Resin powder, sealing material, electronic component, and resin powder production method
阅读说明：本技术 树脂粉末、密封材料、电子部件以及树脂粉末制造方法 (Resin powder, sealing material, electronic component, and resin powder production method ) 是由 续贵德 高城顺一 马场大三 于 2019-03-18 设计创作，主要内容包括：这种树脂粉末包含树脂组合物的球形粒子的聚集体。这种树脂组合物含有：包含热固性树脂的树脂组分；和包含电绝缘性无机粒子和/或磁性粒子的非树脂组分。(This resin powder comprises an aggregate of spherical particles of the resin composition. This resin composition contains: a resin component comprising a thermosetting resin; and a non-resin component containing electrically insulating inorganic particles and/or magnetic particles.)
1. A resin powder comprising an aggregate of spherical particles of a resin composition,
the resin composition contains:
a resin component comprising a thermosetting resin; and
a non-resin component comprising at least one electrically insulating inorganic particle and/or at least one magnetic particle.
2. The resin powder as claimed in claim 1, wherein
Each of the spherical particles comprises
A core comprising said at least one electrically insulating inorganic particle, and
the resin component covering the core.
3. The resin powder as claimed in claim 1, wherein
Each of the spherical particles comprises
A core comprising said at least one magnetic particle, and
the resin component covering the core.
4. The resin powder as claimed in any one of claims 1 to 3, wherein
The resin powder has an average particle diameter of 10 μm or more and 200 μm or less in a volume particle size distribution.
5. The resin powder as claimed in any one of claims 1 to 4, wherein
In the volume particle size distribution, the ratio of spherical particles having a particle diameter of 50 μm or more and 100 μm or less to the resin powder is 70% by weight or more.
6. The resin powder as claimed in any one of claims 1 to 5, wherein
The volume particle size distribution has one frequency peak.
7. The resin powder as claimed in any one of claims 1 to 6, wherein
The aggregates have an average circularity greater than or equal to 0.90 and less than or equal to 1.00.
8. The resin powder as claimed in any one of claims 1 to 7, wherein
The resin component is in an uncured state.
9. The resin powder of any one of claims 1 to 8, wherein
The resin powder also contains a nanofiller.
10. The resin powder as claimed in claim 9, wherein
The content of the nanofiller is greater than or equal to 0.1% by weight and less than or equal to 2% by weight with respect to the resin powder.
11. The resin powder as claimed in claim 9 or 10, wherein
The average particle size of the nanofiller is greater than or equal to 1nm and less than or equal to 150 nm.
12. The resin powder of any one of claims 1 to 11, wherein
The resin powder has an angle of repose of 26 ° or less.
13. A sealing material comprising the resin powder according to any one of claims 1 to 12.
14. An electronic component comprising a molded body containing the resin powder according to any one of claims 1 to 12.
15. A resin powder manufacturing method comprising:
preparing a slurry containing:
a resin component comprising a thermosetting resin, and
a non-resin component comprising at least one electrically insulating inorganic particle and/or at least one magnetic particle; and
the slurry was granulated by spray drying.
16. A method for producing a resin powder, comprising
Adding nanofillers to the resin powder obtained by the process of claim 15.
Technical Field
The present disclosure relates generally to a resin powder, a sealing material, an electronic component, and a resin powder manufacturing method, and particularly to a resin powder used in an electronic component, a sealing material, an electronic component, and a resin powder manufacturing method.
Background
With higher functionality and further miniaturization of digital home appliances and the like, a compression molding method has been used as a resin sealing technique for semiconductor elements. In the compression molding method, a sealing material is directly inserted into a cavity formed in a mold, and pressure is applied so that the molten resin composition is slowly pressed against the semiconductor element, thereby performing molding.
Since the pelletized resin composition described in
As one of the conditions for obtaining satisfactory characteristics of the powder magnetic core at high frequencies,
However, when the particles of the magnetic powder are atomized to reduce the turbine among the particles of the metal magnetic powder, scattering of fine particles may cause equipment contamination, measurement trouble, and the like, and thus the metal magnetic powder must be carefully handled.
Reference list
Patent document
Patent document 1: JP 2015-116768A
Patent document 2: JP H09-102409A
Summary of The Invention
An object of the present disclosure is to provide a resin powder, a sealing material, an electronic component, and a resin powder manufacturing method that are easy to handle.
A resin powder according to one aspect of the present disclosure includes an aggregate of spherical particles of a resin composition. The resin composition contains: a resin component comprising a thermosetting resin; and a non-resin component comprising at least one electrically insulating inorganic particle and/or at least one magnetic particle.
A sealing material according to one aspect of the present disclosure includes the resin powder.
An electronic component according to an aspect of the present disclosure includes a molded body including the resin powder.
A method of manufacturing a resin powder according to one aspect of the present disclosure includes preparing a slurry, and granulating the slurry by a spray drying method. The slurry contains: a resin component comprising a thermosetting resin; and a non-resin component comprising at least one electrically insulating inorganic particle and/or at least one magnetic particle.
Brief Description of Drawings
FIG. 1 is a Scanning Electron Microscope (SEM) image (magnification: 100 times) of the resin powder obtained in example 1-1;
FIG. 2A is a graph showing the number particle size distribution of the resin powder obtained in example 1-1, and FIG. 2B is a graph showing the volume particle size distribution of the resin powder obtained in example 1-1;
FIG. 3A is a graph of the aspect ratio of the resin powder obtained in example 1-1, and FIG. 3B is a graph of the circularity of the resin powder obtained in example 1-1;
FIG. 4A is an image of a sample of example 1-1, and FIG. 4B is an image of a sample of comparative example 1-1; and
fig. 5A is an image of the sample in the tube in example 1-1 and the sample in the tube in comparative example 1-2 after tapping the bottom surface of the respective tubes three times, and fig. 5B is an enlarged image of the sample in the tube in example 1-1 and the sample in the tube in comparative example 1-2 of fig. 5A, in which the sample on the left side is the sample in example 1-1 and the sample on the right side is the sample in comparative example 1-2 in fig. 5A and 5B.
Description of the embodiments
Embodiments will be described below based on the drawings. Note that the embodiments described below are merely examples of various embodiments of the present disclosure. Various changes may be made in the following embodiments depending on the design and the like as long as the object of the present disclosure is achieved.
< first embodiment >
(1) Resin powder
The resin powder of the present embodiment (hereinafter referred to as resin powder) comprises an aggregate of spherical particles of the resin composition. The resin composition contains a resin component and a non-resin component (in the present embodiment, electrically insulating inorganic particles).
As used herein, "spherical" means that the average circularity of the resin powder is greater than or equal to 0.90, and the average aspect ratio of the resin powder is greater than or equal to 0.80. The average circularity is an average value of circularities of spherical particles, and can be obtained in a similar manner to the method described in the examples. Circularity is synonymous with "Circularity" as defined in ISO 9276-6. The average aspect ratio is an average of aspect ratios of spherical particles, and can be obtained in a manner similar to the method described in examples. Aspect Ratio is synonymous with "Aspect Ratio" as defined in ISO 9276-6.
In contrast, the granular resin composition described in
Further, the expression that the resin composition contains the aggregate of spherical particles includes not only the case where the resin powder is composed of spherical particles of the resin composition but also the case where the resin powder contains non-spherical particles of the resin composition within a range in which the effect of the present disclosure is not impaired.
The resin powder has the above-described constitution, and therefore, when the resin powder is processed, friction of spherical particles is less likely to be caused, and fine particles are less likely to be generated. Therefore, when the resin powder is used as a semiconductor sealing material in a compression molding method, it is less likely to cause contamination of equipment, trouble in measurement, and the like due to scattering of fine particles. Further, the resin powder is not an aggregate of conventional fragment particles but an aggregate of spherical particles, and thus is not bulky. Therefore, when the resin powder is used as a semiconductor sealing material in a compression molding method, it is easy to uniformly put the resin powder into a cavity formed in a mold, whereby the occurrence of a poor appearance of a sealing resin obtained by melting and then curing the resin powder can be reduced as compared with the case of using an aggregate of conventional chip particles.
In the volume particle size distribution of the resin powder, the upper limit of the average particle diameter (hereinafter referred to as volume average particle diameter) is preferably 200 μm, more preferably 100 μm. The lower limit of the volume average particle diameter of the resin powder is preferably 1 μm, more preferably 10 μm. When the volume average particle diameter of the resin powder is within the above range, for example, the resin powder can be suitably used as a semiconductor sealing material. The volume average particle diameter of the resin powder can be obtained in a similar manner to the method described in the examples.
In the volume particle size distribution, the ratio of spherical particles of the resin composition having a particle diameter (hereinafter referred to as volume particle diameter) of 50 μm or more and 100 μm or less to the whole spherical particles of the resin composition is preferably 100% by weight. The lower limit of the ratio of spherical particles of the resin composition having a volume particle diameter of 50 μm or more and 100 μm or less to the whole spherical particles of the resin composition is more preferably 70% by weight, still more preferably 80% by weight, and particularly preferably 90% by weight. When the ratio of spherical particles of the resin composition having a volume particle diameter of 50 μm or more and 100 μm or less is within the above range, the volume particle size distribution of the resin powder can be evaluated as narrow (sharp), and when the resin powder is used as a semiconductor sealing material in a compression molding method, it is easier to put the resin powder at a target position in a cavity formed in a mold.
In contrast, the granular resin composition described in
The ratio of spherical particles of the resin composition having a particle diameter of 50 μm or more and 100 μm or less can be obtained in a similar manner to the method described in examples. Examples of the method for adjusting the ratio of spherical particles of the resin composition having a volume particle diameter of 50 μm or more and 100 μm or less to be within the above-mentioned range include a method for granulating a slurry by a spray drying method as described later and a method for classifying a resin powder by sieving the resin powder.
The resin powder preferably has a frequency peak in the volume particle size distribution. Therefore, it is easier to put the resin powder into a target position in the cavity formed in the mold. Further, when the resin powder is exposed to a temperature at which the resin powder is melted, it is easy to uniformly melt the resin powder, so that the sealing material thus obtained is unlikely to have a poor appearance. The presence of frequency peaks can be confirmed in a similar manner to the method described in the examples.
Examples of the method of adjusting the resin powder to have one frequency peak include a method for granulating the slurry by a spray drying method as described later and a method for classifying the resin powder by sieving the resin powder.
In the number particle size distribution, the resin powder preferably has at least one frequency peak in each of a range in which the particle diameter is greater than or equal to 1 μm and less than or equal to 10 μm and a range in which the particle diameter is greater than 10 μm and less than or equal to 100 μm. Therefore, spherical particles having a small particle diameter enter respective gaps formed between spherical particles having a large particle diameter, thereby reducing bulkiness (bulkiness) of the resin powder, and it becomes easy to more uniformly put the resin powder into a cavity formed in a mold. The presence of frequency peaks can be confirmed in a similar manner to the method described in the examples.
Examples of a method of adjusting the resin powder to have at least one frequency peak in each of a range in which the particle diameter is greater than or equal to 1 μm and less than or equal to 10 μm and a range in which the particle diameter is greater than 10 μm and less than or equal to 100 μm in the number particle size distribution include: a method for granulating the slurry by a spray drying method as described later and a method for classifying the resin powder by sieving the resin powder.
The upper limit of the average circularity of the resin powder is preferably 1.00. The lower limit of the average circularity of the resin powder is preferably 0.90, more preferably 0.95, and still more preferably 0.98. When the average circularity of the resin powder is within the above range, it is easier to uniformly put the resin powder into the cavity formed in the mold when the resin powder is used as a semiconductor sealing material in a compression molding method.
Examples of the method for adjusting the average circularity of the resin powder to be within the above range include the following methods: wherein when the slurry is granulated by a spray drying method as described later, a rotary atomizer method is employed, and the rotation speed of a disc of the rotary atomizer is adjusted.
The upper limit of the average aspect ratio of the resin powder is preferably 1.00. The lower limit of the average aspect ratio of the resin powder is preferably 0.80, more preferably 0.85, and still more preferably 0.90. When the average aspect ratio of the resin powder is within the above range, it is easier to uniformly put the resin powder into the cavity formed in the mold when the resin powder is used as a semiconductor sealing material in a compression molding method.
Examples of the method for adjusting the average aspect ratio of the resin powder to be within the above-mentioned range include the following methods: wherein when the slurry is granulated by a spray drying method as described later, a rotary atomizer method is employed, and the rotation speed of a disc of the rotary atomizer is adjusted.
Each spherical particle preferably comprises: a core comprising at least one or more electrically insulating inorganic particles; and a resin component covering the entire core. This reduces fine particles generated due to friction of the spherical particles when the resin powder is processed, as compared with the case of including spherical particles having an uncovered surface of the electrically insulating inorganic particles. Further, when the resin powder is thermally melted during molding, the resin components of adjacent spherical particles form a skin layer, thereby improving wettability and obtaining an easily flowable spherical particle.
Whether each spherical particle includes a core and a resin component covering the entire core can be confirmed in a manner similar to the method described in the examples. Each spherical particle may be adjusted to include a core and a resin component covering the entire core, for example, by changing the viscosity of the slurry as described later. Examples of a method for adjusting each spherical particle to include a core and a resin component covering the entire core include a granulation method by a spray drying method.
The resin component is preferably in an uncured state. That is, the resin component is preferably evaluated to be in a state corresponding to the a stage. Therefore, when the resin powder is used as a semiconductor sealing material in a compression molding method, the occurrence of a poor appearance of the resulting sealing agent can be reduced.
In contrast, when the granular resin composition described in
Here, the a stage, the B stage and the C stage are respectively equivalent to Japanese Industrial Standard (JIS) K6900: 1994 is synonymous with stage A (A-stage), stage B (B-stage) and stage C (C-stage). That is, the a-stage refers to an initial stage during the preparation of a certain thermosetting resin. In the initial stage, the material for the thermosetting resin is still soluble and meltable in a certain liquid. The B stage refers to an intermediate stage during the reaction of a certain thermosetting resin. In an intermediate stage, the material swells when contacted with a certain liquid, and the material softens when heated, but the material does not completely dissolve or melt. The C stage refers to the final stage during the reaction of a certain thermosetting resin. In the final stage, the material used for the thermosetting resin is practically insoluble and infusible. The resin component may be brought into an uncured state, for example, by changing the concentration of the slurry as described later. Examples of the method for bringing the resin component into an uncured state include a granulation method by a spray drying method.
The upper limit of the metal content of the resin powder is preferably 1ppm, more preferably 0.5ppm, with respect to the resin powder. When the upper limit of the metal content of the resin powder is within the above range, corrosion of the wire rod and the like is suppressed and the reliability of the resulting sealing material is improved when the resin powder is used as a semiconductor sealing material in a compression molding method. In contrast, the granular resin composition described in
The upper limit of the amount of acetone-insoluble matter in the resin powder is preferably 1ppm, more preferably 0.5ppm, relative to the resin powder. When the acetone-insoluble component of the resin powder is within the above range, the resin powder contains almost no component similar to the cured material. When the resin powder is used as a semiconductor sealing material in a compression molding method, filling defects are less likely to occur at the time of melting and molding the resin powder, and the occurrence of a poor appearance of the resulting sealing material can be reduced. The acetone insoluble component can be obtained in a manner similar to the method described in the examples. Examples of the method for adjusting the acetone-insoluble component to be within the above-mentioned range include granulating the slurry by a spray drying method as described later.
The upper limit of the amount of the residual solvent of the resin powder is preferably 1% by weight, more preferably 0.5% by weight, relative to the resin powder. When the residual solvent amount of the resin powder is within the above range, when the resin powder is used as a semiconductor sealing material in a compression molding method, occurrence of voids and the like in the resulting sealing material is suppressed, and the reliability of the resulting sealing material is improved. The residual solvent amount of the resin powder can be obtained in a similar manner to the method described in the examples. Examples of the method for adjusting the residual solvent amount of the resin powder to be within the above-mentioned range include granulating the slurry by a spray drying method as described later.
(1.1) resin composition
The resin composition contains a non-resin component and a resin component.
(1.1.1) non-resin component
The electrically insulating inorganic particles are electrically insulating, "electrically insulating" means that the volume specific resistivity of the material used for the electrically insulating inorganic particles is greater than or equal to 1 × 109Omega/cm. Examples of materials for such electrically insulating inorganic particles include metal oxides, metal nitrides, metal carbonates, and metal hydroxides. Examples of the metal oxide include aluminum oxide, fused silica, crystalline silica, magnesium oxide, calcium oxide, titanium oxide, beryllium oxide, copper oxide, cuprous oxide, and zinc oxide. Examples of the metal nitride include boron nitride, aluminum nitride, and silicon nitride. Examples of the metal carbonate include magnesium carbonate and calcium carbonate. Examples of the metal hydroxide include aluminum hydroxide and magnesium hydroxide. The electrically insulating inorganic particles in the resin powder may include one material, or may include two or more materials.
The shape of the electrically insulating inorganic particles can be selected accordingly depending on the application of the resin powder and the like. Examples of shapes include spherical, flat, elliptical, tubular, linear, needle, plate, peanut, or indeterminate shapes. The molten material of the resin composition obtained by melting the resin powder is preferably spherical because of its excellent fluidity and the like. The electrically insulating inorganic particles in the resin powder may include one shape, or may include two or more shapes.
The size of the electrically insulating inorganic particles in the resin powder is smaller than at least the size of the spherical particles of the resin powder. The content of the electrically insulating inorganic particles in the spherical particles of the resin composition is not particularly limited. The upper limit of the content of the electrically insulating inorganic particles with respect to the spherical particles of the resin composition is preferably 90 vol%, and more preferably 85 vol%. The lower limit of the content of the electrically insulating inorganic particles with respect to the spherical particles of the resin composition is preferably 40% by volume, and more preferably 50% by volume.
(1.1.2) resin component
The resin component includes a thermosetting resin. Thermosetting resins are reactive compounds that can cause a crosslinking reaction due to heating. Examples of the thermosetting resin include epoxy resins, imide resins, phenol resins, cyanate resins, melamine resins, and acrylic resins. Examples of the epoxy resin include bisphenol a epoxy resin, bisphenol F epoxy resin, polyfunctional epoxy resin, biphenyl epoxy resin, cresol novolac epoxy resin, and phenol novolac epoxy resin. The polyfunctional epoxy resin is a resin having three or more epoxy groups per molecule. Examples of the imide resin include bisallylnadimide resin (bisallylnadimide resin). The resin component may contain one kind of thermosetting resin, or may contain two or more kinds of thermosetting resins. The content of the resin component is not particularly limited. The upper limit of the resin component is preferably 60% by volume, more preferably 50% by volume, relative to the spherical particles of the resin composition. The lower limit of the resin component is preferably 10% by volume, more preferably 15% by volume, relative to the spherical particles of the resin composition.
The resin component may further contain a curing agent depending on the kind of the thermosetting resin and the like. The curing agent is an additive that cures the thermosetting resin. Examples of the curing agent include dicyandiamide (dicyandiamide), phenol-based curing agents, cyclopentadiene, amine-based curing agents, and acid anhydrides. The phenol-based curing agent has two or more phenolic hydroxyl groups per molecule. Examples of the phenol-based curing agent include phenol novolac resins, phenol aralkyl resins, naphthalene-type phenol resins, and bisphenol resins. Examples of the bisphenol resin include bisphenol a resin and bisphenol F resin.
The resin component may further contain a curing accelerator depending on the kind of the thermosetting resin and the like. Examples of the curing accelerator include tertiary amines, tertiary amine salts, imidazoles, phosphines, and phosphonium salts. As imidazole, 2-ethyl-4-methylimidazole and the like can be used.
The resin component may further contain a coupling agent depending on the kind of the thermosetting resin and the like. Therefore, when the slurry is granulated by a spray drying method as described later, the uniformity of the resin component and the electrically insulating inorganic particles is improved to obtain a more uniform slurry. Examples of the silane coupling agent include epoxy silane, amino silane, aluminum titanate chelate (titanate aluminate), and zirconium aluminate (zirconia).
The resin component may further contain a dispersant depending on the kind of the thermosetting resin and the like. Therefore, when the slurry is granulated by a spray drying method as described later, the viscosity of the slurry is reduced, and the uniformity of the resin component and the electrically insulating inorganic particles is improved to obtain a more uniform slurry. Examples of the dispersant include higher fatty acid phosphate esters, amine bases of higher fatty acid phosphate esters, and alkylene oxides of higher fatty acid phosphate esters. Examples of the higher fatty acid phosphate ester include octyl phosphate, decyl phosphate, and lauryl phosphate.
The resin component may further contain a thermoplastic resin, an elastomer, a flame retardant, a colorant, a thixotropy-imparting agent, an ion trapping agent, a colorant, a thixotropy-imparting agent, a surfactant, a leveling agent, an antifoaming agent, and a reactive diluent, depending on the application of the resin powder and the like. Examples of the thermoplastic resin include phenoxy resins. Examples of elastomers include thermoset elastomers and thermoplastic elastomers. Examples of flame retardants include brominated epoxy resins and antimony oxide.
(1.2) use of resin powder
The resin powder is preferably used as a raw material for semiconductor sealing materials and insulating materials for printed circuit boards. When the resin powder is used for a semiconductor sealing material, the resin sealing technique of the semiconductor element is not particularly limited. Examples of the resin sealing technique include a transfer molding method, a compression molding method, and an underfill technique. Among them, the compression molding method is preferably used, for example, because fine particles are less likely to be generated when the resin powder is handled, and the resin powder is easily uniformly put into a cavity formed in a mold. Further, a molten substance of the resin composition obtained by melting the resin powder is preferably used for the underfill technique and/or the insulating material for a printed circuit board, for example, because the molten substance has excellent fluidity, filling efficiency, and embeddability of a circuit of a printed wiring.
(2) Semiconductor sealing material
The semiconductor sealing material (hereinafter referred to as semiconductor sealing material) of the present embodiment includes the above-described resin powder. The form of the semiconductor sealing material may be selected accordingly depending on the application of the semiconductor sealing material and the like, and may be, for example, a solid form, a liquid form, a paste form or a film form. Examples of solid forms include powder forms and tablet forms. The paste form means that the semiconductor sealing material has fluidity at room temperature even when the semiconductor sealing material does not contain a solvent. The material for the semiconductor sealing material may be only a resin powder, or may contain a solvent, an ultraviolet curable resin, a thermosetting resin, a thermoplastic resin, or the like in addition to the resin powder, depending on the use form of the semiconductor sealing material, or the like. These resins other than the resin powder may be in a liquid form or a solid form such as powder at ordinary temperature.
(3) Method for producing resin powder
The method of manufacturing the resin powder according to the present embodiment includes preparing a slurry, and granulating the slurry by a spray drying method. The slurry contains a resin component and electrically insulating inorganic particles. Thereby, the resin powder was obtained. Further, the spray drying method enables the preparation of a resin powder from the constituent components of the resin component which are not melt-kneaded and cannot be molded into a powder or a sheet even in the case of kneading at 100 ℃ with a conventional kneader.
(3.1) preparation of slurry
Examples of the method for preparing the slurry include a method in which a powder including the above-described electrically insulating inorganic particles (hereinafter referred to as an inorganic powder), the above-described resin component, and an optional solvent are added and stirred to be mixed uniformly.
The average particle diameter of the inorganic powder is selected accordingly depending on the application of the resin powder and the like. The upper limit of the average particle diameter of the inorganic powder is preferably 75 μm, and more preferably 50 μm. The lower limit of the average particle diameter of the inorganic powder is preferably 1 μm, more preferably 5 μm. The average particle diameter of the inorganic powder means a particle diameter at an integrated value of 50% in a particle size distribution measured based on a particle size distribution measuring apparatus based on a laser light scattering/diffraction method.
The addition ratio of the inorganic powder is selected accordingly depending on the application of the resin powder and the like. The upper limit of the blending ratio of the inorganic powder is preferably 95 parts by mass, more preferably 85 parts by mass, with respect to 100 parts by mass of the solid content of the slurry. The lower limit of the addition ratio of the inorganic powder is preferably 40 parts by mass, and more preferably 50 parts by mass, relative to 100 parts by mass of the solid content of the slurry. When the blending ratio of the inorganic powder is within the above range, the resin powder can be suitably used as a semiconductor sealing material. The solid content in the slurry is the content of the electrically insulating inorganic particles and the resin component excluding the solvent.
The constituent components constituting the resin component such as thermosetting resin and the like may be in a liquid form or a solid form such as powder at ordinary temperature as long as they can be prepared into a slurry. That is, the constituent components of the resin component are not particularly limited, and may be a resin that cannot be melt-kneaded at the time of kneading with a kneader at 100 ℃, such as a conventional resin, as long as the resin can be prepared as a slurry.
Examples of the constituent components which cannot be melt-kneaded at the time of kneading the constituent components at 100 ℃ include resins having a melting point of 140 ℃ or higher, and the like. Examples of the resin having a melting point of 140 ℃ or higher include imide resins, 4' -bismaleimide diphenylmethane and the like from which a cured material having excellent heat resistance is obtained.
The upper limit of the content of the thermosetting resin is preferably 65 parts by mass, more preferably 55 parts by mass, relative to 100 parts by mass of the solid content of the slurry. The lower limit of the content of the thermosetting resin is preferably 10 parts by mass, more preferably 15 parts by mass, with respect to 100 parts by mass of the solid content of the slurry.
The upper limit of the content of the curing agent is preferably 50 parts by mass with respect to the solid content of the slurry. The content of the curing accelerator is adjusted accordingly depending on the kinds of the thermosetting resin and the curing agent. The upper limit of the content of the coupling agent is preferably 1 part by mass with respect to 100 parts by mass of the solid content of the slurry.
As the solvent, Methyl Ethyl Ketone (MEK), N-Dimethylformamide (DMF), acetone, methyl isobutyl ketone (MIBK), or the like can be used. Only one solvent may be used, or two or more solvents may be used in combination. When two or more solvents are combined with each other, the mixing ratio (mass ratio and volume ratio) is not particularly limited. The content of the solvent is not particularly limited. The upper limit of the content ratio of the solid matter (solid content) in the slurry is preferably 99% by weight, more preferably 98% by weight, with respect to the slurry. The lower limit of the content ratio of the solid matter in the slurry is preferably 50% by weight, more preferably 60% by weight, with respect to the slurry.
(3.2) granulation by spray drying
Examples of the method for granulating the slurry by the spray drying method include a method of collecting powder obtained by putting the slurry into a spray dryer. The spray dryer atomizes the slurry by spraying the slurry in the dryer, and continuously contacts the slurry with hot air while increasing a surface area per unit volume, thereby performing instantaneous drying and granulation. That is, the slurry is formed into a plurality of droplets each having a certain size, the droplets are rapidly dried, and the droplets are formed into a spherical shape by surface tension, thereby obtaining spherical powders having substantially the same particle diameter. Therefore, it is unlikely that a very fine and easily scattered powder is generated. In contrast, when the viscosity of the slurry is appropriate, the slurry can be formed into not too large droplets. Therefore, a resin powder having a substantially uniform particle diameter is obtained, and therefore, the problems associated with the pulverized powder are unlikely to be caused. As described above, when the spray dryer is used, spherical particles including resin powder having a narrow frequency (sharp frequency) in volume particle size distribution are obtained, and thus, unlike the conventional case, the granular resin composition is not sieved again for classification. Therefore, for example, the resin powder collected from the spray dryer can be used as a semiconductor sealing material as it is, and a classification step performed at the time of producing a semiconductor sealing material can be omitted, which significantly reduces the time as compared with the conventional case. Further, unlike the conventional case, it is no longer necessary to melt-knead the inorganic powder and the resin component with a kneader to obtain a product and cut the product with a pulverization-type pelletizer, and therefore, the obtained resin powder does not contain metallic foreign substances. Further, the resin component of the obtained resin powder is in instantaneous contact with hot air only, and therefore, the resin component has almost no heat history, and can be evaluated as being in a state corresponding to the a stage.
The spraying method of the slurry is not particularly limited, and examples of the spraying method include a rotary atomizer method and a nozzle method. In the rotary atomizer method, a solution of the slurry is continuously fed to a disk rotating at high speed, and is sprayed by using centrifugal force. When the rotary atomizer method is used, a resin powder having a particle diameter of 20 μm or more and 200 μm or less and a narrow frequency in the volume particle size distribution is easily obtained. The upper limit of the rotational speed of the disc is preferably 25000rpm, more preferably 20000 rpm. The lower limit of the rotational speed of the disc is preferably 5000rpm, more preferably 10000 rpm. As the rotation speed of the disk increases, the volume average particle diameter of the resulting resin powder decreases. As the rotation speed of the disk is decreased, the volume average particle diameter of the obtained resin powder is increased, and thus, truly round particles are obtained. That is, as the rotational speed of the disk decreases, resin powders each having an average circularity and an average aspect ratio close to 1.0 are easily obtained. Examples of the nozzle method include a two-fluid nozzle method and a one-fluid nozzle method. When the two-fluid nozzle method is used, resin powder having a particle diameter of 20 μm or less in volume particle size distribution is easily obtained, and adjusting the slurry feed rate enables adjustment of the volume average particle diameter of the obtained resin powder. The upper limit of the slurry feed rate is preferably 2.0 kg/hour. The lower limit of the slurry feed rate is preferably 0.5 kg/hour. Increasing the slurry feed rate increases the volume average particle size of the resulting resin powder.
The thermal drying conditions of the spray dryer are not particularly limited, and for example, drying is performed at normal pressure. The upper limit of the temperature of the supplied hot air (inlet temperature) is preferably 200 deg.c, more preferably 150 deg.c. The lower limit of the inlet temperature is preferably 60 c, more preferably 80 c. The upper limit of the temperature at the outlet of the dryer (outlet temperature) is preferably 170 c, more preferably 120 c. The lower limit of the outlet temperature is preferably 30 c, more preferably 50 c.
The collecting method of the resin powder is not particularly limited, and may be selected accordingly depending on the application of the resin powder and the like. Examples of the collection method include a two-point collection method, a cyclone collection method, and a bag filter collection method. The two-point collection method performs collection at two points, i.e., below the drying chamber and below the cyclone connected to the dryer, and has a classification effect. Spherical resin powder was obtained below the dryer, and resin powder including fine particles was obtained below the cyclone. Cyclone collection methods the collection is performed entirely by a cyclone connected to the drying chamber. The bag filter collection method is a method in which the whole is collected by a bag filter connected to a drying chamber, and is suitable for collecting fine particles that cannot be obtained by the cyclone method.
< second embodiment >
(1) Resin powder
The resin powder of the present embodiment (hereinafter referred to as resin powder) comprises an aggregate of spherical particles of the resin composition. The resin composition contains a resin component and a non-resin component (magnetic particles in the present embodiment). Detailed descriptions of components similar to those in the first embodiment are omitted below.
The resin powder has the above-described constitution, and therefore, is easy to handle. That is, when the resin powder is processed, friction of spherical particles is less likely to be caused, and generation of fine particles is further suppressed. Therefore, contamination of equipment, trouble of measurement, and the like due to scattering of fine particles are less likely to be caused. Further, the resin powder is not an aggregate of conventional fragment particles but an aggregate of spherical particles, and thus is not bulky. Therefore, the resin powder has excellent packing efficiency.
In the volume particle size distribution of the resin powder, the upper limit of the average particle diameter (hereinafter referred to as volume average particle diameter) is preferably 200 μm, more preferably 100 μm. The lower limit of the volume average particle diameter of the resin powder is preferably 1 μm, more preferably 10 μm. When the volume average particle diameter of the resin powder is within the above range, the property that eddy currents in the magnetic particles can be reduced and moldability are balanced. That is, the resin powder is easily filled at a high density, and the viscosity of the thermally fused resin powder is also less likely to increase as compared with a resin powder having a volume average particle diameter (particle) outside the above range. Therefore, the moldability is less likely to be lowered, and when the resin powder is used as a raw material of the powder magnetic core, the eddy current loss of the powder magnetic core can be suppressed. The volume average particle diameter of the resin powder can be obtained in a similar manner to the method described in the examples.
In the volume particle size distribution, the ratio of spherical particles of the resin composition having a particle diameter (hereinafter referred to as volume particle diameter) of 50 μm or more and 100 μm or less to the whole spherical particles of the resin composition is preferably 100% by weight. The lower limit of the ratio of spherical particles of the resin composition having a volume particle diameter of 50 μm or more and 100 μm or less to the whole spherical particles of the resin composition is preferably 70% by weight, and more preferably 80% by weight. When the ratio of spherical particles of the resin composition having a volume particle diameter of 50 μm or more and 100 μm or less is within the above range, the volume particle size distribution of the resin powder can be evaluated to be narrow, and the resin powder is less likely to scatter.
The resin powder preferably has a frequency peak in the volume particle size distribution. Therefore, the resin powder is less likely to scatter.
In the number particle size distribution, the resin powder preferably has at least one frequency peak in each of a range in which the particle diameter is greater than or equal to 1 μm and less than or equal to 10 μm and a range in which the particle diameter is greater than 10 μm and less than or equal to 100 μm. Therefore, the spherical particles having a small particle diameter enter the gaps each formed between the spherical particles having a large particle diameter, the bulkiness of the resin powder is further reduced, and the resin powder has more excellent packing efficiency.
The upper limit of the average circularity of the resin powder is preferably 1.00. The lower limit of the average circularity of the resin powder is preferably 0.90, more preferably 0.95, and still more preferably 0.98. When the average circularity of the resin powder is within the above range, friction of spherical particles is less likely to be caused when the resin powder is processed, and generation of fine particles is further suppressed, and the resin powder is easier to process.
The average circularity of the resin powder can be adjusted to be within the above range, for example, by changing the viscosity of the slurry as described later. Examples of the method for adjusting the average circularity of the resin powder to be within the above range include the following methods: wherein, when the granulation is carried out by the spray drying method, a rotary atomizer method is adopted, and the rotating speed of a disc of the rotary atomizer is adjusted.
The upper limit of the average aspect ratio of the resin powder is preferably 1.00. The lower limit of the average aspect ratio of the resin powder is preferably 0.80, more preferably 0.85, and still more preferably 0.90. When the average aspect ratio of the resin powder is within the above range, friction of spherical particles is less likely to be caused when the resin powder is processed, and generation of fine particles is further suppressed, and the resin powder is more easily processed.
The average aspect ratio of the resin powder can be adjusted to be within the above range, for example, by changing the viscosity of the slurry as described later. Examples of the method for adjusting the average aspect ratio of the resin powder to be within the above-mentioned range include the following methods: wherein when granulation is performed by a spray drying method, a rotary atomizer method is employed, and the rotation speed of a disc of the rotary atomizer is adjusted.
Each spherical particle preferably comprises: a core comprising at least one or more magnetic particles, and a resin component covering the entire core. This reduces friction of the spherical particles at the time of processing the resin powder, as is less likely to be caused, and further suppresses generation of fine particles, as compared with the case of including spherical particles having surfaces in an uncovered state of magnetic particles. Further, when the resin powder is thermally melted during molding, the resin components of adjacent spherical particles form a skin layer, thereby improving wettability and obtaining an easily flowable spherical particle.
Whether each spherical particle includes a core and a resin component covering the entire core can be confirmed in a manner similar to the method described in the examples. Each spherical particle may be adjusted to include a core and a resin component covering the entire core, for example, by changing the viscosity of the slurry as described later. Examples of a method for adjusting each spherical particle to include a core and a resin component covering the entire core include a granulation method by a spray drying method.
The resin component is preferably in an uncured state. That is, the resin component is preferably evaluated to be in a state corresponding to the a stage. Therefore, the resin component thus obtained does not contain particles in a state corresponding to the C stage (hereinafter referred to as cured particles), and therefore, for example, the occurrence of a poor appearance of a cured material obtained by thermally melting and curing a resin powder can be reduced. The solidified particles do not melt even when exposed to heat, and therefore, the resulting solidified material may have a poor appearance.
The upper limit of the acetone-insoluble content of the resin powder is preferably 2ppm, more preferably 1ppm, relative to the resin powder. When the acetone-insoluble component of the resin powder is within the above range, the resin powder contains almost no component similar to the cured material, and filling defects are less likely to occur when the resin powder is melted and molded, and the occurrence of a poor appearance of the resulting cured material can be reduced. The acetone insoluble component can be obtained in a manner similar to the method described in the examples. Examples of the method for adjusting the acetone-insoluble component to be within the above-mentioned range include granulating the slurry by a spray drying method as described later.
The upper limit of the amount of the residual solvent of the resin powder is preferably 1% by weight, more preferably 0.5% by weight, relative to the resin powder. When the residual solvent amount of the resin powder is within the above range, the formation of voids in the cured material obtained by melting and then curing the resin powder is suppressed. The residual solvent amount of the resin powder can be obtained in a similar manner to the method described in the examples. Examples of the method for adjusting the residual solvent amount of the resin powder to be within the above-mentioned range include granulating the slurry by a spray drying method as described later.
(1.1) resin composition
The resin composition contains a non-resin component and a resin component.
(1.1.1) non-resin component
The non-resin component includes magnetic particles. The magnetic particles are particles including a substance (magnetic body) that can be magnetized by an external magnetic field.
Examples of materials for the magnetic particles include hard magnetic materials and softA magnetic material. Examples of hard magnetic materials include NdFeB, NdFe bonded magnets, and LaCoSr ferrite (La)xSr1-xFe12O19). Examples of the soft magnetic material include metallic-based soft magnetic materials, spinel-based ferrites, garnet-based ferrites, hexagonal crystal ferrites, iron oxides, chromium oxides, and cobalt. The metallic soft magnetic material is a non-oxide material containing iron as a main component. Examples of the metallic soft magnetic material include carbonyl iron, electromagnetic steel sheet, Permalloy (Permalloy), amorphous alloy, and nanocrystalline metallic magnetic material. Examples of the amorphous alloy include Fe-based amorphous alloys and Co-based amorphous alloys. The nanocrystalline metal magnetic material is a material obtained by nanocrystalline an Fe-based amorphous alloy by means of heat treatment. The spinel-based ferrite includes MFe2O3The composition of (1). M is a divalent metal, and may include Mn, Zn, and Fe (MnZn ferrite), or may mainly include Ni, Zn, and Cu (NiZn ferrite). Examples of the garnet-based ferrite include GdxY3-xFe5O12(Gd-substituted YIG). Examples of the hexagonal crystal-series ferrite include a magnetoplumbite (M) type ferrite and a ferrite planar (Ferroxplana) type ferrite. The M-type ferrite has Ba ferrite or Sr ferrite as an initial composition, a part of which is substituted by Ti, Ca, Cu, Co, or the like. Examples of ferrite planes include W-type (Ba)1M2Fe16O27) Y type (Ba)2M2Fe12O22) And Z type (Ba)3M2Fe24O41). In this formula, M is a divalent metal. The magnetic particles in the resin powder may include one material, or may include two or more materials.
The shape of the magnetic particles may be selected accordingly depending on the application of the resin powder, etc. Examples of shapes include spherical, flat, elliptical, tubular, linear, needle, plate, peanut, or indeterminate shapes. The magnetic particles in the resin powder may include one shape, or may include two or more shapes.
The magnetic particles may be subjected to an insulating treatment according to the application of the resin powder or the like. That is, each magnetic particle may have a surface covered by an electrically insulating coating. This suppresses the generation of inter-particle eddy currents flowing between adjacent magnetic particles, and enables further reduction in eddy current loss. Examples of the method of the insulation treatment include a method in which a magnetic powder and an aqueous solution containing an electrically insulating filler are mixed with each other and dried. Examples of materials for the electrically insulating filler include phosphoric acid, boric acid, and magnesium oxide.
The size of the magnetic particles in the resin powder is at least smaller than the size of the spherical particles of the resin powder. The content of the magnetic particles in the spherical particles of the resin composition is not particularly limited. The upper limit of the content of the electrically insulating inorganic particles with respect to the spherical particles of the resin composition is preferably 90 vol%, and more preferably 85 vol%. The lower limit of the content of the electrically insulating inorganic particles with respect to the spherical particles of the resin composition is preferably 40% by volume, and more preferably 50% by volume.
(1.1.2) resin component
The resin component may further contain a coupling agent depending on the kind of the thermosetting resin and the like. Therefore, when the slurry is granulated by a spray drying method as described later, the uniformity of the resin component and the magnetic particles is improved to obtain a more uniform slurry. Examples of the silane coupling agent include epoxy silane, amino silane, aluminum titanate chelate, and zirconium aluminate.
The resin component may further contain a dispersant depending on the kind of the thermosetting resin and the like. Therefore, when the slurry is granulated by a spray drying method as described later, the viscosity of the slurry is reduced, and the uniformity of the resin component and the magnetic particles is improved to obtain a more uniform slurry. Examples of the dispersant include higher fatty acid phosphate esters, amine bases of higher fatty acid phosphate esters, and alkylene oxides of higher fatty acid phosphate esters. Examples of the higher fatty acid phosphate ester include octyl phosphate, decyl phosphate, and lauryl phosphate.
(1.2) use of resin powder
The resin powder is suitably used as a raw material for, for example: line filters, radio wave absorbers, transformers, magnetic shields, inductors (coils), temperature switches, actuators, static magnetic wave elements, toner for copiers, marking of explosives, semiconductor encapsulation materials, and insulating materials for printed circuit boards.
(2) Method for producing resin powder
The method of manufacturing the resin powder according to the present embodiment includes preparing a slurry, and granulating the slurry by a spray drying method. The slurry contains a resin component and magnetic particles. As described above, since the magnetic powder as a raw material of the magnetic particles is mixed in the slurry, there is no risk of scattering of the resin powder at the time of producing the resin powder. Further, the spray drying method enables the preparation of a resin powder from the constituent components of the resin component which are not melt-kneaded and cannot be molded into a powder or a sheet even in the case of kneading at 100 ℃ with a conventional kneader.
(2.1) preparation of slurry
Examples of the method for preparing the slurry include a method in which a powder including the above-described magnetic particles (hereinafter referred to as a magnetic powder), the above-described resin component, and an optional solvent are added and stirred to be uniformly mixed.
The average particle diameter of the magnetic powder is selected accordingly depending on the application of the resin powder and the like. The upper limit of the average particle diameter of the magnetic powder is preferably 75 μm, and more preferably 50 μm. The lower limit of the average particle diameter of the magnetic powder is preferably 1 μm, more preferably 5 μm. The average particle diameter of the magnetic powder means a particle diameter at a 50% integrated value in a particle size distribution measured based on a particle size distribution measuring apparatus based on a laser light scattering/diffraction method.
The addition ratio of the magnetic powder is selected accordingly depending on the application of the resin powder and the like. The upper limit of the blending ratio of the magnetic powder is preferably 95 parts by mass, more preferably 85 parts by mass, with respect to 100 parts by mass of the solid content of the slurry. The lower limit of the addition ratio of the magnetic powder is preferably 40 parts by mass, and more preferably 50 parts by mass, with respect to 100 parts by mass of the solid content of the slurry. When the blending ratio of the magnetic powder is within the above range, the resin powder may be preferably used as the magnetic material. The solid content in the slurry is the content of the magnetic particles and the resin component excluding the solvent.
The upper limit of the content of the thermosetting resin is preferably 65 parts by mass, more preferably 55 parts by mass, relative to 100 parts by mass of the solid content of the slurry. The lower limit of the content of the thermosetting resin is preferably 2 parts by mass, more preferably 5 parts by mass, with respect to 100 parts by mass of the solid content of the slurry.
(2.2) granulation by spray drying
Examples of the method for granulating the slurry by the spray drying method include a method of collecting powder obtained by putting the slurry into a spray dryer. The spray dryer atomizes the slurry by spraying the slurry in the dryer, and continuously contacts the slurry with hot air while increasing a surface area per unit volume, thereby performing instantaneous drying and granulation. That is, the slurry is formed into a plurality of droplets each having a certain size, the droplets are rapidly dried, and the droplets are formed into a spherical shape by surface tension, thereby obtaining spherical powders having substantially the same particle diameter. Therefore, it is unlikely that a very fine and easily scattered powder is generated. In contrast, when the viscosity of the slurry is appropriate, the slurry can be formed into not too large droplets. Therefore, a resin powder having a substantially uniform particle diameter is obtained, and therefore, the problems associated with the pulverized powder are unlikely to be caused. As described above, when the spray dryer is used, spherical particles including resin powder having a narrow frequency in the volume particle size distribution are obtained, and therefore, sieving for classification is no longer required. Further, it is no longer necessary to melt-knead the magnetic powder and the resin component with a kneader to obtain a product and cut the product with a pulverization-type pelletizer, and therefore, the obtained resin powder does not contain metallic foreign substances. Further, the resin component of the resulting resin powder is in instantaneous contact with hot air only, and therefore, the resin component has almost no thermal history, and can be evaluated as being in a state corresponding to the a-stage.
< third embodiment >
(1) Resin powder
The resin powder of the present embodiment (hereinafter referred to as resin powder) comprises an aggregate of spherical particles of the resin composition and a nanofiller. The resin composition contains a resin component and a non-resin component (in the present embodiment, electrically insulating inorganic particles and/or magnetic particles). Detailed descriptions of components similar to those in the first and second embodiments are omitted below.
(1.1) resin composition
(1.1.1) nanofiller
The nanofiller is not particularly limited, and examples of the nanofiller include silica, alumina, ferrite, zeolite, titanium oxide, and pigments such as carbon black.
The content of the nanofiller is preferably greater than or equal to 0.1% by weight and less than or equal to 2% by weight with respect to the resin powder. When the content of the nanofiller is within the above range, the flowability of the resin powder can be improved. The upper limit of the content of the nanofiller is more preferably less than or equal to 1% by weight, still more preferably less than or equal to 0.5% by weight.
The average particle diameter of the nanofiller is selected accordingly depending on the application of the resin powder and the like. The upper limit of the average particle diameter of the nanofiller is preferably 150nm, more preferably 100 nm. The lower limit of the average particle diameter of the nanofiller is preferably 1nm, more preferably 10 nm. When the average particle diameter of the nanofiller is within the above range, the flowability of the resin powder can be improved. The average particle diameter of the nanofiller means a particle diameter at a 50% integral value in a particle size distribution measured based on a particle size distribution measuring apparatus based on a laser scattering/diffraction method.
Examples of the index of the fluidity of the resin powder include an angle of repose. The angle of repose is the maximum angle of the slope at which the stacked body of resin powder maintains stability without spontaneously collapsing. Specifically, the angle of repose can be obtained in a manner similar to the method described in the examples. As the angle of repose decreases, the flowability of the powder increases. The filling efficiency is also improved.
The angle of repose of the resin powder is preferably 26 ° or less, more preferably 25.5 ° or less, and still more preferably 25 ° or less. The lower limit of the angle of repose of the resin powder is preferably greater than or equal to 20 °, more preferably greater than or equal to 21 °, and still more preferably greater than or equal to 22 °.
(1.1.2) non-resin component and resin component
The non-resin component and the resin component are the same as those in the first embodiment or the second embodiment.
(1.2) use of resin powder
The use of the resin powder is not particularly limited, but the resin powder may be used for, for example, electronic parts. The electronic component includes a molded body of resin powder. The electronic component is not particularly limited, but examples of the electronic component include a transistor, a diode, a capacitor, a resistor, an inductor (coil), and a connector.
(2) Method for producing resin powder
(2.1) preparation of slurry and granulation by spray drying
The preparation of the slurry and granulation by the spray drying method are the same as those in the first embodiment or the second embodiment.
(2.2) addition of nanofillers
The resin powder is obtained by: a dry powder is obtained by spray drying, and a nanofiller is added to the dry powder. Between the spherical particles of the resin composition, a nanofiller smaller than the spherical particles is provided, thereby further improving the flowability of the resin powder as compared with the first and second embodiments. In addition, the operability is also improved.
< modification >
The resin powder of the first embodiment may further include magnetic particles.
The resin powder of the second embodiment may further contain electrically insulating inorganic particles.
The sealing material containing the resin powder described in any one of the first to third embodiments may seal electronic parts other than semiconductor elements.
The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to the following examples.
The raw materials for the slurry are shown below.
[ electrically insulating inorganic particles ]
Spherical alumina ("DAW-07", D50: 8 μm; manufactured by Denka Company Limited)
[ magnetic particles ]
Magnetic powder ("27 μm-product", particle size 27 μm-product; produced by EPSON ATMIX Corporation)
[ resin component ]
(epoxy resin)
Bisphenol A liquid epoxy resin ("EPICLON 850S", manufactured by DIC Corporation)
Biphenyl-aralkyl type epoxy resin ("NC-3000", produced by Nippon Kayaku Co., Ltd.)
(imide resin)
Bismaleimide ("BMI-2300", melting point: 70 to 145 ℃ C.; manufactured by Daiwa Kasei Industry Co., Ltd.)
Bis-allyl-norbornene-dicarboximide ("BANI-M", melting point: 75 ℃ C.; manufactured by Maruzen Petrochemical CO, LTD.) (curing agent)
Dicyandiamide ("dicyandiamide", produced by Nippon Carbide Industries co., inc.)
(hardening accelerator)
2-Ethyl-4-methylimidazole ("
(coupling agent)
Epoxy silane ("A187", produced by Momentive Performance Materials Japan LLC)
(nanofiller)
Nano-silica ("YA 050C-
The measurement methods of the particle shape, particle size distribution, metal content, acetone-insoluble component, and residual solvent amount of the resin powder will be described below.
[ particle shape ]
The particle shape of the resin powder was evaluated by obtaining the average aspect ratio and average circularity of the resin powder and based on the following criteria. The average aspect ratio and the average circularity of the resin powder were obtained by measuring the aspect ratio and circularity of each particle with a particle image analyzer ("Morphologi G3", manufactured by Malvern Instruments Ltd, and similarly applicable to the following description) and based on the average value of the measured values. The apparatus measures physical properties of a sample by uniformly dispersing the sample with an automatic dry dispersion unit and analyzing a static image of the sample.
When the average aspect ratio was 0.80 or more and the average circularity was 0.90 or more, the particle shape of the resin powder was evaluated as "spherical". When neither the average aspect ratio nor the average circularity satisfies the above-described condition, the particle shape of the resin powder is evaluated as "variable shape".
[ particle size distribution ]
The particle size distribution of the resin powder was evaluated by obtaining the volume particle size distribution of the resin powder and based on the following criteria. The volume particle size distribution of the resin powder was measured with a particle image analyzer.
When the spherical particles having a particle diameter of 50 μm or more and 100 μm or less are 80% by weight or more relative to the resin powder in the volume particle size distribution, the particle size distribution of the resin powder is evaluated as "narrow". When spherical particles having a particle diameter of 50 μm or more and 100 μm or less fail to satisfy the above condition, the particle size distribution is evaluated to be broad.
[ metallic foreign substance ]
The metallic foreign substances of the resin powder were evaluated based on the following criteria. The metal content of the resin powder was obtained by inductively coupled plasma mass spectrometry (ICP/MS). When the metal content thus obtained was less than or equal to 1ppm with respect to the resin powder, the metal foreign matter of the resin powder was evaluated as "absent". When the metallic foreign matter thus obtained was more than 1ppm with respect to the resin powder, the metal content in the resin powder was evaluated as "present".
[ acetone-insoluble component ]
The acetone-insoluble component of the resin powder was evaluated based on the following criteria. First, 300g of the resin powder was dissolved in acetone and filtered through a 100-mesh wire net to extract insoluble components. The residual substance was dropped onto the powder paper, which was weighed and divided by the initial mass of the resin (the initial mass was 300g), thereby calculating the acetone insoluble amount (ppm). When the amount of acetone-insoluble matter thus obtained was less than or equal to 1ppm with respect to the resin powder, the acetone-insoluble component of the resin powder was evaluated as "absent". When the amount of acetone-insoluble matter thus obtained was more than 1ppm with respect to the resin powder, the acetone-insoluble component in the resin powder was evaluated as "present".
[ residual solvent amount ]
The residual volume ratio of the resin powder was measured as described below. A resin powder corresponding to 5g in weight was put into a drier at 163 ℃/15 minutes, whereby volatile components (solvent) were removed. The mass reduction of the resin powder was measured by measuring the mass of the resin powder before and after the resin powder was put into the dryer. The mass reduction with respect to the mass of the resin powder before the resin powder was put into the dryer was calculated as the residual solvent amount.
[ angle of repose ]
The angle of repose was measured as follows. First, 6g of resin powder was put into a test tube (outer diameter: 12mm, inner diameter: 10mm, length: 120 mm). Next, the opening of the test tube was closed with a flat plate, and in this state, the test tube was turned upside down and placed on a horizontal base. The plate is then slid and removed horizontally, and the tube is slowly lifted vertically. Thereafter, based on the diameter and height of the conical deposit of the resin powder overflowing the test tube, the base angle of the conical deposit was calculated, and this base angle was defined as the angle of repose.
(examples 1 to 1 and 1 to 7)
A slurry was obtained by mixing a resin composition obtained by blending the components in the blending ratio shown in table 1 with a solvent. The solvent used was a solvent (hereinafter referred to as a combined solvent) prepared so that the mass ratio (MEK/DMF) of methyl ethyl ketone (MEK, boiling point: 79 ℃) to N, N-dimethylformamide (DMF, boiling point: 153 ℃) was (7/3). The content ratio of the solid content in the slurry was 92% by weight with respect to the slurry.
The slurry thus obtained was spray-dried, and the dried powder thus obtained was collected as a whole to obtain a resin powder. The spray drying was carried out using a spray dryer ("P260", manufactured by PRECI co., spray method: rotary atomizer method, collection method: cyclone collection method) under the following operating conditions.
Rotation speed of rotary atomizer: 20000rpm
Slurry feed rate: 2 kg/hour
Hot air temperature (inlet temperature): 100 deg.C
Exhaust air temperature (outlet temperature): 60 deg.C
FIG. 1 is an SEM image (magnification: 100 times) of the resin powder obtained in example 1-1, the SEM photograph being taken with a particle image analyzer. FIG. 2A is a graph showing the number particle size distribution of the resin powder obtained in example 1-1, which was measured with a particle image analyzer. FIG. 2B is a graph of the volume particle size distribution of the resin powder obtained in example 1-1, which was measured with a particle image analyzer. FIG. 3A is a graph of the aspect ratio of the resin powder obtained in example 1-1, which was measured with a particle image analyzer. FIG. 3B is a graph of circularity of the resin powder obtained in example 1-1, which is measured with a particle image analyzer.
As confirmed from fig. 1, the
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