JP7711080B2 - Spherical alumina powder, resin composition, semiconductor sealing material - Google Patents

Description

The present invention relates to a spherical alumina powder, a resin composition, and a semiconductor encapsulation material.

In recent years, in response to the demand for smaller, lighter, and more powerful electronic devices, the miniaturization, thinning, and narrowing of semiconductor packages have been accelerating rapidly. In addition, the mounting method has become dominated by surface mounting, which is suitable for high-density mounting on wiring boards and the like. As such, as semiconductor packages and their mounting methods progress, there is a demand for improved performance in semiconductor encapsulation materials, and research has been actively conducted into highly filling epoxy resins with ceramic powder, particularly spherical alumina powder. The problem with highly filling ceramic powder is that it increases the viscosity of the material, increasing defects in molding such as non-filling, wire sweep, wire breakage, and chip shift.

To solve this problem, improvements have been made from both the resin and the ceramic powder side. Improvements from the ceramic powder side include, for example, a method of increasing Wardle's sphericity to 0.7 to 1.0 (Patent Document 1), a method of broadening the particle size distribution by setting the gradient of the straight line shown in the Rosin-Rammler diagram to 0.6 to 0.95 (Patent Document 2), and a method of providing several peaks in the particle size distribution to make it multimodal, thereby bringing the ceramic powder closer to a close-packed structure (Patent Document 3). However, these improvements are still insufficient, and increasing the packing rate causes a sudden increase in the viscosity of the material.

Japanese Patent Application Publication No. 3-066151 Japanese Unexamined Patent Publication No. 6-080863 Japanese Patent Application Publication No. 8-003365

The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a practical spherical alumina powder which exhibits good fluidity.

Means of the Invention The present inventors have conducted intensive research to solve the above problems, and as a result have found that the above problems can be solved by the present invention described below, thereby completing the present invention.
That is, the present invention is as follows.

[1] A spherical alumina powder having, from the small diameter side, a first maximum peak and a second maximum peak in a particle size distribution measured with a laser diffraction/scattering particle size distribution measuring device, a first maximum particle diameter indicating the first maximum peak being in a range of 3 to 9 μm, a second maximum particle diameter indicating the second maximum peak being in a range of 30 to 50 μm, and a cumulative value of the frequency of each of five particle diameters obtained by dividing the range from the second maximum particle diameter -10 μm to the second maximum particle diameter +10 μm into four equal parts is 25 to 45 vol %.
[2] The spherical alumina powder according to [1], wherein the cumulative frequency in the range of the peak having the second maximum peak is 55 volume % or more.
[3] The spherical alumina powder according to [1] or [2], wherein the cumulative frequency in the range of peaks having the first maximum peak is 35 volume % or less.
[4] The spherical alumina powder according to any one of [1] to [3], wherein the frequency at the first maximum particle diameter -1 μm and the frequency at the first maximum particle diameter +1 μm are each 50% or more of the frequency at the first maximum particle diameter.
[5] The spherical alumina powder according to any one of [1] to [4], wherein the content of particles having a particle diameter of 55 μm or more is 0.1 mass% or less.
[6] A resin composition comprising a resin and the alumina powder according to any one of [1] to [5]. [7] A semiconductor encapsulation material comprising the resin composition according to [6].

According to the present invention, it is possible to provide a practical spherical alumina powder which exhibits good fluidity.

The spherical alumina powder of the present invention has a first maximum peak and a second maximum peak from the small diameter side in a particle size distribution measured by a laser diffraction/scattering type particle size distribution measuring device, the first maximum particle diameter showing the first maximum peak is in the range of 3 to 9 μm, the second maximum particle diameter showing the second maximum peak is in the range of 30 to 50 μm, and the cumulative frequency of each of the five particle diameters obtained by dividing the range from the second maximum particle diameter -10 μm to the second maximum particle diameter +10 μm into four equal parts is 25 to 45 volume %.

As described above, in the present invention, the first maximum particle diameter showing the first maximum peak and the second maximum particle diameter showing the second maximum peak of a spherical alumina powder having a first maximum peak and a second maximum peak from the small diameter side are set within respective predetermined ranges, and the shape of the second maximum peak is specified, thereby achieving an even greater improvement in fluidity than in the past.

The reason why the above-mentioned effect of improving fluidity is obtained is presumed to be as follows. Usually, when the powder is densely packed, liquid bridges are formed between the powder particles due to the influence of moisture in the atmosphere. When liquid bridges are formed, the viscosity increases and the fluidity decreases when the powder is made into a resin composition. In consideration of this phenomenon, in the present invention, the spherical alumina powder having a smaller diameter within the first maximum peak is present between the particles and in the gaps of the spherical alumina powder having a larger particle size within the second maximum peak, so that liquid bridges are suppressed, and it is presumed that high fluidity is exhibited even when the powder is in a dense state.
Hereinafter, an embodiment of the present invention (the present embodiment) will be described in detail.
[Spherical alumina powder]
The spherical alumina powder according to this embodiment has a first maximum peak and a second maximum peak from the small diameter side in the particle size distribution measured by a laser diffraction scattering type particle size distribution measuring device. By making it at least multimodal having the first maximum peak and the second maximum peak, the spherical alumina powder with a small particle size (spherical alumina powder within the first maximum peak) enters between particles or gaps of the spherical alumina powder with a large particle size (spherical alumina powder within the second maximum peak) and it becomes easy to obtain close packing. In addition, as described above, the spherical alumina powder within the first maximum peak suppresses liquid bridging, resulting in a practical spherical alumina powder.

Here, the first maximum particle diameter showing the first maximum peak is in the range of 3 to 9 μm, and preferably in the range of 4 to 8 μm. If the first maximum particle diameter is outside the range of 3 to 9 μm, the liquid crosslinking suppression effect is reduced, and the viscosity of the resin composition containing the spherical alumina powder increases, resulting in a decrease in spiral flow.
The second maximum particle diameter showing the second maximum peak is in the range of 30 to 50 μm, preferably in the range of 35 to 48 μm. If the second maximum particle diameter is outside the range of 30 to 50 μm, the rolling resistance increases, the viscosity of the resin composition containing the spherical alumina powder increases, and the spiral flow decreases.
The first maximum peak and the second maximum peak are measured by a laser diffraction scattering type particle size distribution measuring device as described above, but specifically, they can be measured and calculated by the method described in the Examples.

The cumulative value of the frequency of each of the five particle diameters obtained by dividing the range from the second maximum particle diameter -10 μm to the second maximum particle diameter +10 μm into four equal parts (i.e., the particle diameters of the second maximum particle diameter -10 μm, the second maximum particle diameter -5 μm, the second maximum particle diameter, the second maximum particle diameter +5 μm, and the second maximum particle diameter +10 μm) is 25 to 45 vol%, and preferably 34 to 41 vol%. The fact that the cumulative value is within the above range means that the second maximum peak has a sharper shape than the first maximum peak. And, by having such a shape, good flowability with reduced rolling resistance can be obtained. Conversely, if the cumulative value is outside the range of 25 to 45 vol%, good flowability is difficult to obtain.

The frequency at the first maximum particle diameter -1 μm and the frequency at the first maximum particle diameter +1 μm are preferably 50% or more of the frequency at the first maximum particle diameter, and more preferably 70 to 95%. As described above, the frequency at the first maximum particle diameter is 50% or more, so that the second maximum peak is broad. In such a broad state, the spherical alumina that contributes to reducing liquid bridging has a large variation in particle size, and it is easy to be evenly present from small gaps to large gaps between the spherical alumina powders in the second maximum peak, resulting in better fluidity.

The cumulative frequency of the particle size region in the range of the peak having the first maximum peak is preferably 35% by volume or less, and more preferably 15 to 30%. By having the cumulative frequency of 35% by volume or less, good fluidity and viscosity can be achieved.

In addition, the cumulative frequency of the particle size region in the range of the peak having the second maximum peak is preferably 55% by volume or more, and more preferably 65 to 85%. By having the cumulative frequency of 65% by volume or more, good fluidity and viscosity can be achieved.

The spherical alumina powder according to this embodiment preferably has a particle content of 55 μm or more in particle diameter of 0.1% by mass or less, more preferably 0.05% or less. By making the particle content 0.1% by mass or less, it is possible to improve the injection property into minute spaces such as between wires and between elements. In order to make the particle content of 55 μm or more in particle diameter 0.1% by mass or less, it is sufficient to adjust it by classification processing by sieving.

Here, the range of the peak having the first maximum peak is the range from the particle size detected from the lower limit of measurement through the first maximum peak to the particle size showing the minimum frequency, and the range of the peak having the second maximum peak is the range from the minimum value through the second maximum peak to 55 μm.
The diameter at which the frequency is maximum within the above range is the maximum particle diameter.

The average particle size of the spherical alumina powder according to the present embodiment is preferably 20 to 40 μm, and more preferably 25 to 35 μm. By setting the average particle size to 20 to 40 μm, it is possible to prevent an increase in viscosity and keep the spiral flow in a good range.
Here, the average particle size is a cumulative 50% diameter (D50) on a volume basis measured by a laser diffraction scattering type particle size distribution measuring device, and can be measured and calculated by the method described in the Examples.

The average sphericity of the spherical alumina powder according to the present embodiment is preferably 0.9 or more, and more preferably 0.92 or more. By having an average sphericity of 0.9 or more, an increase in viscosity can be prevented and the spiral flow can be kept in a good range.
Here, the average sphericity can be measured and calculated by the method described in the Examples.

The specific surface area is preferably 0.25 to 0.45 ^{m 2} /g, and more preferably 0.3 to 0.4 m ² /g. By having the specific surface area of 0.25 to 0.45 ^{m 2} /g, it is possible to prevent an increase in viscosity and keep the spiral flow within a good range.
Here, the specific surface area is a value based on the BET method, and can be measured and calculated by the BET single point method.

In this embodiment, the cumulative value up to 10 μm is preferably 10 to 35 vol%, and more preferably 15 to 30 vol%. By setting it to 10 to 35 vol%, an increase in viscosity can be prevented and the spiral flow can be kept in a good range. The cumulative value up to 10 μm is measured using a laser diffraction scattering type particle size distribution measuring device.

The spherical alumina powder according to this embodiment can be produced, for example, as follows.
First, the alumina raw material powder serving as the raw material is preferably an alumina powder or an aluminum hydroxide powder.
Then, alumina raw material powder having an average particle diameter approximately the same as the desired first maximum particle diameter is introduced into a high-temperature flame formed with a fuel gas such as hydrogen, natural gas, acetylene gas, propane gas, butane, or LPG, and melted and spheroidized to produce a first spherical alumina powder.
Similarly, a second spherical alumina powder is produced by melting and spheroidizing an alumina raw material powder having an average particle size substantially the same as the desired second maximum particle size.
The average sphericity and specific surface area of the spherical alumina powder can be adjusted by controlling at least one of the temperature inside the furnace in which the high-temperature flame is formed, the particle size of the alumina raw material powder, and the input amount.

Next, the particle size distribution of the first spherical alumina powder is adjusted to a desired range using a sieve or a precision air classifier, etc. Similarly, the particle size distribution of the second spherical alumina powder is also adjusted to a desired range using a sieve or a precision air classifier, etc.
The desired range in this case refers to a range in which the cumulative value of the frequency of each of the five particle diameters obtained by dividing the range from the second maximum particle diameter -10 μm to the second maximum particle diameter +10 μm into four equal parts is 25 to 45 volume %, a range in which the frequency at the first maximum particle diameter -1 μm and the frequency at the first maximum particle diameter +1 μm are each 50% or more of the frequency at the first maximum particle diameter, and the like.
In addition, by adjusting the feed amount in precision air classification, the peak shape of the particle size distribution can be made sharper or broader.

Thereafter, the first spherical alumina powder and the second spherical alumina powder are mixed in a volume ratio of 5:95 to 25:75 to obtain the spherical alumina powder according to this embodiment.

[Resin composition, semiconductor encapsulation material]
The resin composition according to the present invention contains a resin and the alumina powder according to the present invention described above. Also, the semiconductor encapsulation material according to the present invention contains the resin composition according to the present invention described above.

Examples of the resin that can be used include epoxy resin, silicone resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyamide such as polyimide, polyamideimide, polyetherimide, polyester such as polybutylene terephthalate, polyethylene terephthalate, 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 the like.

Among these, the resin for semiconductor encapsulation material is preferably an epoxy resin having two or more epoxy groups in one molecule. Examples thereof include phenol novolac type epoxy resins, orthocresol novolac type epoxy resins, epoxidized novolac resins of phenols and aldehydes, glycidyl ethers of bisphenol A, bisphenol F, bisphenol S, etc., glycidyl ester acid epoxy resins obtained by reacting polybasic acids such as phthalic acid and dimer acid with epochlorohydrin, linear aliphatic epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, alkyl-modified polyfunctional epoxy resins, β-naphthol novolac type epoxy resins, 1,6-dihydroxynaphthalene type epoxy resins, 2,7-dihydroxynaphthalene type epoxy resins, biphenyl type epoxy resins, and further epoxy resins into which halogens such as bromine have been introduced to impart flame retardancy. Among these, from the viewpoints of moisture resistance and solder reflow resistance, orthocresol novolac type epoxy resin, biphenyl type epoxy resin, naphthalene skeleton epoxy resin, and the like are preferable.

Examples of the curing agent for the epoxy resin include a novolak type resin obtained by reacting one or a mixture of two or more selected from the group consisting of phenol, cresol, xylenol, resorcinol, chlorophenol, t-butylphenol, nonylphenol, isopropylphenol, octylphenol, and the like, with formaldehyde, paraformaldehyde, or paraxylene in the presence of an oxidation catalyst; a polyparahydroxystyrene resin; bisphenol compounds such as bisphenol A and bisphenol S; trifunctional phenols such as pyrogallol and phloroglucinol; acid anhydrides such as maleic anhydride, phthalic anhydride, and pyromellitic anhydride; aromatic amines such as metaphenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone; and phenol aralkyl resins such as phenol aralkyl resins having a biphenylene skeleton.
In order to accelerate the reaction between the epoxy resin and the curing agent, a curing accelerator such as triphenylphosphine or 1,8-diaza-bicyclo(5,4,0)undecene-7 can be used.

The resin composition or semiconductor encapsulating material of the present invention may contain the following components as necessary: Stress reducing agents include rubber-like substances such as silicone rubber, polysulfide rubber, acrylic rubber, butadiene rubber, styrene block copolymers, and saturated elastomers, resin-like substances such as various thermoplastic resins and silicone resins, and further resins obtained by modifying a part or the whole of an epoxy resin or phenol resin with aminosilicone, epoxysilicone, alkoxysilicone, or the like.
Examples of the silane coupling agent include epoxy silanes such as γ-glycidoxypropyltrimethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino silanes such as aminopropyltriethoxysilane, ureidopropyltriethoxysilane, phenylaminosilane and N-phenylaminopropyltrimethoxysilane; hydrophobic silane compounds such as phenyltrimethoxysilane, methyltrimethoxysilane and octadecyltrimethoxysilane; and mercaptosilanes.
Examples of the surface treatment agent include Zr chelate, titanate coupling agents, and aluminum-based coupling agents.
Examples of the flame retardant include halogenated epoxy resins and phosphorus compounds, and examples of the colorant include carbon black, iron oxide, dyes, and pigments.
Examples of the flame retardant aid include Sb ₂ O ₃ , Sb ₂ O ₄ , and Sb ₂ O ₅ .
Examples of the release agent include natural waxes, synthetic waxes, metal salts of linear fatty acids, acid amides, esters, and paraffin.

The content of the spherical alumina powder of the present invention in the resin composition or the semiconductor encapsulation material is preferably 50 to 95% by mass. By being in this range, it is possible to impart functions such as heat resistance and thermal conductivity.

The resin composition or semiconductor encapsulating material of the present embodiment can be produced by blending predetermined amounts of the above-mentioned materials using a blender, a Henschel mixer, or the like, kneading the mixture using a heated roll, a kneader, a single-screw or twin-screw extruder, or the like, cooling the mixture, and then appropriately pulverizing the mixture.

Furthermore, in order to encapsulate a semiconductor using the semiconductor encapsulation material of this embodiment, a conventional molding method such as transfer molding or multi-plunger is used.

The present invention will be described in more detail below using examples and comparative examples. However, the present invention is not limited to the following examples as long as it does not deviate from the gist of the present invention.

[Example 1]
(Preparation of first spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 4 μm.

(Preparation of second spherical alumina powder)
Alumina powder was introduced into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification, to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 35 μm.
The average particle size and average sphericity were measured as follows (the same applies to the following Examples and Comparative Examples).

(Method of measuring average particle size)
The average particle size (volume basis) of the spherical alumina powder was measured by a laser diffraction scattering method (Microtrac (manufactured by Nikkiso Co., Ltd., product name "MT3300EX II")).

(Method of measuring average sphericity)
The average sphericity of the spherical alumina powder was measured using a flow type particle image analyzer, trade name "FPIA-3000" manufactured by Sysmex Corporation, as follows. The projected area (A) and perimeter (PM) of the particle were measured from the particle image. If the area of a perfect circle corresponding to the perimeter (PM) is (B), the sphericity of the particle can be expressed as A/B. If a perfect circle having the same perimeter as the perimeter (PM) of the sample particle is assumed, PM = 2πr, B = πr ² , so B = π × (PM/2π) ² , and the sphericity of each particle can be calculated as circularity = A/B = A × 4π/(PM) ^2. This was measured for 100 or more particles selected at random, and the average value was squared to obtain the average sphericity. The measurement solution was prepared by adding 20 ml of distilled water and 10 ml of propylene glycol to 0.1 g of the sample, and performing ultrasonic dispersion treatment for 3 minutes.

The first spherical alumina powder and the second spherical alumina powder were mixed in a volume ratio of 25:75 to prepare the spherical alumina powder of Example 1 (average particle size 33 μm, specific surface area 0.32 ^{m 2} /g, cumulative value up to 10 μm 20 volume %).
The particle size distribution (particle size and frequency) of the spherical alumina powder of Example 1 was measured by a laser diffraction scattering method. The above-mentioned Microtrac was used as a particle size distribution measuring device for the measurement.
The results are shown in Table 1 below.

89 parts by mass of the prepared spherical alumina powder, 5.5 parts by mass of biphenyl type epoxy resin (YX-4000HK manufactured by Japan Epoxy Resins Co., Ltd.), 4.8 parts by mass of phenolic resin (MEHC-7800S manufactured by Meiwa Kasei Co., Ltd.), 0.15 parts by mass of triphenylphosphine (TPP manufactured by Hokko Chemical Industry Co., Ltd.), and 0.35 parts by mass of phenylaminosilane (KBM-573 manufactured by Shin-Etsu Chemical Co., Ltd.) were dry blended in a Henschel mixer, and then heated and kneaded in a co-rotating intermeshing twin-screw extrusion kneader (screw diameter D = 25 mm, L / D = 10.2, paddle rotation speed 50 to 120 rpm, discharge rate 3.0 kg / Hr, kneaded product temperature 98 to 100 ° C.) to obtain a resin composition. The spiral flow (fluidity) of the prepared resin composition was performed as follows. The spiral flow is preferably 100 cm or more.
The viscosity was measured by adding the spherical alumina powder thus prepared to 65% by volume (88.1% by mass) of the resin composition to a bisphenol F liquid epoxy resin (epoxy equivalent: 169, Epicoat 807; manufactured by Mitsubishi Chemical Corporation), followed by stirring and degassing to prepare a resin composition for viscosity measurement. The results are shown in Table 1. The viscosity is preferably 100 Pa·s or less.

(Liquidity)
The flowability of the resin composition was evaluated using a spiral flow mold in accordance with EMMI-66 (Epoxy Molding Material Institute; Society of Plastics Industry) at a mold temperature of 175° C., molding pressure of 7.4 MPa, and pressure dwell time of 90 seconds.

(viscosity)
A B-type viscometer (manufactured by Toki Sangyo Co., Ltd., product name "TVB-10") was used at a temperature of 30°C and 10 rpm.
The viscosity of the resin composition for viscosity measurement was measured at a rotation speed of 100/s.

[Example 2]
(Preparation of first spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 4 μm.

(Preparation of second spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification, to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 38 μm.

The first spherical alumina powder and the second spherical alumina powder were mixed in a volume ratio of 25:75 to prepare the spherical alumina powder of Example 2 (average particle size 31 μm, specific surface area 0.30 ^{m 2} /g, cumulative value up to 10 μm 17% by volume).

Using the spherical alumina powder, a resin composition was prepared in the same manner as in Example 1, and the spiral flow (fluidity) and viscosity of the prepared resin composition were measured. The results are shown in Table 1 below.

[Example 3]
(Preparation of first spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification, to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 8 μm.

(Preparation of second spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 33 μm.

The first spherical alumina powder and the second spherical alumina powder were mixed in a volume ratio of 25:75 to prepare the spherical alumina powder of Example 3 (average particle size 32 μm, specific surface area 0.31 ^{m 3} /g, cumulative value up to 10 μm 23 vol%).

Using the spherical alumina powder, a resin composition was prepared in the same manner as in Example 1, and the spiral flow (fluidity) and viscosity of the prepared resin composition were measured. The results are shown in Table 1 below.

[Example 4]
(Preparation of first spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 4 μm.

(Preparation of second spherical alumina powder)
Alumina powder was introduced into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification, to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 43 μm.

The first spherical alumina powder and the second spherical alumina powder were mixed in a volume ratio of 25:75 to prepare the spherical alumina powder of Example 4 (average particle size 32 μm, specific surface area 0.32 ^{m 2} /g, cumulative value up to 10 μm 24 vol%).

Using the spherical alumina powder, a resin composition was prepared in the same manner as in Example 1, and the spiral flow (fluidity) and viscosity of the prepared resin composition were measured. The results are shown in Table 1 below.

[Example 5]
(Preparation of first spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification, to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 5 μm.

(Preparation of second spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 36 μm.

The first spherical alumina powder and the second spherical alumina powder were mixed in a volume ratio of 35:65 to prepare the spherical alumina powder of Example 5 (average particle size 29 μm, specific surface area 0.38 ^{m 2} /g, cumulative value up to 10 μm 28 vol%).

Using the spherical alumina powder, a resin composition was prepared in the same manner as in Example 1, and the spiral flow (fluidity) and viscosity of the prepared resin composition were measured. The results are shown in Table 1 below.

[Example 6]
(Preparation of first spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification, to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 5 μm.

(Preparation of second spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 36 μm.

The first spherical alumina powder and the second spherical alumina powder were mixed in a volume ratio of 20:80 to prepare the spherical alumina powder of Example 6 (average particle size 36 μm, specific surface area 0.30 ^{m 2} /g, cumulative value up to 10 μm 15 volume %).

Using the spherical alumina powder, a resin composition was prepared in the same manner as in Example 1, and the spiral flow (fluidity) and viscosity of the prepared resin composition were measured. The results are shown in Table 1 below.

[Comparative Example 1]
(Preparation of first spherical alumina powder)
Alumina powder was introduced into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification, to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 2 μm.

(Preparation of second spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 36 μm.

The first spherical alumina powder and the second spherical alumina powder were mixed in a volume ratio of 25:75 to prepare the spherical alumina powder of Comparative Example 1 (average particle size 33 μm, specific surface area 0.40 ^{m 2} /g, cumulative value up to 10 μm 20 volume %).

Using the spherical alumina powder, a resin composition was prepared in the same manner as in Example 1, and the spiral flow (fluidity) and viscosity of the prepared resin composition were measured. The results are shown in Table 1 below.

[Comparative Example 2]
(Preparation of first spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 10 μm.

(Preparation of second spherical alumina powder)
Alumina powder was introduced into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification, to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 43 μm.

The first spherical alumina powder and the second spherical alumina powder were mixed in a volume ratio of 25:75 to prepare a spherical alumina powder of Comparative Example 2 (average particle size 36 μm, specific surface area 0.27 ^{m 2} /g, cumulative value up to 10 μm 15 volume %).

Using the spherical alumina powder, a resin composition was prepared in the same manner as in Example 1, and the spiral flow (fluidity) and viscosity of the prepared resin composition were measured. The results are shown in Table 1 below.

[Comparative Example 3]
(Preparation of first spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification, to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 5 μm.

(Preparation of second spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification, to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 28 μm.

The first spherical alumina powder and the second spherical alumina powder were mixed in a volume ratio of 25:75 to prepare the spherical alumina powder of Comparative Example 3 (average particle size 26 μm, specific surface area 0.30 ^{m 2} /g, cumulative value up to 10 μm 22 vol%).

Using the spherical alumina powder, a resin composition was prepared in the same manner as in Example 1, and the spiral flow (fluidity) and viscosity of the prepared resin composition were measured. The results are shown in Table 1 below.

[Comparative Example 4]
(Preparation of first spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification, to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 5 μm.

(Preparation of second spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification, to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 51 μm.

The first spherical alumina powder and the second spherical alumina powder were mixed in a volume ratio of 25:75 to prepare the spherical alumina powder of Comparative Example 4 (average particle size 38 μm, specific surface area 0.29 ^{m 2} /g, cumulative value up to 10 μm 23 vol%).

Using the spherical alumina powder, a resin composition was prepared in the same manner as in Example 1, and the spiral flow (fluidity) and viscosity of the prepared resin composition were measured. The results are shown in Table 1 below.

[Comparative Example 5]
(Preparation of first spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification, to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 5 μm.

(Preparation of second spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 39 μm.

The first spherical alumina powder and the second spherical alumina powder were mixed in a volume ratio of 40:60 to prepare the spherical alumina powder of Comparative Example 5 (average particle size 25 μm, specific surface area 0.42 ^{m 2} /g, cumulative value up to 10 μm 41 vol%).

Using the spherical alumina powder, a resin composition was prepared in the same manner as in Example 1, and the spiral flow (fluidity) and viscosity of the prepared resin composition were measured. The results are shown in Table 1 below.

[Comparative Example 6]
(Preparation of first spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification, to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 5 μm.

(Preparation of second spherical alumina powder)
Alumina powder was charged into a flame formed by LPG and oxygen gas, and subjected to a spheroidizing treatment. After that, classification treatment was performed by cyclone classification to obtain alumina powder with an average sphericity of 0.92 and an average particle size of 36 μm.

The first spherical alumina powder and the second spherical alumina powder were mixed in a volume ratio of 15:85 to prepare the spherical alumina powder of Comparative Example 6 (average particle size 39 μm, specific surface area 0.27 ^{m 2} /g, cumulative value up to 10 μm 12 volume %).

Using the spherical alumina powder, a resin composition was prepared in the same manner as in Example 1, and the spiral flow (fluidity) and viscosity of the prepared resin composition were measured. The results are shown in Table 1 below.

The spherical alumina powder of the present invention can be used as a filler for resin molded parts such as molding compounds for automobiles, portable electronic devices, household appliances, etc., as well as putty, sealant, buoyancy material for ships, synthetic wood, reinforced cement exterior wall material, lightweight exterior wall material, sealing material, etc. The resin composition of the present invention can be used to manufacture, for example, prepregs for printed circuit boards, which are impregnated and cured into woven glass fabric, nonwoven glass fabric, or other organic substrates, electronic parts obtained by heat molding one or more sheets of prepregs together with copper foil, etc., as well as wire coating materials, sealing materials, varnishes, etc. The semiconductor sealing material of the present invention can be used as a sealing material that can be easily molded into small, thin, narrow-pitch semiconductor packages.

Claims (4)

In a particle size distribution measured by a laser diffraction scattering type particle size distribution measuring device, there are a first maximum peak and a second maximum peak from the small diameter side,
The first maximum particle size showing the first maximum peak is in the range of 3 to 9 μm,
The second maximum particle size showing the second maximum peak is in the range of 34 to 50 μm,
a cumulative value of the frequency of each of five particle diameters obtained by dividing a range from the second maximum particle diameter -10 μm to the second maximum particle diameter +10 μm into four equal parts is 25 to 45% by volume;
the cumulative value of the frequency in the range of the peak having the second maximum peak is 55% by volume or more;
a cumulative value of the frequency in a range of peaks having the first maximum peak is 35% by volume or less;
A spherical alumina powder in which the frequency at the first maximum particle diameter -1 μm and the frequency at the first maximum particle diameter +1 μm are each 50% or more of the frequency at the first maximum particle diameter . 2. The spherical alumina powder according to claim 1 , wherein the content of particles having a particle diameter of 55 μm or more is 0.1 mass % or less. A resin composition comprising a resin and the alumina powder according to claim 1 or 2 . A semiconductor encapsulating material comprising the resin composition according to claim 3 .