WO2015119198A1 - 窒化ホウ素凝集粒子、窒化ホウ素凝集粒子の製造方法、該窒化ホウ素凝集粒子含有樹脂組成物、成形体、及びシート - Google Patents
窒化ホウ素凝集粒子、窒化ホウ素凝集粒子の製造方法、該窒化ホウ素凝集粒子含有樹脂組成物、成形体、及びシート Download PDFInfo
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Definitions
- the present invention relates to boron nitride aggregated particles (hereinafter referred to as “BN aggregated particles”) and a method for producing the particles, and more specifically, boron nitride primary particles (hereinafter referred to as “BN primary particles”) are aggregated.
- BN aggregated particles boron nitride primary particles
- the present invention relates to BN aggregated particles and a method for producing the same.
- the present invention also relates to a BN aggregated particle-containing resin composition containing the BN aggregated particles and a molded body formed by molding the BN aggregated particle-containing resin composition.
- the present invention also relates to a sheet containing specific BN primary particles in a specific state.
- Boron nitride (hereinafter referred to as “BN”) is an insulating ceramic, and includes various materials such as c-BN having a diamond structure, h-BN having a graphite structure, ⁇ -BN having a turbulent structure, and ⁇ -BN. Crystal forms are known.
- h-BN has the same layered structure as graphite, has a feature that it is relatively easy to synthesize and has excellent thermal conductivity, solid lubricity, chemical stability, and heat resistance. Therefore, it is widely used in the field of electrical and electronic materials.
- h-BN is insulating, it has attracted attention as such a heat conductive filler for a heat radiating member, taking advantage of its high thermal conductivity.
- h-BN has a plate-like particle shape and exhibits high thermal conductivity in the plate surface direction (in the ab plane or (002) plane) (usually about 400 W / mK as thermal conductivity).
- the plate thickness direction C-axis direction
- the plate-shaped h-BN is orientated in the plate surface direction of the molded body, which is the flow direction of the BN particle-containing resin composition during molding.
- the thermal conductivity is excellent in the surface direction, there is a problem that only the low thermal conductivity is shown in the thickness direction.
- h-BN has a shape other than the scale-like shape with little orientation as described above.
- Agglomerated particles have been investigated. Examples of such h-BN agglomerated particles include h-BN agglomerated particles granulated by spray drying or the like, and h-BN agglomerated particles produced by sintering h-BN and pulverizing a sintered body. (Patent Documents 1 and 2). Further, h-BN aggregated particles produced from a mixture of boric acid and melamine, and pine cone-shaped h-BN aggregated particles in which primary particles are aggregated without being oriented have been proposed (Patent Document 3).
- a conventional BN aggregated particle As a use of such a conventional BN aggregated particle, it is known to be used for a heat dissipation sheet required for a power semiconductor device or the like, but in order to reduce the contact resistance between the BN aggregated particles, a certain pressure is used. Since the molding underneath is required, the BN aggregated particles are collapsed by the pressure, and the primary particles are oriented in the direction of the molding surface. As a result, the heat conduction in the direction perpendicular to the molding surface is low, reaching the practical level. The current situation is not.
- BN aggregated particles capable of imparting high thermal conductivity in the vertical direction of the heat-dissipating sheet even under a constant pressure are desired, and further development of aggregated particles in which the BN aggregated particles themselves have high thermal conductivity is desired.
- Patent Document 4 discloses that the specific surface area is 10 m 2 / g or more, the total pore volume is 2.15 cm 3 / g or less, and the surface of the boron nitride aggregated particles has an average particle diameter of 0.05 ⁇ m or more and 1 ⁇ m or less. Boron nitride aggregated particles composed of boron nitride primary particles are described, and h-BN aggregated particles having a card house structure are disclosed. Although the boron nitride agglomerated particles described in Patent Document 4 have improved disintegration resistance, the particle size of the agglomerated particles is small, and further improvements are required in terms of relatively heat conduction and withstand voltage.
- Patent Document 5 In addition to improving the performance of the BN aggregated particles in this way, for example, in Patent Document 5, as a result of containing two kinds of secondary aggregates having different average major axes of primary particles at a specific ratio, Compositions containing secondary aggregates and small secondary aggregate inorganic fillers are disclosed. Patent Document 6 discloses a composition of a flat filler and a particulate filler. However, in Patent Documents 5 and 6, the strength of the particles themselves is insufficient, and the heat conduction and withstand voltage have not yet reached the practical level.
- a conventional BN aggregated particle As a use of such a conventional BN aggregated particle, it is widely known to be used for a heat dissipation sheet required for a power semiconductor device or the like, and obtained using a composition containing the BN aggregated particle or the composition. A compact is applied. From the viewpoint of the use, it is desired that the composition or the molded body has high thermal conductivity and high withstand voltage performance. In order to achieve these performances, it is necessary to reduce voids and contact resistance between BN aggregated particles. However, in order to reduce the contact resistance between the BN aggregated particles, since molding under a certain pressure is required, the BN aggregated particles are collapsed by the pressure, and the primary particles are oriented in the molding surface direction.
- the interface between the primary particles constituting the BN aggregated particles and the low crystallinity of the primary particles are one of the causes of decreasing the heat conduction of the BN aggregated particles. It has been found that That is, it was considered that these causes were due to scattering of phonons, which are responsible for heat conduction, at the primary particle interface and the crystal grain boundaries in the primary particles.
- the contact resistance between the aggregated particles can be reduced to some extent by increasing the BN aggregated particles, but the orientation of the BN primary particles constituting the BN aggregated particles is It has been found that the contact resistance between the BN aggregated particles is increased and the thermal conductivity is lowered. That is, in order to improve the thermal conductivity of the molded body, the orientation of the BN primary particles constituting the BN aggregated particles is controlled to reduce the contact resistance between the BN aggregated particles, and the BN constituting the BN aggregated particles. It was considered effective to increase the crystallinity of the primary particles and further reduce the grain boundaries in the BN primary particles constituting the BN aggregated particles.
- the present invention solves the above-mentioned conventional problems, produces BN aggregated particles in which the BN primary particles constituting the BN aggregated particles have high thermal conductivity, and also has reduced contact resistance between the BN aggregated particles.
- An object of the present invention is to provide a BN aggregated particle excellent in applicability to the present invention and a method for producing the same.
- Another object of the present invention is to provide a BN aggregated particle-containing resin composition containing the BN aggregated particles and a resin, and a molded body obtained by molding the BN aggregated particle-containing resin composition.
- Another object of the present invention is to further develop the above knowledge and provide a sheet having high thermal conductivity and high voltage resistance.
- the inventors have made the average crystallite diameter in the BN primary particles constituting the BN aggregated particles large by making the raw material slurry viscosity within a specific range when producing the BN aggregated particles. I found out that By increasing the average crystallite diameter, the grain boundary between the crystallites in the primary particles was reduced, and as a result, the thermal conductivity of the BN aggregated particles was successfully improved. Further surprisingly, the BN aggregated particles thus prepared have a specific crystal plane of the BN primary particles constituting the BN aggregated particles, and therefore, when the BN aggregated particles are used to form a molded body. As a result, it has been found that it is possible to produce a molded product having higher thermal conductivity than conventional BN aggregated particles, and the present invention has been completed.
- the first gist of the present invention is the following (a-1) to (a-13).
- (A-1) Boron nitride aggregated particles (hereinafter referred to as “BN aggregated particles”) obtained by agglomerating primary boron nitride particles (hereinafter referred to as “BN primary particles”), and a 10 mm ⁇ powder tablet molding machine
- the peak area intensity ratio between the (100) plane and the (004) plane of BN primary particles obtained by powder X-ray diffraction measurement of a pellet-like sample obtained by molding at a molding pressure of 0.85 ton / cm 2 ((100) / (004)) is 0.25 or more, and the BN aggregated particles are filled in a 0.2 mm deep glass sample plate so that the surface is smooth, and powder X-ray diffraction measurement is performed.
- the obtained BN aggregated particles wherein the average crystallite size of the BN primary particles obtained from the (002) plane peak of the BN primary particles is 375 mm or more.
- A-2 The BN aggregated particles according to (a-1), wherein the BN aggregated particles have an average particle diameter D 50 of 26 ⁇ m or more.
- A-3) The BN aggregated particles according to (a-1) or (a-2), wherein the specific surface area of the BN aggregated particles is 8 m 2 / g or less.
- A-4) The BN aggregated particles according to any one of (a-1) to (a-3), wherein the BN aggregated particles are spherical.
- A-5) The BN aggregated particles according to any one of (a-1) to (a-4), wherein the BN aggregated particles have a card house structure.
- a BN aggregated particle composition which is a mixture of the BN aggregated particles according to any one of (a-1) to (a-5) and other fillers.
- a BN aggregated particle-containing resin composition comprising (a-7) a resin and the BN aggregated particles according to any one of (a-1) to (a-5).
- A-8) A molded article comprising the BN aggregated particles according to any one of (a-1) to (a-5).
- a method for producing BN aggregated particles comprising a step of granulating a raw material boron nitride powder slurry (hereinafter referred to as “BN slurry”) and a heat treatment step, In the granulation step, the BN slurry has a viscosity of 200 mPa ⁇ s or more and 5000 mPa ⁇ s or less, and in the heating step, heat treatment is performed at 1800 ° C. or more and 2300 ° C. or less.
- A-10) The method for producing BN aggregated particles according to (a-9), wherein the oxygen concentration in the raw material boron nitride powder is 1% by mass or more and 10% by mass or less.
- A-11 BN aggregated particles obtained by the production method described in (a-9) or (a-10).
- BN aggregated particles a sheet containing boron nitride aggregated particles (hereinafter referred to as “BN aggregated particles”), Peak intensity ratio of (100) plane to (004) plane of boron nitride primary particles (hereinafter referred to as “BN primary particles”) in the sheet obtained by X-ray diffraction measurement of the sheet ((100) / (004)) is 1.0 or more, and the average crystallite diameter of the BN primary particles obtained from the (002) plane peak of the BN primary particles in the sheet obtained by X-ray diffraction measurement of the sheet is A sheet characterized by being 375 mm or more.
- Peak area intensity ratio ((100) of (100) plane and (004) plane of boron nitride primary particles (hereinafter referred to as “BN primary particles”) in the sheet obtained by X-ray diffraction measurement of the sheet. / (004)) is a sheet according to (a-12), which is 0.6 or more.
- the second gist of the present invention is the following (b-1) to (b-10).
- (B-1) A composition comprising boron nitride aggregated particles (A) obtained by agglomerating primary boron nitride particles and inorganic particles (B), wherein at least the boron nitride aggregated particles (A) have a card house structure.
- the volume average particle diameter of the boron nitride agglomerated particles (a) (D 50) is not less 25 ⁇ m or more, and the volume of the volume average particle diameter of the boron nitride agglomerated particles (a) (D 50)> inorganic particles (B)
- the boron nitride aggregated particles (A) have a card house structure, and the volume average particle diameter (D 50 ) of the boron nitride aggregated particles (A) and the inorganic particles satisfies the above relationship. Phonon scattering generated at the crystal grain boundaries in the BN primary particles constituting the aggregated particles can be reduced, and as a result, high thermal conductivity is exhibited.
- (B-2) A composition comprising boron nitride aggregated particles (A) formed by agglomeration of boron nitride primary particles and inorganic particles (B), wherein the boron nitride aggregated particles (A) are measured by powder X-ray diffraction measurement.
- the peak intensity ratio ((100) / (004)) between the (100) plane and the (004) plane of the boron nitride primary particles obtained in this way is 3 or more, and the boron nitride primary particles are obtained from the (002) plane peak.
- the boron nitride aggregated particle-containing composition, wherein the boron nitride primary particles have an average crystallite size of 375 mm or more.
- the composition maintains the orientation of the specific crystal plane of the BN primary particles, that is, the peak intensity ratio ((100) / (004)) between the (100) plane and the (004) plane by powder X-ray diffraction measurement. Since the average crystallite diameter is maintained at 3 or more, the molded product when combined with the resin exhibits high thermal conductivity in addition to high thermal conductivity as aggregated particles.
- the volume average particle diameter of the boron nitride agglomerated particles (A) (D 50) is not less 25 ⁇ m or more and a volume average particle diameter (D 50) of the boron nitride agglomerated particles (A)> inorganic particles (B).
- the content ratio of the boron nitride aggregated particles (A) is 30 to 95% by mass with respect to the total of the boron nitride aggregated particles (A) and the inorganic particles (B).
- the inorganic particles (B) are at least one selected from the group consisting of boron nitride, aluminum nitride, alumina, zinc oxide, magnesium oxide, beryllium oxide, and titanium oxide (b-1) to (b- 5)
- B-7 A coating solution comprising the boron nitride aggregated particle-containing composition according to any one of (b-1) to (b-6).
- B-8) A molded article obtained by molding the boron nitride aggregated particle-containing composition according to any one of (b-1) to (b-6).
- Peak intensity ratio between (100) plane and (004) plane of boron nitride primary particles obtained by X-ray diffraction measurement of a sheet containing boron nitride aggregated particles (A) ((100) / (004)) is 1.0 or more and / or the peak area intensity ratio ((100) / (004)) is 0.6 or more.
- B-10 Further, the average crystallite diameter of the boron nitride aggregated particles obtained from the (002) plane peak of the BN primary particles in the sheet obtained by X-ray diffraction measurement of the sheet is 300 mm or more.
- the BN aggregated particles of the present invention have a peak intensity ratio ((100) / (004)) between the (100) plane and (004) plane of the BN primary particles constituting the BN aggregated particles obtained by powder X-ray diffraction measurement. Since it is 3 or more, the specific crystal plane of the BN primary particles constituting the BN aggregated particles is oriented, and the BN obtained from the (002) plane peak of the BN primary particles in the powder X-ray diffraction measurement of the BN aggregated particles Since the average crystallite diameter of the primary particles is 375 mm or more, phonon scattering generated at the crystal grain boundaries in the BN primary particles constituting the BN aggregated particles can be reduced, and as a result, high thermal conductivity is exhibited.
- the peak area intensity ratio ((100) / (004)) between the (100) face and the (004) face of the BN primary particles is 0.25 or more.
- the orientation of a specific crystal plane of the BN primary particles constituting the BN aggregated particles is maintained even after molding. Therefore, it exhibits high thermal conductivity in the direction perpendicular to the molding surface (molded body thickness direction), and is very useful for a heat-dissipating sheet that is preferably used in power semiconductor devices and the like.
- SEM scanning electron microscope
- the BN aggregated particles of the present invention are formed by aggregation of BN primary particles, and may contain components other than the BN primary particles as long as the effects of the present invention are not impaired.
- components other than the BN primary particles include components derived from a binder, a surfactant, and a solvent that may be added to the slurry, which will be described later in [Method for producing BN aggregated particles].
- the form of the BN aggregated particles of the present invention is not particularly limited, but preferably has a spherical form as shown in FIG. 1, and the form of the BN aggregated particles can be confirmed by SEM.
- spherical means that the aspect ratio (ratio of major axis to minor axis) is 1 or more and 2 or less, preferably 1 or more and 1.5 or less.
- the aspect ratio of the BN aggregated particles of the present invention is determined by arbitrarily selecting 200 or more particles from an image taken with an SEM, obtaining the ratio of the major axis to the minor axis, and calculating the average value.
- the BN aggregated particles are a sea urchin-like form in which the crystals of BN primary particles grow radially from the center side to the surface side of the BN aggregated particles, and the BN primary particles are platelets. Is preferably a sea urchin-like spherical form that is sintered and agglomerated.
- the BN aggregated particles preferably have a card house structure.
- the card house structure is, for example, ceramic 43 No. 2 (issued by the Ceramic Society of Japan in 2008), and has a structure in which plate-like particles are laminated in a complicated manner without being oriented.
- the BN aggregated particles having a card house structure are aggregates of BN primary particles, and have a structure in which the flat surface portion and the end surface portion of the primary particles are in contact (see FIG. 3). Particles, preferably spherical. Moreover, it is preferable that the card house structure is the same structure also inside the particle. The aggregation form and internal structure of these BN aggregated particles can be confirmed by a scanning electron microscope (SEM).
- the BN primary particles constituting the BN aggregated particles have specific physical properties, and will be described in detail below.
- the sample (powder) used for the physical property measurement specified in this specification may be a BN aggregated particle powder before being molded into a molded body, or taken out of a molded body or molded body containing BN aggregated particles.
- BN aggregated particle powder may be used.
- it is a BN aggregated particle powder before being formed into a molded body.
- the major axis of the BN primary particles constituting the BN aggregated particles is usually 0.5 ⁇ m or more, preferably 0.6 ⁇ m or more, more preferably 0.8 ⁇ m or more, still more preferably 1.0 ⁇ m or more, particularly Preferably it is 1.1 micrometers or more. Moreover, it is 10 micrometers or less normally, Preferably it is 5 micrometers or less, More preferably, it is 3 micrometers or less.
- the major axis is the maximum length of BN primary particles that can be observed on an image of the BN primary particles constituting one BN aggregated particle by enlarging one BN aggregated particle obtained by SEM measurement. The average value.
- the crystal structure of the BN primary particles is not particularly limited, but those containing hexagonal h-BN as a main component in terms of ease of synthesis and thermal conductivity. preferable.
- inorganic components other than BN are contained as a binder, they crystallize in the process of heat processing, but BN should just be contained as a main component.
- the crystal structure of the BN primary particles can be confirmed by powder X-ray diffraction measurement.
- the average crystallite diameter of BN primary particles obtained from the (002) plane peak of BN primary particles obtained by powder X-ray diffraction measurement of BN aggregated particles is not particularly limited.
- a large average crystallite size is preferable from the viewpoint of thermal conductivity.
- it is usually at least 300 mm, preferably at least 320 mm, more preferably at least 375 mm, more preferably at least 380 mm, even more preferably at least 390 mm, particularly preferably at least 400 mm, usually at most 5000 mm, preferably at most 2000 mm, further Preferably it is 1000 mm or less.
- the average crystallite diameter is too large, the BN primary particles grow too much, so that there are more gaps in the BN aggregated particles, the moldability when forming a molded body is deteriorated, and the heat conduction is increased by increasing the gaps. Tend not to improve. If the average crystallite diameter is too small, the number of grain boundaries in the BN primary particles increases, so that phonon scattering occurs at the grain boundaries and the thermal conductivity tends to be low.
- the powder X-ray diffraction measurement is performed by filling BN aggregated particles with a 0.2 mm deep glass sample plate with a smooth surface.
- the “average crystallite diameter” is a crystallite obtained by the Scherrer equation as described in Examples below from the (002) plane peak of BN primary particles obtained by powder X-ray diffraction measurement. Is the diameter.
- Powder BN aggregated particles before being formed into a molded body such as a sheet are filled in a 0.2 mm deep glass sample plate so that the surface is smooth, and powder X-ray diffraction measurement is performed.
- the peak intensity ratio ((100) / (004)) between the (100) plane and the (004) plane of the BN primary particles obtained in this way is 3 or more.
- the peak intensity ratio between the (100) plane and the (004) plane of the BN aggregated particles is usually 3 or more, preferably 3.2 or more, more preferably 3.4 or more, still more preferably 3.5 or more, and usually 10 or less. , Preferably 8 or less, more preferably 7 or less.
- the peak intensity ratio can be calculated from the intensity ratio of the corresponding peak intensity measured by powder X-ray diffraction measurement.
- BN primary particles Obtained by powder X-ray diffraction measurement of a pellet-like sample obtained by molding BN aggregated particles with a 10 mm ⁇ powder tablet molding machine at a molding pressure of 0.85 ton / cm 2.
- the BN primary particles can be expressed even if the peak area intensity ratio ((100) / (004)) between the (100) plane and the (004) plane is 0.25 or more.
- This peak area intensity ratio ((100) / (004)) is preferably 0.3 or more, preferably 0.5 or more, more preferably 0.7 or more, still more preferably 0.81 or more, and particularly preferably 0. .85 or more, particularly preferably 0.91 or more.
- the upper limit is not particularly limited, but is usually 10.0 or less, preferably 5.0 or less, more preferably 4.0 or less, still more preferably 2.0 or less, and particularly preferably 1.6 or less. It is.
- BN in a pellet-like sample obtained by molding BN aggregated particles with a molding tablet of 10 mm ⁇ at a molding pressure of 0.85 ton / cm 2 or more and 2.54 ton / cm 2 or less is usually 0.25 or more, preferably 0.30 or more, more preferably It is 0.35 or more, more preferably 0.40 or more, usually 2.0 or less, preferably 1.5 or less, more preferably 1.2 or less. If it is too large, the contact resistance between the BN aggregated particles tends to increase when formed into a molded product, and if it is too small, the BN aggregated particles tend to collapse and the thermal conductivity in the thickness direction does not tend to improve.
- the optimum press pressure condition for a heat radiating sheet or the like varies depending on the type of heat radiating sheet.
- the BN agglomerated particles dispersed in the resin matrix are exposed to pressure conditions depending on the application, but usually the BN particles tend to have an ab plane oriented in a direction perpendicular to the pressure direction. Even when BN aggregated particles are used, particle deformation occurs with respect to the molding pressure, and as a result, the ab surface tends to be oriented in a direction perpendicular to the pressure direction.
- high heat dissipation substrate made of resin for complete contact of BN agglomerated grains obtained by void reduction and dispersion of the internal resin substrate, 0.85ton / cm 2 or more 2.54ton / cm 2 or less, such as It is thought that it is molded at a relatively high pressure. For this reason, BN aggregated particles with little change in the orientation of BN primary particles even in the above pressure range are necessary for improving the thermal conductivity.
- the BN aggregated particles satisfying the physical properties defined in the present specification preferably the BN primary particles constituting the BN aggregated particles are in a card house structure, that is, the BN primary particles are in contact with each other at the primary particle plane portion and the end surface portion. Therefore, it is possible to suppress the deformation of the BN aggregated particles in a wide molding pressure range.
- the optimum pressure range varies depending on the application, in order to achieve high thermal conductivity in the thickness direction of the molded body, primary particle orientation is at least a certain level in the range of 0.85 ton / cm 2 to 2.54 ton / cm 2. Is preferably achieved.
- the primary particle orientation above a certain level is expressed by, for example, the peak area intensity ratio ((100) / (004)) between the (100) plane and the (004) plane of the primary particle.
- This expresses how much the ab plane is oriented in the direction orthogonal to the pressure direction. Therefore, the larger the above-described peak area intensity ratio, the less deformation of the BN aggregated particles due to the molding pressure.
- it is considered necessary that at least the peak area intensity ratio is 0.25 or more.
- the lower limit and upper limit of the peak area intensity ratio are as described above.
- the peak area intensity ratio in the range of 0.85 ton / cm 2 or more and 2.54 ton / cm 2 has no problem if it satisfies a predetermined numerical value even at one point in the pressure range, and it is necessary to achieve it in the entire pressure range of the present invention. Absent. Also, preferably, 0.85ton / cm 2, 1.69ton / cm 2, to meet the predetermined numerical at three points 2.54ton / cm 2.
- the above peak area intensity ratio is obtained by filling a tablet machine (10 mm ⁇ ) with about 0.2 g of powder and using a manual hydraulic pump (P-1B-041 manufactured by Riken Seiki Co., Ltd.) at various press pressures.
- a tablet-shaped sample is used for measurement (for example, 0.85 ton / cm 2 , 1.69 ton / cm 2 , 2.54 ton / cm 2, etc.).
- the measurement can be carried out using an X'Pert Pro MPD powder X-ray diffractometer manufactured by The Netherlands PANalytical, and the intensity ratio of the corresponding peak area can be calculated.
- the average particle diameter (D 50 ) of the BN aggregated particles is usually 5 ⁇ m or more, preferably 10 ⁇ m or more, more preferably 25 ⁇ m or more, further preferably 26 ⁇ m or more, particularly preferably 30 ⁇ m or more, and most preferably 40 ⁇ m or more. Yes, even if it is 45 ⁇ m or more, it is preferable even if it is 50 ⁇ m or more. Moreover, it is 200 micrometers or less normally, Preferably it is 150 micrometers or less, More preferably, it is 100 micrometers or less.
- D 50 means the particle diameter when the cumulative volume is 50% when the cumulative curve is drawn with the volume of the powder subjected to measurement as 100%, and the measurement method is a wet measurement method.
- the breaking strength of the BN aggregated particles is usually 2.5 MPa or more, preferably 3.0 MPa or more, more preferably 3.5 MPa or more, still more preferably 4.0 MPa or more, usually 20 MPa or less, preferably 15 MPa or less. More preferably, it is 10 MPa or less. If the particle size is too large, the strength of the particles is too strong, so that the surface smoothness tends to deteriorate when formed into a molded product, and the thermal conductivity tends to decrease. It tends to be deformed and the thermal conductivity tends not to improve.
- the breaking strength can be calculated by the following equation by compressing one particle according to JIS R 1639-5. Usually, 5 or more particles are measured, and the average value is adopted.
- Cs 2.48P / ⁇ d 2
- Cs fracture strength (MPa)
- N Destructive test force (N)
- d Particle diameter (mm)
- the total pore volume of the BN aggregated particles is usually 2.2 cm 3 / g or less.
- a particle having a small total pore volume has a dense BN aggregated particle, so that it is possible to reduce the boundary surface that hinders heat conduction, resulting in a BN aggregated particle having higher thermal conductivity. If the total pore volume of the BN aggregated particles is too large, when used as a filler in the composition, the resin may be taken into the pores and the apparent viscosity may increase, and the composition may be molded or applied. It may be difficult to apply the coating.
- the lower limit value of the total pore volume of the BN aggregated particles is not particularly limited, but is usually 0.01 cm 3 / g.
- the total pore volume of the present invention is preferably 0.01 cm 3 / g or more, more preferably 0.02 cm 3 / g or more, preferably 2 cm 3 / g or less, more preferably 1.5 cm 3 / g or less. It is.
- the total pore volume of the aggregated BN powder can be measured by a nitrogen adsorption method and a mercury intrusion method.
- the specific surface area of the BN aggregated particles is usually 1 m 2 / g or more, preferably 3 m 2 / g or more and 50 m 2 / g or less, more preferably 5 m 2 / g or more and 40 m 2 / g or less. Moreover, it is also preferable that it is 8 m ⁇ 2 > / g or less, and it is also preferable that it is 7.25 m ⁇ 2 > / g or less.
- the specific surface area can be measured by the BET single point method (adsorption gas: nitrogen).
- the bulk density of the BN aggregated particles should be large in order to minimize resin uptake, and is usually preferably 0.3 g / cm 3 or more. More preferably, it is 0.35 g / cm 3 or more, and still more preferably 0.4 g / cm 3 or more.
- the bulk density of the BN aggregated particles is too small, the apparent volume increases, and the volume of the BN aggregated particles to be added increases with respect to the resin in the BN aggregated particle-containing resin composition, and the resin uptake increases. In addition, the handleability of the BN aggregated particles tends to be remarkably deteriorated.
- the bulk density of a BN aggregated particle Usually, 0.95 g / cm ⁇ 3 > or less, Preferably it is 0.9 g / cm ⁇ 3 > or less, More preferably, it is 0.85 g / cm ⁇ 3 > or less. If the bulk density of BN aggregated particles is too large, the dispersion of aggregated BN tends to occur in the BN aggregated particle-containing resin composition and tends to settle. Note that the bulk density of the BN aggregated particles can be determined using a normal apparatus or method for measuring the bulk density of the powder.
- the BN aggregated particles of the present invention are preferably granulated by using a slurry containing raw material BN powder having a viscosity of 200 to 5000 mPa ⁇ s (hereinafter sometimes referred to as “BN slurry”), and granulated.
- BN slurry a slurry containing raw material BN powder having a viscosity of 200 to 5000 mPa ⁇ s
- the viscosity of the BN slurry is preferably 300 mPa ⁇ s or more, more preferably 500 mPa ⁇ s or more, still more preferably 700 mPa ⁇ s or more, particularly preferably 1000 mPa ⁇ s or more, preferably 4000 mPa ⁇ s or less, more preferably 3000 mPa ⁇ s. -S or less.
- the viscosity of the BN slurry is produced BN average volume-based aggregate particle diameter D 50 and the greatly affect the average crystallite size of BN primary particles constituting the BN agglomerated particles, the the viscosity 200 mPa ⁇ s or more and by, it is possible to increase the average particle diameter D 50 of the volume-based average crystallite diameter and BN agglomerated particles of BN primary particles.
- granulation can be facilitated by setting the viscosity of the BN slurry to 5000 mPa ⁇ s or less. A method for adjusting the viscosity of the BN slurry will be described later.
- the viscosity of the BN slurry in the present invention is a viscosity measured at a blade rotation speed of 100 rpm using a rotational viscometer “VISCO BASIC Plus R” manufactured by FUNGILAB.
- a BN aggregated particle-containing resin composition is prepared using the BN aggregated particles of the present invention as a filler, the thermal conductivity of the molded product obtained compared with other BN particles is dramatically increased even with the same filling amount. Can improve.
- the increase in the average crystal particle diameter of the BN primary particles constituting the BN aggregated particles reduces the crystal grain boundary in the BN primary particles, and the BN primary particles constituting the BN aggregated particles. is presumed to be due to the specific surface of the particles are oriented, it is considered preferably, by greater average particle size D 50 based on volume of the agglomerated particles, and the contact resistance between BN agglomerated particles also affects reducing .
- the BN aggregated particles of the present invention not only have high thermal conductivity of the BN aggregated particles themselves, but also increase the thermal conductivity of a molded product produced by combining with a resin. That is, according to the present invention, the average crystallite diameter of the BN primary particles constituting the BN aggregated particles is increased by controlling the slurry viscosity, which is not assumed to be normally controlled by those skilled in the art, within a specific range. It has been found out a manufacturing method that is possible.
- the inventors have found a method for producing BN aggregated particles defined in the present invention by controlling the slurry viscosity within a specific range.
- the peak intensity ratio and the crystallite diameter can also be controlled by the firing temperature when the granulated particles produced from the BN slurry are heat-treated and the oxygen concentration present in the raw material BN powder.
- the peak intensity ratio can be set to 3 or more by setting the firing temperature range when the granulated particles produced from the BN slurry are heat-treated to 1800 ° C. or higher and 2300 ° C. or lower.
- the crystallite diameter can be controlled within a desired range. That is, the peak intensity ratio and the average crystallite diameter can be controlled simultaneously by using a raw material BN powder having an appropriate firing temperature range and an appropriate oxygen concentration.
- BN aggregated particles having high thermal conductivity in which specific crystal planes of the BN primary particles constituting the material are oriented. Since the BN aggregated particles obtained by the present invention can be designed in various sizes while maintaining high thermal conductivity, they can be applied to a wide range of uses as molded articles.
- the raw material BN powder used in the present invention includes commercially available h-BN, commercially available ⁇ and ⁇ -BN, BN produced by a reductive nitriding method of boron compound and ammonia, boron compound and melamine, etc. Any of BN synthesized from a nitrogen-containing compound can be used without any limitation, and h-BN is particularly preferably used since the effects of the present invention are more exhibited.
- the peak half-value width of the (002) plane obtained from powder X-ray diffraction measurement is an angle of 2 ⁇ , usually 0.4 ° or more, preferably 0.45 ° or more, more preferably 0.5. It is more than °. Moreover, it is 2.0 degrees or less normally, Preferably it is 1.5 degrees or less, More preferably, it is 1 degree or less.
- the crystallite is not sufficiently large, and it takes a long time to increase the crystallite, so that the productivity tends to deteriorate. If it is less than the above lower limit, the crystallinity is too high and sufficient crystal growth cannot be expected, and the dispersion stability at the time of slurry preparation tends to deteriorate.
- the powder X-ray-diffraction measuring method is described in the item of the below-mentioned Example.
- the total oxygen concentration in the raw material BN powder is usually 1% by mass. As mentioned above, Preferably it is 2 mass% or more, More preferably, it is 3 mass% or more, More preferably, it is 4 mass% or more. Moreover, it is 10 mass% or less normally, More preferably, it is 9 mass% or less. If it is larger than the above upper limit, oxygen tends to remain even after heat treatment, so that the effect of improving thermal conductivity tends to be small. If it is less than the above lower limit, the crystallinity is too high, crystal growth cannot be expected, and the peak intensity ratio that can be confirmed by powder X-ray diffraction measurement tends to be out of the desired range.
- the average crystallite diameter of the BN primary particles constituting the BN aggregated particles can be controlled within a desired range by using a raw material having an oxygen concentration of 1.0% by weight or more present in the raw material BN powder.
- a method for adjusting the total oxygen concentration of the raw material BN powder to the above range for example, a method in which the synthesis temperature at the time of BN synthesis is a low temperature of 1500 ° C. or lower, a raw material BN in a low-temperature oxidizing atmosphere of 500 ° C. to 900 ° C.
- the method of heat-processing powder is mentioned.
- the total oxygen concentration of the raw material BN powder can be measured by an inert gas melting-infrared absorption method using an oxygen / nitrogen analyzer manufactured by Horiba, Ltd.
- the total pore volume of the raw material BN powder is usually 1.0 cm 3 / g or less, preferably 0.3 cm 3 / g or more and 1.0 cm 3 / g or less, more preferably not more than 0.5 cm 3 / g or more 1.0 cm 3 / g.
- the total pore volume is 1.0 cm 3 / g or less, since the raw material BN powder is dense, granulation with high sphericity is possible.
- the specific surface area of the raw material BN powder is usually 50 m 2 / g or more, preferably 60 m 2 / g or more, and more preferably 70 m 2 / g or more. Usually, although 1000 m 2 / g or less, preferably 500 meters 2 / g, more preferably at most 300m 2 / g. It is preferable that the raw material BN powder has a specific surface area of 50 m 2 / g or more because the dispersed particle diameter in the BN slurry used for spheronization by granulation can be reduced. Moreover, since it can suppress the increase in a slurry viscosity by setting it as 1000 m ⁇ 2 > / g or less, it is preferable.
- the total pore volume of the raw material BN powder can be measured by a nitrogen adsorption method and a mercury intrusion method, and the specific surface area can be measured by a BET one-point method (adsorption gas: nitrogen). Specific measurement methods for the total pore volume and specific surface area of the raw material BN powder are described in the Examples section below.
- the medium used for the preparation of the BN slurry is not particularly limited, and water and / or various organic solvents can be used, but water is preferably used from the viewpoints of ease of spray drying and simplification of the apparatus. Pure water is more preferable.
- the amount of the medium used for the preparation of the BN slurry is preferably added so that the viscosity of the BN slurry is 200 to 5000 mPa ⁇ s.
- the amount of the medium used for the preparation of the BN slurry is usually 10% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, and usually 70% by mass or less, preferably 65% by mass. % Or less, more preferably 60% by mass or less.
- the slurry viscosity becomes too low, so the uniformity of the BN slurry due to sedimentation or the like is impaired, and the crystallite size of the BN primary particles constituting the obtained BN aggregated particles is in a desired range. There is a tendency to deviate from. If it is less than the lower limit, the slurry viscosity is too high, so that granulation tends to be difficult. That is, when the amount of the medium used is outside the above range, the size of the BN aggregated particles, the crystallinity of the BN primary particles constituting the BN aggregated particles, and the reduction of the crystal grain boundaries in the BN primary particles can be satisfied at the same time. It becomes difficult.
- ⁇ Surfactant> It is preferable to add various surfactants to the BN slurry from the viewpoint of adjusting the viscosity of the slurry and dispersion stability (inhibition of aggregation) of the raw material BN powder in the slurry.
- the surfactant an anionic surfactant, a cationic surfactant, a nonionic surfactant or the like can be used. These may be used alone or in combination of two or more. May be used.
- the surfactant can change the viscosity of the slurry. Accordingly, when a surfactant is added to the BN slurry, the amount thereof is adjusted so that the viscosity of the BN slurry is 200 to 5000 mPa ⁇ s.
- a surfactant is added to the BN slurry, the amount thereof is adjusted so that the viscosity of the BN slurry is 200 to 5000 mPa ⁇ s.
- a slurry having a solid content of 50% by mass using BN having a (002) plane peak half-value width 2 ⁇ of 0.67 ° and an oxygen concentration of 7.5% by mass obtained by powder X-ray diffraction measurement.
- Is usually added as an active ingredient of an anionic surfactant usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, based on the total amount of the slurry. Usually, it is added at 10% by mass or less, preferably 7% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass or less.
- an anionic surfactant usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, based on the total amount of the slurry.
- the slurry viscosity tends to decrease too much and the surfactant-derived carbon component tends to remain in the generated BN aggregated particles. If it is less than the above lower limit, the slurry viscosity becomes too high and granulation itself tend
- 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.
- Any binder can be used for the BN slurry as long as it can enhance the adhesion between the BN particles.
- the high temperature in this heat-treatment step since the granulated particles are heat-treated after the formation of particles, the high temperature in this heat-treatment step. What has the heat resistance with respect to conditions is preferable.
- metal oxides such as aluminum oxide, magnesium oxide, yttrium oxide, calcium oxide, silicon oxide, boron oxide, cerium oxide, zirconium oxide, and titanium oxide are preferably used.
- aluminum oxide and yttrium oxide are preferable from the viewpoints of thermal conductivity and heat resistance as an oxide, bonding strength for bonding BN particles, and the like.
- the binder may be a liquid binder such as alumina sol, or may be one that reacts during heat treatment and is converted into another inorganic component. These binders may be used individually by 1 type, and 2 or more types may be mixed and used for them.
- the amount of the binder used (in the case of a liquid binder, the amount used as a solid content) is usually 0% by mass to 30% by mass, preferably 0% by mass to 20% with respect to the raw material BN powder in the BN slurry. It is 0 mass% or less, More preferably, it is 0 mass% or more and 15 mass% or less. When the above upper limit is exceeded, the content of the raw material BN powder in the granulated particles decreases, which not only affects the crystal growth but also reduces the effect of improving thermal conductivity when used as a thermally conductive filler.
- the slurry preparation method is not particularly limited as long as the raw material BN powder and medium, and if necessary, the binder and the surfactant are uniformly dispersed and prepared in a desired viscosity range, but the raw material BN powder and medium, and further if necessary When a binder or a surfactant is used, it is preferably prepared as follows.
- a predetermined amount of the raw material BN powder is weighed into a resin bottle, and then a predetermined amount of binder is added. Further, after adding a predetermined amount of the surfactant, zirconia ceramic balls are added, and the mixture is stirred for about 0.5 to 5 hours with a pot mill rotary table until a desired viscosity is obtained.
- the order of addition is not particularly limited, but when slurrying a large amount of raw material BN powder, it becomes easy to form agglomerates such as debris, so after preparing an aqueous solution in which a surfactant and a binder are added to water, a predetermined amount
- the raw material BN powder may be added little by little, and zirconia ceramic balls may be added thereto, and dispersed and slurried with a pot mill rotary table.
- a dispersing device such as a bead mill or a planetary mixer may be used.
- the temperature of the slurry is 10 ° C. or higher and 60 ° C. or lower. If it is lower than the lower limit, the slurry viscosity increases and tends to deviate from the desired viscosity range. If it is higher than the upper limit, the raw material BN powder is easily decomposed into ammonia in the aqueous solution.
- it is 10 ° C. or more and 60 ° C. or less, preferably 15 ° C. or more and 50 ° C. or less, more preferably 15 ° C. or more and 40 ° C. or less, and further preferably 15 ° C. or more and 35 ° C. or less.
- granulated particles from the BN slurry In order to obtain the granulated particles from the BN slurry, general granulation methods such as a spray drying method, a rolling method, a fluidized bed method, and a stirring method can be used, and among these, the spray drying method is preferable.
- spray drying method granulated particles of a desired size are produced based on the concentration of the slurry used as a raw material, the amount of liquid fed per unit time introduced into the apparatus, and the pressure and pressure when the liquid is sprayed. It is possible to obtain spherical granulated particles.
- the average particle diameter of the granulated particles obtained by granulation is the volume-based average particle diameter D when the volume-based average particle diameter range of the BN aggregated particles of the present invention is preferably 5 ⁇ m or more and 200 ⁇ m or less.
- 50 is usually 3 ⁇ m or more, preferably 5 ⁇ m or more, more preferably 10 ⁇ m or more, still more preferably 15 ⁇ m or more, still more preferably 20 ⁇ m or more, particularly preferably 25 ⁇ m or more, more particularly preferably 25 ⁇ m or more, even 26 ⁇ m or more.
- 30 ⁇ m or more is preferable, and 35 ⁇ m or more is also preferable.
- the volume-based average particle diameter D 50 of the granulated particles can be measured by, for example, “LA920” manufactured by Horiba, Ltd. for wet, “Morphology” manufactured by Malvern, for dry.
- the above BN granulated particles can be further heat-treated in a non-oxidizing gas atmosphere to produce BN aggregated particles.
- the non-oxidizing gas atmosphere is an atmosphere of nitrogen gas, helium gas, argon gas, ammonia gas, hydrogen gas, methane gas, propane gas, carbon monoxide gas, or the like.
- the crystallization speed of the aggregated BN particles varies depending on the type of the atmospheric gas used here, and in order to perform crystallization in a short time, nitrogen gas or a mixed gas using a combination of nitrogen gas and other gas is preferably used. It is done.
- the heat treatment temperature is usually 1800 ° C. or higher and 2300 ° C. or lower, preferably 1900 ° C.
- the heat treatment temperature is too low, the average crystallite growth of BN becomes insufficient, and the thermal conductivity of the BN aggregated particles and the compact may be reduced. If the heat treatment temperature is too high, BN may be decomposed.
- the peak intensity ratio ((100) / (004)) between the (100) plane and the (004) plane of the BN primary particles is set to a desired value. it can.
- the heat treatment time is usually 3 hours or longer, preferably 4 hours or longer, more preferably 5 hours or longer, and usually 20 hours or shorter, preferably 15 hours or shorter.
- crystal growth becomes insufficient, and when it exceeds the upper limit, BN may be partially decomposed.
- the firing furnace is evacuated using a vacuum pump and then heated to a desired temperature while introducing a non-oxidizing gas.
- the temperature may be increased by heating while introducing the non-oxidizing gas under normal pressure.
- firing furnaces include batch furnaces such as muffle furnaces, tubular furnaces, and atmospheric furnaces, and rotary kilns, screw conveyor furnaces, tunnel furnaces, belt furnaces, pusher furnaces, vertical furnaces, and other continuous furnaces. Can be used properly.
- the granulated particles to be heat-treated are heated and fired in a circular graphite crucible with a lid in order to reduce the non-uniformity of the composition at the time of firing.
- a graphite partition may be inserted for the purpose of suppressing sintering of the BN aggregated 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. If the number of divisions is larger than the upper limit, sintering can be suppressed, but the crystals of BN primary particles tend not to grow sufficiently. If the number of divisions is smaller than the lower limit, sintering may proceed.
- the BN aggregated particles after the heat treatment are preferably classified in order to reduce the particle size distribution and suppress an increase in viscosity when blended in the BN aggregated particle-containing resin composition.
- This classification is usually performed after the heat treatment of the granulated particles, but may be performed on the granulated particles before the heat treatment and then subjected to the heat treatment.
- dry classification is preferable from the viewpoint of suppressing the decomposition of BN.
- dry classification is particularly preferably used.
- dry classification includes wind classification that uses a difference between centrifugal force and fluid drag, etc., but swirling air classifiers, forced vortex centrifugal classifiers, semi-free vortex centrifugal classifiers, etc. It can also be performed using a classifier.
- particles to be classified such as a swirling air classifier to classify small particles in the submicron to single micron range, and a semi-free vortex centrifugal classifier to classify relatively larger particles. What is necessary is just to use properly according to the particle diameter of this.
- the BN aggregated particle-containing resin composition of the present invention contains at least the BN aggregated particles of the present invention and a resin.
- the BN aggregated particles of the present invention are suitably used as a filler for the BN aggregated particle-containing resin composition because of its shape characteristics.
- the content ratio of the BN aggregated particles in the BN aggregated particle-containing resin composition (hereinafter sometimes referred to as “filler filling amount”) is usually 5% by mass or more, where the total of the BN aggregated particles and the resin is 100% by mass.
- it is 30 mass% or more, More preferably, it is 50 mass% or more, and is 95 mass% or less normally, Preferably it is 90 mass% or less. If it is larger than the above upper limit, the viscosity becomes too high and molding processability cannot be secured, and there is a tendency for the thermal conductivity to decrease because the dense filling of BN aggregated particles is inhibited. Although molding processability can be ensured, there is a tendency that thermal conductivity is not improved due to too few BN aggregated particles.
- the BN aggregated particle-containing resin composition according to another aspect (second aspect) of the present invention includes at least the BN aggregated particles (A) having the specific physical properties described above and inorganic particles different from the BN aggregated particles ( And B).
- the kind of the inorganic particles (B) different from the BN aggregated particles (A) having the specific physical properties is not particularly limited, and any kind may be used.
- boron nitride, aluminum nitride, alumina, zinc oxide, magnesium oxide, beryllium oxide, titanium oxide, and the like are mentioned, and preferably at least one selected from the group consisting of these, particularly from the viewpoint of reducing thermal resistance. Boron nitride is preferred.
- the BN aggregated particles (A) and inorganic particles (B) to be used satisfy the volume average particle diameter (D 50 ) of the BN aggregated particles (A)> the volume average particle diameter (D 50 ) of the inorganic particles (B). It is preferable. If this is not satisfied, the particles cannot be closely packed and the thermal conductivity decreases.
- D 50 of the inorganic particles (B) is preferably 0.95 times or less of the D 50 of the BN agglomerated particles (A), more preferably 0.8 times or less, particularly preferably 0.5 times or less. By being in this range, it becomes possible to fill the voids existing between the BN aggregated particles having the above specific properties without gaps, and it becomes possible to sufficiently reduce the thermal resistance and defects in the composition.
- the molded body obtained from the composition containing the slag has high thermal conductivity and voltage resistance.
- the lower limit of the ratio of the volume average particle diameter of the inorganic particles (B) to the volume average particle diameter of the BN aggregated particles (A) is not particularly limited as long as the above is satisfied, but the handling properties of the inorganic particles (B) are not limited.
- the thermal resistance and the effect of reducing defects in the composition tend not to change greatly, so that they are usually 0.01 times or more, preferably 0.05 times or more.
- the volume average particle size of the inorganic particles (B) is usually 100 ⁇ m or less, preferably 60 ⁇ m or less, and on the other hand, 0.5 ⁇ m or more, preferably 1 ⁇ m or more, and more preferably 3 ⁇ m or more. By being in this range, there is a tendency that high withstand voltage performance and high thermal conductivity are obtained because voids between particles can be efficiently filled. As long as satisfying the volume average particle diameter of BN agglomerated particles (A) (D 50)> The volume average particle diameter (D 50) of the inorganic particles (B), the inorganic particles (B) may be agglomerated particles .
- the content ratio of the BN aggregated particles (A) in the BN aggregated particle-containing composition is usually 30% by mass or more, preferably 50% by mass with respect to the total of the BN aggregated particles (A) and the inorganic particles (B). In addition, it is usually 95% by weight or less, preferably 90% by weight or less. By being in this range, percolation occurs due to the aggregated particles, and the thermal conductivity tends to be high.
- the total content ratio of BN aggregated particles (A) and inorganic particles (B) in the BN aggregated particle-containing composition (hereinafter sometimes referred to as “filler filling amount”) is the same as BN aggregated particles (A) and inorganic particles.
- the total of (B) and the resin is 100% by mass, usually 5% by mass or more, preferably 30% by mass or more, more preferably 50% by mass or more, and usually 95% by mass or less, preferably 90%. It is below mass%.
- the resin used for the BN aggregated particle-containing resin composition is not particularly limited, but is preferably a curable resin and / or a thermoplastic resin.
- the curable resin include thermosetting, photocurable, and electron beam curable.
- thermosetting resins and / or thermoplastic resins are used.
- epoxy resins are more preferable. Two or more of these resins may be used in combination.
- the epoxy resin may be only an epoxy resin having one type of structural unit, but a plurality of epoxy resins having different structural units may be combined. Moreover, an epoxy resin is used with the hardening
- the Tg is not particularly limited, but is usually 0 ° C. or higher, preferably 10 ° C. or higher, more preferably 25 ° C. or higher, and usually 350 ° C. or lower, preferably 300 ° C. or lower, more preferably 250 ° C. It is as follows.
- epoxy resin a phenoxy resin described later as an epoxy resin.
- the mass ratio of the epoxy resin (A) to the total amount of the epoxy resin is not particularly limited, but is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, and particularly preferably 16.0% by mass. % Or more, particularly preferably 18.0% by mass or more, preferably 95% by mass or less, more preferably 90% by mass or less, and further preferably 80% by mass or less.
- the phenoxy resin usually refers to a resin obtained by reacting an epihalohydrin and a dihydric phenol compound, or a resin obtained by reacting a divalent epoxy compound and a divalent phenol compound.
- a phenoxy resin having a high molecular weight having a weight average molecular weight of 10,000 or more is referred to as an epoxy resin (A).
- the weight average molecular weight is a value in terms of polystyrene measured by gel permeation chromatography.
- the epoxy resin (A) includes a phenoxy resin having at least one skeleton selected from the group consisting of naphthalene skeleton, fluorene skeleton, biphenyl skeleton, anthracene skeleton, pyrene skeleton, xanthene skeleton, adamantane skeleton and dicyclopentadiene skeleton, bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, naphthalene type phenoxy resin, phenol novolac type phenoxy resin, cresol novolac type phenoxy resin, phenol aralkyl type phenoxy resin, biphenyl type phenoxy resin, triphenylmethane type phenoxy resin, dicyclopentadiene type Phenoxy resin, glycidyl ester type phenoxy resin, and glycidylamine type phenoxy resin are preferred.
- the epoxy resin according to the present invention contains an epoxy resin having two or more epoxy groups in the molecule (hereinafter sometimes referred to as “epoxy resin (B)”).
- epoxy resin (B) examples include bisphenol A type epoxy resin, bisphenol F type epoxy resin, naphthalene type epoxy resin, phenol novolac type epoxy resin, cresol novolak type epoxy resin, phenol aralkyl type epoxy resin, and biphenyl type epoxy resin.
- various epoxy resins such as triphenylmethane type epoxy resin, dicyclopentadiene type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, and polyfunctional phenol type epoxy resin.
- bisphenol A type epoxy resin bisphenol F type epoxy resin, glycidylamine type epoxy resin, and polyfunctional phenol type epoxy resin are preferable in terms of improving heat resistance and adhesion. These may be used alone or in combination of two or more.
- the epoxy resin (B) has a weight average molecular weight of preferably 100 to 5000, more preferably 200 to 2000, from the viewpoint of melt viscosity control.
- the weight average molecular weight is lower than 100, the heat resistance tends to be inferior.
- the weight average molecular weight is higher than 5000, the melting point of the epoxy resin tends to increase and the workability tends to decrease.
- the epoxy resin according to the present invention is an epoxy resin other than the epoxy resin (A) and the epoxy resin (B) (hereinafter, may be referred to as “other epoxy resin”) as long as the purpose is not impaired. May be included.
- the content of the other epoxy resin is usually 50% by mass or less, preferably 30% by mass or less, based on the total of the epoxy resin (A) and the epoxy resin (B).
- the epoxy resin curing agent is appropriately selected according to the type of resin used.
- an acid anhydride curing agent and an amine curing agent can be used.
- the acid anhydride curing agent include tetrahydrophthalic acid anhydride, methyltetrahydrophthalic acid anhydride, hexahydrophthalic acid anhydride, and benzophenone tetracarboxylic acid anhydride.
- amine curing agent examples include aliphatic polyamines such as ethylenediamine, diethylenetriamine, and triethylenetetramine, aromatic polyamines such as diaminodiphenylsulfone, diaminodiphenylmethane, diaminodiphenyl ether, and m-phenylenediamine, and dicyandiamide. These may be used alone or in combination of two or more. These epoxy resin curing agents are usually blended in an equivalent ratio with respect to the epoxy resin in the range of 0.3 to 1.5.
- the curing accelerator is appropriately selected according to the type of resin and curing agent used.
- examples of the curing accelerator for the acid anhydride curing agent include boron trifluoride monoethylamine, 2-ethyl-4-methylimidazole, 1-isobutyl-2-methylimidazole, and 2-phenyl-4-methylimidazole. Can be mentioned. These may be used alone or in combination of two or more.
- These curing accelerators are usually used in the range of 0.1 to 30 parts by mass with respect to 100 parts by mass of the epoxy resin.
- the resin of the BN aggregated particle-containing resin composition of the present invention may be a thermoplastic resin.
- the thermoplastic resin include polyolefin resins such as polyethylene resin, polypropylene resin, and ethylene-vinyl acetate copolymer resin, polyester resins such as polyethylene terephthalate resin, polybutylene terephthalate resin, and liquid crystal polyester resin, polyvinyl chloride resin, and phenoxy.
- examples include resins, acrylic resins, polycarbonate resins, polyphenylene sulfide resins, polyphenylene ether resins, polyamide resins, polyamideimide resins, polyimide resins, polyetheramideimide resins, polyetheramide resins, and polyetherimide resins.
- copolymers such as those block copolymers and a graft copolymer, are also contained. These may be used alone or in combination of two or more.
- the resin of the BN aggregated particle-containing resin composition of the present invention may contain a rubber component.
- the rubber component include natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, Ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer rubber, butadiene-acrylonitrile copolymer rubber, isobutylene-isoprene copolymer rubber, chloroprene rubber, silicon rubber, fluorine rubber, chloro-sulfonated polyethylene, polyurethane rubber Etc. These may be used alone or in combination of two or more.
- the BN aggregated particle-containing resin composition of the present invention may contain additional components as long as the effects of the present invention are obtained.
- additional components include, in addition to the above-described resins, nitride particles such as aluminum nitride, silicon nitride, fibrous, plate-like, and particulate aggregate BN, which are inorganic fillers, alumina, fibrous alumina, and zinc oxide.
- Insulating metal oxides such as magnesium oxide, beryllium oxide and titanium oxide, inorganic fillers such as diamond, fullerene, aluminum hydroxide and magnesium hydroxide, silane coupling agents which improve the interfacial bond strength between inorganic filler and matrix resin, etc.
- Insulating carbon components such as surface treatment agents, reducing agents, resin curing agents, resin curing accelerators, viscosity modifiers, and dispersants.
- nitride particles are preferable and particulate agglomerated BN is more preferable from the viewpoint of improvement of thermal conductivity and withstand voltage.
- a dispersing agent when using the slurry of this invention, it is preferable to use a dispersing agent from the viewpoint of improving the film formability.
- a solvent can be used for the BN aggregated particle containing resin composition of this invention from a viewpoint of reducing the viscosity of a BN aggregated particle containing resin composition.
- a solvent that dissolves the resin from among known solvents is used.
- solvents include methyl ethyl ketone, acetone, cyclohexanone, toluene, xylene, monochlorobenzene, dichlorobenzene, trichlorobenzene, phenol, and hexafluoroisopropanol as organic solvents. These may be used alone or in combination of two or more.
- the solvent is usually used in the range of 0 to 10,000 parts by mass with respect to 100 parts by mass of the resin such as epoxy resin.
- the BN aggregated particle-containing resin composition of the present invention is obtained by uniformly mixing the BN aggregated particles of the present invention, optionally inorganic particles, resin, and other components added as necessary by stirring or kneading. be able to.
- a general kneading apparatus such as a mixer, a kneader, a single-screw or twin-screw kneader can be used, and the mixing may be performed as necessary.
- a preparation method for making a slurry Is not particularly limited, and a conventionally known method can be used.
- a paint shaker for the purpose of improving the uniformity of the coating liquid, defoaming, etc., a paint shaker, a bead mill, a planetary mixer, a stirring type disperser, a self-revolving stirring mixer, a three-roll, a kneader, a uniaxial or biaxial It is preferable to mix and stir using a general kneading apparatus such as a kneader.
- each compounding component is arbitrary as long as there is no particular problem such as reaction or precipitation.
- a resin solution is prepared by mixing and dissolving a resin in an organic solvent (for example, methyl ethyl ketone).
- an organic solvent for example, methyl ethyl ketone
- an organic solvent is further added and mixed for viscosity adjustment.
- the molded body of the present invention is formed by molding a molded body using the BN aggregated particles of the present invention, preferably a BN aggregated particle-containing resin composition.
- a generally used method can be used as a molding method of the molded body.
- the BN aggregated particle-containing resin composition of the present invention has plasticity and fluidity, it can be molded by curing the BN aggregated particle-containing resin composition in a desired shape, for example, in a state accommodated in a mold. it can.
- the slurry contains a solvent
- the solvent can be removed by a known heating method such as a hot plate, a hot air furnace, an IR heating furnace, a vacuum dryer, or a high-frequency heater.
- the BN aggregated particle-containing resin composition of the present invention is a thermosetting resin composition such as an epoxy resin or a silicone resin
- the molding of the molded body, that is, curing can be performed under each curing temperature condition.
- the molded body may be molded under conditions of a temperature equal to or higher than the melting temperature of the thermoplastic resin and a predetermined molding speed and pressure. it can.
- the molded product of the present invention can also be obtained by cutting out a cured product of the BN aggregated particle-containing resin composition of the present invention into a desired shape.
- a heat radiating sheet (also simply referred to as a sheet in the present specification) is preferable among the molded bodies.
- a heat radiating sheet is preferable among the molded bodies.
- the sheet manufacturing method applies the slurry (described later) to the base material (application step) and dries it (drying step), and pressurizes and shapes the coated dried product. It includes at least a step (sheet forming step) and a step of thermosetting the molded product (thermosetting step).
- a coating film is formed on the surface of the substrate using BN aggregated particle-containing slurry. That is, using the slurry, a coating film is formed by a dip method, a spin coat method, a spray coat method, a blade method, or any other method.
- a coating device such as a spin coater, slit coater, die coater, blade coater, comma coater, screen printing, doctor blade, applicator, spray coating, etc. It is possible to form a uniform coating film, and a blade coater capable of adjusting the gap is preferable.
- the sheet of the present invention can be used as a self-supporting film, and is further formed on a known base material such as a metal foil or plate (copper, aluminum, silver, gold), a resin film such as PET, PEN, or glass. can do.
- a known base material such as a metal foil or plate (copper, aluminum, silver, gold), a resin film such as PET, PEN, or glass.
- these substrates can be peeled off depending on the form of use, or may have a laminated structure such as a substrate / heat radiation sheet / substrate.
- the copper foil of the below-mentioned thickness is generally used, However, It is not limited to a copper board
- the BN aggregated particle-containing slurry applied to the substrate is dried to obtain a dried product.
- the drying temperature is usually 15 ° C or higher, preferably 20 ° C or higher, more preferably 23 ° C or higher, and usually 100 ° C or lower, preferably 90 ° C or lower, more preferably 80 ° C or lower, and further preferably 70 ° C or lower. . If the drying heating temperature is too low or the heating time is too short, the organic solvent in the coating film cannot be sufficiently removed, and the organic solvent remains in the resulting dried film.
- the sheet is evaporated by the high-temperature pressure treatment in the sheeting step, and the evaporation trace of the residual solvent becomes a void, so that a sheet having high thermal conductivity, high insulating properties, predetermined physical strength, etc. cannot be formed.
- the drying heating temperature is too high or the heating time is too long, curing of the resin proceeds and a good dry film cannot be obtained.
- the drying time is usually 1 hour or more, preferably 2 hours or more, more preferably 3 hours or more, and further preferably 4 hours or more, and usually 168 hours or less, preferably 144 hours or less, more preferably 120 hours or less. More preferably, it is 96 hours or less.
- the drying time is less than the lower limit, the organic solvent in the coating film cannot be sufficiently removed, the organic solvent remains in the resulting dried film, and the remaining organic solvent is pressed at a high temperature in the next sheet forming step.
- a sheet having high thermal conductivity, high insulation, predetermined physical strength, and the like cannot be formed due to the evaporation of the residual solvent resulting in evaporation of the residual solvent.
- the drying time exceeds the upper limit, the resin is too dry to obtain a coating film with good strength, and sufficient fluidity cannot be obtained even by plasticizing the resin in the sheeting process.
- the resin cannot sufficiently penetrate into the voids present in the sheet, and there is a tendency that a sheet having high thermal conductivity, high insulation, predetermined physical strength and the like cannot be formed.
- the thickness of the sheet before drying is usually 100 ⁇ m or more, preferably 150 ⁇ m or more, more preferably 200 ⁇ m or more, further preferably 300 ⁇ m or more, and usually 800 ⁇ m or less, preferably 700 ⁇ m or less, more preferably 600 ⁇ m or less, and further preferably. Is 500 ⁇ m or less.
- the film thickness exceeds the above upper limit, it becomes difficult to control the evaporation rate of the organic solvent inside the film, the amount of the remaining organic solvent increases, and it evaporates by the high-temperature pressure treatment in the sheeting process, and the remaining solvent evaporates.
- the mark becomes a void, and a sheet having high thermal conductivity, high insulation, predetermined physical strength, etc. cannot be formed.
- the organic solvent evaporates in a short time, so that the resin is too dry and a coating film having a good strength cannot be obtained.
- sufficient fluidity cannot be obtained, and the resin cannot sufficiently penetrate into the voids existing in the sheet, so that there is a tendency that a sheet having high thermal conductivity, high insulation, predetermined physical strength, etc. cannot be formed.
- the heat treatment may be performed at a constant temperature, but the heat treatment may be performed under a reduced pressure condition in order to smoothly remove volatile components such as an organic solvent in the coating solution.
- you may perform the heat processing by stepwise temperature rise in the range in which hardening of resin does not advance.
- a heat treatment can be performed at 25 to 40 ° C., for example, 30 ° C., and then at 40 to 90 ° C., for example, 50 ° C., for about 30 to 60 minutes each.
- the sheet obtained by this production method exhibits high thermal conductivity and a withstand voltage value.
- the amount of the organic compound having a boiling point of 100 ° C. or less in the dried product is usually more than 0 ppm, preferably 0.01 ppm or more, more preferably 1 ppm or more, still more preferably 5 ppm or more, and particularly preferably 7 ppm or more. In general, it is 50 ppm or less, preferably 30 ppm or less, more preferably 19 ppm or less, and still more preferably 18 ppm or less. Within the above range, the effects of the present invention can be more effectively exhibited. In addition, content of the organic compound mentioned above in the application dried product can be measured by headspace gas chromatography.
- a process (sheet forming process) of pressurizing and molding the coated dried product is performed.
- a coated and dried product applied and dried on a copper substrate is cut into a predetermined size.
- the heating temperature (pressing temperature) for forming into a sheet is usually 80 ° C. or higher, preferably 90 ° C. or higher, more preferably 100 ° C. or higher, still more preferably 110 ° C. or higher, and usually 300 ° C. or lower, preferably 250. ° C or lower, more preferably 200 ° C or lower.
- thermosetting reaction does not proceed sufficiently, and contact between BN aggregated particles or contact between BN aggregated particles and the resin interface becomes insufficient, so that high thermal conductivity, high insulation, predetermined A sheet having physical strength or the like cannot be formed.
- the upper limit of the above range is exceeded, the resin is likely to be decomposed, and the tendency to be unable to form a sheet having high thermal conductivity, high insulation, predetermined physical strength, etc. due to voids and molecular weight reduction due to the decomposition. There is.
- a press method in a pressurizing step (also referred to as a press process) performed to promote adhesion to the copper substrate can be performed using a known technique, for example, an isostatic press, a vacuum press, a belt press, or a hot press. It can be formed by a known method such as a servo press or a calender roll.
- the dry film on a copper substrate usually 10 kgf / cm 2 or higher, preferably 150 kgf / cm 2 or more, more preferably 200 kgf / cm 2 or more, further preferably 250 kgf / cm 2 or more, usually, 2,000 kgf / cm 2 or less, preferably 1000 kgf / cm 2 or less, more preferably 900 kgf / cm 2 or less, more preferably pressurizes the 800 kgf / cm 2 or less.
- the weight at the time of pressurization to the above upper limit or less, the BN aggregated particles are not destroyed, and a sheet having high thermal conductivity without voids in the sheet can be obtained. Further, by setting the weight to the above lower limit or more, the contact between the BN aggregated particles becomes good and it becomes easy to form a heat conduction path, so that a sheet having high heat conductivity can be obtained.
- the composition film coated and dried on the copper substrate is usually pressurized at a temperature of 80 ° C. or higher, preferably 100 ° C. or higher, for example, 100 to 200 ° C. with a predetermined load for about 1 to 30 minutes.
- a curing step in which a sheet is produced by performing a curing reaction by heating in an oven at a curing temperature of 150 ° C. or higher, for example, for about 2 to 4 hours.
- the upper limit of the heating temperature at the time of complete curing in the curing step is a temperature at which the resin to be used is not decomposed or deteriorated and is appropriately determined depending on the type and grade of the resin, but is usually performed at 300 ° C. or lower.
- a circuit board having a heat dissipation sheet in which both sides are bonded with copper to a sheet of the present invention formed using BN aggregated particles is not high because the BN aggregate filler of the present invention is used. Due to the heat dissipation effect due to thermal conductivity, high output and high density of the device can be achieved with high reliability. Therefore, it is suitable as a heat dissipation substrate and a heat dissipation sheet for power semiconductor device devices.
- conventionally known members can be appropriately employed as members such as aluminum wiring, sealing material, package material, heat sink, thermal paste, and solder other than the heat dissipation sheet of the present invention.
- the circuit board has a shape in which copper and aluminum, preferably copper are bonded to both sides of the heat dissipation sheet of the present invention, and the circuit is patterned on one side.
- the lamination method can also be manufactured by film-forming press molding.
- the circuit board patterning method is not particularly limited, and can be manufactured by a known method as described in, for example, Japanese Unexamined Patent Application Publication No. 2014-209608.
- the thickness of the circuit board is not particularly limited, but is usually 10 ⁇ m or more, preferably 100 ⁇ m or more, more preferably 300 ⁇ m or more, further preferably 500 ⁇ m or more, and particularly preferably 1000 ⁇ m or more. Moreover, it is 5000 micrometers or less normally.
- the layer thickness of the heat radiating sheet is not particularly limited, but is usually 80 ⁇ m or more, preferably 100 ⁇ m or more, and more preferably 200 ⁇ m or more. Moreover, it is usually 1000 micrometers or less. Further, the layer thickness of the copper part serving as the heat radiating part is not particularly limited, but is usually 10 ⁇ m or more, preferably 100 ⁇ m or more, more preferably 300 ⁇ m or more, particularly preferably 500 ⁇ m or more, and particularly preferably 1000 ⁇ m or more. It is. Moreover, it is 5000 micrometers or less normally.
- the sheet of the present invention is a sheet containing boron nitride aggregated particles (hereinafter referred to as "BN aggregated particles”), and obtained by X-ray diffraction measurement of the sheet.
- the peak intensity ratio [(100) / (004)] of the (100) plane to the (004) plane of the boron nitride primary particles (hereinafter referred to as “BN primary particles”) is 1.0 or more
- the sheet Is obtained by X-ray diffraction measurement, and the average crystallite diameter of the BN primary particles obtained from the (002) plane peak of the BN primary particles in the sheet is 375 mm or more.
- the sheet of the present invention satisfies such physical properties, thereby having a high thermal conductivity and an excellent withstand voltage performance, and can be suitably used as a heat radiating member.
- the reason for the sheet exhibiting such excellent performance is that the ratio of the ab surfaces of the primary particles is oriented in the vertical direction of the sheet when the strength ratio of [(100) / (004)] is greater than or equal to the above. It is possible to demonstrate the high thermal conductivity of BN as a sheet, and to increase the primary particle size to 375 mm or more, thereby reducing the interface between the primary particles and providing a thermal resistance between the interfaces. This is to prevent it.
- ) / (004)) is 1.0 or more.
- This peak intensity ratio ((100) / (004)) is preferably 1.5 or more, more preferably 2.0 or more, still more preferably 2.5 or more, and particularly preferably 3.0 or more.
- the upper limit is not particularly limited, but is usually 10.0 or less, preferably 7.0 or less, more preferably 5.0 or less.
- this numerical value is too large, the ratio of the BN primary particles facing in the vertical direction with respect to the sheet surface becomes too high, and minute cracks in the sheet are likely to occur when a molding process such as pressing is performed. Such cracks tend to lower electrical characteristics such as withstand voltage.
- the numerical value is too small, the ratio of the BN primary particles facing the sheet surface in the vertical direction is low, and the thermal conductivity tends to be low.
- the BN primary particle average crystallite diameter obtained from the (002) plane peak of the BN primary particles in the sheet obtained by X-ray diffraction measurement of the sheet is not particularly limited, but is usually 300 mm or more, preferably Is at least 320 mm, more preferably at least 375 mm, more preferably at least 380 mm, even more preferably at least 390 mm, particularly preferably at least 400 mm, usually at most 5000 mm, preferably at most 2000 mm, more preferably at most 1000 mm.
- the card house structure in the agglomerated particles is destroyed at the time of sheet molding such as a pressing process, the ratio of the ab surface of the BN primary particles to be perpendicular to the sheet surface is reduced, and the thermal conductivity is reduced. Tend to be lower. Moreover, since a BN primary particle interface will increase when a numerical value is too small, it becomes a heat transfer resistance and there exists a tendency for thermal conductivity to become low.
- the sheet of the present invention is a sheet containing at least boron nitride agglomerated particles, and the sheet is obtained by X-ray diffraction measurement, and has a (100) plane and a (004) plane of BN primary particles in the sheet.
- the peak area intensity ratio ((100) / (004)) is not particularly limited, but is usually 0.6 or more, preferably 0.65 or more, preferably 0.7 or more, more preferably 0.75 or more, and further Preferably it is 0.8 or more, particularly preferably 0.85 or more.
- an upper limit does not have a restriction
- the thermal conductivity (W / mK) of the heat dissipation sheet is not particularly limited, but is usually 5 W / mK or higher, preferably 10 W / mK or higher, more preferably 13 W / mK, particularly preferably 15 W / mK or higher. Preferably it is 17 W / mK or more.
- the withstand voltage performance is usually 10 kV / mm or more, preferably 15 kV / mm or more, particularly preferably 20 kV / mm or more.
- the glass transition temperature of the sheet of the present invention is usually 100 ° C. or higher, preferably 130 ° C. or higher, particularly preferably 175 ° C. or higher.
- the adhesive strength (N / cm) of the heat dissipation sheet is not particularly limited, but is usually 0.5 N / cm or more, preferably 1 N / cm or more, more preferably 2 N / cm, particularly preferably 3 N / cm or more, Especially preferably, it is 5 N / cm or more.
- the present invention will be described in more detail with reference to examples.
- the present invention is not limited to the following examples unless it exceeds the gist.
- the various conditions in the following Examples and the values of the evaluation results show the preferable range of the present invention as well as the preferable range in the embodiment of the present invention, and the preferable range of the present invention is in the above-described embodiment. It can be determined in consideration of a preferable range and a range indicated by a combination of values of the following examples or values of the examples.
- ⁇ Measurement condition The characteristics in the present invention were measured by the methods described below. ⁇ viscosity: Using a rotational viscometer “VISCO BASIC Plus R” manufactured by FUNGILAB, the measurement was performed at a blade rotation speed of 100 rpm.
- Average particle size of the BN agglomerated particles (D 50) The D 50 ( ⁇ m) of BN aggregated particles was measured using “Morphology” manufactured by Malvern.
- D crystallite diameter
- K Scherrer constant
- ⁇ X-ray (CuK ⁇ 1 ) wavelength
- ⁇ peak half width
- ⁇ Bragg angle derived from CuK ⁇ 1 .
- ⁇ ( ⁇ o 2 ⁇ i 2 ) 0.5
- ⁇ i is the half-value width derived from the apparatus determined by standard Si
- ⁇ o is the peak half-value width derived from the (002) plane of h-BN. The following values were used for each constant.
- -Peak intensity ratio of BN aggregated particles Calculate the ratio ((100) / (004)) of the peak intensity of (100) plane and (004) plane of BN primary particles obtained by powder X-ray diffraction measurement of BN aggregated particles.
- the peak intensity ratio of the BN aggregated particles was evaluated.
- an X-ray diffractometer “X′Pert Pro MPD” manufactured by PANalytical was used for powder X-ray diffraction measurement. The powder X-ray diffraction measurement was carried out using a sample prepared by filling a 0.2 mm deep glass sample plate with BN aggregated particles and preparing a measurement surface so that the surface was smooth.
- Peak area intensity ratio of BN aggregated particles About 0.2 g of BN aggregated particles are filled in a tablet molding machine (10 mm ⁇ ), and tableting is performed at a press pressure of 0.85 ton / cm 2 using a manual hydraulic pump (P-1B-041 manufactured by Riken Seiki Co., Ltd.). did. About the obtained sample, the peak area intensity ratio ((100) / (004)) of the (100) plane and (004) plane of BN primary particles was calculated
- thermal diffusivity in the thickness direction of the molded body was measured using a thermal diffusivity measuring apparatus "ai-Phase Mobile 1u" manufactured by I-Phase Co., Ltd., and was determined as follows.
- Thermal conductivity in the thickness direction of the molded body thermal diffusivity in the thickness direction of the molded body ⁇ specific gravity of the molded body ⁇ specific heat of the molded body
- BN Aggregated Particles (BN-A Aggregated Particles)
- the BN granulated particles were evacuated at room temperature, then nitrogen gas was introduced and the pressure was restored, and the temperature was raised to 2000 ° C. at 83 ° C./hour while introducing nitrogen gas as it was. The gas was held for 5 hours while being introduced. Thereafter, the mixture was cooled to room temperature to obtain spherical BN-A aggregated particles having a card house structure.
- the BN-A aggregated particles after the heat treatment were lightly pulverized using a mortar and pestle, and then classified using a sieve having an opening of 90 ⁇ m. After classification, the average crystallite size of the BN primary particles constituting the BN-A aggregated particles, the peak intensity ratio ((100) / (004)) between the (100) plane and the (004) plane of the BN primary particles, BN- The D 50 of the A aggregated particles was measured. The measurement results are shown in Table 1.
- a BN aggregated particle-containing resin composition comprising a filler and a resin composition was prepared.
- [Resin composition] “157S70”: “828US”: “157S70”: “828US”: “157S70”, “828US”, “4275”, which are epoxy resins manufactured by Mitsubishi Chemical Corporation, and “C11Z-CN”, which is a curing agent manufactured by Shikoku Kasei Kogyo Co., Ltd. 4275 ”:“ C11Z-CN ” 1: 0.25: 0.25: 0.11 (mass ratio) to obtain a resin composition.
- BN-A (BN agglomerated particles) and the above resin composition are mixed so that the filling amount of the BN-A agglomerated particles (the content ratio of the BN-aggregated particles with respect to the total of the resin composition and the BN-A agglomerated particles) is 80% by mass.
- Blended into 100 parts by mass of the prepared resin composition / BN-A aggregated particle mixture and 50 parts by mass of methyl ethyl ketone are placed in a cup with a cap made of polypropylene, and 6 parts by mass of 1-
- cyanoethyl-2-undecylimidazole curing agent
- a self-rotating stirrer Shintaro Foam AR-250 manufactured by Shinky
- the obtained BN aggregated particle-containing resin composition coating solution was applied onto a copper substrate having a thickness of 100 ⁇ m and 10 cm ⁇ 20 cm with a bar coater (“Auto Film Applicator” manufactured by Tester Sangyo Co., Ltd.) having a gap interval of 400 ⁇ m. Then, it vacuum-dried at 50 degreeC for 30 minutes, and formed the coating film on the copper substrate.
- a bar coater Auto Film Applicator” manufactured by Tester Sangyo Co., Ltd.
- Example 2 In Example 1, except that the slurry A was changed to the BN slurry (slurry B) in which the mixing ratio of the raw materials was changed to the following, the same procedure as in Example 1 was performed, and spherical BN aggregated particles (aggregated BN- B) and BN aggregated particle-containing resin composition and molded body were produced. The measurement results are shown in Table 1.
- Example 3 In Example 1, except that the slurry A was changed to the BN slurry (slurry C) in which the mixing ratio of the raw materials was changed to the following, the same procedure as in Example 1 was performed, and spherical BN aggregated particles (aggregated BN- C) and BN aggregated particle-containing resin composition and molded body were produced. The measurement results are shown in Table 1.
- BN aggregated particles (BN-D aggregated particles) and BN aggregated particle-containing resin composition were carried out in the same manner as in Example 2 except that the slurry B in Example 2 was changed to the slurry D shown below with the mixing ratio of raw materials changed. Articles and molded bodies were produced. The viscosity of the slurry was 155 mPa ⁇ s. The measurement results are shown in Table 1.
- Example 2 The slurry was prepared and granulated in the same manner as in Example 1, and BN aggregated particles were prepared in the same manner as in Example 1 except that the firing temperature during the preparation of BN aggregated particles was 1300 ° C. and the holding time was 24 h (aggregated BN -E). Using the BN aggregated particles, a BN aggregated particle-containing resin composition and a molded body were produced in the same manner as in Example 1. Table 1 shows the results.
- Example 3 A BN aggregated particle-containing resin composition and a molded body were produced in the same manner as in Example 1 except that PTX60 manufactured by Momentive was used instead of the BN-A aggregated particles of Example 1. Table 1 shows the results.
- Example 4 The same procedure as in Example 1 was performed except that PTX25 manufactured by Momentive was used instead of the BN-A aggregated particles of Example 1. Table 1 shows the results.
- Example 5 A BN aggregated particle-containing resin composition and a molded body were produced in the same manner as in Example 1 except that SGPS manufactured by Denki Kagaku Kogyo Co., Ltd. was used instead of the BN-A aggregated particles of Example 1. Table 1 shows the results.
- Example 6 A BN aggregated particle-containing resin composition and a molded product were produced in the same manner as in Example 1 except that CTS7M manufactured by Saint-Gobain was used instead of the BN-A aggregated particles of Example 1. Table 1 shows the results.
- Example 7 The slurry was prepared and granulated in the same manner as in Example 1, and BN aggregated particles were prepared in the same manner as in Example 1 except that the firing temperature during the preparation of BN aggregated particles was 1600 ° C. and the holding time was 24 h (aggregated BN). -F). Using the BN aggregated particles, a BN aggregated particle-containing resin composition and a molded body were produced in the same manner as in Example 1. Table 1 shows the results.
- Example 2 In Example 2, it carried out like Example 1 except having set it as the BN slurry (slurry E) which changed the compounding ratio of the raw material of the slurry B below.
- Example 5 The (100) surface of the BN primary particles and the (100) surface were obtained in the same manner as in Example 4 except that the BN-B aggregated particles prepared in Example 2 were used as about 0.2 g of BN aggregated particles in a tablet molding machine (10 mm ⁇ ). The peak area intensity ratio ((100) / (004)) of the (004) plane was determined. The results are shown in Table 2.
- Comparative Example 11 The peak area intensity ratio ((100) / (004)) between the (100) face and the (004) face of the BN primary particles is obtained in the same manner as in Example 4 except that PTX25 manufactured by Momentive is used as the BN aggregated particles. It was. The results are shown in Table 2.
- Comparative Example 12 Except for using SGPS manufactured by Denki Kagaku Kogyo Co., Ltd. as the BN aggregated particles, the peak area intensity ratio ((100) / (004)) between the (100) plane and the (004) plane of the BN primary particles in the same manner as in Example 4. Asked. The results are shown in Table 2.
- Comparative Example 13 The peak area intensity ratio ((100) / (004)) between the (100) face and the (004) face of the BN primary particles is obtained in the same manner as in Example 4 except that CTS7M manufactured by Saint-Gobain Co. is used as the BN aggregated particles. It was. The results are shown in Table 2.
- Comparative Example 14 The peak area intensity ratio ((100) / (004)) between the (100) plane and the (004) plane of the BN primary particles was the same as in Example 4 except that BN—F aggregated particles were used as the BN aggregated particles. Asked. The results are shown in Table 2.
- the average crystallite size of the BN primary particles constituting the BN aggregated particles is 375 mm or more, and the peak intensity ratio ((100) between the (100) plane and the (004) plane of the BN primary particles by powder X-ray diffraction measurement.
- BN agglomerated particles of the present invention having a / (004)) of 3 or more exhibit unprecedented performance as a thermally conductive filler, and can be widely applied to various applications such as the electric and electronic fields where there are many thermal problems. .
- the peak area intensity ratio ((100) / (004)) between the (100) plane and the (004) plane of the BN primary particles is 0.25 or more even at a specific pressure or higher.
- (100) / (004) plane peak intensity ratio of BN primary particles It was determined by calculating the ratio of peak intensity ((100) / (004)) between the (100) plane and the (004) plane of BN primary particles obtained by powder X-ray diffraction measurement of BN aggregated particles.
- X-ray diffraction measurement of heat dissipation sheet An X-ray diffractometer (X'Pert Pro MPD) manufactured by PANalytical was used. In addition, the sample sample was implemented using the heat-release sheet
- (100) / (004) plane peak intensity ratio of heat dissipation sheet It calculated
- Average crystallite size of BN primary particles of heat dissipation sheet In accordance with the above-described method for measuring the average crystallite size of the BN primary particles.
- Adhesion test A heat dissipation sheet obtained by coating on a base material was cut into a size of 25 mm ⁇ 60 mm, and a measurement sample bonded and bonded to a 25 mm ⁇ 110 mm base material by a heating press was fixed to a resin plate and then peeled 90 °. It was determined by carrying out the test. The test was performed using STA-1225 manufactured by ORIENTEC .
- Example 6 4.7 g of BN aggregated particles BN-A having a card house structure, boron nitride PTX25 having a non-card house structure (manufactured by Momentive Co., Ltd., D 50 : 19.8 ⁇ m, (100) / (004) plane peak of BN primary particles) Strength ratio: 1.4, average crystallite size of BN primary particles: 537 cm), and epoxy resin (Tg: 16.7% by mass of phenoxy resin containing bisphenol A type phenoxy resin with respect to the total amount of epoxy resin) 190 ° C.) 2.12 g, solvent (cyclohexanone / methyl ethyl ketone) 6.2 g, dispersant (trade name: BYK-2155, manufactured by BYK Japan Japan Co., Ltd.) 0.41 g, 1-cyanoethyl-2-undecylimidazole (product) Name: C11Z-CN, manufactured by Shikoku Kasei Kogyo Co., Ltd
- the prepared slurry for a heat-dissipating sheet was applied to a substrate by a doctor blade method, and after drying by heating, pressing was performed to obtain a heat-dissipating sheet having a sheet thickness of about 200 ⁇ m.
- Example 7 4.7 g of BN aggregated particles BN-A having a card house structure, boron nitride PTX25 having a non-card house structure (manufactured by Momentive Co., Ltd., D 50 : 19.8 ⁇ m, (100) / (004) plane peak of BN primary particles) Intensity ratio: 1.4, average crystallite diameter of BN primary particles: 537 kg), and epoxy resin (Tg: 31 ° C.) containing 20% by mass of phenoxy resin containing bisphenol F-type phenoxy resin with respect to the total amount of epoxy resin 2.12 g, 6.2 g of solvent (cyclohexanone / methyl ethyl ketone), dispersant (trade name: BYK-2155, manufactured by BYK Japan KK) 0.41 g, 1-cyanoethyl-2-undecylimidazole (trade name: C11Z-CN (manufactured by Shikoku Kasei Kogyo Co.
- Example 8 BN aggregated particles BN-A having a card house structure BN-A (D 50 : 50 ⁇ m) 5.5 g, BN aggregated particles BN-D having a card house structure BN-D (D 50 : 14 ⁇ m) 1.8 g, and epoxy resin (Tg: 190 ° C.) ) 1.0 g, solvent (cyclohexanone / methyl ethyl ketone) 6.2 g, dispersant (trade name: BYK-2155, manufactured by Big Chemie Japan Co., Ltd.) 0.40 g, 1-cyanoethyl-2-undecylimidazole (trade name: C11Z-CN (manufactured by Shikoku Kasei Kogyo Co., Ltd.) (0.06 g) was mixed to prepare a heat dissipation sheet slurry.
- solvent cyclohexanone / methyl ethyl ketone
- dispersant trade name: BYK-21
- the prepared slurry for a heat-dissipating sheet was applied to a substrate by a doctor blade method, and after drying by heating, pressing was performed to obtain a heat-dissipating sheet having a sheet thickness of about 200 ⁇ m.
- a heat dissipation sheet having a sheet thickness of about 200 ⁇ m was obtained in the same manner as in Example 6.
- the obtained heat radiation sheet was subjected to thermal conductivity, withstand voltage, and X-ray diffraction measurement.
- the sheet press pressure at this time is 300 kg weight / cm 2
- FIG. 5 is a sheet cross-sectional SEM photograph.
- the BN aggregated particles of the present invention are considered to be one of the reasons that the effect of the present invention is exerted even when the BN aggregated particles of the present invention are pressed at the above-mentioned pressing pressure, and retain the shape of the powder before pressing. More specifically, as shown in FIG. 5, at a sheet press pressure of 300 kg weight / cm 2, the BN aggregated particles can be observed as aggregated particles, and particularly the card house structure can be observed.
- Example 6 Using the prepared heat-dissipating sheet slurry, it was applied to a substrate by the doctor blade method in the same manner as in Example 6. After heat drying, pressing was performed to obtain a heat-dissipating sheet having a sheet thickness of about 200 ⁇ m. The obtained heat radiation sheet was subjected to thermal conductivity, withstand voltage, and X-ray diffraction measurement.
- Example 3 Using the prepared slurry for heat dissipation sheet, a heat dissipation sheet having a sheet thickness of about 200 ⁇ m was obtained in the same manner as in Example 6. The obtained heat radiation sheet was subjected to thermal conductivity, withstand voltage, and X-ray diffraction measurement. The measurement results of Examples 2, 6, 7, and 8 and Comparative Examples 1, 3, 15, and 16 are shown in Table 3.
- the molded body containing these has high thermal conductivity and high voltage resistance, and thus a molded sheet with higher heat dissipation performance and higher voltage resistance performance can be obtained.
- Detailed mechanisms are not well understood, for example, high heat dissipation performance by the use of BN agglomerated particles, since the BN primary particles, D 50 of BN agglomerated particles is increased, between primary particles, aggregate particles to each other This is considered to be because the interfacial resistance was reduced.
- the inorganic particles smaller than the BN aggregated particles the voids between the large particles can be efficiently reduced, and the withstand voltage performance is further improved.
- the prepared slurry for an insulating heat dissipation sheet was applied to a copper foil (105 ⁇ m). Then, after heat-drying, the application surfaces were bonded together and pressed to obtain a double-sided copper foil beam insulation heat dissipation sheet.
- the film thickness of the insulating heat radiating sheet portion was about 300 ⁇ m.
- One side of the insulating heat dissipation sheet was patterned by etching to obtain an insulating circuit substrate shown in FIG. Further, die bonding and wire bonding were performed to produce a device. The result is shown in FIG.
- the BN aggregated particles of the present invention it is possible to form a high-quality heat-dissipating sheet having high thermal conductivity required for power semiconductor devices, for example.
- the BN aggregated particle-containing composition of the present invention it is possible to form a high-quality heat-dissipating sheet having high thermal conductivity required for, for example, a power semiconductor device.
- the power semiconductor device having the heat dissipation sheet is useful for producing a power semiconductor device using a high-efficiency substrate capable of high-temperature operation, such as next-generation SiC and GaN.
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Abstract
Description
本発明はまた、このBN凝集粒子を含有するBN凝集粒子含有樹脂組成物と、このBN凝集粒子含有樹脂組成物を成形してなる成形体に関する。
本発明はまた、特定のBN一次粒子を特定の状態で含む、シートに関する。
これらの中で、h-BNは、黒鉛と同じ層状構造を有し、合成が比較的容易でかつ熱伝導性、固体潤滑性、化学的安定性、耐熱性に優れるという特徴を備えていることから、電気・電子材料分野で多く利用されている。
(a-1)窒化ホウ素一次粒子(以下「BN一次粒子」と称する。)が凝集してなる窒化ホウ素凝集粒子(以下「BN凝集粒子」と称す。)であって、10mmφの粉末錠剤成形機で0.85ton/cm2の成型圧力で成型して得られたペレット状の試料を粉末X線回折測定して得られる、BN一次粒子の(100)面と(004)面のピーク面積強度比((100)/(004))が0.25以上であり、かつ該BN凝集粒子を0.2mm深さのガラス試料板に表面が平滑になるように充填し、粉末X線回折測定して得られる、BN一次粒子の(002)面ピークから求めたBN一次粒子の平均結晶子径が375Å以上であることを特徴とするBN凝集粒子。
(a-2)BN凝集粒子の平均粒子径D50が26μm以上である、(a-1)に記載のBN凝集粒子。
(a-3)BN凝集粒子の比表面積が8m2/g以下である、(a-1)又は(a-2)に記載のBN凝集粒子。
(a-4)BN凝集粒子が球状である(a-1)ないし(a-3)のいずれかに記載のBN凝集粒子。
(a-5)BN凝集粒子がカードハウス構造を有する(a-1)ないし(a-4)のいずれかに記載のBN凝集粒子。
(a-6)(a-1)ないし(a-5)のいずれかに記載のBN凝集粒子と他のフィラーの混合物であるBN凝集粒子組成物。
(a-7)樹脂と、(a-1)ないし(a-5)のいずれかに記載のBN凝集粒子を含むBN凝集粒子含有樹脂組成物。
(a-8)(a-1)ないし(a-5)のいずれかに記載のBN凝集粒子を含む成形体。
前記造粒ステップにおいて該BNスラリーの粘度が200mPa・s以上5000mPa・s以下であり、前記加熱ステップにおいて加熱処理を1800℃以上2300℃以下で行うことを特徴とするBN凝集粒子の製造方法。
(a-10)原料窒化ホウ素粉末中の酸素濃度が、1質量%以上10質量%以下である(a-9)に記載のBN凝集粒子の製造方法。
(a-11)(a-9)または(a-10)に記載された製造方法によって得られるBN凝集粒子。
該シートをX線回折測定して得られる、該シート中の窒化ホウ素一次粒子(以下「BN一次粒子」と称す。)の(100)面と(004)面のピーク強度比((100)/(004))が1.0以上であり、かつ
該シートをX線回折測定して得られる、該シート中のBN一次粒子の(002)面ピークから求めたBN一次粒子の平均結晶子径が375Å以上であることを特徴とするシート。
(a-13)
前記シートをX線回折測定して得られる、該シート中の窒化ホウ素一次粒子(以下「BN一次粒子」と称す。)の(100)面と(004)面のピーク面積強度比((100)/(004))が0.6以上である(a-12)に記載のシート。
(b-1)窒化ホウ素一次粒子が凝集してなる窒化ホウ素凝集粒子(A)と無機粒子(B)とを含む組成物であって、少なくとも窒化ホウ素凝集粒子(A)がカードハウス構造を有し、窒化ホウ素凝集粒子(A)の体積平均粒子径(D50)が25μm以上であり、かつ、窒化ホウ素凝集粒子(A)の体積平均粒子径(D50)>無機粒子(B)の体積平均粒子径(D50)であることを特徴とする窒化ホウ素凝集粒子含有組成物。
該組成物は、窒化ホウ素凝集粒子(A)がカードハウス構造を有し、窒化ホウ素凝集粒子(A)と無機粒子の体積平均粒子径(D50)が上記の関係を満足することにより、BN凝集粒子を構成するBN一次粒子中の結晶粒界で生じるフォノン散乱を減らすことができ、その結果として、高い熱伝導性を示す。
該組成物は、BN一次粒子の特定の結晶面の配向を保ったまま、すなわち粉末X線回折測定による(100)面と(004)面のピーク強度比((100)/(004))が3以上に保たれ、かつ平均結晶子径が大きいため、凝集粒子としての高熱伝導性に加え、樹脂と複合化した際の成形体においても高熱伝導性を示すという効果を奏するものである。
(b-4)窒化ホウ素凝集粒子(A)及び無機粒子(B)が球状である(b-1)~(b-3)のいずれかに記載の窒化ホウ素凝集粒子含有組成物。
(b-5)窒化ホウ素凝集粒子(A)の含有割合が、窒化ホウ素凝集粒子(A)と無機粒子(B)の合計に対して、30~95質量%である(b-1)~(b-4)のいずれかに記載の窒化ホウ素凝集粒子含有組成物。
(b-6)無機粒子(B)が窒化ホウ素、窒化アルミニウム、アルミナ、酸化亜鉛、酸化マグネシウム、酸化ベリリウム及び、酸化チタンからなる群から選ばれる一種以上である(b-1)~(b-5)のいずれかに記載の窒化ホウ素凝集粒子含有組成物。
(b-7)(b-1)~(b-6)のいずれかに記載の窒化ホウ素凝集粒子含有組成物を含む塗布液。
(b-8)(b-1)~(b-6)のいずれかに記載の窒化ホウ素凝集粒子含有組成物を成形してなる成形体。
(b-10)更に、該シートをX線回折測定して得られる、該シート中のBN一次粒子の(002)面ピークから求めた窒化ホウ素凝集粒子の平均結晶子径が300Å以上であることを特徴とするシート。
本発明のBN凝集粒子は、BN一次粒子が凝集して形成されたものであり、本願発明の効果を損なわない範囲で、上記BN一次粒子以外の成分を含有してもよい。BN一次粒子以外の成分としては、後記の[BN凝集粒子の製造方法]で述べる、スラリーに添加してもよいバインダー、界面活性剤、溶媒に由来する成分を挙げることができる。
ここで「球状」とは、アスペクト比(長径と短径の比)が1以上2以下、好ましくは1以上1.5以下であることをさす。本発明のBN凝集粒子のアスペクト比は、SEMで撮影された画像から200個以上の粒子を任意に選択し、それぞれの長径と短径の比を求めて平均値を算出することにより決定する。
・一次粒子の大きさ
BN凝集粒子を構成するBN一次粒子の長軸は通常0.5μm以上、好ましくは0.6μm以上、より好ましくは、0.8μm以上、更に好ましくは1.0μm以上、特に好ましくは1.1μm以上である。また通常10μm以下、好ましくは5μm以下、より好ましくは3μm以下である。
尚、上記長軸とはSEM測定により得られたBN凝集粒子1粒を拡大し、1粒のBN凝集粒子を構成しているBN一次粒子について、画像上で観察できるBN一次粒子の最大長を平均した値である。
BN一次粒子の結晶構造は、特に限定されないが、合成の容易さと熱伝導性の点で六方晶系のh-BNを主成分として含むものが好ましい。また、バインダーとしてBN以外の無機成分が含まれる場合、熱処理の過程でそれらが結晶化するが、BNが主成分として含まれていればよい。なお、上記BN一次粒子の結晶構造は、粉末X線回折測定により確認することができる。
BN凝集粒子を粉末X線回折測定して得られるBN一次粒子の(002)面ピークから求めたBN一次粒子の平均結晶子径は、特に制限はされないが、平均結晶子径は大きいことが熱伝導率の点から好ましい。例えば、通常300Å以上、好ましくは320Å以上、より好ましくは375Å以上であり、更に好ましくは380Å以上、より更に好ましくは390Å以上、特に好ましくは400Å以上であり、通常5000Å以下、好ましくは2000Å以下、更に好ましくは1000Å以下である。上記平均結晶子径が大きすぎると、BN一次粒子が成長しすぎるため、BN凝集粒子内の間隙が多くなり、成形体とする際の成形性が悪化するとともに、間隙が多くなることにより熱伝導性が向上しなくなる傾向がある。上記平均結晶子径が小さすぎると、BN一次粒子内の粒界が増えるため、フォノン散乱が結晶粒界で発生し、低熱伝導になる傾向がある。
なお、ここで、「平均結晶子径」とは、粉末X線回折測定によって得られるBN一次粒子の(002)面ピークから、後述の実施例において記載の通り、Scherrer式にて求められる結晶子径である。
シート等の成形体に成形する前の粉末のBN凝集粒子を0.2mm深さのガラス試料板に表面が平滑になるように充填し、粉末X線回折測定して得られるBN一次粒子の(100)面と(004)面のピーク強度比((100)/(004))が3以上である。
BN凝集粒子の(100)面と(004)面のピーク強度比は通常3以上、好ましくは3.2以上、より好ましくは3.4以上、更に好ましくは3.5以上であり、通常10以下、好ましくは8以下、更に好ましくは7以下である。上記上限より大きいと、成形体とした際に粒子が崩壊しやすくなる傾向があり、上記下限未満だと、厚み方向の熱伝導性が向上しない傾向がある。
なお、ピーク強度比は粉末X線回折測定により測定された該当するピーク強度の強度比から計算することができる。
BN凝集粒子を10mmφの粉末錠剤成形機で0.85ton/cm2の成形圧力で成形して得られたペレット状の試料を粉末X線回折測定して得られる、BN一次粒子の(100)面と(004)面のピーク面積強度比((100)/(004))が0.25以上であるとしても表現ができる。このピーク面積強度比((100)/(004))は、好ましくは0.3以上、好ましくは0.5以上、より好ましくは0.7以上、更に好ましくは0.81以上、特に好ましくは0.85以上、とりわけ好ましくは0.91以上である。また、上限は特に制限はないが、通常10.0以下、好ましくは5.0以下、より好ましくは4.0以下であり、更に好ましくは2.0以下であり、特に好ましくは1.6以下である。
例えば、樹脂製の高放熱基板は、樹脂製基板内部の空隙低減や分散させたBN凝集粒子同士の完全な接触のために、0.85ton/cm2以上2.54ton/cm2以下のような比較的高い圧力で成形されると考えられる。このため、上記圧力範囲でもBN一次粒子の配向変化が少ないBN凝集粒子が熱伝導性向上には必要である。
尚、0.85ton/cm2以上2.54ton/cm2の範囲におけるピーク面積強度比は、上記圧力範囲において一点でも所定の数値を満たせば問題なく、本発明の圧力範囲全てにおいて達成する必要はない。また、好ましくは、0.85ton/cm2、1.69ton/cm2、2.54ton/cm2の3点にて所定の数値を満たすことである。
BN凝集粒子の平均粒子径(D50)は、通常5μm以上であり、好ましくは10μm以上、より好ましくは25μm以上、更に好ましくは26μm以上であり、特に好ましくは30μm以上、最も好ましくは40μm以上であり、45μm以上であっても好ましく、50μm以上であっても好ましい。また、通常200μm以下、好ましくは150μm以下、更に好ましくは100μm以下である。大きすぎると成形体とした際に表面の平滑性が悪くなる、BN凝集粒子間の間隙が多くなる等により、熱伝導性が向上しない傾向があり、小さすぎると成形体とした際にBN凝集粒子間の接触抵抗が大きくなる、BN凝集粒子自体の熱伝導性が低くなる等の傾向がある。
BN凝集粒子の破壊強度は、通常2.5MPa以上、好ましくは3.0MPa以上、より好ましくは3.5MPa以上、更に好ましくは4.0MPa以上であり、通常20MPa以下、好ましくは15MPa以下、更に好ましくは10MPa以下である。大きすぎると、粒子の強度が強すぎるため、成形体とした際に表面平滑性が悪くなり、熱伝導性が低下する傾向があり、小さすぎると、成形体を作製する際の圧力で粒子が変形しやすくなり、熱伝導性が向上しない傾向がある。
式:Cs=2.48P/πd2
Cs:破壊強度(MPa)
P:破壊試験力(N)
d:粒子径(mm)
BN凝集粒子の全細孔容積は、通常2.2cm3/g以下である。全細孔容積が小さいものは、BN凝集粒子内が密になっているために、熱伝導を阻害する境界面を少なくすることが可能となり、より熱伝導性の高いBN凝集粒子となる。BN凝集粒子の全細孔容積が大きすぎると、組成物中のフィラーとして用いた場合に、細孔に樹脂が取り込まれ、見かけの粘度が上昇する場合があり、組成物の成形加工或いは塗布液の塗工が困難となる可能性がある。
凝集BN粉末の全細孔容積は、窒素吸着法および水銀圧入法で測定することができる。
BN凝集粒子の比表面積は通常1m2/g以上であるが、好ましくは3m2/g以上50m2/g以下、より好ましくは5m2/g以上40m2/g以下である。また、8m2/g以下であることも好ましく、7.25m2/g以下であることも好ましい。BN凝集粒子の比表面積が、この範囲であると、樹脂と複合化した際に、BN凝集粒子同士の接触抵抗が低減される傾向にあり、BN凝集粒子含有樹脂組成物の粘度上昇も抑制できるため好ましい。比表面積は、BET1点法(吸着ガス:窒素)で測定することができる。
BN凝集粒子をフィラーとして用いる場合には、樹脂の取り込みを最小限とするためにBN凝集粒子のバルク密度は大きい方が良く、通常0.3g/cm3以上であることが好ましく、より好ましくは0.35g/cm3以上、更に好ましくは0.4g/cm3以上である。BN凝集粒子のバルク密度が小さすぎる場合、見かけの体積が大きくなり、BN凝集粒子含有樹脂組成物中の樹脂に対して、添加するBN凝集粒子の体積が多くなるとともに、樹脂の取り込みが大きくなり、また、BN凝集粒子の取り扱い性が著しく悪化する傾向がある。BN凝集粒子のバルク密度の上限については特に制限はないが、通常0.95g/cm3以下、好ましくは0.9g/cm3以下、より好ましくは0.85g/cm3以下である。BN凝集粒子のバルク密度が大きすぎるとBN凝集粒子含有樹脂組成物中で凝集BNの分散に偏りが生じ、沈降しやすくなる傾向がある。
なお、BN凝集粒子のバルク密度は、粉体のバルク密度を測定する通常の装置や方法を用いて求めることができる。
本発明のBN凝集粒子は、好ましくは、粘度が200~5000mPa・sである原料BN粉末を含むスラリー(以下「BNスラリー」と称す場合がある。)を用いて粒子を造粒し、造粒粒子を加熱処理することによって、該造粒粒子の大きさを保持したままBN凝集粒子を構成するBN一次粒子の結晶子を成長させて、製造することができる。BNスラリーの粘度は、好ましくは300mPa・s以上、より好ましくは500mPa・s以上、更に好ましくは700mPa・s以上、特に好ましくは1000mPa・s以上であり、好ましくは4000mPa・s以下、より好ましくは3000mPa・s以下である。
一方BNスラリーの粘度を5000mPa・s以下とすることにより、造粒を容易にすることができる。BNスラリーの粘度の調製方法は、後述する。
さらに、本発明のBN凝集粒子をフィラーとしてBN凝集粒子含有樹脂組成物を作製する場合、同一の充填量においても、他のBN粒子と比較して得られる成形体の熱伝導率が劇的に改善できる。これは、本発明のBN凝集粒子では、BN凝集粒子を構成するBN一次粒子の平均結晶粒子径の増大により、BN一次粒子中の結晶粒界が減少すること、BN凝集粒子を構成するBN一次粒子の特定面が配向していることによると推察され、好ましくは、凝集粒子の体積基準の平均粒子径D50が大きいことにより、BN凝集粒子間の接触抵抗が低減することも影響すると考えられる。
すなわち、本願発明によれば、当業者では通常制御することを想定していなかったスラリー粘度を特定の範囲に制御することにより、BN凝集粒子を構成するBN一次粒子の平均結晶子径を大きくすることが可能である製造方法を見出したものである。
なお、上記ピーク強度比および結晶子径は、BNスラリーから製造する造粒粒子を加熱処理する際の焼成温度、原料BN粉末中に存在する酸素濃度によっても制御できる。具体的には、後程述べる通り、BNスラリーから製造する造粒粒子を加熱処理する際の焼成温度範囲を1800℃以上2300℃以下とすることでピーク強度比を3以上とすることができ、原料BN粉末中に存在する酸素濃度が1.0重量%以上の原料を用いることで、結晶子径を所望の範囲に制御できる。即ち、適切な焼成温度範囲と適切な酸素濃度の原料BN粉末を用いることで上記ピーク強度比と上記平均結晶子径を同時に制御できる。
本発明によって得られるBN凝集粒子は、高熱伝導性を維持しながら様々な大きさに設計することが可能なため、成形体として幅広い用途に適用可能である。
<原料BN粉末>
・原料BN粉末の種類
本発明で用いる原料BN粉末としては、市販のh-BN、市販のαおよびβ-BN、ホウ素化合物とアンモニアの還元窒化法により作製されたBN、ホウ素化合物とメラミンなどの含窒素化合物から合成されたBNなど何れも制限なく使用できるが、特にh-BNが本発明の効果をより発揮する点で好ましく用いられる。
本発明で用いる原料BN粉末の形態としては、粉末X線回折測定により得られるピークの半値幅が広く、結晶性が低い粉末状のBN粒子が好適である。結晶性の目安として、粉末X線回折測定から得られる(002)面のピーク半値幅が、2θの角度で、通常0.4°以上、好ましくは0.45°以上、より好ましくは0.5°以上である。また、通常2.0°以下、好ましくは1.5°以下、更に好ましくは1°以下である。上記上限より大きいと、結晶子が十分大きくならず、大きくするためには長時間を要するため、生産性が悪くなる傾向がある。上記下限未満だと、結晶性が高すぎて、十分な結晶成長が見込めず、また、スラリー作製時の分散安定性が悪くなる傾向がある。なお、粉末X線回折測定方法は後述の実施例の項に記載する。
BN結晶成長の観点からは、原料BN粉末中に酸素原子がある程度存在することが好ましく、本発明では、原料BN粉末中の全酸素濃度は、通常1質量%以上、好ましくは2質量%以上、より好ましくは3質量%以上、更に好ましくは4質量%以上である。また、通常、10質量%以下、更に好ましくは9質量%以下である。上記上限より大きいと、熱処理後も酸素が残存しやすくなるため、熱伝導性の改善効果が小さくなる傾向がある。上記下限未満だと、結晶性が高すぎて、結晶成長が見込めず、粉末X線回折測定から確認できるピーク強度比が所望の範囲から外れる傾向がある。
なお、原料BN粉末の全酸素濃度を上記範囲に調製する方法としては、例えばBN合成時の合成温度を1500℃以下の低温で行う方法、500℃~900℃の低温の酸化雰囲気中で原料BN粉末を熱処理する方法などが挙げられる。
なお、原料BN粉末の全酸素濃度は、不活性ガス融解-赤外線吸収法により、株式会社堀場製作所製の酸素・窒素分析計を用いて測定することができる。
原料BN粉末の全細孔容積は通常1.0cm3/g以下であるが、好ましくは0.3cm3/g以上1.0cm3/g以下、より好ましくは0.5cm3/g以上1.0cm3/g以下である。全細孔容積が1.0cm3/g以下であることにより、原料BN粉末が密になっているために、球形度の高い造粒が可能となる。
なお、原料BN粉末の全細孔容積は、窒素吸着法および水銀圧入法で測定することができ、比表面積は、BET1点法(吸着ガス:窒素)で測定することができる。原料BN粉末の全細孔容積及び比表面積の具体的測定方法は、後述の実施例の項に記載する。
BNスラリーの調製に用いる媒体としては特に制限はなく、水及び/又は各種の有機溶媒を用いることができるが、噴霧乾燥の容易さ、装置の簡素化などの観点から、水を用いることが好ましく、純水がより好ましい。
具体的にはBNスラリーの調製に用いる媒体の使用量は、通常10質量%以上、好ましくは20質量%以上、より好ましくは30質量%以上であり、通常、70質量%以下、好ましくは65質量%以下、より好ましくは60質量%以下である。媒体の使用量が上記上限より大きいと、スラリー粘度が低くなりすぎるため、沈降などによるBNスラリーの均一性が損なわれ、得られるBN凝集粒子を構成するBN一次粒子の結晶子径が所望の範囲から外れる傾向がある。下限未満であるとスラリー粘度が高すぎるため、造粒が困難になる傾向がある。すなわち、上記媒体の使用量が上記範囲外であると、BN凝集粒子の大きさとBN凝集粒子を構成するBN一次粒子の結晶性とBN一次粒子中の結晶粒界の低減を同時に満足することが困難になる。
BNスラリーには、スラリーの粘度を調節すると共に、スラリー中の原料BN粉末の分散安定性(凝集抑制)の観点から、種々の界面活性剤を添加するのが好ましい。
界面活性剤としては、アニオン系界面活性剤、カチオン系界面活性剤、非イオン性界面活性剤等を用いることができ、これらは、1種を単独で用いてもよく、2種以上を混合して用いてもよい。
BNスラリーは、原料BN粉末を効果的に粒子状に造粒するために、バインダーを含んでもよい。バインダーは、BN一次粒子を強固に結びつけ、造粒粒子を安定化するために作用する。
BNスラリーに用いるバインダーとしては、BN粒子同士の接着性を高めることができるものであればよいが、本発明においては、造粒粒子は粒子化後に加熱処理されるため、この加熱処理工程における高温条件に対する耐熱性を有するものが好ましい。
スラリー調製方法は、原料BN粉末及び媒体、更に必要により、バインダー、界面活性剤が均一に分散し、所望の粘度範囲に調製されていれば特に限定されないが、原料BN粉末及び媒体、更に必要により、バインダー、界面活性剤を用いる場合、好ましくは以下のように調製する。
添加の順番は特に制限はないが、大量の原料BN粉末をスラリー化する場合、だまなどの凝集物ができやすくなるため、水に界面活性剤とバインダーを加えた水溶液を作製した後、所定量の原料BN粉末を少量ずつ添加し、ここにジルコニア性のセラミックボールを加えて、ポットミル回転台で分散、スラリー化しても良い。
BNスラリーから造粒粒子を得るには、スプレードライ法、転動法、流動層法、そして撹拌法などの一般的な造粒方法を用いることができ、この中でもスプレードライ法が好ましい。
スプレードライ法では、原料となるスラリーの濃度、装置に導入する単位時間当たりの送液量と送液したスラリーを噴霧する際の圧空圧力及び圧空量により、所望の大きさの造粒粒子を製造することが可能であって、球状の造粒粒子を得ることも可能である。使用するスプレードライ装置に制限はないが、より大きな球状の造粒粒子とするためには、回転式ディスクによるものが最適である。このような装置としては、大川原化工機社製スプレードライヤーFシリーズ、藤崎電機社製スプレードライヤー「MDL-050M」などが挙げられる。
上記のBN造粒粒子は、更に非酸化性ガス雰囲気下に加熱処理することでBN凝集粒子を製造することができる。
ここで、非酸化性ガス雰囲気とは、窒素ガス、ヘリウムガス、アルゴンガス、アンモニアガス、水素ガス、メタンガス、プロパンガス、一酸化炭素ガスなどの雰囲気のことである。ここで用いる雰囲気ガスの種類により凝集BN粒子の結晶化速度が異なるものとなり、結晶化を短時間で行うためには特に窒素ガス、もしくは窒素ガスと他のガスを併用した混合ガスが好適に用いられる。
加熱処理温度は通常1800℃以上、2300℃以下であるが、好ましくは1900℃以上であり、また好ましくは2200℃以下である。加熱処理温度が低すぎると、BNの平均結晶子の成長が不十分となり、BN凝集粒子および成形体の熱伝導率が小さくなる場合がある。加熱処理温度が高すぎると、BNの分解などが生じてしまうおそれがある。
加熱処理時間は、通常3時間以上、好ましくは4時間以上、より好ましくは5時間以上、また通常20時間以下、好ましくは15時間以下である。加熱処理時間が上記下限未満の場合、結晶成長が不十分となり、上記上限を超えるとBNが一部分解するおそれがある。
上記加熱処理後のBN凝集粒子は、粒子径分布を小さくし、BN凝集粒子含有樹脂組成物に配合したときの粘度上昇を抑制するために、好ましくは分級処理する。この分級は、通常、造粒粒子の加熱処理後に行われるが、加熱処理前の造粒粒子について行い、その後加熱処理に供してもよい。
乾式の分級には、篩による分級のほか、遠心力と流体抗力の差によって分級する風力分級などがあるが、旋回気流式分級機、強制渦遠心式分級機、半自由渦遠心式分級機などの分級機を用いて行うこともできる。これらの中で、サブミクロンからシングルミクロン領域の小さな微粒子を分級するには旋回気流式分級機を、それ以上の比較的大きな粒子を分級するには半自由渦遠心式分級機など、分級する粒子の粒子径に応じて適宜使い分ければよい。
本発明のBN凝集粒子含有樹脂組成物は、少なくとも本発明のBN凝集粒子と樹脂とを含有するものである。なお本発明のBN凝集粒子は、その形状的な特徴から、BN凝集粒子含有樹脂組成物のフィラーとして好適に用いられる。
BN凝集粒子含有樹脂組成物中におけるBN凝集粒子の含有割合(以下「フィラー充填量」と称する場合がある。)は、BN凝集粒子と樹脂の合計を100質量%として、通常5質量%以上、好ましくは30質量%以上、より好ましくは50質量%以上であり、通常95質量%以下、好ましくは90質量%以下である。上記上限より大きいと、粘度が高くなりすぎて成形加工性が確保できなくなるとともに、BN凝集粒子の密な充填が阻害されるために熱伝導性が低下する傾向があり、上記下限未満だと、成形加工性は確保できるものの、BN凝集粒子が少なすぎて熱伝導性が向上しない傾向がある。
なお、BN凝集粒子(A)の体積平均粒子径(D50)>無機粒子(B)の体積平均粒子径(D50)を満足する限り、無機粒子(B)が凝集粒子であってもよい。
BN凝集粒子含有組成物中のBN凝集粒子(A)の含有割合は、BN凝集粒子(A)と無機粒子(B)の合計に対して、通常30質量%以上であり、好ましくは50質量%以上であり、また、通常95重量%以下であり、好ましくは90質量%以下である。この範囲であることにより、凝集粒子によりパーコレーションが起こり高熱伝導率となる傾向にある。
BN凝集粒子含有組成物中におけるBN凝集粒子(A)と無機粒子(B)の合計の含有割合(以下「フィラー充填量」と称する場合がある。)は、BN凝集粒子(A)と無機粒子(B)と樹脂との合計を100質量%として、通常5質量%以上、好ましくは30質量%以上、より好ましくは50質量%以上であり、また、通常95質量%以下であり、好ましくは90質量%以下である。上記範囲であることにより、該組成物を用いて成形体を製造する際の成形性が確保でき、かつ、得られた成形体の熱伝導性が良好となる傾向がある。
BN凝集粒子含有樹脂組成物に用いる樹脂としては、特に制限はないが、好ましくは硬化性樹脂および/または熱可塑性樹脂である。例えば、硬化性樹脂としては、熱硬化性、光硬化性、電子線硬化性などが挙げられ、耐熱性、吸水性、寸法安定性などの点で、熱硬化性樹脂および/または熱可塑性樹脂が好ましく、これらの中でもエポキシ樹脂がより好ましい。これらの樹脂は2種以上組わせて用いてもよい。
エポキシ樹脂を用いる場合、そのTgは特段限定されないが通常0℃以上、好ましくは10℃以上、より好ましくは25℃以上であり、また通常350℃以下、好ましくは300℃以下、より好ましくは250℃以下である。
ここで、重量平均分子量とは、ゲルパーミエイションクロマトグラフィーで測定したポリスチレン換算の値である。
これらは1種を単独で用いてもよく、2種以上を混合して用いてもよい。
これらは1種を単独で用いてもよく、2種以上を混合して用いてもよい。
本発明のBN凝集粒子含有樹脂組成物は、本発明の効果が得られる範囲において、さらなる成分を含有していてもよい。このようなさらなる成分としては、例えば、上述した樹脂の他、無機フィラーである窒化アルミニウム、窒化ケイ素、繊維状、板状、粒子状凝集BN等の窒化物粒子、アルミナ、繊維状アルミナ、酸化亜鉛、酸化マグネシウム、酸化ベリリウム、酸化チタン等の絶縁性金属酸化物、ダイヤモンド、フラーレン、水酸化アルミニウム、水酸化マグネシウムなどの無機フィラー、無機フィラーとマトリックス樹脂の界面接着強度を改善するシランカップリング剤などの表面処理剤、還元剤等の絶縁性炭素成分、樹脂硬化剤、樹脂硬化促進剤、粘度調整剤、分散剤が挙げられる。この中でも、熱伝導度の向上、耐電圧の向上から、窒化物粒子が好ましく、粒子状凝集BNがより好ましい。
なお、本発明のスラリーを用いる場合、分散剤を用いることが、成膜性を上げる上で好ましい。
これらは、1種を単独で用いてもよく、2種以上を混合して用いてもよい。
本発明のBN凝集粒子含有樹脂組成物は、本発明のBN凝集粒子、場合によっては無機粒子、樹脂、及び必要に応じて添加されるその他の成分を撹拌や混練によって均一に混合することによって得ることができる。その混合には、例えば、ミキサー、ニーダー、単軸又は二軸混練機等の一般的な混練装置を用いることができ、混合に際しては、必要に応じて加熱してもよい。
なお、溶媒を含む系や樹脂が液体状態で、本発明のBN凝集粒子含有組成物が流動性を有するスラリー状態(本明細書では塗布用スラリーともいう)の場合、スラリーにする際の調製方法は、特に限定されず、従来公知の方法を用いることができる。なお、その際、塗布液の均一性の向上、脱泡等を目的として、ペイントシェーカーやビーズミル、プラネタリミキサ、攪拌型分散機、自公転攪拌混合機、三本ロール、ニーダー、単軸又は二軸混練機等の一般的な混練装置などを用いて混合・撹拌することが好ましい。
本発明の成形体は、本発明のBN凝集粒子を使用した成形体、好ましくはBN凝集粒子含有樹脂組成物を成形してなるものである。成形体の成形方法は一般に用いられる方法を用いることができる。
例えば、本発明のBN凝集粒子含有樹脂組成物が可塑性や流動性を有する場合、該BN凝集粒子含有樹脂組成物を所望の形状で、例えば型へ収容した状態で硬化させることによって成形することができる。
上述スラリーが溶媒を含む場合は、ホットプレート、熱風炉、IR加熱炉、真空乾燥機、高周波加熱機など公知の加熱方法で溶媒を除去することができる。
また、本発明のBN凝集粒子含有樹脂組成物がエポキシ樹脂やシリコーン樹脂等の熱硬化性樹脂組成物である場合、成形体の成形、すなわち硬化は、それぞれの硬化温度条件で行うことができる。
また、本発明の成形体は、本発明のBN凝集粒子含有樹脂組成物の硬化物を所望の形状に削り出すことによっても得ることができる。
以下、BN凝集粒子を含むBN凝集粒子含有スラリーを用いて放熱シートを製造する方法を具体的に説明する。シートの製造方法は、上述したスラリーを調製する工程の他、後述する該スラリーを基材に塗布して(塗布工程)、乾燥させる工程(乾燥工程)、該塗布乾燥物を加圧して成形する工程(シート化工程)、及び該成形物を熱硬化させる工程(熱硬化工程)を少なくとも有する。
まず基板の表面に、BN凝集粒子含有スラリーを用いて塗膜を形成する。
即ち、スラリーを用いて、ディップ法、スピンコート法、スプレーコート法、ブレード法、その他の任意の方法で塗膜を形成する。組成物塗布液の塗布には、スピンコーター、スリットコーター、ダイコーター、ブレードコーター、コンマコーター、スクリーン印刷、ドクターブレード、アプリケーター、スプレー塗布などの塗布装置を用いることにより、基板上に所定の膜厚の塗膜を均一に形成することが可能であり、ギャップを調整可能なブレードコーターが好ましい。
本発明のシートは、自立膜としても用いることができ、さらには金属箔もしくは板(銅、アルミ、銀、金)、PET,PENなどの樹脂フィルム、ガラスなど公知の基材の上に製膜することができる。なお、これらの基板は使用の形態によっては、剥がして使用することもできし、基板/放熱シート/基板のように積層構造としてもよい。
なお、基板としては、後述の厚さの銅箔が一般的に用いられるが、何ら銅基板に限定されるものではない。また、基板の表面には凹凸があったり、また、表面処理が為されていてもよい。
次に、基板に塗布されたBN凝集粒子含有スラリーを乾燥させ塗布乾燥物を得る。乾燥温度は、通常15℃以上、好ましくは20℃以上、より好ましくは23℃以上であり、通常100℃以下、好ましくは90℃以下、より好ましくは80℃以下、更に好ましくは70℃以下である。
この乾燥の加熱温度が低過ぎたり、加熱時間が短過ぎたりすると、塗膜中の有機溶媒を十分に除去し得ず、得られる乾燥膜中に有機溶媒が残留し、残留した有機溶媒が次のシート化工程における高温加圧処理で蒸発し、残留溶媒の蒸発跡がボイドとなって、高熱伝導性、高絶縁性、所定の物理的強度等を有するシートを形成し得ない。逆に、乾燥の加熱温度が高過ぎたり、加熱時間が長過ぎたりすると、樹脂の硬化が進行し、良好な乾燥膜とすることができない。
この乾燥の時間が下限未満の場合、塗膜中の有機溶媒を十分に除去し得ず、得られる乾燥膜中に有機溶媒が残留し、残留した有機溶媒が次のシート化工程における高温加圧処理で蒸発し、残留溶媒の蒸発跡がボイドとなって、高熱伝導性、高絶縁性、所定の物理的強度等を有するシートを形成し得ない。逆に、乾燥の時間が上限を超えると、樹脂が乾燥しすぎて、良好な強度の塗布膜が得られないばかりか、シート化工程における樹脂の可塑化によっても十分な流動性が得られず、シート内に存在するボイドに十分樹脂が浸透できなくなって、高熱伝導性、高絶縁性、所定の物理的強度等を有するシートを形成できない傾向がある。
この乾燥工程において得られた塗布乾燥物中の150℃以上を有する有機化合物量は、0ppm超、好ましくは0.001ppm以上、より好ましくは0.1ppm以上、更に好ましくは1ppm以上であり、1800ppm以下、好ましくは1500ppm以下、より好ましくは1300ppm以下である。この範囲内であると、本製造方法で得られたシートは、高い熱伝導性と耐電圧値を示す。
乾燥工程の後には、塗布乾燥物を加圧、成形する工程(シート化工程)を行う。シート化工程では、通常、銅基板に塗布、乾燥した塗布乾燥物を所定の大きさにカットする。
シート化をする際の加熱温度(プレス温度)は、通常80℃以上、好ましくは90℃以上、より好ましくは、100℃以上、更に好ましくは110℃以上であり、通常300℃以下、好ましくは250℃以下、より好ましくは200℃以下である。
この加熱温度が上記下限未満の場合、熱硬化反応が十分進行せず、BN凝集粒子同士の接触やBN凝集粒子と樹脂界面の接触も不十分となるため高熱伝導性、高絶縁性、所定の物理的強度等を有するシートを形成し得ない。逆に、前記範囲の上限を超える場合、樹脂の分解が生じやすくなり、該分解によるボイドや分子量の低下により、高熱伝導性、高絶縁性、所定の物理的強度等を有するシートを形成できない傾向がある。
プレス圧力は、銅基板上の乾燥膜に、通常10kgf/cm2以上、好ましくは150kgf/cm2以上、より好ましくは200kgf/cm2以上、更に好ましくは250kgf/cm2以上であり、通常、2000kgf/cm2以下、好ましくは1000kgf/cm2以下、より好ましくは900kgf/cm2以下、更に好ましくは800kgf/cm2以下を加圧する。この加圧時の加重を上記上限以下とすることにより、BN凝集粒子が破壊することなく、シート中に空隙などがない高い熱伝導性を有するシートを得ることが出来る。また、加重を上記下限以上とすることにより、BN凝集粒子間の接触が良好となり、熱伝導パスを形成しやすくなるため、高い熱伝導性を有するシートを得ることが出来る。
熱硬化工程では、銅基板に塗布、乾燥した組成物膜を通常80℃以上、好ましくは100℃以上、例えば100~200℃の温度で1~30分程度所定の加重をかけて加圧することにより、塗布・乾燥膜中の樹脂の溶融粘度を低下させると同時に、ある程度硬化反応を進めて、銅基板への接着を促進する加圧工程と、その後、樹脂膜を完全に硬化させるために、所望の硬化温度、例えば150℃以上で2~4時間程度、オーブンなどで加熱することにより硬化反応を行わせてシートを作製する硬化工程とが行われる。硬化工程において完全硬化させる際の加熱温度の上限は、使用する樹脂が分解、変質しない温度であり、樹脂の種類、グレードにより適宜決定されるが、通常300℃以下で行われる。
回路基板パターニングの方法は特段限定されず、例えば、特開2014-209608号公報の文献に記載のような既知の方法により製造できる。また、回路基板とした際の層厚についても特段限定されないが、通常10μm以上、好ましくは100μm以上、より好ましくは300μm以上、さらに好ましくは500μm以上、特に好ましくは1000μm以上である。また通常5000μm以下である。
また、放熱部となる銅部分の層厚についても特段限定されないが、通常10μm以上、好ましくは100μm以上であり、さらに好ましくは300μm以上であり、特に好ましくは500μm以上であり、殊更好ましくは1000μm以上である。また通常5000μm以下である。
また、本発明のシートは、窒化ホウ素凝集粒子(以下「BN凝集粒子」と称す。)を含有するシートであって、該シートをX線回折測定して得られる、該シート中の窒化ホウ素一次粒子(以下「BN一次粒子」と称す。)の(100)面と(004)面のピーク強度比[(100)/(004)]が1.0以上であり、かつ 該シートをX線回折測定して得られる、該シート中のBN一次粒子の(002)面ピークから求めたBN一次粒子の平均結晶子径が375Å以上であることを特徴とするシートである。
この数値が大きすぎると、シート面に対してBN一次粒子の垂直方向に向く割合が高くなりすぎて、プレス等の成形工程を行うときに、シート内の微小なクラックが入りやすくなる。このようなクラックは、耐電圧等の電気特性が低くなる傾向がある。また、数値が小さすぎると、シート面に対するBN一次粒子の垂直方向に向く割合が低くなり、熱伝導率が低くなる傾向がある。
この数値が大きすぎると、プレス工程などのシート成形時に、凝集粒子内のカードハウス構造が破壊され、シート面に対してBN一次粒子のab面が垂直方向に向く割合が減り、熱伝導度が低くなる傾向がある。また、数値が小さすぎると、BN一次粒子界面が増えるため、伝熱抵抗となって熱伝導度が低くなる傾向がある。
この数値が大きすぎると、凝集粒子内のカードハウス構造が破壊され、シート面に対してBN一次粒子のab面が垂直方向に向く割合が減り、熱伝導度が低くなる傾向がある。また、数値が小さすぎるとBN一次粒子界面が増えるため、伝導抵抗となって熱伝導度が低くなる傾向がある。
耐電圧性能は、通常、10kV/mm以上、好ましくは15kV/mm以上、特に好ましくは20kV/mm以上である。また、本発明のシートのガラス転移温度は、通常100℃以上、好ましくは130℃以上、特に好ましくは175℃以上である。
また、放熱シートの接着強度(N/cm)は、特に制限はないが通常、0.5N/cm以上、好ましくは1N/cm以上、更に好ましくは2N/cm、特に好ましくは3N/cm以上、とりわけ好ましくは5N/cm以上である。
本発明における特性は以下に記載の方法にて測定した。
・粘度:
FUNGILAB社の回転粘度計「VISCO BASIC Plus R」を用い、ブレード回転数100rpmにて測定した。
BN凝集粒子をMalvern社製「Morphologi」を用いてD50(μm)を測定した。
粉末X線回折測定によって得られたBN一次粒子の(002)面由来のピークから、Scherrer式を用いて平均結晶子径を求めた。粉末X線回折測定は、PANalytical社製X線回折装置「X‘Pert Pro MPD」を用いた。Scherrer式とは次の式である。
D=(K・λ)/(β・cosθ)
ここで、D:結晶子径、K:Scherrer定数、λ:X線(CuKα1)波長、β:ピーク半値幅、θ:CuKα1由来のブラッグ角、である。またβは、次の補正式を用いて求めた。
β=(βo 2-βi 2)0.5
ここで、βiは、標準Siにより求めておいた装置由来の半価幅であり、βoは、h-BNの(002)面由来のピーク半値幅である。各定数の値は、以下を用いた。
K=0.9、λ=1.54059Å
BN凝集粒子の粉末X線回折測定によって得られたBN一次粒子の(100)面および(004)面のピーク強度の比((100)/(004))を計算することによりBN凝集粒子のピーク強度比を評価した。粉末X線回折測定は、PANalytical社製X線回折装置「X‘Pert Pro MPD」を用いた。
尚、上記粉末X線回折測定は、0.2mm深さのガラス試料板にBN凝集粒子を充填し、表面が平滑になるように測定面を調製した試料を用いて実施した。
錠剤成形機(10mmφ)に約0.2gのBN凝集粒子を充填し、手動油圧式ポンプ(理研精機社製P-1B-041)を用いて、0.85ton/cm2のプレス圧で錠剤成形した。得られた試料について、粉末X線回折測定と同様の装置を用いて、BN一次粒子の(100)面および(004)面のピーク面積強度比((100)/(004))を求めた。結果を表1に示した。
成形体の厚み方向の熱拡散率を株式会社アイフェイズ製の熱拡散率測定装置「ai―Phase Mobile 1u」を用いて測定し、以下により求めた。
成形体の厚み方向熱伝導率=成形体の厚み方向の熱拡散率×成形体の比重×成形体の比熱
(実施例1)
<BNスラリーからのBN凝集粒子の作製>
[BNスラリー(スラリーA)の調製]
(原料)
原料h-BN粉末(粉末X線回折測定により得られる(002)面ピークの半値幅が2θ=0.67°、酸素濃度が7.5質量%):10000g バインダー(多木化学(株)製「タキセラムM160L」、固形分濃度21質量%):11496g 界面活性剤(花王(株)製界面活性剤「アンモニウムラウリルサルフェート」:固形分濃度14質量%):250g
(スラリーの調製)
原料h-BN粉末を樹脂製のボトルに所定量計量し、次いでバインダーを所定量添加した。さらに、界面活性剤を所定量添加した後、ジルコニア性のセラミックボールを添加して、ポットミル回転台で1時間撹拌した。
スラリーの粘度は、810mPa・sであった。
BNスラリーからの造粒は、大河原化工機株式会社製FOC-20を用いて、ディスク回転数20000~23000rpm、乾燥温度80℃で実施し、球状のBN凝集粒子を得た。
上記BN造粒粒子を、室温で真空引きをした後、窒素ガスを導入して復圧し、そのまま窒素ガスを導入しながら2000℃まで83℃/時で昇温し、2000℃到達後、そのまま窒素ガスを導入しながら5時間保持した。その後、室温まで冷却し、カードハウス構造を有する球状のBN-A凝集粒子を得た。
更に、上記加熱処理後のBN-A凝集粒子を、乳鉢および乳棒を用いて軽粉砕した後、目開き90μmの篩を用いて分級した。分級後、BN-A凝集粒子を構成するBN一次粒子の平均結晶子径、該BN一次粒子の(100)面と(004)面のピーク強度比((100)/(004))、BN-A凝集粒子のD50を測定した。測定結果は表1に示す。
上記で得られたBN-A凝集粒子をフィラーとして用い、フィラーと樹脂組成物とからなるBN凝集粒子含有樹脂組成物を調製した。
[樹脂組成物]
三菱化学(株)製エポキシ樹脂である「157S70」、「828US」、「4275」および四国化成工業(株)製の硬化剤である「C11Z-CN」を、「157S70」:「828US」:「4275」:「C11Z-CN」=1:0.25:0.25:0.11(質量比)の割合で混合して樹脂組成物を得た。
BN-A(BN凝集粒子)と上記樹脂組成物をBN-A凝集粒子の充填量(樹脂組成物とBN―A凝集粒子の合計に対するBN-凝集粒子の含有割合)が80質量%になるように配合した。
調製された樹脂組成物/BN-A凝集粒子混合物100質量部と、メチルエチルケトン50質量部をポリプロピレン製の蓋付きカップに入れ、さらに、樹脂組成物成分100質量部に対して6質量部の1-シアノエチル-2-ウンデシルイミダゾール(硬化剤)を加え、自公転攪拌機(シンキー社製「泡取り錬太郎 AR-250」))を用いて混合して、BN凝集粒子含有樹脂組成物塗布液を調製した。
得られたBN凝集粒子含有樹脂組成物塗布液を、ギャップ間隔400μmのバーコーター(テスター産業株式会社製「オートフィルムアプリケーター」)で、厚さ100μm、10cm×20cmの銅基板上に塗布した。その後、50℃で、30分間真空乾燥を行って、銅基板に塗布膜を形成した。
得られた塗布膜が形成された銅版を4cm角に切断した。金型に入れて、130℃、500kg/cm2で3分間ホットプレスを行い、さらにオーブン中で160℃、2時間硬化させることにより、熱伝導率評価用の成形体(4cm×4cm)を得た。測定結果は表1に示す。
実施例1において、スラリーAを原料の配合比を以下に変更したBNスラリー(スラリーB)とした以外は、実施例1と同様に行い、カードハウス構造を有する球状のBN凝集粒子(凝集BN-B)及びBN凝集粒子含有樹脂組成物、成形体を作製した。測定結果を表1に示す。
(原料)
原料h-BN粉末:10000g
純水:7500g
バインダー:5750g
界面活性剤:250g
(スラリー調製)
原料h-BN粉末を樹脂製のボトルに所定量計量し、次いで純水、バインダーの順に所定量添加した。さらに、界面活性剤を所定量添加した後、ジルコニア性のセラミックボールを添加して、ポットミル回転台で1時間撹拌した。スラリーの粘度は、2200mPa・sであった。
実施例1において、スラリーAを原料の配合比を以下に変更したBNスラリー(スラリーC)とした以外は、実施例1と同様に行い、カードハウス構造を有する球状のBN凝集粒子(凝集BN-C)及びBN凝集粒子含有樹脂組成物、成形体を作製した。測定結果を表1に示す。
(原料)
原料h-BN粉末:10000g
バインダー:11496g
界面活性剤:250g
(スラリー調製)
原料h-BN粉末を樹脂製のボトルに所定量計量し、次いでバインダーを所定量添加した。さらに、界面活性剤を所定量添加した後、ジルコニア性のセラミックボールを添加して、ポットミル回転台で1時間撹拌した。スラリーの粘度は、1600mPa・sであった。
実施例2におけるスラリーBを、原料の配合比を変更した以下に示すスラリーDとした以外は、実施例2と同様に行い、BN凝集粒子(BN-D凝集粒子)及びBN凝集粒子含有樹脂組成物、成形体を作製した。スラリーの粘度は155mPa・sであった。測定結果を表1に示す。
スラリーD配合
(原料)
原料h-BN粉末:2400g
純水:2199g
バインダー:1380g
界面活性剤:60g
実施例1と同様にスラリーの調製および造粒を行い、BN凝集粒子作製時の焼成温度を1300℃、保持時間を24hとした以外は実施例1と同様にBN凝集粒子を作製した(凝集BN-E)。このBN凝集粒子を用いて、実施例1と同様の方法でBN凝集粒子含有樹脂組成物の作製、成形体の製造を行った。表1に結果を示す。
実施例1のBN-A凝集粒子に変えてモメンティブ社製PTX60を用いた以外は実施例1と同様にBN凝集粒子含有樹脂組成物及び成形体の製造を行った。表1に結果を示す。
実施例1のBN-A凝集粒子に変えてモメンティブ社製PTX25を用いた以外は実施例1と同様に行った。表1に結果を示す。
実施例1のBN-A凝集粒子に変えて電気化学工業社製SGPSを用いた以外は実施例1と同様にBN凝集粒子含有樹脂組成物及び成形体の製造を行った。表1に結果を示す。
実施例1のBN-A凝集粒子に変えてサンゴバン社製CTS7Mを用いた以外は実施例1と同様にBN凝集粒子含有樹脂組成物及び成形体の製造を行った。表1に結果を示す。
実施例1と同様にスラリーの調製および造粒を行い、BN凝集粒子作製時の焼成温度を1600℃、保持時間を24hとした以外は実施例1と同様にBN凝集粒子を作製した(凝集BN-F)。このBN凝集粒子を用いて、実施例1と同様の方法でBN凝集粒子含有樹脂組成物の作製、成形体の製造を行った。表1に結果を示す。
実施例2において、スラリーBの原料の配合比を以下に変更したBNスラリー(スラリーE)とした以外は、実施例1と同様に行った。
(原料)
原料h-BN粉末:10000g
純水:7750g
バインダー:5750g
原料h-BN粉末を樹脂製のボトルに所定量計量し、次いで純水、バインダーの順に所定量添加した。さらに、ジルコニア性のセラミックボールを添加して、ポットミル回転台で1時間撹拌した。スラリーの粘度は、8000mPa・sであった。
実施例4
錠剤成形機(10mmφ)に約0.2gの実施例1で作製したBN-A凝集粒子を充填し、手動油圧式ポンプ(理研精機社製P-1B-041)を用いて、表2に記載の種々のプレス圧で錠剤成形した。得られた試料について、粉末X線回折測定と同様の装置を用いて、BN一次粒子の(100)面および(004)面のピーク面積強度比((100)/(004))を求めた。結果を表2に示した。
錠剤成形機(10mmφ)に約0.2gのBN凝集粒子として実施例2で作製したBN-B凝集粒子を用いた以外は、実施例4と同様にしてBN一次粒子の(100)面および(004)面のピーク面積強度比((100)/(004))を求めた。結果を表2に示した。
BN凝集粒子としてBN-E凝集粒子を用いた以外は、実施例4と同様にしてBN一次粒子の(100)面と(004)面のピーク面積強度比((100)/(004))を求めた。結果を表2に示した。
BN凝集粒子としてモメンティブ社製PTX60凝集粒子を用いた以外は、実施例4と同様にしてBN一次粒子の(100)面と(004)面のピーク面積強度比((100)/(004))を求めた。結果を表2に示した。
BN凝集粒子としてモメンティブ社製PTX25を用いた以外は、実施例4と同様にしてBN一次粒子の(100)面と(004)面のピーク面積強度比((100)/(004))を求めた。結果を表2に示した。
BN凝集粒子として電気化学工業社製SGPSを用いた以外は、実施例4と同様にしてBN一次粒子の(100)面と(004)面のピーク面積強度比((100)/(004))を求めた。結果を表2に示した。
BN凝集粒子としてサンゴバン社製CTS7Mを用いた以外は、実施例4と同様にしてBN一次粒子の(100)面と(004)面のピーク面積強度比((100)/(004))を求めた。結果を表2に示した。
BN凝集粒子としてBN-F凝集粒子を用いた以外は、実施例4と同様にしてBN一次粒子の(100)面と(004)面のピーク面積強度比((100)/(004))を求めた。結果を表2に示した。
BN凝集粒子の粉末X線回折測定によって得られたBN一次粒子の(100)面と(004)面とのピーク強度の比((100)/(004))を計算することにより求めた。
錠剤成形機(10mmφ)に約0.2gの粉末を充填し、手動油圧式ポンプ(理研精機社製P-1B-041)を用いて、プレス圧0.85ton/cm2で錠剤成形した試料を測定に供する。測定は、オランダPANalytical社製X‘Pert Pro MPD粉末X線回折装置を用いて行うことで、該当するピーク面積の強度比を計算することができる。
PANalytical社製X線回折装置 (X’Pert Pro MPD)を用いた。尚、試料サンプルは、プレス成形した放熱シートを用いて実施した。
測定条件を以下に示す。
試料ホルダー: 無反射試料板,ターゲット:CuKα,出力:40kV,30mA
測定範囲:5-100°,ステップ角度:0.016°,走査速度:0.05°/sec,可変スリット10mm
放熱シートのX線回折測定によって得られたBN一次粒子の(100)面と(004)面とのピーク強度の比((100)/(004))を計算することにより求めた。
放熱シートのX線回折測定によって得られたBN一次粒子の(100)面と(004)面とのピーク面積強度の比((100)/(004))を計算することにより求めた。
上記BN一次粒子の平均結晶子径の測定方法に準じる。
密着性試験:
基材上に塗布して得られた放熱シートを25mm×60mmの大きさに切り出し、25mm×110mmの基材と加熱プレスによって貼り合せて接着した測定サンプルを、樹脂板に固定した後に90°ピール試験を実施することで求めた。試験にはORIENTEC社製STA-1225を用いて行った。
カードハウス構造を有するBN凝集粒子BN-A4.7g、非カードハウス構造である窒化ホウ素PTX25(モメンティブ(株)製、D50:19.8μm、BN一次粒子の(100)/(004)面ピーク強度比:1.4、BN一次粒子の平均結晶子径:537Å)1.6g、及びエポキシ樹脂全量に対するビスフェノールA型フェノキシ樹脂を含有したフェノキシ樹脂が16.7質量%含有したエポキシ樹脂(Tg:190℃)2.12g、溶剤(シクロヘキサノン/メチルエチルケトン)6.2g、分散剤(商品名:BYK-2155、ビックケミー・ジャパン(株)製)0.41g、1-シアノエチル-2-ウンデシルイミダゾール(商品名:C11Z-CN、四国化成工業(株)製)0.13gを混合し、放熱シート用スラリーを調製した。
調製した放熱シート用スラリーをドクターブレード法で基材に塗布し、加熱乾燥を行った後にプレスを行ってシート厚が約200μmの放熱シートを得た。
カードハウス構造を有するBN凝集粒子BN-A4.7g、非カードハウス構造である窒化ホウ素PTX25(モメンティブ(株)製、D50:19.8μm、BN一次粒子の(100)/(004)面ピーク強度比:1.4、BN一次粒子の平均結晶子径:537Å)1.6g、及びエポキシ樹脂全量に対するビスフェノールF型フェノキシ樹脂が含有したフェノキシ樹脂が20質量%含有したエポキシ樹脂(Tg:31℃)2.12g、溶剤(シクロヘキサノン/メチルエチルケトン)6.2g、分散剤(商品名:BYK-2155、ビックケミー・ジャパン(株)製)0.41g、1-シアノエチル-2-ウンデシルイミダゾール(商品名:C11Z-CN、四国化成工業(株)製)0.13gを混合し、放熱シート用スラリーを調製した。
調製した放熱シート用スラリーをドクターブレード法で基材に塗布し、加熱乾燥を行った後にプレスを行ってシート厚が約200μmの放熱シートを得た。
カードハウス構造を有するBN凝集粒子BN-A(D50:50μm) 5.5g、カードハウス構造を有するBN凝集粒子BN-D(D50:14μm) 1.8g、及びエポキシ樹脂(Tg:190℃)1.0g、溶剤(シクロヘキサノン/メチルエチルケトン)6.2g、分散剤(商品名:BYK-2155、ビックケミー・ジャパン(株)製)0.40g、1-シアノエチル-2-ウンデシルイミダゾール(商品名:C11Z-CN、四国化成工業(株)製)0.06gを混合し、放熱シート用スラリーを調製した。
調製した放熱シート用スラリーをドクターブレード法で基材に塗布し、加熱乾燥を行った後にプレスを行ってシート厚が約200μmの放熱シートを得た。調製した放熱シート用スラリーを用い、実施例6と同様にしてシート厚が約200μmの放熱シートを得た。得られた放熱シートの熱伝導率、耐電圧、X線回折測定を行った。この際のシートプレス圧は300kg重/cm2であり、図5がシート断面SEM写真である。このように本発明のBN凝集粒子は上記プレス圧でプレスしてもプレス前の粉末の形状を保持していることが本発明の効果を奏する理由の一つであると考えられる。より具体的には、図5に示すように、300kg重/cm2のシートプレス圧において、BN凝集粒子が凝集粒子として観察できるシートであり、特にカードハウス構造も観察できるようなシートである。
非カードハウス構造である窒化ホウ素PTX60(モメンティブ(株)製、D50:55.8μm、BN一次粒子の(100)/(004)面ピーク強度比:2.8、BN一次粒子の平均結晶子径:370Å)4.6g、非カードハウス構造である窒化ホウ素PTX25(モメンティブ(株)製、D50:19.8μm、BN一次粒子の(100)/(004)面ピーク強度比:1.4、BN一次粒子の平均結晶子径:537Å) 1.5g、及びエポキシ樹脂(Tg:190℃)2.1g、溶剤(シクロヘキサノン/メチルエチルケトン)7.2g、分散剤(商品名:BYK-2155、ビックケミー・ジャパン(株)製)0.40g、1-シアノエチル-2-ウンデシルイミダゾール(商品名:C11Z-CN、四国化成工業(株)製)0.13gを混合し、放熱シート用スラリーを調製した。
調製した放熱シート用スラリーを用い、実施例6と同様にしてドクターブレード法で基材に塗布し、加熱乾燥を行った後にプレスを行ってシート厚が約200μmの放熱シートを得た。得られた放熱シートの熱伝導率、耐電圧、X線回折測定を行った。
非カードハウス構造である窒化ホウ素PTX60 5.5g(モメンティブ(株)製、D50:55.8μm、BN一次粒子の(100)/(004)面ピーク強度比:2.8、BN一次粒子の平均結晶子径:370Å)、カードハウス構造を有するBN凝集粒子BN-D(D50:14μm)1.8g、及びエポキシ樹脂(Tg:190℃)1.0g、溶剤(シクロヘキサノン/メチルエチルケトン)6.1g、分散剤(商品名:BYK-2155、ビックケミー・ジャパン(株)製)0.40g、1-シアノエチル-2-ウンデシルイミダゾール(商品名:C11Z-CN、四国化成工業(株)製)0.06gを混合し、放熱シート用スラリーを調製した。
調製した放熱シート用スラリーを用い、実施例6と同様にしてシート厚が約200μmの放熱シートを得た。得られた放熱シートの熱伝導率、耐電圧、X線回折測定を行った。
上記、実施例2、6、7、8及び比較例1、3、15、16の測定結果を表3に示す。
詳細なメカニズムは良くわかっていないが、例えば、高放熱性能は、BN凝集粒子を使用することにより、BN一次粒子、BN凝集粒子のD50が大きくなっているため、一次粒子同士、凝集粒子同士の界面抵抗を低減できたためであると考える。さらにBN凝集粒子より小さい無機粒子を併用することで、大粒子間の空隙を効率よく低減することができ、耐電圧性能がより改善されている。
カードハウス構造を有するBN凝集粒子(A)-1を22.2g、カードハウス構造である窒化ホウ素凝集粒子(A)-2)を7.3g、及びエポキシ樹脂(Tg:190℃)6.7g、溶剤(シクロヘキサノン/メチルエチルケトン)21.3g、分散剤(商品名:BYK-2155、ビックケミー・ジャパン(株)製)2.3g、1-シアノエチル-2-ウンデシルイミダゾール(商品名:C11Z-CN、四国化成工業(株)製)0.24gを混合し、放熱シート用スラリーを調製した。
調製した絶縁放熱シート用スラリーを、銅箔(105μm)に塗布した。その後、加熱乾燥を行った後に、塗布面同士を張り合わせて、プレスを行い、両面銅箔はり絶縁放熱シートを得た。絶縁放熱シート部分の膜厚は、約300μmであった。
さらに、ダイボンド、ワイヤボンディングを行い、デバイスを作製した。その結果を図6に示す。
該放熱シートを有するパワー半導体デバイスは、次世代のSiC、GaNなど、高温動作が可能な高効率基板を用いたパワー半導体デバイスの作製に有用である。
Claims (14)
- 窒化ホウ素一次粒子(以下「BN一次粒子」と称する。)が凝集してなる窒化ホウ素凝集粒子(以下「BN凝集粒子」と称す。)であって、10mmφの粉末錠剤成形機で0.85ton/cm2の成型圧力で成型して得られたペレット状の試料を粉末X線回折測定して得られる、BN一次粒子の(100)面と(004)面のピーク面積強度比((100)/(004))が0.25以上であり、かつ該BN凝集粒子を0.2mm深さのガラス試料板に表面が平滑になるように充填し、粉末X線回折測定して得られる、BN一次粒子の(002)面ピークから求めたBN一次粒子の平均結晶子径が375Å以上であることを特徴とするBN凝集粒子。
- BN凝集粒子の平均粒子径D50が26μm以上である、請求項1に記載のBN凝集粒子。
- BN凝集粒子の比表面積が8m2/g以下である、請求項1又は2に記載のBN凝集粒子。
- BN凝集粒子が球状である請求項1ないし3のいずれか1項に記載のBN凝集粒子。
- BN凝集粒子がカードハウス構造を有する請求項1ないし4のいずれか1項に記載のBN凝集粒子。
- 請求項1ないし5のいずれか1項に記載のBN凝集粒子と他のフィラーの混合物であるBN凝集粒子組成物。
- 樹脂と、請求項1ないし5のいずれか1項に記載のBN凝集粒子を含むBN凝集粒子含有樹脂組成物。
- 請求項1ないし5のいずれか1項に記載のBN凝集粒子を含む成形体。
- 原料窒化ホウ素粉末のスラリー(以下「BNスラリー」と称す。)を造粒するステップ、及び加熱処理をするステップを含むBN凝集粒子を製造する方法であって、
前記造粒ステップにおいて該BNスラリーの粘度が200mPa・s以上5000mPa・s以下であり、前記加熱ステップにおいて加熱処理を1800℃以上2300℃以下で行うことを特徴とするBN凝集粒子の製造方法。 - 原料窒化ホウ素粉末中の酸素濃度が、1質量%以上10質量%以下である請求項9に記載のBN凝集粒子の製造方法。
- 請求項9又は10に記載された製造方法によって得られるBN凝集粒子。
- 窒化ホウ素凝集粒子(以下「BN凝集粒子」と称す。)を含有するシートであって、
該シートをX線回折測定して得られる、該シート中の窒化ホウ素一次粒子(以下「BN一次粒子」と称す。)の(100)面と(004)面のピーク強度比((100)/(004))が1.0以上であり、かつ
該シートをX線回折測定して得られる、該シート中のBN一次粒子の(002)面ピークから求めたBN一次粒子の平均結晶子径が375Å以上であることを特徴とするシート。 - 前記シートをX線回折測定して得られる、該シート中の窒化ホウ素一次粒子(以下「BN一次粒子」と称す。)の(100)面と(004)面のピーク面積強度比((100)/(004))が0.6以上である請求項12に記載のシート。
- 請求項12又は13に記載のシートを部材の一部として有するデバイス。
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KR (1) | KR102400206B1 (ja) |
CN (2) | CN106029561B (ja) |
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US10106413B2 (en) | 2018-10-23 |
JPWO2015119198A1 (ja) | 2017-03-23 |
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JP7207384B2 (ja) | 2023-01-18 |
JP7455047B2 (ja) | 2024-03-25 |
EP3103766A4 (en) | 2017-03-01 |
CN113788465A (zh) | 2021-12-14 |
JP2016135730A (ja) | 2016-07-28 |
TWI757686B (zh) | 2022-03-11 |
EP3103766A1 (en) | 2016-12-14 |
JP2019137608A (ja) | 2019-08-22 |
CN106029561A (zh) | 2016-10-12 |
US20180354793A1 (en) | 2018-12-13 |
JP2016135732A (ja) | 2016-07-28 |
US20160340191A1 (en) | 2016-11-24 |
JP6773153B2 (ja) | 2020-10-21 |
CN113788465B (zh) | 2024-01-12 |
JP6493226B2 (ja) | 2019-04-03 |
MY195160A (en) | 2023-01-11 |
JP2021006507A (ja) | 2021-01-21 |
JP2016135731A (ja) | 2016-07-28 |
KR20160117472A (ko) | 2016-10-10 |
JP6447202B2 (ja) | 2019-01-09 |
JP2024003261A (ja) | 2024-01-11 |
KR102400206B1 (ko) | 2022-05-19 |
CN106029561B (zh) | 2021-11-02 |
US10414653B2 (en) | 2019-09-17 |
TWI687393B (zh) | 2020-03-11 |
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MY179291A (en) | 2020-11-03 |
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