Particulate material, manufacturing method thereof, and filler material

Abstract

To provide a particle material having high thermal conductivity and high electrical insulation.SOLUTION: A particle material may maintain a high insulation property by adhering closely to a metal material on the surface of the metal material and forming an insulating film comprising a metal oxide with a predetermined amount of pores having a predetermined pore diameter distribution. The particle material has a core composed of the metal material and the insulating film formed of the metal oxide having a thickness of 20 nm or more to cover the core without gaps. The particle material has a BET specific surface area of 0.1-10 m2 / g. The particle material has a maximum pore volume peak between 1.7 nm and 100 nm in pore diameter in the analysis of pore distribution by BJH method. The volume of pores with pore diameters of 1.7-300 nm ranges from 0.3 mm3 / g to 8.0 mm3 / g. They have a volume-average particle size of 10 μm or more, a sphericity of 0.9 or more, and are dispersed to primary particles. Here, the pore diameter peak is calculated based on the pore volume calculated from the adsorption side of the BJH method.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a particulate material, a method for producing the same, and a filler material, and more particularly to a particulate material having excellent thermal conductivity, a method for producing the same, and a filler material. [Background technology]

[0002] As semiconductor devices become smaller, the generation of large amounts of heat has become a problem. The generated heat must be quickly transferred from the semiconductor device to the outside. To achieve this, thermal interface materials (TIMs) with high thermal conductivity are desired.

[0003] Conventional TIMs are generally made of resin compositions in which particulate material such as alumina is dispersed in a resin material such as silicone resin (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-190267 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the trend toward higher density packaging of semiconductors is expected to continue, and the accompanying increase in heat generation is unavoidable. In addition, as signals become increasingly higher in frequency, even faint noise is likely to have an effect, raising the risk of electronic components malfunctioning.

[0006] Here, particulate materials made of metal materials with high thermal conductivity are known, but metal materials have high electrical conductivity and may cause short circuits when used as is in electronic devices.

[0007] The present invention was completed in consideration of the above-mentioned circumstances, and aims to solve the problem of providing a particulate material using a metal material with high thermal conductivity and having a coating with high electrical insulation formed on the surface thereof, a method for producing the same, and a filler material. [Means for solving the problem]

[0008] As a result of extensive research aimed at solving the above problems, the inventors discovered that high insulation properties can be maintained by forming an insulating coating made of a metal oxide that adheres closely to the surface of a metal material. The insulating coating can maintain high insulation properties by providing a predetermined amount of pores with a predetermined pore diameter distribution.

[0009] That is, the particulate material of the present invention that solves the above-mentioned problems comprises a core portion made of a metal material; an insulating coating formed of a metal oxide having a thickness of 20 nm or more that covers the core portion without any gaps; and BET specific surface area is 0.1 to 10 m 2 / g, In the pore distribution analysis by the BJH method, the maximum value of the pore volume peak exists between pore diameters of 1.7 nm and 100 nm, and the pore volume of pore diameters of 1.7 nm to 300 nm is 0.3 mm 3 / g~8.0mm 3 / g, Volume average particle size is 10 μm or more, Sphericity is 0.9 or more, It is dispersed down to the primary particles.

[0010] Here, the pore diameter peak is calculated based on the pore volume calculated from the adsorption side of the BJH method.

[0011] The metal material preferably contains at least one of Al, Cu, and Si in an amount of 50 mass% or more, and the insulating coating is preferably an oxide of the metal material. It is preferable that D10 is 25 μm or more and D90 is 65 μm or less. It is also preferable that D90 / D10 is 4.5 or less.

[0012] The method for producing a particulate material of the present invention, which solves the above-mentioned problems, includes a granulation step in which a molten material containing 50% by mass or more of a metal element is granulated by an atomization method in an inert atmosphere to produce a raw particulate material having a sphericity of 0.9 or more; In the pore distribution analysis by the BJH method, the maximum value of the pore volume peak exists between pore diameters of 1.7 nm and 100 nm, and the pore volume of pore diameters of 1.7 nm to 300 nm is 0.3 mm 3 / g~8.0mm 3 an acid treatment step of immersing the raw particle material in an acid aqueous solution having a pH of 1.3 to 2.4 until the particle size reaches 1 / g; a dehydration step of dehydrating the acid aqueous solution to obtain a dehydrated product; a washing step of washing the dehydrated product with an organic solvent to obtain a washed product; a drying step of drying the washed product to obtain a dried product; an oxide film forming step of heating the dried product in an oxidizing atmosphere at 500°C or higher, at a temperature at which deformation to a sphericity of less than 0.9 does not occur, to form an oxide film having a thickness of 20 nm or more on the surface; It has.

[0013] By carrying out a cleaning process using an organic solvent after the acid treatment process, it is possible to form an insulating film with high insulating properties.

[0014] Preferably, the method further comprises a dehydration step of dehydrating the acid aqueous solution to form a dehydrated material after the acid treatment step and before the cleaning step. Furthermore, the atomization method is preferably a step of supplying the molten material onto the surface of a rotating metal disk. [Effects of the Invention]

[0015] The particulate material of the present invention having the above-described configuration has an insulating coating formed on its surface, allowing it to maintain high insulation even when placed in direct contact with a semiconductor circuit. Furthermore, despite the insulating coating, its high sphericity allows for excellent packing and ensures contact between individual particles, resulting in high thermal conductivity. The particulate material has a core made of metal, allowing it to exhibit high thermal conductivity. This particulate material can be suitably used as a filler material. [Brief explanation of the drawings]

[0016] [Figure 1] 1 shows the results of pore size distribution analysis of the raw particle material of Test 2 using the BJH method. [Figure 2] This shows the results of pore distribution analysis by the BJH method for a sample that was subjected to a single acid treatment step in Test 2. [Figure 3] This shows the results of pore distribution analysis using the BJH method for the sample that underwent the acid treatment process six times in Test 2. [Figure 4] 1 is an SEM photograph of Test 3. [Figure 5] 1 shows the results of measuring the amount of electromagnetic wave reflection, the amount of absorption, and the sum of these (electromagnetic wave shielding amount) for the resin composition of Sample 1 in Test 5. [Figure 6] 1 shows the results of measuring the amount of electromagnetic wave reflection, the amount of absorption, and the sum of these (electromagnetic wave shielding amount) for the resin composition of Sample 4 in Test 5. DETAILED DESCRIPTION OF THE INVENTION

[0017] The particulate material, its manufacturing method, and filler material of the present invention will be described in detail below based on embodiments. Because the particulate material of this embodiment has high thermal conductivity, it can be dispersed in a medium as a filler material (the filler material of this embodiment) and used as a TIM. A TIM with particularly excellent insulating properties can be provided. The medium may be either liquid or solid, and examples of the medium include oil, resin materials, and resin material precursors (monomers, etc.). Examples of resin materials and their precursors include epoxy resins and silicone resins. Furthermore, since the particulate material is expected to exhibit the ability to reflect and absorb electromagnetic waves, it can be used as an electromagnetic wave shielding material, an electromagnetic wave reflecting material, and an electromagnetic wave absorber. Furthermore, since the dielectric constant can be increased, it can be used as a filler for resin compositions for substrates, insulating materials, antenna materials, and the like.

[0018] Furthermore, it can be dispersed in these media as a filler material. When used as a filler material, the particulate material of this embodiment can be used alone, or it can be mixed with a second particulate material made of another material. The second particulate material is preferably made of an insulating material such as a ceramic, such as alumina or silica.

[0019] (particle material) The particulate material of this embodiment has a volume average particle size of 10 μm or more. The lower limit of the volume average particle size is preferably about 15 μm, 20 μm, or 25 μm, and the upper limit is preferably about 100 μm, 90 μm, 80 μm, 65 μm, 70 μm, or 75 μm. These lower and upper limits can be arbitrarily combined. Furthermore, a mixture of two or more particles with different particle sizes may also be used. The overall filling rate is improved by inserting smaller particles into the gaps formed between larger particles.

[0020] Furthermore, by having D10 of 15 μm or more and D90 of 95 μm or less, the particle size distribution of the particles constituting the particulate material becomes sharp. In particular, the lower limit of D10 can be 20 μm or 25 μm, and the upper limit of D90 can be 65 μm, 70 μm, 75 μm, 80 μm, or 85 μm. These lower and upper limits can be combined arbitrarily. Furthermore, it is preferable that D90 / D10 is 4.5 or less, and more preferably 3.5 or less.

[0021] The particulate material of this embodiment has a BET specific surface area of 0.1 to 10 m 2 / g. The lower limit of the BET specific surface area is 0.1 m 2 / g, 0.5m 2 / g, 1.0m 2 / g can be exemplified, and the upper limit is 1.0m 2 / g, 5.0m 2 / g, 10m 2 / g is an example. These upper and lower limits can be combined arbitrarily. The BET specific surface area is measured using nitrogen gas.

[0022] In the particulate material of this embodiment, the maximum value of the pore volume peak exists between pore diameters of 1.7 nm and 100 nm in pore distribution analysis by the BJH method. Examples of lower limit values of the pore diameters at which the maximum value of the pore volume peak exists are 1.7 nm, 5.0 nm, and 20 nm, and examples of upper limit values are 10 nm, 20 nm, and 100 nm. These upper and lower limit values can be arbitrarily combined. The BET specific surface area is measured using nitrogen gas. Furthermore, the pore volume of pores with diameters of 1.7 nm to 300 nm is 0.3 mm 3 / g~8.0mm 3 / g, the lower limit of which is 0.3 mm 3 / g, 1.0mm 3 / g, 3.0mm 3 / g can be exemplified, and the upper limit is 1.0 mm 3 / g, 5.0mm 3 / g, 8.0mm 3 / g is an example. These upper and lower limits can be combined arbitrarily. The pore diameter and pore volume are measured by the BJH method and calculated from the amount of adsorption using nitrogen gas.

[0023] The particulate material of this embodiment has a sphericity of 0.9 or more, preferably 0.95 or more, more preferably 0.98 or more, and even more preferably 0.99 or more. The sphericity is determined by taking a photograph with an SEM, and using the area and perimeter of the observed particles, the sphericity is calculated as follows: (sphericity) = {4π × (area) ÷ (perimeter)} 2 The closer to 1 the particle is to a perfect sphere. Specifically, the average value measured for 100 particles using image analysis software (Asahi Kasei Engineering Co., Ltd.: A-zo-kun) is used.

[0024] The particulate material of this embodiment has a core and an insulating coating. The core is made of a metal material. There are no limitations on the metal material, but it is preferable that the total content of Al, Cu, and Si is 50 mass % or more. The metal material may be a simple metal composed of only one element selected from Al, Cu, and Si, or an alloy composed of two or more of these elements. 。

[0025] The shape of the core is not particularly limited, but is preferably spherical. In particular, the sphericity is preferably 0.9 or more, more preferably 0.95 or more, 0.98 or more, or 0.99 or more. The particle size of the core is not particularly limited, but is preferably approximately the same as the diameter of the particulate material described above.

[0026] The insulating coating is a film that covers the periphery of the core portion. The insulating coating is composed of a metal oxide. The insulating coating covers the surface of the core portion without any gaps. The thickness of the insulating coating is 20 nm or more. It is also preferable that the thickness is such that insulation can be maintained when a DC voltage of 10 V (preferably DC voltage of 50 V) is applied to one particle. The thickness of the insulating coating is preferably 30 nm or more, and more preferably 50 nm or more. The insulating coating and the core portion are in close contact. "Close contact" means that when a cross section of the particle material is observed, the gap between the insulating coating and the core portion is 5 nm or less.

[0027] The thickness of the insulating film is measured by analyzing the constituent elements using XPS while scraping the surface of the particle material with an Ar laser at a speed of 10 nm / min. Specifically, the metal elements in the metal oxide that makes up the insulating film and the metal elements that make up the core are quantified, and the depth at which the amounts reverse is taken as the thickness of the insulating film. The scraping speed with the Ar laser is calibrated using the material that makes up the insulating film.

[0028] For example, when an insulating coating made of alumina is formed on the surface of an aluminum core, the relative amounts of Al are calculated from the peak intensities attributable to metallic Al and alumina Al in XPS measurement, and the depth at which the amount of metallic Al becomes relatively greater than that of alumina (depth cut with an Ar laser) is taken as the thickness of the insulating coating. For Al, the peak intensities of metallic Al and oxidized Al are considered to directly correspond to the relative amounts of Al in each state, and the depth at which the peak intensities are reversed is taken as the thickness of the oxide coating.

[0029] The metal oxide may be an oxide of a metal element contained in the metal material constituting the core part, and in this case, the composition ratio may be the same as or different from the composition ratio of the core part. Furthermore, the metal oxide may contain an element not contained in the core part, or may not contain an element contained in the core part.

[0030] The insulation properties were determined to be maintained when the current flowing when a specified voltage (10V or 50V) required for insulation was applied directly to the particulate material was measured, and the insulation properties were determined to be maintained if the current flowing was 0 mA when rounded to one decimal place.

[0031] As an example of a specific measurement device, a pair of tungsten needles with a tip diameter of 1.5 μm connected to a manipulator were clamped under a microscope around one of the particulate materials, and the value of the current flowing was observed while gradually increasing the voltage from 0 V to a specified voltage using a DC voltage / current generator R6144 (ADC Corporation).As a result, it was determined that insulation was maintained when the current flowing was 0 mA.

[0032] In addition, a resin composition containing 50% or more of particulate material by volume was prepared, and molded into a shape with a diameter of 20 mm and a height of 10 mm. The volume resistivity of the molded piece was measured using a Hiresta-UP resistivity meter manufactured by Mitsubishi Chemical Analytical Co., Ltd. Here, when a voltage of 1000 V was applied, the resistivity was 10 11 If the resistance is Ω·cm or more, it is judged to have insulating properties.

[0033] The thicker the insulating coating, the higher the voltage at which insulation can be maintained. Furthermore, the voltage at which insulation can be maintained varies depending on the material of the insulating coating. Therefore, if the insulating properties of the particle material are not sufficient, this can be achieved by either making the insulating coating thicker or by changing the insulating coating material to one with higher insulating properties.

[0034] The particulate material of this embodiment may have a surface treatment layer formed by reacting a surface treatment agent such as a silane coupling agent, a silane compound, or an organosilazanes. Examples of silane compounds include compounds having a SiH structure in which an organic functional group such as an alkyl group, a phenyl group, an amino group, a phenylamino group, an epoxy group, an acrylic group, a methacrylic group, a vinyl group, an isocyanate group, or a styryl group is connected to a silicon atom directly or via a spacer, and hexamethyldisilazane. The thickness of the surface treatment layer formed on the surface of the particulate material is not particularly limited. For example, when the amount sufficient to bond with all reactive groups such as OH groups present on the surface of the particulate material is taken as 100%, examples of the thickness of the surface treatment layer include approximately 30%, 50%, 75%, 100%, 150%, and 200% of the total thickness.

[0035] (filler material) The filler material of this embodiment includes the particulate material of this embodiment. The filler material can be used in TIM, semiconductor encapsulation materials, underfill materials, etc. The filler material can be in the form of a particulate material itself, a resin composition dispersed in a resin material, or a slurry composition dispersed in a solvent or the like. The filler material can contain particles other than the particulate material of this embodiment, such as alumina or silica particles. The content of the other particles can be approximately 10% to 90% based on the mass of the entire filler material. Examples of the content include 20%, 30%, 40%, 50%, 60%, 70%, and 80%, and any range can be set using these contents as the lower or upper limit.

[0036] (Thermal transfer material: TIM) The TIM of this embodiment includes the filler material of this embodiment and a resin material in which the filler material is dispersed in particulate form. The resin material is not particularly limited, but examples include silicone and epoxy resin. These resin materials may be in a pre-polymerized state.

[0037] It is preferable to include as much filler material as possible. For example, the upper limit of the filler material content based on the total volume can be set to about 70% or 80%.

[0038] (Method of manufacturing particulate material) The method for producing a particulate material of this embodiment is one of the methods for producing the particulate material of this embodiment described above. This production method is a method for producing a particulate material from a metal material, and includes a granulation step, an acid treatment step, a washing step, a drying step, an oxide film formation step, and other necessary steps. The metal material is a material containing metal elements that constitute the core portion. In particular, it is preferable that the total content of Al, Cu, and Si is 50 mass% or more.

[0039] The granulation process is a process for producing raw particle material by granulating a molten material obtained by melting a metal material using an atomization method under an inert atmosphere. The raw particle material obtained by granulation under an inert atmosphere can have highly spherical particles. In this specification, the inert atmosphere refers to an atmosphere consisting of a gas whose main component is an inert gas, such as nitrogen gas or argon. The inert atmosphere is used only during the process up to the solidification of the molten material to produce the raw particle material. The inert atmosphere does not necessarily have to be used during the process of melting the metal material to produce the molten material or after the molten material has solidified to produce a highly spherical raw particle material.

[0040] The atomization method is not particularly limited, but it is a method of granulating a molten material by rapidly cooling it. To convert a metal material into a molten material, any heating method can be used, or a plasma atomization method can be used as the atomization method, in which the molten material is also produced as part of the atomization method. Examples of rapid cooling methods include contacting the material with the surface of a rotating metal disk, spraying an inert gas such as nitrogen gas, or spraying a liquid such as water. Contacting the material with the surface of a rotating metal disk is particularly desirable. The particle size distribution of the resulting raw material particles can be controlled by changing the size, mass, material, rotation speed, etc. of the metal disk. For example, increasing the rotation speed of the metal disk increases the shear force applied to the molten material, thereby reducing the particle size of the resulting raw material particles.

[0041] Since the sphericity of the raw particle material obtained in the granulation step directly affects the sphericity of the final particle material, it is desirable that the raw particle material have a high sphericity. For example, the sphericity of the raw particle material is preferably 0.9 or more, more preferably 0.95 or more, 0.98 or more, or even 0.99 or more.

[0042] The acid treatment step is a step in which raw particle material is immersed in an acid aqueous solution containing an acid and having a pH of 1.3 to 2.4 to obtain an acid-treated product. The acid aqueous solution is an aqueous solution containing an acid, and contains 50% or more (preferably 70% or more, 90% or more, or 100%) of water based on the mass of the solvent, and may also contain an organic solvent that is miscible with water. The acid is not particularly limited, and examples include hydrochloric acid, nitric acid, sulfuric acid, acetic acid, and oxalic acid. The pH is preferably in the range of 1.4 to 1.6.

[0043] In the acid treatment step, the immersion conditions such as the temperature of the acid aqueous solution and the immersion time are not particularly limited. However, in the acid treatment step, the pore volume peak has a maximum value between 1.7 nm and 100 nm in the immersed raw particle material, and the pore volume of the pore diameter of 1.7 nm to 300 nm is 0.3 mm 3 / g~8.0mm 3The acid treatment step is carried out until an acid-treated product of 0.1g / g is obtained. The acid treatment step can be carried out multiple times by changing the aqueous acid solution. When the acid treatment step is carried out for a long period of time or multiple times, pore generation progresses, and the pore diameter and pore volume tend to increase. In particular, examples of lower limits of the pore diameter that indicates the maximum value of the pore volume peak include 1.7nm, 5.0nm, and 20nm, and examples of upper limits include 10nm, 20nm, and 100nm. These upper and lower limits can be combined arbitrarily.

[0044] The pore volume for pores with diameters of 1.7 nm to 300 nm has a lower limit of 0.3 mm 3 / g, 1.0mm 3 / g, 3.0mm 3 / g can be exemplified, and the upper limit is 1.0 mm 3 / g, 5.0mm 3 / g, 8.0mm 3 / g can be exemplified. These upper and lower limits can be arbitrarily combined. It is preferable that the pore diameter D90 / D10 is 10 or less. Here, D10 is the pore diameter that accounts for 10% of the total volume when integrating the pore volumes from the smallest pore diameter, and D90 is the pore diameter that accounts for 90%. The pore diameter distribution and pore volume are measured by the BJH method, which utilizes the adsorption action of nitrogen gas.

[0045] The temperature of the aqueous acid solution in the acid treatment step is not particularly limited, but examples of the lower limit include 0°C, 10°C, and 20°C, and examples of the upper limit include 50°C, 60°C, and 70°C. These upper and lower limit values can be combined as desired. The treatment time for the acid treatment step is not particularly limited, but examples of the lower limit include approximately 10 minutes, 30 minutes, and 60 minutes, and examples of the upper limit include approximately 60 minutes, 120 minutes, and 600 minutes. These upper and lower limit values can be combined as desired. By combining the temperature of the aqueous acid solution and the treatment time, the appropriate pore diameter peak and pore volume as described above can be achieved.

[0046] The washing step is a step in which the acid-treated product is washed with an organic solvent to obtain a washed product. The organic solvent is not particularly limited, but one that is miscible with water is preferred. For example, ethanol, isopropyl alcohol, or ethyl methyl ketone can be used as the organic solvent, and isopropyl alcohol or ethyl methyl ketone is particularly preferred. The washing step is preferably carried out to such an extent that the amount of aqueous acid solution remaining in the organic solvent can be reduced to less than 2%.

[0047] It is preferable to have a dehydration step before the washing step, in which the acid-treated product is dehydrated and removed from the acid aqueous solution. The dehydration step is a step of separating the acid-treated product from the acid aqueous solution by filtration, centrifugation, natural sedimentation, or the like, and in particular, a step of washing with pure water can also be included. When a step of washing with pure water is adopted, a step of removing the adhering pure water by drying can be included. Drying can be performed by heating or under reduced pressure.

[0048] The drying step is a step of drying the washed material to obtain a dried material. The drying method is not particularly limited, but it is preferable to separate and remove the organic solvent by filtration, centrifugation, or the like, and then evaporate the organic solvent by heating or reducing the pressure. The drying step is preferably carried out until the remaining amount of the organic solvent is less than about 2%.

[0049] The oxide film formation process involves heating the dried material in an oxidizing atmosphere at a temperature of 500°C or higher, at which the sphericity does not become less than 0.9. This dehydrates the oxide film, resulting in a strong bond between the core and the oxide film, with no gaps.

[0050] The oxidizing atmosphere may be oxygen gas, air, or other gas containing oxygen, or may be in the presence of a substance that releases oxygen when heated.

[0051] An example of a heating temperature at which the sphericity does not decrease to less than 0.9 is a temperature near the melting point of the metal material constituting the core particles. Heating the dried material to a temperature above the melting point of the metal material does not necessarily melt and deform the dried material, and temperatures above the melting point can also be used. For example, when aluminum is used as the metal material, there are conditions under which the sphericity of the dried material does not decrease even when heated to a temperature of about 800°C, which is higher than the melting point of aluminum.

[0052] The lower limit of the heating temperature can be 550°C, 600°C, 650°C, etc., and the upper limit can be a temperature that is about 100°C to 140°C higher than the melting point of the metal material. For example, when aluminum, which has a melting point of 660°C, is used as the metal material, the upper limit of the heating temperature can be about 760°C to 800°C.

[0053] The heating time is continued until an oxide film with a thickness of 20 nm or more is formed on the surface. For example, when forming an alumina oxide film from raw material particles composed of aluminum, an oxide film with the desired thickness can be formed by heating for about 1 to 480 minutes in an air atmosphere. The appropriate heating time varies depending on the heating temperature. A relatively long heating time is preferable when the heating temperature is low, and a relatively short heating time is preferable when the heating temperature is high. The upper limit of the heating time can be 300 minutes, 240 minutes, 180 minutes, 120 minutes, 60 minutes, 30 minutes, or 20 minutes, and the lower limit of the heating time can be 3 minutes, 4 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, or 30 minutes. The heating method is not particularly limited. For example, heating can be performed using a kiln such as a roller hearth kiln, a pusher kiln, or a rotary kiln.

[0054] An oxide film containing elements other than those constituting the raw particle material can be formed by attaching elements other than those constituting the raw particle material to the surface of the raw particle material before the oxide film forming step. For example, the raw particle material can be immersed in a solution containing metal elements other than those constituting the raw particle material and then dried, or by sputtering or vapor deposition to include different types of elements on the surface.

[0055] After the oxide film formation step, a surface treatment layer can be formed on the surface. The surface treatment is carried out by contacting a surface treatment agent with the surface of the particulate material. The surface treatment agent can be contacted with the surface of the particulate material either directly or after dissolving in an appropriate solvent. When contacting directly, the surface treatment agent can be contacted in liquid or gaseous form. The reaction can be accelerated by heating at an appropriate temperature after or during contact. Examples of appropriate temperatures include 80°C, 100°C, 150°C, 200°C, and 250°C. [Example]

[0056] (Test 1: Sample preparation and specific surface area evaluation) A metal material made of metallic aluminum was heated to 750°C and melted. The molten material was then processed in a disk atomizer in an inert atmosphere (nitrogen atmosphere) to obtain raw particle material (granulation process). The obtained raw particle material had a sphericity of 0.99 and volume average particle sizes of 80 μm, 55 μm, 35 μm, and 10 μm. The volume average particle size was controlled by adjusting the rotation speed of the disk of the disk atomizer. Specifically, increasing the rotation speed of the disk reduced the volume average particle size.

[0057] The obtained raw particle material was immersed in a 0.03N hydrochloric acid solution (pH 1.5) to obtain an acid-treated product (acid treatment process). The immersion conditions were 25°C and 6 hours, with one cycle. The acid-treated material was dehydrated by centrifugation to obtain a dehydrated product, and then washed with an organic solvent (isopropyl alcohol) to remove any remaining acid. The washing process was completed when the amount of acid solution remaining in the organic solvent was less than 2%. Note that even without the dehydration process, samples without residual acid could be obtained by repeating the washing process. However, by performing the dehydration process, it was possible to reduce the amount of organic solvent used in the washing process.

[0058] The raw particle material and the washed material were heated in an air atmosphere at 600°C for 180 minutes to form an oxide film, producing the particle material of this example (oxide film formation process). The oxide film had a thickness of 80 to 100 nm. There was no change in the volume average particle size even after the oxide film formation process. Furthermore, the D90 / D10 was 1.6 to 3.0, and was below 3.0. Furthermore, the sphericity was 0.99, showing no change. Furthermore, it was confirmed by SEM that the particles had been dispersed into primary particles. The measurement results of the specific surface area for each are shown in Table 1.

[0059] [Table 1]

[0060] For all particle sizes, the specific surface area increased with acid treatment.

[0061] (Test 2: Evaluation of pore volume) Next, raw particle material with a volume average particle size of 55 μm was evaluated. The particle materials were prepared by performing an oxide film formation process on the samples that had undergone the acid treatment process 0, 1, or 6 times. The samples that had undergone the acid treatment process 1 or 6 times were subjected to a dehydration process and a washing process before the oxide film formation process. The results of the pore distribution analysis using the BJH method are shown in Figures 1 to 3.

[0062] As is clear from Figures 1 to 3, when comparing the measurement results of the pore volume distribution and pore surface area distribution of the raw particle material before acid treatment (Figure 1) and the acid-treated product after one acid treatment (Figure 2), the maximum pore volume peak in the raw particle material was present at over 100 nm, but after one acid treatment, the maximum pore volume peak appeared in the pore diameter range of 1.7 nm to 100 nm (3.5 nm). The height of the maximum pore volume peak was slightly less than 10 times higher than before acid treatment, suggesting that new pores were formed after the acid treatment process.

[0063] Furthermore, when the acid treatment was repeated six times, the maximum peak height of the pore volume and the pore diameter of the maximum peak did not change much (3.5 nm), but the pore volume at pore diameters larger than the maximum peak increased, and the overall pore volume also increased (Figure 3). This is thought to be because the pore diameters of the pores generated by the acid treatment process were roughly the same, and the formed pores merged with adjacent pores to form larger pores with larger diameters.

[0064] The change in the pore volume of pores with diameters of 1.7 nm to 300 nm before and after acid treatment was examined. The results are shown in Table 2.

[0065] [Table 2]

[0066] As is clear from Table 2, the pore volume increased with the acid treatment. It was found that the pore volume also increased with increasing number of acid treatments.

[0067] (Test 3: Examination of conditions for the acid treatment process) A raw particle material with a volume average particle size of 55 μm was subjected to an acid treatment process at pH 1.0, 1.4, and 2.5, followed by an oxide film formation process, and the resulting particle material was evaluated. Furthermore, for samples subjected to the acid treatment process at pH 2.5, a dehydration process was performed after the acid treatment process, but washing with an organic solvent (isopropyl alcohol) was not performed. The temperature and time for the acid treatment process were the same as those described above. The pore volume of the resulting particle material with pore diameters of 1.7 nm to 300 nm was measured, and the results are shown in Table 3. SEM photographs are shown in Figure 4.

[0068] [Table 3]

[0069] As is clear from Table 3 and Figure 4, the particle shape of the sample that was subjected to the acid treatment at pH 1.0 was significantly deformed. 3 The sample that underwent the acid treatment at pH 2.5 did not have many pores formed on the surface, but because the washing step was not performed, precipitates were formed and the pore volume was 28.446 mm 3 / g, which is very large.

[0070] In contrast, the sample that underwent the acid treatment at pH 1.4 had a pore volume of 0.320 mm 3 / g, and although the formation of pores was observed on the surface, it was very smooth.

[0071] (Test 4: Evaluation of thermal conductivity, volume resistivity and dielectric constant) The raw particle material with a volume average particle size of 55 μm was subjected to an acid treatment process at pH 1.5 (sample 1) and pH 2.5 (sample 2), and an oxide film was formed on each sample (sample 3) without the acid treatment process. The samples that had undergone the acid treatment process were subjected to a dehydration process and a washing process before the oxide film formation process to ensure that no acid remained.

[0072] Resin compositions were prepared for each sample by preparing and curing resin compositions with the formulations shown in Table 4 for samples that underwent an acid treatment process at pH 1.5 and 2.5, samples that did not undergo an acid treatment process, and a sample consisting of alumina (sample 4). The thermal conductivity of these resin compositions was measured. The volume average particle size of the samples used was 45 μm for alumina and 55 μm for the other samples. Thermal conductivity was measured by cutting disks 20 mm in diameter and 8 mm in thickness from the cured resin compositions and using the hot disk method.

[0073] Furthermore, the volume resistivity of the sample that underwent the acid treatment at pH 1.5, the sample that did not undergo the acid treatment, and the cured product of the resin composition using alumina, molded into a diameter of 20 mm and a height of 10 mm, was measured using a Hiresta-UP resistivity meter manufactured by Mitsubishi Chemical Analytical Co., Ltd. The results are also shown in Table 4.

[0074] In addition, the dielectric constant of a sample that had undergone the acid treatment at pH 1.5 and a cured product of a resin composition using alumina, molded into a diameter of 9 mm and a height of 30 mm, was measured using an Agilent Technologies HP8362B device by the cavity resonance perturbation method at a measurement frequency of 1 GHz and a measurement temperature of 23°C. The results are also shown in Table 4.

[0075] [Table 4]

[0076] As is clear from the table, sample 1 (pH 1.5) had higher thermal conductivity than samples 2 (pH 2.5) and 4 (alumina), and was comparable to sample 3 (no acid treatment process). Furthermore, sample 1 (pH 1.5) exhibited a high volume resistivity comparable to sample 4 (alumina only), while sample 3 exhibited a very low volume resistivity.

[0077] From the above results, it was found that the oxide film formed after the acid treatment process at pH 1.5 has properties that combine insulating properties comparable to alumina with thermal conductivity.

[0078] Furthermore, it was found that the resin composition using sample 1 had a higher dielectric constant than the resin composition using sample 4. This is thought to be because the core contains aluminum, which has high conductivity, so the filler acts as a type of conductor rather than a dielectric, and the insulating coating formed on the particle surface gives it insulating properties comparable to alumina.

[0079] (Test 5: Evaluation of electromagnetic wave shielding performance) A resin composition was obtained by mixing and curing 40% by volume of Samples 1 and 4 prepared in Test 4 and 60% by volume of silicone resin (KR-220LP). The amount of electromagnetic wave reflection, absorption, and the sum of these (electromagnetic wave shielding amount) of the obtained resin composition were measured using the coaxial waveguide method, and the results are shown in Figures 5 and 6.

[0080] 5 and 6, the resin composition using Sample 1 reflected and absorbed a large amount of electromagnetic waves, demonstrating excellent electromagnetic wave shielding performance. In contrast, the resin composition using Sample 4, which is made of alumina, exhibited only poor electromagnetic wave shielding performance.

[0081] Other exams The same tests as above were conducted using metallic copper and metallic silicon instead of metallic aluminum, and it was confirmed that a particulate material dispersed into primary particles exhibiting the same insulating properties as when metallic aluminum was used could be obtained.

Claims

1. a core portion made of a metal material containing 50% by mass or more of aluminum; an insulating coating formed of a metal oxide having a thickness of 20 nm or more that covers the core portion without any gaps; and the metal oxide is an oxide of a metal element contained in the metal material constituting the core portion, BET specific surface area: 0.1 to 10 m ２ / g, In the pore distribution analysis by the BJH method, the maximum value of the pore volume peak exists between pore diameters of 1.7 nm and 100 nm, and the pore volume of pore diameters of 1.7 nm to 300 nm is 0.3 mm ３ / g to 8.0 mm ３ / g, A volume average particle size of 10 μm or more, Sphericity is 0.9 or more, Particulate material that is dispersed into primary particles.

2. the metal material is a simple metal composed of aluminum alone, The particulate material according to claim 1 , wherein the insulating coating is an oxide of the metallic material.

3. 3. The particulate material according to claim 1, wherein D10 is 25 μm or more and D90 is 65 μm or less.

4. 4. The particulate material according to claim 1, wherein D90 / D10 is 4.5 or less.

5. A method for producing a particulate material according to any one of claims 1 to 4, comprising the steps of: a granulation step in which a molten material containing 50% by mass or more of a metal element consisting of aluminum is granulated by an atomization method in an inert atmosphere to produce a raw material granular material having a sphericity of 0.9 or more; In the pore distribution analysis by the BJH method, the maximum value of the pore volume peak exists between pore diameters of 1.7 nm and 100 nm, and the pore volume of pore diameters of 1.7 nm to 300 nm is 0.3 mm ３ / g to 8.0 mm ３ an acid treatment step of immersing the raw particle material in an acid aqueous solution having a pH of 1.3 to 2.4 until the acid treatment reaches 1 / g; a washing step of washing the acid-treated product with an organic solvent to obtain a washed product; a drying step of drying the washed product to obtain a dried product; an oxide film forming step of heating the dried product in an oxidizing atmosphere at 500°C or higher, at a temperature at which deformation to a sphericity of less than 0.9 does not occur, to form an insulating film made of a metal oxide having a thickness of 20 nm or more on the surface; A method for producing a particulate material having the following structure:

6. The method for producing a particulate material according to claim 5 , further comprising a dehydration step of dehydrating the aqueous acid solution to form a dehydrated product after the acid treatment step and before the washing step.

7. The method for producing a particulate material according to claim 5 or 6, wherein the atomization method is a step of supplying the molten material onto the surface of a rotating metal disk.

8. A filler material comprising the particulate material according to any one of claims 1 to 4.

9. A filler material according to claim 8; a resin material in which the filler material is dispersed in particulate form; A heat transfer material having

10. 10. The heat transfer material of claim 9, wherein the filler material further comprises a particulate material comprised of alumina.

Images