off the sheet-like cured product formed on a base material different from the metal part from the base material and then thermocompression bonding it onto a metal member serving as the metal part. In this case, after forming a sheet-like cured product composed of the composition of the present invention in the same manner as above except for coating it on a base material such as a PET film that may be treated with a release agent, this sheet-like cured product is peeled off from the base material, and this sheet-like cured product is placed on another metal plate, or integrated by pressing it in a state of being sandwiched between two metal plates.

[0132] In this case, as the metal plate, a metal plate having a thickness of about 10 to 10,000 μm made of copper, aluminum, nickel-plated metal, or the like can be used. The surface of the metal plate may be physically roughened or chemically treated with a surface treatment agent or the like. From the viewpoint of adhesion between the resin composition and the metal plate, it is more preferable that these treatments are performed.

[0133] 〔Semiconductor device〕 The semiconductor device of the present invention is one in which the heat dissipation sheet of the present invention is mounted as a heat dissipation substrate. Due to its high heat conduction and heat dissipation effect and withstand voltage characteristics, high output and high density can be achieved with high reliability. In the semiconductor device, members such as aluminum wiring, encapsulant, package material, heat sink, thermal paste, and solder other than the heat dissipation sheet of the present invention can be appropriately adopted from conventionally known members.

Examples

[0134] Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Note that the various conditions and values of the evaluation results in the following examples indicate the preferable ranges in the embodiments of the present invention. The preferable range of the present invention can be determined in consideration of the preferable ranges in the above-described embodiments and the ranges indicated by the values in the following examples or combinations of the values of the examples.

[0135] [Measurement conditions] The various characteristics and physical properties in the following examples and comparative examples were measured by the methods described below.

[0136] <Average particle diameter (D50) of BN agglomerated powder> BN agglomerated particles were dispersed in a pure water medium containing naphthalene sulfonate-formalin condensate as a dispersion stabilizer, and the volume-based particle size distribution was measured in a flow cell type of a laser diffraction / scattering particle size distribution measuring device LA-300 (manufactured by Horiba, Ltd.). The cumulative volume 50% particle diameter (average particle diameter (D50)) was determined from the obtained particle size distribution.

[0137] <Tap density of BN agglomerated powder> The BN agglomerated powder was put into a 10 ml graduated cylinder, and tapping was performed manually until the sample volume became constant. The tap density was calculated by dividing the weight of the sample by the volume after tapping. The above method was performed in accordance with JIS R1628 except for using a 10 ml graduated cylinder.

[0138] <DBP absorption amount and maximum torque value of BN agglomerated powder> In accordance with JIS-K-6217-4, using Asahi R & D Co., Ltd.'s S-500, the curve with the horizontal axis: DBP dropping amount (ml) and the vertical axis: torque (Nm) was measured, and the maximum torque (Nm) and DBP absorption amount (ml / 100g) were obtained from the resulting curve. The measurement conditions were a DBP dropping speed of 4 ml / min, a stirring blade rotation speed of 125 rpm, a sample input amount of 30 g, and the dropping amount at 70% of the maximum torque was used as the DBP absorption amount. For DBP, Wako Pure Chemical Industries, Ltd.'s special grade reagent (sales source code 021-06936) was used.

[0139] <Boron nitride purity of BN agglomerated powder> (Measurement of boron nitride purity by XPS) Using Shimadzu Corporation's photoelectron spectrometer "KRATOS ULTRA2", it was performed under the following conditions. · X-ray source: Monochromatic Al Kα, output 15 kV - 225 W · Analysis area: 700 μm × 300 μm · Take-off angle: 90° · Sample holding: Powder sample case supplied by the manufacturer · Quantification method: For B1s, C1s, N1s, O1s, Na1s, Ca2p, Mg1s, narrow spectra were measured. For the photoelectron peaks of each element, after performing linear method background removal processing, the area intensity was obtained, and the element concentration was calculated using the relative sensitivity correction coefficient provided by the device manufacturer. Note that ESCApe manufactured by Shimadzu Corporation was used as the analysis software.

[0140] (Preparation of samples for XRF analysis) Using a hydraulic press (manufactured by MAEKAWA TESTING MACHINE MFG. CO., LTD, BRIQUETING PRESS TYPE, M. No. 50), approximately 0.4 g of BN agglomerated powder was placed into a PVC ring with an inner diameter of 13 mm and a thickness of 5 mm, and it was pressure-molded under the conditions of 10 tf (ram diameter 129 mm) and 30 seconds.

[0141] (Measurement of boron nitride purity by XRF) Using a wavelength-dispersive X-ray fluorescence analyzer (ZSX100e manufactured by Rigaku Corporation), measurements were taken in a vacuum atmosphere under the conditions of a measurement diameter of 10 mm and with sample holder rotation, and the amount of impurities was quantified by the fundamental parameter method.

[0142] (Measurement of thermal conductivity) (Preparation of samples for thermal conductivity measurement) The sheet-shaped molded bodies obtained in the examples and comparative examples were pressed at 120 °C and 60 kgf / cm 2 for 40 minutes to obtain sheet-shaped cured products. Also, two, three, four, or five sheets of the sheet-shaped resin compositions obtained in the examples and comparative examples were stacked and pressed in the same manner as above to obtain five types of sheet-shaped cured products (heat dissipation sheets) with different thicknesses (thicknesses of approximately 150 μm, 300 μm, 450 μm, 600 μm, and 750 μm).

[0143] (Measurement of thermal conductivity) The thermal conductivity of the heat dissipation sheet was measured by the steady-state method (conforming to ASTM D5470) from the slope represented by the thermal resistance value with respect to the sheet thickness by measuring the thermal resistance values of five sheets with different thicknesses under the following apparatus and conditions. (1) Thickness: The thickness (μm) when the press pressure was 3400 kPa using T3Ster-DynTIM manufactured by Mentor Graphics (2) Measurement area: The area (cm 2 ) (3) Thermal resistance value: The thermal resistance value (K / W) when pressed at a pressing pressure of 3400 kPa using T3Ster-DynTIM manufactured by Mentor Graphics (4) Thermal conductivity: The thermal resistance values of five sheets with different thicknesses were measured, and the thermal conductivity (W / m·K) was calculated from the following formula. Formula: Thermal conductivity (W / m·K) = 1 / ((Slope (thermal resistance value / thickness): K / (W·μm)) × (Area: cm 2 )) × 10 -2

[0144] (Relative thermal conductivity) The relative thermal conductivity is the value obtained by dividing the thermal conductivity of the sheet-shaped molded body obtained in the examples and comparative examples by the thermal conductivity of the sheet-shaped molded body obtained in Comparative Example 5. That is, it is the relative value when the thermal conductivity of the sheet-shaped molded body obtained in Comparative Example 5 is set to 1.

[0145] [Preparation of BN agglomerated powder from BN slurry] The BN agglomerated powder was prepared by the following method. [Preparation of BN slurry] [Examples 1 to 3] Raw material h-BN powder (the half-value width of the (002) plane peak obtained by powder X-ray diffraction measurement is 2θ = 0.67°, total oxygen concentration = 7.5 wt%, specific surface area 116 m 2 / g, total pore volume 0.754 cm 3 / g): 10000 g Binder (「Taxelam M160L」manufactured by Taki Chemical Co., Ltd., solid content concentration 21 wt%): 11496 g Surfactant (surfactant 「Ammonium lauryl sulfate」manufactured by Kao Corporation, solid content concentration 14 wt%): 250 g

[0146] [Preparation of slurry] A predetermined amount of the raw material h-BN powder was weighed into a resin bottle, and then a predetermined amount of the binder was added. Further, after adding a predetermined amount of the surfactant, zirconia ceramic balls were added and stirred on a pot mill turntable for 1 hour to prepare a BN slurry.

[0147] [Granulation] Granulation from the BN slurry was carried out using a spray dryer P260 manufactured by Pulice Co., Ltd. at a disk rotation speed of 8000 - 20000 rpm and a drying temperature of 85°C.

[0148] <Production of BN Agglomerated Powder> After subjecting the above BN granulated powder to calcination (700°C, 5 hours), the powder after calcination was heat-treated at 1400°C - 2000°C under a nitrogen flow. The BN agglomerated powder used in Examples 1 - 3 was produced by the following procedure. Firing was carried out under a N2 flow using a vacuum firing furnace manufactured by Fuji Denpa Kogyo Co., Ltd. 30 g of the powder after calcination was filled into a BN crucible (with a lid, φ60 mm) and placed inside a BN inner crucible. The BN inner crucible was set in the vacuum firing furnace and heated at a heating rate of 1200°C / hr to the first firing temperature. Heat treatment was carried out for 2 hours at each desired firing temperature. After natural cooling, the samples were collected.

[0149] When re-firing was carried out, the sample once fired at the first treatment temperature was taken out, and 30 g of the powder after the first firing was newly filled into the crucible (with a lid, φ60 mm) described in Table 1 and then placed inside a BN inner crucible. The BN inner crucible was set in the vacuum firing furnace and heated at a heating rate of 1200°C / hr up to 2000°C under a N2 flow. Then, heat treatment was carried out at 2000°C for 2 hours. After natural cooling, the samples were collected. The production conditions of the BN agglomerated powder were summarized in Table 1. It was confirmed by SEM observation that the BN agglomerated powder in Examples 1 - 3 is all an aggregate of BN agglomerated particles having a card house structure.

[0150] <Comparative Examples 1 - 3> The following BN agglomerated powder was used as a comparison target. Comparative Example 1: "PT350" manufactured by Momentive Comparative Example 2: "PT620" manufactured by Momentive Comparative Example 3: "PTX60" manufactured by Momentive

[0151] For the BN agglomerated powders of Examples 1 to 3 and Comparative Examples 1 to 3, a graph created with the horizontal axis: average particle diameter (D50) (μm) and the vertical axis: DBP absorption (ml) is shown in FIG. 1. As shown in FIG. 1, the BN agglomerated powders obtained in Examples 1 to 3 satisfy the above relational expression: A ≥ DBP absorption ≥ B.

[0152] [Table 1]

[0153] [Production and Evaluation of Sheet Molding] In the following Examples and Comparative Examples, the BN agglomerated powders obtained above were each used as an inorganic filler, and a resin composition containing the BN agglomerated powder was prepared by the following method, and a sheet molding was produced.

[0154] [Preparation of Resin Composition Containing BN Agglomerated Powder] The raw materials used are as follows. (Thermosetting Resin Component) · Resin Component 1: A specific epoxy resin produced according to the production method of the epoxy resin disclosed in the examples of JP-A-2006-176658, having structure (2) (R 3 = group represented by structural formula (4)) and structure (3) (R 4 , R 5 , R 6 , R 7 = methyl group) Weight average molecular weight in terms of polystyrene: 30,000 Epoxy equivalent: 9,000 g / equivalent · Resin Component 2: Bisphenol A type liquid epoxy resin manufactured by Mitsubishi Chemical Corporation · Resin Component 3: A polyfunctional epoxy resin manufactured by Nagase ChemteX Corporation and containing a structure having 4 or more glycidyl groups per molecule

[0155] (Inorganic Filler Component) · Inorganic Filler 1: BN agglomerated powder obtained in each example · Inorganic Filler 2: Spherical alumina particles manufactured by Admatechs Co., Ltd. New Mohs hardness: 9 Volume average particle diameter (D50): 6.5 μm Thermal conductivity: 20 - 30 W / m·K

[0156] (Hardener component) · Hardener 1: "MEH - 8000H" manufactured by Meiwafosis Co., Ltd. Phenolic resin - based hardener

[0157] (Hardening catalyst component) · Hardening catalyst 1: "2E4MZ - A" manufactured by Shikoku Kasei Co., Ltd. 2,4 - Diamino - 6 - [2’ - ethyl - 4’ - methylimidazolyl - (17’)] - ethyl - s - triazine (having both a structure derived from imidazole and a structure derived from triazine in one molecule) Molecular weight: 247 Physical properties: Solid Melting point: 215 - 225 °C · Hardening catalyst 2: "2PHZ - PW" manufactured by Shikoku Kasei Co., Ltd. 2 - Phenyl - 4,5 - dihydroxymethylimidazole Molecular weight: 204 Physical properties: Solid Melting point: dec. 230, so the melting point is 230 °C or higher

[0158] <Example 4> Using a planetary stirrer, a mixture was prepared such that resin component 1: 6.3 wt%, resin component 2: 10.2 wt%, resin component 3: 5.1 wt%, hardener 1: 3.5 wt%, hardening catalyst 1: 0.25 wt%, hardening catalyst 2: 0.25 wt%, inorganic filler 1 (BN agglomerated powder obtained in Example 1): 54.1 wt%, inorganic filler 2: 20.3 wt%. Also, when preparing the above mixture, methyl ethyl ketone and cyclohexanone were each used at 18.6 wt% so that the above mixture would be 62.8 wt% (solid content concentration) of the coating slurry.

[0159] The obtained coating slurry (sheet - forming slurry) was applied to a PET - based substrate by the doctor - blade method, and after heating and drying at 60 °C for 120 minutes, it was at 42 °C, 1500 kgf / cm 2Press for 10 minutes to obtain a sheet-shaped molded body with a thickness of 150 μm. The total content of methyl ethyl ketone and cyclohexanone in the sheet-shaped molded body was 1 wt% or less. The average particle diameter (D50), tap density, and DBP absorption amount of the BN agglomerated particles constituting the used BN agglomerated powder are shown in Table 2. The relative thermal conductivity of the sheet-shaped molded body obtained using the BN agglomerated powder is also shown in Table 2.

[0160] <Examples 5 to 6, Comparative Examples 4 to 5> Table 2 shows the evaluation results of sheet-shaped molded bodies prepared by changing only the BN agglomerated powder according to the method of Example 4 to those shown in Table 2.

[0161] <Comparative Example 6> Table 2 shows the evaluation results of sheet-shaped molded bodies prepared according to the method of Example 4 except that the BN agglomerated powder was changed to that shown in Table 2 and the solid content concentration of the mixture in the coating slurry was changed to 55.0 wt%.

[0162]

Table 2

[0163] From Table 2, it can be seen that when comparing fillers with the same average particle diameter (D50), high heat dissipation characteristics can be obtained when using the filler of the present invention. Therefore, by using the BN agglomerated powder in the first aspect where the average particle diameter (D50), tap density, and DBP absorption amount are in a specific range, or the BN agglomerated powder in the second aspect where the value obtained by dividing the DBP absorption amount, average particle diameter (D50), and DBP absorption amount by the maximum torque value and the average particle diameter (D50) is in a specific range, a heat dissipation sheet excellent in heat dissipation characteristics can be realized, especially on the small particle size side.

Claims

1. A boron nitride agglomerated powder containing hexagonal boron nitride agglomerated particles, having an average particle diameter (D50) of 10 μm or more and 100 μm or less, a tap density of 0.5 g / cc or more and 1.0 g / cc or less, and a DBP absorption amount [ml / 100 g] calculated by measurement in accordance with JIS-K-6217-4 satisfying the following relational expression. Relational expression: A ≥ DBP absorption amount ≥ B A: A numerical value obtained by substituting the average particle diameter (D50) into the relational expression A = -1.2 × D50 + 180 B: A numerical value obtained by substituting the average particle diameter (D50) into the relational expression B = -0.6 × D50 + 110 However, D50 is 10 μm or more and 100 μm or less.

2. A boron nitride agglomerated powder containing hexagonal boron nitride agglomerated particles, having a DBP absorption amount calculated by measurement in accordance with JIS-K-6217-4 of 50 ml / 100 g or more and less than 170 ml / 100 g, a maximum torque value calculated by measurement in accordance with JIS-K-6217-4 of 0.010 Nm or more and 1.000 Nm or less, an average particle diameter (D50) of 10 μm or more and 100 μm or less, and a value obtained by dividing the DBP absorption amount by the maximum torque value and the average particle diameter (D50) (DBP absorption amount / maximum torque value / D50) of 11.0 [ml / (100 g·Nm·μm)] or more and 100 [ml / (100 g·Nm·μm)] or less.

3. The boron nitride agglomerated powder according to claim 1 or 2, wherein the hexagonal boron nitride agglomerated particles have a card house structure.

4. The boron nitride agglomerated powder according to claim 1 or 2, having a boron nitride purity measured by XPS of 97.0 wt% or more and 99.0 wt% or less, and a boron nitride purity measured by XRF of 95.0 wt% or more.

5. A resin composition containing the boron nitride agglomerated powder according to claim 1 or 2.

6. A heat dissipation sheet made of the resin composition according to claim 5.

7. A semiconductor device including the heat dissipation sheet according to claim 6.

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