Alumina powder, resin composition, and adhesive

Abstract

Provided is an alumina powder which gives a resin composition exhibiting a satisfactory thermal conductivity and a satisfactory shear adhesion strength.　The alumina powder has a 50% volume-cumulative diameter D50 of 10-70 μm and gives a volume-based particle size frequency distribution which has a first-peak maximal value in a particle diameter range of 20 μm and larger and a second-peak maximal value in the particle diameter range of 1-20 μm, excluding 20 μm.

Description

Alumina powder, resin composition, and adhesive

[0001] The present disclosure relates to an alumina powder, a resin composition, and an adhesive.

[0002] Electrical and electronic devices are becoming increasingly sophisticated and dense. This has led to a demand for measures to prevent heat generation from electronic components mounted on circuit boards. To improve the heat dissipation of circuit boards, adhesives used to bond electronic components are required to have good thermal conductivity.

[0003] JP 2012-77123 A

[0004] An object of the present disclosure is to provide an alumina powder that provides a resin composition exhibiting good thermal conductivity and good shear bond strength.

[0005] The present disclosure includes the following aspects: [1] An alumina powder having a volume-based cumulative 50% diameter D50 of 10 μm or more and 70 μm or less, a first peak having a maximum value in a particle size range of 20 μm or more in a volume-based frequency particle size distribution, and a second peak having a maximum value in a particle size range of 1 μm or more and less than 20 μm.

[0006] According to the present disclosure, it is possible to provide an alumina powder that provides a resin composition exhibiting good thermal conductivity and good shear bond strength.

[0007] 1 is a graph showing the frequency particle size distribution of alumina powders of Examples 1 to 3 (represented by (1) to (3) in the figure). The vertical axis indicates the frequency (%) of powders having a specific particle size, and the horizontal axis indicates particle size (μm). 2 is a graph showing the frequency particle size distribution of alumina powders of Examples 4 to 6 (represented by (4) to (6) in the figure). The vertical axis indicates the frequency (%) of powders having a specific particle size, and the horizontal axis indicates particle size (μm). 3 is a graph showing the frequency particle size distribution of alumina powders of Comparative Examples 1 to 3 (represented by (7) to (9) in the figure). The vertical axis indicates the frequency (%) of powders having a specific particle size, and the horizontal axis indicates particle size (μm).

[0008] An embodiment of the present disclosure will be described in detail below. However, the scope of the present disclosure is not limited to the embodiment described herein, and various modifications can be made without departing from the spirit of the present disclosure. Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Each configuration and combination thereof in each embodiment is merely an example, and addition, omission, substitution, and other modifications of configurations are possible as appropriate within the spirit of the present disclosure. Furthermore, when multiple upper and lower limits are described for a specific parameter, any of these upper and lower limits can be combined to form a suitable numerical range. Furthermore, the lower and / or upper limits of a numerical range described in this disclosure are numerical values ​​within that range and may be replaced with numerical values ​​shown in the examples. The expression "X to Y" indicating a numerical range means "X or more and Y or less." If a specific description described for one embodiment also applies to other embodiments, that description may be omitted in other embodiments. Unless otherwise specified, all numbers expressing features, items, quantities, parameters, characteristics, periods, etc. used in the specification and claims are understood to be modified in all instances by the term "about." As used herein, the term "about" means that the so-specified feature, item, quantity, parameter, characteristic, or period encompasses a range above and below plus or minus 10 percent of the value of the stated feature, item, quantity, parameter, characteristic, or period. At least, and without limiting the application of the doctrine of equivalents to the scope of the claims, each numerical indicator should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Any numerical range or value inherently includes a range of error necessarily resulting from the standard deviation found in their respective testing measurements. Unless otherwise specified, each individual value of a numerical range herein is incorporated herein by reference as if it were individually recited herein.

[0009] [Alumina Powder] The alumina powder according to this embodiment has a volume-based cumulative 50% diameter D50 of 10 μm or more and 70 μm or less, and in the volume-based frequency particle size distribution, has a first peak with a maximum value in a particle size range of 20 μm or more and a second peak with a maximum value in a particle size range of 1 μm or more and less than 20 μm.

[0010] Alumina powders designed in this manner can provide compositions with good thermal conductivity and / or good shear bond strength.

[0011] The "volume-based cumulative 50% diameter D50" (hereinafter simply referred to as "D50") refers to the particle diameter (D50) corresponding to the cumulative value of 50% in a volume-based cumulative particle size distribution measured using a laser diffraction particle size distribution analyzer. The cumulative particle size distribution is expressed by a distribution curve with the particle size (μm) on the horizontal axis and the cumulative value (%) on the vertical axis.

[0012] The "volume-based frequency particle size distribution" is measured by a laser diffraction light scattering method (refractive index: 1.68) and is represented by a distribution curve with the particle size (μm) on the horizontal axis and the volume-based frequency (%) on the vertical axis. The alumina powder according to this embodiment has at least two peaks in the volume-based frequency particle size distribution. The peaks may or may not have shoulders. The "particle size" is the value represented on the horizontal axis of the volume-based frequency particle size distribution. The "peak" refers to a distribution curve that has one maximum value in the volume-based frequency particle size distribution. The "shoulder" refers to an incomplete peak that is not completely separated from the peak (i.e., a step portion where a bulge is formed in the middle of the slope of the distribution curve that constitutes the peak), and refers to a distribution curve that may or may not have one maximum value. The "maximum value" refers to the boundary where the slope of the curve changes from positive to negative in the volume-based frequency particle size distribution.

[0013] (Alumina Powder) The alumina powder according to this embodiment is alumina (Al ２ O ３It is preferable that the alumina powder contains a powder of the above-mentioned compound (I) as at least a part of its constituent components and is made of alumina powder. From the viewpoint of high loading in resin, the alumina powder is preferably spherical alumina. In one embodiment, the alumina powder contains 70 mass % or more, preferably 80 mass % or more, and preferably 90 mass % or more of alumina (preferably spherical).

[0014] The average circularity of the alumina powder is 0.80 or more, preferably 0.85 or more, and more preferably 0.90 or more. When the average circularity is 0.90 or more, it may be 0.90, 0.92, 0.93, 0.94, or 0.95. In one embodiment, the average circularity may be within a range combining any of the above values ​​as the upper and lower limits. When the average circularity of the alumina powder is 0.8 or more, the contact area with the resin in the resin composition is small relative to the powder weight, allowing for high loading.

[0015] The average circularity of the alumina powder is a value calculated by the following method. The alumina powder constituting the alumina powder is fixed with carbon tape and then coated with osmium. Thereafter, the particles are photographed at a magnification of 500 to 50,000 times using a scanning electron microscope (manufactured by JEOL Ltd., product name: JSM-7001F SHL), and the projected area (S) and projected perimeter (L) of the particles are calculated using an image analyzer (manufactured by Nippon Roper Co., Ltd., product name: Image-Pro Premier Ver. 9.3), and then the circularity is calculated using the following formula. The circularity is calculated for any 200 particles, and the average value is taken as the average circularity. Circularity = 4πS / L ２

[0016] Alumina powder may be produced by mixing commercially available alumina powders having a predetermined particle size distribution, or by blending alumina powders having different particle size distributions. Spherical alumina powder may be produced by existing thermal spraying techniques. Existing thermal spraying techniques, for example, are based on "On Thermal Spraying and Collection Technology for Steelmaking Furnaces, Steel Manufacturing Research 1982 No. 310," and involve introducing raw material powder into a high-temperature flame formed with fuel gas such as hydrogen, natural gas, acetylene gas, propane gas, or butane, and melting and spheroidizing the powder. An example of a production apparatus is one that basically comprises a spheroidizing furnace and a collection device connected to the furnace. The spherical inorganic oxide powder produced in the spheroidizing furnace is pneumatically transported by a blower or the like and collected by the collection device. The spherical inorganic oxide powder may be classified as needed before and / or after collection by the collection device. The spheroidizing furnace body and transport piping, etc., are preferably water-cooled using a water-cooled jacket system. Collection devices include cyclones, gravity settling devices, louvers, and bag filters. The collection temperature is determined by the heat generated by the amount of combustible gas and the suction rate of the blower, and is adjusted by adjusting the amount of cooling water and the amount of outside air introduced into the line. Aluminum hydroxide, alumina, metallic aluminum, and the like are used as raw materials for producing spherical alumina powder. It is desirable to adjust the particle size of the raw material powder to the product particle size in advance, but particle size adjustment can also be performed by classification after spheroidization. Furthermore, spherical inorganic powders with the same composition can also be obtained by separating several raw materials with different particle sizes, melting them, forming them into spheres, and then mixing and adjusting them. Mixing can be performed, for example, at room temperature using known equipment such as a blender or mixer.

[0017] Surface treatment of alumina powder with a silane coupling agent or the like can reduce the powder's water absorption, increase the strength of the resin composition, and further reduce the interfacial resistance between the resin and the powder, thereby improving thermal conductivity. Examples of silane coupling agents include vinyltrichlorosilane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, β(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidylmethoxypropylmethyldiethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-chloropropyltrimethoxysilane. Other surface treatment agents that can be used include Zr chelates, titanate coupling agents, and aluminum-based coupling agents.

[0018] (Volume-based cumulative 50% diameter D50) The alumina powder has a volume-based cumulative 50% diameter D50 of 10 μm to 70 μm, preferably 10 μm to 65 μm, and more preferably 14 μm to 63 μm. When the volume-based cumulative 50% diameter D50 is 14 μm to 63 μm, it may be, for example, 14 μm, 17 μm, 24 μm, 28 μm, 53 μm, or 63 μm. In one embodiment, the volume-based cumulative 50% diameter D50 may be within a range combining any of the above values ​​as the upper and lower limits. By setting the volume-based cumulative 50% diameter D50 to 10 μm to 70 μm, a resin composition containing the alumina powder is likely to exhibit good thermal conductivity and / or good shear bond strength. The volume-based cumulative 50% diameter D50 of the alumina powder can be adjusted by classification, or when a plurality of types of alumina powder are mixed, by adjusting the blending ratio of the raw alumina powders.

[0019] (Volume-Based Frequency Particle Size Distribution) In the volume-based frequency particle size distribution, the alumina powder has a first peak with a maximum value in a particle size range of 20 μm or more, and a second peak with a maximum value in a particle size range of 1 μm or more and less than 20 μm. The maximum value of the first peak is preferably in a particle size range of 20 μm to 97 μm. When the particle size at the maximum value of the first peak is in the range of 20 μm to 97 μm, the particle size at the maximum value may be, for example, 20 μm, 25 μm, 30 μm, 43 μm, 97 μm, or 100 μm. In one embodiment, the particle size at the maximum value of the first peak in the volume-based frequency particle size distribution may be in a range combining any of the above values ​​as the upper and lower limits. For example, the particle size at the maximum value of the first peak may be greater than 30 μm, greater than 30 μm and not greater than 100 μm, greater than 30 μm and not greater than 97 μm, or 43 μm to 97 μm. The particle size at the maximum value of the second peak is preferably in the range of 1 μm to 15 μm, more preferably in the range of 3 μm to 11 μm. When the particle size at the maximum value of the first peak is in the range of 3 μm to 11 μm, the particle size at the maximum value may be, for example, 3 μm, 5 μm, or 11 μm. In one embodiment, the particle size at the maximum value of the second peak in the volume-based frequency particle size distribution may be in a range combining any of the above values ​​as the upper and lower limits.

[0020] In one embodiment, the second peak may be a shoulder that is not completely separated from the first peak, while in another embodiment, the second peak may be a peak that is completely separated from the first peak.

[0021] The first peak and the second peak may or may not have a shoulder. In one embodiment, when the second peak does not have a shoulder, the resin composition containing the alumina powder is likely to exhibit good thermal conductivity and / or good shear bond strength.

[0022] In the volume-based frequency particle size distribution, the alumina powder has a first peak with a maximum value in the particle size range of 20 μm or more and a second peak with a maximum value in the particle size range of 1 μm or more and less than 20 μm, so that the resin composition containing the alumina powder is likely to exhibit good thermal conductivity and / or good shear adhesive strength.

[0023] In one embodiment, the maximum frequency of the first peak (frequency at the maximum value) is preferably 3 to 10%, and more preferably 3 to 9%. By setting the maximum frequency of the first peak to 3 to 10%, it is easy to adjust the balance between thermal conductivity and shear bond strength. In one embodiment, the maximum frequency of the second peak (frequency at the maximum value) is preferably 2 to 7%, and more preferably 1 to 6%. By setting the maximum frequency of the second peak to 1 to 7%, it is easy to adjust the balance between thermal conductivity and shear bond strength.

[0024] In one embodiment, the half width (full width at half maximum) of the volume-based frequency particle size distribution curve is preferably 250 or less, and may be 230 or less, 210 or less, 200 or less, 150 or less, 100 or less, or 70 or less.

[0025] In addition to the first and second peak maxima, the alumina powder may further have a third peak maxima in the particle size range of less than 1 μm in the volume-based frequency particle size distribution. The third peak maxima is preferably in the particle size range of 0.8 μm or less, more preferably 0.5 μm or less.

[0026] In one embodiment, the third peak may be a shoulder that is not completely separated from the first and / or second peaks, while in another embodiment, the third peak may be a peak that is completely separated from the first and / or second peaks.

[0027] In the volume-based frequency particle size distribution, when the particle size of the alumina powder further has a maximum value of the third peak in the range of less than 1 μm, the resin composition containing the alumina powder is more likely to exhibit good thermal conductivity and / or good shear bond strength.

[0028] In one embodiment, the maximum frequency of the third peak (the frequency at the maximum value) is preferably 0.2 to 3%, and more preferably 0.5 to 2%. By setting the maximum frequency of the third peak to 0.2 to 3%, it is easy to adjust the balance between thermal conductivity and shear adhesive strength.

[0029] The maximum value of each peak in the volume-based frequency particle size distribution of the alumina powder can be adjusted by adjusting the blending amount of the raw alumina powder. The alumina powder may be produced by mixing and blending alumina powders having different particle size distributions. For example, by blending a plurality of alumina powders having particle size distributions corresponding to the maximum values ​​of the desired plurality of peaks, it is possible to prepare an alumina powder having two or more maximum values ​​of the peaks. In this case, the maximum frequency of each peak can be adjusted by adjusting the blending amount of the raw alumina powder.

[0030] (Composition of Alumina Powder) The alumina powder according to this embodiment may contain two or more alumina powders having different D50s. In this case, the alumina powder according to this embodiment can be prepared by blending two or more alumina powders having different D50s. Specifically, for example, by blending predetermined amounts of an alumina powder having a D50 of 20 μm or more and an alumina powder having a D50 of 1 μm or more and less than 20 μm, an alumina powder having a D50 of 10 μm or more and a maximum value of a first peak in a particle size range of 20 μm or more and a maximum value of a second peak in a particle size range of 1 μm or more and less than 20 μm can be obtained. Furthermore, for example, by blending predetermined amounts of alumina powder having a D50 of 20 μm or more, alumina powder having a D50 of 1 μm or more but less than 20 μm, and alumina powder having a D50 of less than 1 μm, an alumina powder having a first maximum peak in the particle size range of 20 μm or more, a second maximum peak in the particle size range of 1 μm or more but less than 20 μm, and a third maximum peak in the particle size range of less than 1 μm in a volumetric frequency particle size distribution can be obtained. The amount of each alumina powder blended is not limited, but may be, for example, 10% to 90% by mass, 15% to 85% by mass, or, when the amount is 15% to 85% by mass, it may be 15%, 35%, 40%, 50%, 60%, 80%, or 85% by mass, based on the total amount of alumina powder. In one embodiment, the amount of each alumina powder blended may be within a range combining any of the above values ​​as the upper and lower limits. For example, the blending amount of alumina powder having a D50 of 20 μm or more is preferably 40 to 75 mass%, and more preferably 45 to 70 mass%, relative to the total amount of alumina powder. For example, the blending amount of alumina powder having a D50 of 1 μm or more and 20 μm or less is preferably 25 to 50 mass%, and more preferably 30 to 45 mass%, relative to the total amount of alumina powder. For example, the blending amount of alumina powder having a D50 of 1 μm or less is preferably 5 to 25 mass%, and more preferably 10 to 20 mass%, relative to the total amount of alumina powder.In one embodiment, when a predetermined amount of alumina powder having a D50 of 20 μm or more and alumina powder having a D50 of 1 μm or more but less than 20 μm are blended, the blending amount of the alumina powder having a D50 of 20 μm or more is preferably 50 to 70 mass%, and more preferably 55 to 65 mass%, relative to the total amount of alumina powder. When it is 55 to 65 mass%, it may be 60 mass%. When it is 35 to 45 mass%, it may be 40 mass%. In one embodiment, when alumina powder having a D50 of 20 μm or more, alumina powder having a D50 of 1 μm or more but less than 20 μm, and alumina powder having a D50 of less than 1 μm are blended in predetermined amounts, the blending amount of the alumina powder having a D50 of 20 μm or more is preferably 40 to 55 mass%, and more preferably 45 to 55 mass%, relative to the total amount of alumina powder. In the case of 45 to 55 mass%, it may be 50 mass%. The blending amount of the alumina powder having a D50 of 1 μm or more but less than 20 μm is preferably 25 to 40 mass%, and more preferably 30 to 40 mass%, relative to the total amount of alumina powder. In the case of 30 to 40 mass%, it may be 35 mass%. The blending amount of the alumina powder having a D50 of less than 1 μm is preferably 5 to 35 mass%, and more preferably 5 to 25 mass%, relative to the total amount of alumina powder. In the case of 5 to 25 mass%, it may be 15 mass%.

[0031] In one embodiment, the alumina powder contains 50 mass% alumina powder having a D50 of 43 μm, 35 mass% alumina powder having a D50 of 5 μm, and 15 mass% alumina powder having a D50 of 0.5 μm. This blending results in an alumina powder having a D50 of 24 μm and a volume-based frequency particle size distribution with a first peak having a maximum value at a particle size of 43 μm, a second peak having a maximum value at a particle size of 5 μm, and a third peak having a maximum value at a particle size of 0.5 μm. In one embodiment, the alumina powder contains 50 mass% alumina powder having a D50 of 25 μm, 35 mass% alumina powder having a D50 of 3 μm, and 15 mass% alumina powder having a D50 of 0.5 μm. This blending results in an alumina powder having a D50 of 14 μm and a volume-based frequency particle size distribution with a first peak maximum at a particle size of 25 μm, a second peak maximum at a particle size of 3 μm, and a third peak maximum at a particle size of 0.5 μm. In one embodiment, the alumina powder contains 50 mass% alumina powder having a D50 of 97 μm, 35 mass% alumina powder having a D50 of 11 μm, and 15 mass% alumina powder having a D50 of 0.5 μm. This blending results in an alumina powder having a D50 of 53 μm and a volume-based frequency particle size distribution with a first peak maximum at a particle size of 97 μm, a second peak maximum at a particle size of 11 μm, and a third peak maximum at a particle size of 0.5 μm. In one embodiment, the alumina powder contains 60 mass% alumina powder having a D50 of 43 μm and 40 mass% alumina powder having a D50 of 5 μm. This blending results in an alumina powder with a D50 of 28 μm and a first peak maximum at a particle size of 43 μm and a second peak maximum at a particle size of 5 μm in a volume-based frequency particle size distribution. In one embodiment, the alumina powder contains 60 mass% alumina powder having a D50 of 25 μm and 40 mass% alumina powder having a D50 of 3 μm. This blending results in an alumina powder with a D50 of 17 μm and a first peak maximum at a particle size of 25 μm and a second peak maximum at a particle size of 3 μm in a volume-based frequency particle size distribution. In one embodiment, the alumina powder contains 60 mass% alumina powder having a D50 of 97 μm and 40 mass% alumina powder having a D50 of 11 μm.This blending results in an alumina powder having a D50 of 63 μm, and in the volume-based frequency particle size distribution, a first peak with a maximum value at a particle size of 97 μm and a second peak with a maximum value at a particle size of 11 μm.

[0032] (Applications) The alumina powder according to this embodiment exhibits good thermal conductivity and is therefore suitable for use in applications where thermal conductivity is desired. The alumina powder according to this embodiment exhibits good shear bond strength and is therefore suitable for use in applications where good adhesion is desired. The alumina powder according to this embodiment exhibits good thermal conductivity and / or good shear bond strength and is therefore suitable for use in applications where thermal conductivity and / or good adhesion are desired. More specifically, the alumina powder according to this embodiment can be used to produce a resin composition containing the alumina powder and a resin. In one embodiment, the resin composition is preferably an adhesive composition due to its good shear bond strength. That is, the alumina powder can be suitably used to produce an adhesive composition. In one embodiment, the alumina powder is an alumina powder for adhesives. In one embodiment, the alumina powder is an alumina powder for use in an adhesive composition or an adhesive. Furthermore, the resin composition is more preferably an adhesive composition for electronic devices due to its good thermal conductivity and good shear bond strength. That is, the alumina powder can be suitably used to produce an adhesive composition for electronic devices. In one embodiment, the alumina powder is an alumina powder for adhesives for electronic devices. In one embodiment, the alumina powder is for use in an adhesive composition for electronic devices, or for use in an adhesive for electronic devices. The alumina powder for adhesives for electronic devices and the adhesive composition for electronic devices can be suitably used for producing adhesives for electronic components of electronic devices, semiconductor encapsulants for electronic devices, adhesives for heat dissipation sheets for electronic devices and adjacent components, etc.

[0033] [Resin Composition] The resin composition according to this embodiment contains the aforementioned "alumina powder" and a resin. The content of the alumina powder in the resin composition is preferably 80 to 95 mass%, more preferably 83 to 95 mass%, and even more preferably 85 to 95 mass%. When the content of the alumina powder is 85 to 95 mass%, it may be 88 mass%. When the content of the alumina powder in the resin composition is 80 to 95 mass%, the resin composition is more likely to exhibit good thermal conductivity and / or good adhesion.

[0034] Examples of the resin include epoxy resin, silicone resin, urethane resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyamide such as polyimide, polyamideimide, polyetherimide, polyester such as polybutylene terephthalate, polyethylene terephthalate, polyphenylene ether, polyphenylene sulfide, wholly aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide-modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber styrene) resin, AES (acrylonitrile ethylene propylene diene rubber styrene) resin, and it is preferable to include at least one selected from these.

[0035] When the resin composition is used as an adhesive, it is preferable to use a silicone resin as the resin.

[0036] Examples of silicone resins include thermosetting silicone resins and thermoplastic silicone resins, and among these, thermosetting silicone resins are preferred. Examples of thermosetting silicone resins include those having a skeletal structure such as silane, silicone oligomer, silicone resin, organosiloxane, diorganosiloxane, organopolysiloxane, and diorganopolysiloxane, and the skeletal structure has one or more reactive functional groups. The skeletal structure may be a linear or branched chain. Examples of reactive functional groups include hydroxyl groups, alkenyl groups, and epoxy groups. The curing agent is not particularly limited, and known curing agents can be blended. The silicone resin may be a commercially available product, or may be a silicone resin blended with predetermined amounts of two or more commercially available products. Examples of commercially available products include YE5822(A) (manufactured by Momentive Performance Materials) and YE5822(B) (manufactured by Momentive Performance Materials).

[0037] The resin content in the resin composition is preferably 5 to 20% by mass, more preferably 5 to 17% by mass, and even more preferably 5 to 15% by mass. By having the resin content in the resin composition be 5 to 20%, the resin composition is more likely to exhibit good thermal conductivity and / or good shear adhesive strength.

[0038] Other additives may be blended into the resin composition as needed. Examples of such additives include antifoaming agents, leveling agents, rubber-like substances such as polysulfide rubber, acrylic rubber, butadiene rubber, styrene block copolymers, and saturated elastomers, and Sb ２ O ３ , Sb ２ O ４ , Sb ２ O ５ flame retardants such as phosphorus compounds; colorants such as carbon black, iron oxide, dyes, and pigments.

[0039] (Thermal Conductivity) In one embodiment, a resin composition containing alumina powder and a resin is prepared by blending a resin and a filler (alumina powder) in a predetermined ratio and curing the resin at 120°C for 1 hour. A piece of the resin composition is cut from the resin composition for measurement, and the thermal conductivity measured according to ASTM E 1530 is preferably greater than 2.3 W / m·K. By exhibiting a good thermal conductivity of greater than 2.3 W / m·K, the resin composition containing alumina powder and a resin can be suitably used in applications where good thermal conductivity is desired, as described below. The thermal conductivity may be 2.4 W / m·K, 2.5 W / m·K, 2.6 W / m·K, 2.7 W / m·K, or 3.1 W / m·K, and these may be used as upper or lower limits, or a combination of these may be used.

[0040] In one embodiment, a resin composition containing an alumina powder and a resin is prepared by compounding silicone resin:filler (alumina powder) at a ratio of 12:88 (mass%) and curing the resin at 120°C for 1 hour. A piece of the resin composition is cut out from the resin composition for measurement, and the thermal conductivity measured in accordance with ASTM E 1530 is greater than 2.3 W / m K.

[0041] (Shear Bond Strength) In one embodiment, the resin composition containing alumina powder and a resin preferably has a shear bond strength of more than 0.23 MPa measured according to ASTM D1002 for aluminum plates bonded together by bonding two aluminum plates with a resin composition containing a resin and a filler in a predetermined ratio and curing the mixture at 120°C for 1 hour. Having a shear bond strength of more than 0.23 MPa makes the resin composition containing alumina powder and a resin suitable for use in applications requiring high adhesion, as described below. The shear bond strength may be 0.3 MPa, 0.34 MPa, 0.43 MPa, 0.54 MPa, or 0.64 MPa, and these may be used as upper or lower limits, or may be a combination of these ranges.

[0042] In one embodiment, the resin composition containing alumina powder and resin is a resin composition containing silicone resin:filler (alumina powder) = 12:88 (mass%), and the aluminum plates are bonded by laminating them together using the resin composition and curing the mixture at 120°C for 1 hour. The shear bond strength measured in accordance with ASTM D1002 is greater than 0.23 MPa.

[0043] In one embodiment, the resin composition containing alumina powder and a resin has a shear bond strength of 0.26 MPa or more.

[0044] The resin composition can be produced by stirring, dissolving, mixing, and dispersing the predetermined amounts of the above-mentioned materials. Apparatuses for mixing, stirring, dispersing, etc., that can be used include a mortar and pestle machine equipped with a stirring and heating device, a three-roll mill, a ball mill, a planetary mixer, etc. These apparatuses may also be used in appropriate combination.

[0045] (Applications) The resin composition according to this embodiment exhibits good thermal conductivity and is therefore suitable for use in applications where thermal conductivity is desired. The resin composition according to this embodiment exhibits good shear bond strength and is therefore suitable for use in applications where high adhesion is desired. The resin composition according to this embodiment exhibits good thermal conductivity and / or good shear bond strength and is therefore suitable for use in applications where good thermal conductivity and / or good adhesion are desired. In one embodiment, the resin composition is preferably an adhesive composition due to its good shear bond strength. Furthermore, the resin composition is more preferably an adhesive composition for electronic devices due to its good thermal conductivity and good shear bond strength. The adhesive composition for electronic devices can be suitably used for producing adhesives for electronic components of electronic devices, semiconductor encapsulants for electronic devices, adhesives between heat dissipation sheets for electronic devices and adjacent components, etc.

[0046] [Adhesive] The adhesive according to this embodiment includes the resin composition described above in the section "Resin Composition." As described above, the resin composition may contain additives, and the adhesive may also contain, in addition to the resin composition, the additives exemplified above.

[0047] The content of the resin composition in the adhesive is not limited as long as the adhesive required for a specific application has the desired thermal conductivity and shear adhesive strength, but may be, for example, 95 (mass %) or more, or 99 (mass %) or more.

[0048] The adhesive can be produced by stirring, dissolving, mixing, and dispersing predetermined amounts of the resin composition and the other materials. Apparatuses for mixing, stirring, dispersing, etc., such as a mortar and pestle machine equipped with a stirring and heating device, a three-roll mill, a ball mill, and a planetary mixer, may be used. These apparatuses may also be used in combination as appropriate.

[0049] The adhesive according to this embodiment includes a resin composition exhibiting good thermal conductivity and good shear adhesive strength, and is therefore preferably used for bonding components that require good thermal conductivity and good adhesiveness. In one embodiment, the adhesive is an adhesive for electronic devices. More specifically, the adhesive is an adhesive for electronic components of electronic devices, a semiconductor encapsulant for electronic devices, an adhesive for connecting a heat dissipation sheet for electronic devices to adjacent components, or the like. A more specific example of an adhesive for electronic devices is an adhesive for bonding between cells and / or modules of an electric vehicle (EV) battery.

[0050] In one embodiment, an electronic component is provided in which multiple components are bonded together using the adhesive according to the present embodiment, i.e., the electronic component includes the adhesive according to the present embodiment. Such an electronic component exhibits desired thermal conductivity and is likely to have good thermal management due to the adhesive having good thermal conductivity and good adhesive properties.

[0051] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of the present disclosure is disclosed below. [1] An alumina powder having a volume-based cumulative 50% diameter D50 of 10 μm or more and 70 μm or less, and having a first peak maximum value in a particle size range of 20 μm or more and a second peak maximum value in a particle size range of 1 μm or more and less than 20 μm in a volume-based frequency particle size distribution. [2] An alumina powder according to [1], having a third peak maximum value in a particle size range of less than 1 μm in a volume-based frequency particle size distribution. [3] An alumina powder according to [1] or [2], which is used for an adhesive. [4] A resin composition comprising the alumina powder according to any one of [1] to [3] and a resin. [5] The resin composition according to [4], which is used for an adhesive. [6] An adhesive comprising the alumina powder according to any one of [1] to [3] and a resin.

[0052] The present disclosure will be explained in more detail below by showing examples, but interpretation of the present disclosure is not limited to these examples.

[0053] [Examples 1 to 6, Comparative Examples 1 to 3] Alumina powders of Examples 1 to 6 and Comparative Examples 1 to 3 were prepared by blending spherical alumina powders (raw material) having D50 values ​​shown in Table 2 according to the formulations shown in Table 1.

[0054] The volume-based frequency particle size distribution of the obtained alumina powder was measured by laser diffraction light scattering using a particle size distribution analyzer (manufactured by Beckman Coulter, Inc., "LS-13230") with a refractive index of 1.68, water as the measurement solvent, and pretreatment conditions of 60 seconds and 200 W ultrasonic homogenizer. From the obtained frequency particle size distribution, the maximum value (μm) of each peak, the maximum frequency (%) of each peak, and the half-width of the frequency particle size distribution curve were determined. Furthermore, the particle diameter (D50) corresponding to 50% of the cumulative value in the volume-based cumulative particle size distribution was determined.

[0055] The average circularity of the alumina powder was measured. The alumina powder constituting the obtained alumina powder was fixed with carbon tape and then osmium coated. Thereafter, the particles were photographed at a magnification of 500 to 50,000 times using a scanning electron microscope (manufactured by JEOL Ltd., product name: JSM-7001F SHL), and the projected area (S) and projected perimeter (L) of the particles were calculated using an image analyzer (manufactured by Nippon Roper Co., Ltd., product name: Image-Pro Premier Ver. 9.3), and then the circularity was calculated using the following formula. The circularity was calculated for any 200 particles, and the average value was taken as the average circularity. Circularity = 4πS / L ２

[0056] The results are shown in Table 1. In both the Examples and Comparative Examples, the D50 was 14 μm to 97 μm. In the Examples, the D50 was 14 μm to 63 μm. In the Comparative Examples, the D50 was 43 μm to 97 μm. In the Examples and Comparative Examples, the particle size in the volume-based frequency particle size distribution had one or more peak maximum values. In the Examples, the particle size in the volume-based frequency particle size distribution had two or more peak maximum values, while in the Comparative Examples, it had one peak maximum value. In the Examples and Comparative Examples, the first peak maximum value was observed in a particle size range of 25 μm or more. In both the Examples and Comparative Examples, the first peak maximum value was observed in a particle size range of 25 μm to 97 μm. In the Examples, the second peak maximum value was observed in a particle size range of 3 μm to 11 μm. In the Examples, the third peak maximum value was observed at a particle size of 0.5 μm. On the other hand, in the Comparative Examples, no peak maximum value was observed other than the first peak maximum value.

[0057] In Example 1, the maximum frequency of the first peak (frequency at the maximum value) was 5.21, the maximum frequency of the second peak was 1.93, and the maximum frequency of the third peak was 1.04. In Example 2, the maximum frequency of the first peak was 4.02, the maximum frequency of the second peak was 2.80, and the maximum frequency of the third peak was 1.05. In Example 3, the maximum frequency of the first peak was 6.87, the maximum frequency of the second peak was 1.77, and the maximum frequency of the third peak was 1.00. In Example 4, the maximum frequency of the first peak was 6.24, and the maximum frequency of the second peak was 2.21. In Example 5, the maximum frequency of the first peak was 4.85, and the maximum frequency of the second peak was 3.17. In Example 6, the maximum frequency of the first peak was 8.21, and the maximum frequency of the second peak was 2.01. In Comparative Example 1, the maximum frequency of the first peak was 10.41. In Comparative Example 2, the maximum frequency of the first peak was 7.95. In Comparative Example 3, the maximum frequency of the first peak was 13.68.

[0058] In Example 1, the half-maximum width of the first peak was 52.2, the half-maximum width of the second peak was 9.0, and the half-maximum width of the third peak was 10.0. In Example 2, the half-maximum width of the first peak was 56.3, the half-maximum width of the second peak was 5.0, and the half-maximum width of the third peak was 0.74. In Example 3, the half-maximum width of the first peak was 201.4, the half-maximum width of the second peak was 20.9, and the half-maximum width of the third peak was 0.89. In Example 4, the half-maximum width of the first peak was 77.9, and the half-maximum width of the second peak was 9.4. In Example 5, the half-maximum width of the first peak was 74.3, and the half-maximum width of the second peak was 5.7. In Example 6, the half-maximum width of the first peak was 185.3, and the half-maximum width of the second peak was 21.3. In Comparative Example 1, the half width of the first peak was 75.2, in Comparative Example 2, the half width of the first peak was 54.9, and in Comparative Example 3, the half width of the first peak was 185.3.

[0059] The average circularity of the obtained alumina powder was 0.92 to 0.95 in both the Examples and Comparative Examples.

[0060] The obtained alumina powder was blended with silicone resin (YE5822(A) and YE5822(B) (both manufactured by Momentive Performance Materials) in a ratio of 90:10 (wt%)) and silicone resin:filler (alumina powder) = 12:88 (mass%), and the resin was cured at 120°C for 1 hour to obtain a resin composition. A measurement piece (30 mm x 30 mm x 3 mmt) was cut from the resin composition, and the thermal conductivity was measured according to ASTM E 1530. Two aluminum plates were bonded together using a resin composition blended with silicone resin:filler (alumina powder) = 12:88 (mass%) and cured at 120°C for 1 hour. The aluminum plates were then bonded together. The shear bond strength of this aluminum plate was measured according to ASTM D1002.

[0061] Table 1 shows the measurement results of the thermal conductivity (W / m·K) and shear bond strength (MPa) of the resin compositions containing alumina powder and silicone resin in Examples 1 to 6 and Comparative Examples 1 to 3. In the Examples, the thermal conductivity was 2.4 W / m·K or higher, and the shear bond strength was 0.26 MPa or higher. That is, the Examples were able to achieve both good thermal conductivity and good shear bond strength. In contrast, Comparative Examples 1 to 3 were inferior to the Examples in both thermal conductivity and shear bond strength, and were unable to achieve both good thermal conductivity and good shear bond strength.

[0062] The alumina powder according to the present disclosure can provide a resin composition that exhibits good thermal conductivity and good shear bond strength.

[0063] The alumina powder of the present embodiment exhibits good thermal conductivity and good shear adhesive strength, and therefore can be suitably used in applications where thermal conductivity and adhesiveness are desired. Specifically, the alumina powder has industrial applicability, for example, as an adhesive for electronic devices.

Claims

1. An alumina powder having a volume-based cumulative 50% diameter D50 of 10 μm or more and 70 μm or less, a first peak having a maximum value in a particle size range of 20 μm or more in a volume-based frequency particle size distribution, and a second peak having a maximum value in a particle size range of 1 μm or more and less than 20 μm.

2. The alumina powder according to claim 1, which has a third peak with a maximum value at a particle size of less than 1 μm in a volume-based frequency particle size distribution.

3. The alumina powder according to claim 1, which is used for adhesives.

4. A resin composition comprising the alumina powder according to any one of claims 1 to 3 and a resin.

5. The resin composition according to claim 4, which is used as an adhesive.

6. An adhesive comprising the alumina powder according to any one of claims 1 to 3 and a resin.

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