Resin composition

Abstract

This resin composition contains amorphous particles having an aspect ratio of less than 0.90, spherical particles having an aspect ratio of 0.90 or greater, and a resin. On an SEM image of a cross-section of the resin composition imaged at a magnification of 250x, three straight lines parallel to each other each having a length of 500 μm are drawn. In the amorphous particles overlapping at least one of the straight lines and having an overlapping length of 8 μm or greater, the total length X2 obtained by summing the overlapping lengths of 8 μm or greater exceeds 30.0% of the total length X1 of the straight lines.

Description

resin composition

[0001] The present disclosure relates to a resin composition containing particles and a resin, and particularly to a resin composition for use as a heat dissipating material.

[0002] Heat generated by passing current through an electronic component is dissipated via a heat sink. A known technique involves filling the space between the electronic component and the heat sink with a heat dissipation material in order to improve heat dissipation efficiency. One example of the heat dissipation material is a resin composition containing a resin and inorganic particles. Examples of inorganic particles include silicon nitride particles (see, for example, Patent Document 1), alumina particles (see, for example, Patent Document 2), or both (see, for example, Patent Document 3).

[0003] Patent Document 1 discloses a liquid encapsulating resin composition before curing, which contains (A) an epoxy resin, (B) an epoxy resin curing agent, and (C) silicon nitride powder as essential components. Patent Document 2 discloses a liquid encapsulating resin composition before curing, which contains a resin material and a filler made of an inorganic material, and which preferably uses alumina particles as the filler.

[0004] Patent Document 3 discloses a resin composition containing silicon nitride, spherical thermally conductive particles (alumina particles), and a resin. The 50% particle size of the silicon nitride is 0.1 to 15 μm, and the 50% particle size of the alumina particles is 10 to 100 μm. The resin composition contains 2 to 30% by volume of silicon nitride, 30 to 80% by volume of alumina particles, and 55 to 85% by volume of silicon nitride and alumina particles combined.

[0005] JP 2000-109651 A JP 2013-134983 A Japanese Patent No. 6508508 A

[0006] In recent years, the increase in heat generation in electronic components has become a problem due to the increased integration of ICs in electronic devices and the use of high-current-driven electronic components due to the electrification of electric vehicles, aircraft, etc. In order to achieve more effective heat dissipation, it is important to improve the thermal conductivity of resin compositions. Although the resin compositions disclosed in Patent Documents 1 to 3 use inorganic particles with high thermal conductivity, such as silicon nitride particles and alumina particles, as fillers to increase the thermal conductivity of the resin compositions, further improvements in thermal conductivity are desired. Therefore, an object of one embodiment of the present invention is to provide a resin composition having better thermal conductivity than conventional resin compositions.

[0007] Aspect 1 of the present invention is a resin composition containing irregular particles having an aspect ratio of less than 0.90, spherical particles having an aspect ratio of 0.90 or more, and a resin, wherein three parallel lines, each 500 μm long, are drawn on an SEM image of a cross section of the resin composition photographed at 250x magnification, and the irregular particles overlap with at least one of the lines, with the overlap length being 8 μm or more, and the total length X2, calculated by adding up all of the overlap lengths of 8 μm or more, exceeds 30.0% of the total length X1 of the lines.

[0008] A second aspect of the present invention is the resin composition according to the first aspect, wherein the irregular particles are silicon nitride particles, and the spherical particles are alumina particles.

[0009] In a third aspect of the present invention, the specific surface area of ​​the silicon nitride particles is 2.66 m ２ / g or less.

[0010] A fourth aspect of the present invention is the resin composition according to the second or third aspect, wherein the silicon nitride particles have a particle diameter D50 of 15 μm or more at 50% cumulative particle size from the finest particle side in a volume-based cumulative particle size distribution.

[0011] A fifth aspect of the present invention is the resin composition according to any one of the second to fourth aspects, wherein the alumina particles have a particle diameter D50 of 50% cumulative from the finest particle side in their volume-based cumulative particle size distribution that is 70% or less of the particle diameter D50 of the silicon nitride particles, which are 50% cumulative from the finest particle side in their volume-based cumulative particle size distribution.

[0012] A sixth aspect of the present invention is the resin composition according to any one of the second to fifth aspects, wherein the silicon nitride particles have a β-phase ratio of 65% or more.

[0013] According to one embodiment of the present invention, it is possible to provide a resin composition having a thermal conductivity superior to that of conventional resin compositions.

[0014] 1 is a part of a cross-sectional SEM image of a sheet-shaped resin composition.

[0015] The inventors conducted extensive research to provide a resin composition with excellent thermal conductivity. As a result, they discovered for the first time that the thermal conductivity of a resin composition can be improved by mixing particles of different shapes (irregular particles and spherical particles) as filler particles and increasing the content of irregular particles of a predetermined size or larger in the resin composition. In this embodiment, the content of irregular particles of a predetermined size or larger is measured by using the ratio of the length of an imaginary line drawn on the cross section of the resin composition to the length of the line that overlaps the line and irregular particles of a predetermined size or larger.

[0016] [Resin Composition 10] The resin composition according to this embodiment will be described in detail below. Fig. 1 is a partial cross-sectional SEM image of a sheet-like resin composition 10. The resin composition 10 contains particles having an aspect ratio of less than 0.90 (referred to as "irregular particles 20"), particles having an aspect ratio of 0.90 or more (referred to as "spherical particles 30"), and a resin 40.

[0017] In this specification, "irregular particles 20" refers to all particles having an aspect ratio of less than 0.90. However, particles generally used in resin compositions for heat dissipation materials rarely contain particles having an aspect ratio of less than 0.10. Therefore, the "irregular particles 20" according to one embodiment may be limited to particles having an aspect ratio of 0.10 or more and less than 0.90. Even in this case, the resin composition according to this embodiment may contain a small amount of particles having an aspect ratio of less than 0.10 (for example, 10% by mass or less when all particles are taken as 100% by mass).

[0018] In this specification, the term "spherical particles 30" refers to all particles having an aspect ratio of 0.90 or more. Since the maximum aspect ratio is 1.00, the aspect ratio of the "spherical particles 30" may be expressed as 0.90 or more and 1.00 or less.

[0019] In the cross-sectional SEM image of Figure 1 (taken at 250x magnification), the resin 40 is the dark gray area, and the irregular particles 20 and spherical particles 30 are the light gray areas. In this example, spherical particles 30 with small particle diameters are dispersed among irregular particles 20 with large particle diameters. The resin 40 fills the gaps between the plurality of irregular particles 20 and the plurality of spherical particles 30. By including an appropriate amount of resin 40, a dense resin composition with little internal space can be molded.

[0020] In this embodiment, three or more straight lines LN are drawn on a cross-sectional SEM image of the resin composition 10 observed at 250x magnification. The three or more straight lines LN are drawn parallel to one another. Furthermore, the three or more straight lines LN are drawn so that the total length of the three or more straight lines LN (referred to as the "total length X1") is 1500 μm. It is preferable that the lengths of the three or more straight lines LN are all equal. For example, three straight lines LN, each 500 μm long and parallel to one another, are drawn. Only irregular particles 20 whose overlap length between each straight line LN and each irregular particle 20 (referred to as the "overlap length Lov") is 8 μm or more are identified. Note that when one irregular particle 20 overlaps with multiple straight lines LN, multiple "overlap lengths Lov" exist for one irregular particle 20. When one or more of the multiple "overlap lengths Lov" are 8 μm or more, the irregular particle 20 is also identified.

[0021] When the total length (overlap length Lov) of the overlap between each of the identified irregular particles 20 and the line LN (this is referred to as the total length "X2") is calculated, the ratio of the total length X2 of the overlap lengths Lov to the total length X1 of the line LN exceeds 30.0%. In other words, the resin composition 10 according to this embodiment satisfies the following formula (1). Here, X1 is 1500 μm, so this may be rewritten as (1)'. X2 / X1×100>30.0(%) (1) X2(μm) / 1500(μm)×100>30.0(%) (1)'

[0022] Note that when one irregular particle 20 overlaps with multiple straight lines LN, only overlap lengths Lov that are 8 μm or greater are added together to calculate the total length X2. For example, assume that three straight lines LN overlap one irregular particle 20, resulting in three overlap lengths Lov (first to third overlap lengths Lov), with the first and second overlap lengths Lov being 8 μm or greater but the third overlap length Lov being less than 8 μm. When calculating the total length X2, the first and second overlap lengths Lov are added together, but the third overlap length Lov is not added.

[0023] The inventors conducted extensive research to determine whether it would be appropriate to consider only irregular particles 20 having a certain size or larger when calculating the total length X2, because small irregular particles 20 have a small contribution to the thermal conductivity of the resin composition 10. As a result, they found that when only irregular particles 20 having an overlap length Lov of 8 μm or more with the line LN are considered when calculating the total length X2, there is a good correlation between the ratio of the total length X2 to the total length X1 of the line LN and the thermal conductivity of the resin composition 10. Therefore, only irregular particles 20 having an overlap length Lov of 8 μm or more were considered when calculating the total length X2.

[0024] It can be said that the resin composition 10 satisfying the above formula (1) contains a sufficient amount of irregular particles 20 having a size that mainly contributes to the formation of heat conduction paths within the resin composition 10. Therefore, it is possible to obtain a resin composition 10 having excellent thermal conductivity. The resin composition 10 satisfying the formula (1) can be produced, for example, by adding a relatively large amount of relatively large irregular particles 20 (for example, irregular particles 20 having a D50 of more than 15 μm) (for example, the content of irregular particles 20 is more than 30% by volume).

[0025] The ratio of the total length X2 to the total length X1 of the straight lines LN (corresponding to the left side of formula (1)) is preferably 40.0% or more, more preferably 50.0% or more, even more preferably 55.0% or more, particularly preferably 60.0% or more, and may be 62.0% or more, from the viewpoint of improving the thermal conductivity of the resin composition. The ratio of the total length X2 to the total length X1 of the straight lines LN (corresponding to the left side of formula (1)) is preferably 95% or less, more preferably 90% or less, even more preferably 80% or less, and particularly preferably 70% or less, from the viewpoint of the moldability of the resin composition.

[0026] A method for distinguishing the particles contained in the resin composition 10 into the irregular particles 20 and the spherical particles 30, and a method for measuring the total length X1 of the line segments LN and the total length X2 of the line segments will be described.

[0027] First, a cross-sectional SEM image of the resin composition 10 is obtained. The cross section of the resin composition 10 for SEM observation is as follows. In the case of a sheet-shaped resin composition 10, the cross section is taken along the thickness direction (T direction in FIG. 1). In the case of a resin composition 10 in a shape other than a sheet, where the heat conduction direction can be identified, the cross section is taken along the heat conduction direction. In the case of a resin composition 10 in a shape other than a sheet, where the heat conduction direction cannot be identified, the cross section can be taken in any direction. As an example, if the resin composition 10 has one or more planes, a cross section perpendicular to one of the planes may be taken. The conditions for capturing the cross-sectional SEM image are a magnification of 100 to 100,000 times, and the observation area is, for example, 1,000 μm × 2,000 μm at a magnification of 250 times, and 4 μm × 3 μm at a magnification of 100,000 times.

[0028] A cross-sectional SEM image of the resin composition 10 is subjected to image analysis to determine the aspect ratio of the particles shown in the cross-sectional SEM image. This makes it possible to distinguish between irregular particles 20 and spherical particles 30. Each particle shown in the cross-sectional SEM image is analyzed using image processing software (e.g., Image J (manufactured by the National Institute of Health)). The maximum particle size (referred to as the "major axis") of the particle is identified, and the particle size in the direction perpendicular to the major axis is referred to as the "minor axis." For each particle, the ratio of the minor axis to the major axis (minor axis / major axis) is taken as the aspect ratio of that particle.

[0029] The straight lines LN are drawn within the area in which the resin composition 10 is visible on a cross-sectional SEM image of the resin composition 10 observed at 250x magnification. The number of straight lines LN is three or more, preferably three to 15. As described above, the total length X1 of the three or more straight lines LN is 1500 μm. The length of each straight line LN is 100 μm or more, preferably 100 μm to 500 μm. It is preferable that all straight lines LN have the same length. For example, three straight lines LN, each 500 μm long, are drawn. The method of drawing the straight lines LN and the total length X1 of the straight lines LN are determined according to the shape of the resin composition 10.

[0030] In the case of a sheet-like resin composition 10, a straight line LN is drawn along the thickness direction (direction T in FIG. 1). In this specification, the term "sheet-like" refers to a sheet having a thickness sufficient to allow the upper and lower surfaces of the sheet to be imaged in a cross-sectional SEM image, and these surfaces being approximately parallel. FIG. 1 is a cross-sectional SEM image of a sheet-like resin composition 10, which has two approximately parallel surfaces (upper surface A and lower surface B in FIG. 1). The straight line LN is drawn in a direction perpendicular to each of the upper surface A and the lower surface B (i.e., the thickness direction of the sheet-like resin composition 10).

[0031] For resin compositions 10 in other forms, the straight line LN is drawn in one of the following ways: - If two non-parallel surfaces appear in the cross-sectional SEM image, draw the straight line LN in a direction perpendicular to one of the surfaces. - If one surface of the resin composition 10 appears in the cross-sectional SEM image, draw the straight line LN in a direction perpendicular to that surface. - If the surface of the resin composition 10 is not visible in the cross-sectional SEM image and the thermal conduction direction of the resin composition 10 can be identified, draw the straight line LN along the thermal conduction direction.

[0032] If the surface of the resin composition 10 is not visible in the cross-sectional SEM image and the direction of heat conduction of the resin composition 10 cannot be identified, a straight line LN can be drawn in any direction. For example, the straight line LN can be drawn parallel to any side of the rectangular observation area.

[0033] The three or more straight lines LN are drawn parallel to each other and at equal intervals. As an example, when drawing three straight lines LN parallel to the vertical sides on an SEM image with an observation area of ​​1000 μm (vertical) × 2000 μm (horizontal), the three straight lines LN can be drawn in accordance with the positions of the three lines that divide the horizontal width into four equal parts. When drawing straight lines LN parallel to the sides (e.g., vertical sides) of the observation area, it is desirable to draw the straight lines LN so that the vertical sides of the observation area and the straight lines LN do not overlap (preferably, they are spaced apart by 50 μm or more).

[0034] Each overlapping portion between an irregular particle 20 having an overlap length Lov of 8 μm or more and the straight line LN is referred to herein as a "line segment." Furthermore, an irregular particle 20 having an overlap length Lov of 8 μm or more is referred to herein as a "line segment measurement particle." The left side of equation (1) is the ratio of the total length X2 of the line segments to the total length X1 of the straight lines LN, and this is referred to as the "straight line-segment ratio" or simply the "line segment ratio."

[0035] The specific procedure for determining the total length X2 of the line segments will be described in detail with reference to a cross-sectional SEM image of a sheet-shaped resin composition 10 shown in FIG. 1 . The sheet-shaped resin composition 10 in FIG. 1 has two substantially parallel surfaces (top surface A and bottom surface B). A line LN with length X11 (500 μm in FIG. 1 ) is drawn in the thickness direction of the sheet-shaped resin composition 10 (direction T in FIG. 1 ; in other words, the direction perpendicular to each of the top surface A and bottom surface B). Irregular particles 20 overlapping with the line LN are identified, and the overlap length Lov between the line LN and the irregular particles 20 is measured. Then, the overlapping portion (line segment) between the line LN and the irregular particles 20 (line segment measurement particles) with an overlap length Lov of 8 μm or more is identified. In FIG. 1 , the line segment of the line segment measurement particles (shown as a black solid line) is superimposed on the line LN (shown as a white dashed line). In the sheet-like resin composition 10 of FIG. 1, there are nine line measurement particles and nine line segments, the lengths of which are indicated by X21 to X29.

[0036] Repeat the same procedure as many times as necessary (for example, three times in total if there are three straight lines LN) to measure the lengths of all the line segments in the total length X1 = 1500 μm (for example, three straight lines LN each 500 μm long). The total length X2 of the line segments is calculated by adding up the lengths of all the line segments.

[0037] Another method for determining the total line segment length X2 involves identifying irregular particles 20 that overlap a certain line LN, listing the measurement data for the overlap length Lov between the line LN and the irregular particles 20, and then extracting and summing only those with an overlap length of 8 μm or more (this is referred to as the "line segment subtotal"). This operation is performed for each of three or more lines LN, and the total line segment length X2 can be determined by summing the line segment subtotals determined for each line LN. While this method does not identify which irregular particles 20 overlapping the line LN are line segment measurement particles, it does allow the total line segment length X2 to be determined by a simple procedure.

[0038] The preferred contents (filling rates) of the irregular particles 20 and spherical particles 30 contained in the resin composition 10 are as follows. The "content (filling rate)" refers to the content (volume %) of the target particles when the total of the irregular particles 20, spherical particles 30, and resin 40 is 100% by volume. The content (filling rate) of the irregular particles 20 is preferably 10% by volume or more, more preferably 20% by volume or more, and even more preferably 30% by volume or more. It is also preferably 90% by volume or less, more preferably 80% by volume or less, and even more preferably 70% by volume or less. The content (filling rate) of the spherical particles 30 is preferably 5% by volume or more, more preferably 10% by volume or more, and even more preferably 15% by volume or more. It is also preferably 80% by volume or less, more preferably 70% by volume or less, and even more preferably 60% by volume or less.

[0039] The total content (total filling rate) of the irregular particles 20 and the spherical particles 30 is preferably 20% by volume or more, more preferably 30% by volume or more, and particularly preferably 40% by volume or more, and is preferably 98% by volume or less, more preferably 95% by volume or less, and particularly preferably 93% by volume or less.

[0040] The greater the total content of the irregular particles 20 and the spherical particles 30, the higher the thermal conductivity of the resin composition 10, which is preferable. However, if the total content is too high, the content of the resin 40 becomes too low, making it impossible to mold the resin composition 10. The maximum amount of the total content (total filling rate) that can obtain a moldable resin composition 10 is referred to as the "maximum filling rate FR ｍａｘ " (volume%), and the total content (total filling rate) is the maximum filling rate FR ｍａｘ It is desirable to set the maximum filling rate FR as follows: ｍａｘ may vary depending on the types and physical properties of the irregular particles 20, spherical particles 30, and resin 40 used.

[0041] Maximum filling rate FR ｍａｘis determined as follows. First, the compounding ratio of the irregular particles 20 to the spherical particles 30 is determined (this is referred to as the "predetermined compounding ratio"). Next, the irregular particles 20 and the spherical particles 30 are filled into the resin 40 to prepare the resin composition 10. At this time, while the compounding ratio of the irregular particles 20 to the spherical particles 30 is kept constant, a plurality of resin compositions 10 are prepared with different filling amounts of the irregular particles 20 and the spherical particles 30. The thermal conductivity of the obtained resin composition 10 is measured, and the total content (volume %) of the irregular particles 20 and the spherical particles 30 contained in the resin composition 10 that maximizes the thermal conductivity is defined as the "maximum filling rate" at the "predetermined compounding ratio." If the compounding ratio of the irregular particles 20 to the spherical particles 30 changes, the maximum filling rate may also change.

[0042] The total content (volume %) of the irregular particles 20 and the spherical particles 30 is the maximum filling rate FR ｍａｘ The closer the total content (volume %) is to the maximum filling rate FR of the resin composition 10, the greater the content of the irregular particles 20 having an overlap length Lov of 8 μm or more with the straight line LN, and the greater the "line segment ratio" defined on the left side of the above formula (1). This can improve the thermal conductivity of the resin composition 10. Therefore, the total content (volume %) is calculated based on the maximum filling rate FR of the resin composition 10. ｍａｘ (volume%) as the basis, (maximum filling rate FR ｍａｘ It is preferable to set the ratio to (volume %)-10% or more.

[0043] The ratio (compounding ratio) of the content (volume %) of the irregular particles 20 to the spherical particles 30 is preferably 90:10 to 20:80, and more preferably 80:20 to 40:60.

[0044] [Irregular Particles 20 and Spherical Particles 30] The irregular particles 20 and spherical particles 30 suitable for the resin composition 10 according to the embodiment will be described.

[0045] The amorphous particles 20 are preferably silicon nitride particles, and the spherical particles 30 are preferably alumina particles. Since both silicon nitride particles and alumina particles are inorganic materials with high thermal conductivity, the thermal conductivity of the resin composition 10 can be further improved by using particles made of these as a filler.

[0046] The fact that the irregular particles 20 are silicon nitride particles and the spherical particles 30 are alumina particles can be identified, for example, by SEM-EDX analysis of a cross section of the resin composition 10. The irregular particles and spherical particles contained in the resin composition 10 are each identified from the cross-sectional SEM image, and the element mapping (e.g., element mapping of Si element and Al element) obtained by EDX measurement is confirmed. This makes it possible to confirm that the irregular particles are silicon nitride particles and the spherical particles are alumina particles.

[0047] It may also contain a small amount of amorphous alumina particles (e.g., 10.0% by volume or less of the total alumina particles) and a small amount of spherical silicon nitride particles (e.g., 10.0% by volume or less of the total silicon nitride particles), neither of which will interfere with the objectives of the present embodiment.

[0048] Next, silicon nitride particles and alumina particles suitable for the resin composition 10 of this embodiment will be described in detail. Measurement of the physical properties of the silicon nitride particles and alumina particles may be performed on the resin composition 10 containing these particles. However, if measurement is difficult in the resin composition 10, the silicon nitride particles and alumina particles may be isolated from the resin composition 10 and then measured. To isolate the silicon nitride particles and alumina particles from the resin composition 10, the resin contained in the resin composition is first removed, for example, by dissolving it in an organic solvent or by heating it to a temperature of 500°C or higher to thermally decompose the resin. The resulting mixture of silicon nitride particles and alumina particles is separated based on differences in specific gravity, particle size, etc. Separation methods based on differences in specific gravity include sedimentation or centrifugation in liquid, or methods using a dry sieve or specific gravity separator.

[0049] (Specific surface area of ​​silicon nitride particles) The specific surface area of ​​the silicon nitride particles is a BET specific surface area measured by a krypton adsorption method based on JIS Z 8830:2013. The specific surface area of ​​the silicon nitride particles is 2.66 m ２ / g, and by controlling the specific surface area within this range, the dispersibility of the silicon nitride particles in the resin is improved, and it becomes possible to highly load the silicon nitride particles into the resin composition. By adjusting the specific surface area, it becomes easy to produce a resin composition that satisfies formula (1). In addition, the thermal conductivity of the resin composition can be further improved. The specific surface area of ​​the silicon nitride particles is more preferably 2.00 m ２ / g or less, and more preferably 1.50m ２ / g or less, more preferably 1.36 m ２ The lower limit of the specific surface area is not particularly limited, but for example, it is 0.01 m ２ / g or more, and ２ / g or more, and ２ / g or more.

[0050] (D50 of Silicon Nitride Particles) The particle diameter D50 of the cumulative 50% from the finest particle side of the volume-based cumulative particle size distribution of the silicon nitride particles is preferably greater than 15 μm. The silicon nitride particles used as fillers are larger than those used in conventional techniques (for example, the D50 of the silicon nitride particles in Patent Document 1 is 0.1 to 15 μm), which facilitates the formation of heat conduction paths through the silicon nitride particles within the resin composition 10. Furthermore, since the number of silicon nitride particles required to form a heat conduction path can be reduced, the number of interfaces on the heat conduction path can be reduced, resulting in further improved thermal conductivity. Here, the term "interface" is intended to include all of the interfaces between silicon nitride particles and adjacent silicon nitride particles, the interface between silicon nitride particles and resin, and the interface between silicon nitride particles and alumina particles.

[0051] The D50 of the silicon nitride particles is more preferably 20 μm or more, even more preferably 30 μm or more, and particularly preferably 40 μm or more. The D50 of the silicon nitride particles is preferably 300 μm or less, more preferably 200 μm or less. Adjusting the D50 of the silicon nitride particles makes it easy to produce a resin composition that satisfies formula (1).

[0052] (D50 of Alumina Particles) The particle diameter D50 of the alumina particles at the cumulative 50% from the fine side of the volume-based cumulative particle size distribution is preferably 70% or less of the particle diameter D50 of the silicon nitride particles at the cumulative 50% from the fine side of the volume-based cumulative particle size distribution. This allows the relatively large silicon nitride particles to form a skeleton, with the relatively small alumina particles dispersed in the gaps. As a result, within the resin composition 10, the silicon nitride particles form the main heat conduction path, and the alumina particles filling the gaps between the silicon nitride particles form auxiliary heat conduction paths, further improving the heat conduction efficiency of the resin composition 10.

[0053] The ratio of the D50 of the alumina particles to the D50 of the silicon nitride particles is more preferably 60% or less, even more preferably 50% or less, and particularly preferably 40% or less. The ratio of the D50 of the alumina particles to the D50 of the silicon nitride particles is preferably 0.001% or more. The D50 of the alumina particles is preferably less than 10 μm, more preferably 8 μm or less, even more preferably 7 μm or less, and particularly preferably 6 μm or less. When the resin composition 10 contains multiple types of alumina particles, it is preferable that the particle diameter D50 of all types of alumina particles and the particle diameter D50 of the silicon nitride particles satisfy the above relationship.

[0054] The D50 of silicon nitride particles and the D50 of alumina particles are measured by laser diffraction. Specifically, powder dispersed in water is irradiated with a laser beam, and the diffraction is measured to determine the particle size. A measuring device such as the 1090L manufactured by CILAS can be used.

[0055] (β-phase ratio of silicon nitride particles) The β-phase ratio of the silicon nitride particles is preferably 65% ​​or more, which improves the thermal conductivity of the silicon nitride particles and further improves the thermal conductivity of the resin composition 10 containing the silicon nitride particles. The β-phase ratio is more preferably 70% or more, even more preferably 80% or more, even more preferably 85% or more, and particularly preferably 90% or more. The β-phase ratio of the silicon nitride particles may be 100% or less.

[0056] In this specification, the "β-phase ratio" refers to the content (vol %) of β-type silicon nitride relative to all silicon nitride contained in the silicon nitride particles.

[0057] In calculating the β-phase ratio, silicon nitride particles are measured by powder X-ray diffraction, and the diffraction pattern is analyzed by the Gazzara & Messier method (G. P. Gazzara and D. P. Messier, "Determination of Phase Content of Si ３ N ４ The specimen is analyzed by "X-ray Diffraction Analysis", Am. Ceram. Soc. Bull., 56[9]777-80 (1977)).

[0058] [Resin 40] Suitable resins 40 for the resin composition 10 according to the embodiment include known resins such as silicone resins, epoxy resins, and acrylic resins. The type of resin can be selected from thermoplastic resins, thermoplastic elastomers, and thermosetting resins. One type of resin may be used alone, or two or more types may be used in combination. From the viewpoints of moldability and thermal conductivity, it is preferable to use a silicone resin.

[0059] [Other Additives] Furthermore, these resin compositions may contain, as needed, known additives such as plasticizers, curing accelerators, coupling agents, fillers, pigments, flame retardants, antioxidants, surfactants, compatibilizers, weather resistance agents, antiblocking agents, antistatic agents, leveling agents, and release agents, either singly or in combination, within the scope of the invention.

[0060] [Method for Producing Resin Composition 10] A method for producing resin composition 10 will be described. Resin composition 10 can be obtained by using irregular particles and regular particles, each of which has a controlled particle size, and applying a known method to these. For example, when the resin is liquid (e.g., liquid silicone resin), resin composition 10 can be obtained by mixing the liquid resin, irregular particles 20, spherical particles 30, and a curing agent, and then curing the mixture with heat or ultraviolet light. Known curing agents, mixing methods, and curing methods can be used. On the other hand, when the resin is solid, the desired resin composition 10 can be obtained by mixing the irregular particles 20, spherical particles 30, and resin, and then kneading them using a known method such as melt kneading.

[0061] The amorphous particles 20 (e.g., silicon nitride particles) used in the method for producing the resin composition 10 can be produced, for example, by the method described below. The spherical particles 30 (e.g., alumina particles) used in the method for producing the resin composition 10 may be, for example, commercially available spherical alumina particles, or may be spherical alumina particles produced by a known method (e.g., flame fusion method).

[0062] [Method for Producing Irregular Particles 20] A method for producing silicon nitride particles will be described as an example of a method for producing the irregular particles 20 used in the method for producing the resin composition 10. The silicon nitride particles include the following steps: (1) synthesizing silicon nitride synthetic crystals by combustion synthesis under a nitrogen atmosphere using raw materials containing Si, (2) crushing the silicon nitride synthetic crystals to obtain coarsely pulverized silicon nitride powder, (3) finely pulverizing the coarsely pulverized silicon nitride powder to obtain finely pulverized silicon nitride powder, and (4) heat-treating the finely pulverized silicon nitride powder to obtain silicon nitride particles.

[0063] Step (1): Synthesizing silicon nitride composite crystals. For example, Si powder is used as the Si-containing raw material. The D50 of the raw Si material is, for example, in the range of 2 to 10 μm. This allows the amount of oxygen impurities to be suppressed, and the combustion rate to be increased, allowing for a higher synthesis temperature, resulting in good crystal growth. As an example, the D50 of Si is 5 μm.

[0064] The diluent is used to adjust the amount of Si in the mixed raw materials. Separately prepared silicon nitride particles are used as the diluent. The diluent may be either α-type silicon nitride particles or β-type silicon nitride particles, or a mixture of these. The D50 of the diluent is preferably in the range of 0.5 to 2.0 μm. As an example, the D50 of the diluent is 1.0 μm. The amount of diluent added is less than 10% by mass of the total raw materials (including the diluent). As an example, the diluent is added in an amount of 5 to 8% by mass of the total raw materials. By adding the amount of diluent within the above range, a predetermined amount of the desired silicon nitride particles used in the resin composition according to this embodiment can be produced.

[0065] In this embodiment, raw material Si and a diluent are mixed and filled into an insulated heat-resistant container. This insulated heat-resistant container has a thermal conductivity of 1 W / mK or less, and although alumina or zirconia can be used as the material, carbon is preferred to prevent impurities from being mixed in. After the raw materials are filled, the container is covered with a lid made of the same material as the insulated heat-resistant container. Furthermore, to increase the temperature inside the composite during combustion, the thickness of the mixed raw materials is set to more than 100 mm, preferably more than 100 mm and not more than 150 mm. Combustion synthesis is performed in a nitrogen atmosphere in the range of 0.5 to 1 MPa (e.g., 0.9 MPa). Adjusting the pressure range within this range enables efficient synthesis while suppressing increases in equipment costs.

[0066] When the mixed raw material is filled into the crucible, a layer of powder (silicon nitride) having a thickness of 1 mm to 80 mm is spread on the bottom and sides of the crucible, the mixed raw material is then filled, and the top surface is further covered with a layer of powder having a thickness of 1 mm to 80 mm. By covering the entire surface with powder, the mixed raw material can be kept warm, and a predetermined amount of the desired silicon nitride particles used in the resin composition according to this embodiment can be produced.

[0067] To promote crystal growth more effectively, a catalyst may be used, for example, Y ２ O ３ , Fe ２ O ３ , CaO, Ni, Co, C, etc. are added in an amount of about 0.01 to 0.1 mass %. In addition, external auxiliary heating is performed in the range of 500°C to 1700°C (for example, 1500°C), and the combustion temperature is also increased in the combustion synthesis method by self-ignition.

[0068] Step (2): Obtaining a coarsely pulverized silicon nitride powder. The silicon nitride synthetic crystal is in the form of an aggregate of multiple silicon nitride particles. In step (2), the silicon nitride synthetic crystal is crushed to obtain a coarsely pulverized silicon nitride powder. For example, the synthetic crystal is crushed using a general crushing device such as a hammer mill or a disk mill until it passes through a sieve with a specified mesh size (for example, a sieve with mesh sizes in the range of 400 μm to 500 μm).

[0069] Step (3): Obtaining a finely pulverized silicon nitride powder The coarsely pulverized silicon nitride powder is further pulverized to obtain a finely pulverized silicon nitride powder. The pulverization is carried out using a pulverizing device such as a ball mill. If necessary, the obtained finely pulverized powder may be classified. Classification can be carried out by sieving, wet classification, or the like.

[0070] Step (4): Step of Obtaining Silicon Nitride Particles The finely pulverized silicon nitride powder is heat-treated to obtain silicon nitride particles. The heat treatment forms an oxide film on the surface of the silicon nitride particles, chemically stabilizing the silicon nitride particles. The heat treatment is carried out in the atmosphere at a temperature of 500°C or higher and 1200°C or lower. The heat treatment time can be adjusted appropriately according to the heat treatment temperature. The heat treatment time is, for example, 5 hours.

[0071] In the method for producing silicon nitride particles, silicon nitride synthetic crystals are synthesized using the heat generated by the combustion synthesis method, and then the silicon nitride particles according to this embodiment can be produced by crushing, classifying, and pulverizing the synthesized crystals.

[0072] The present invention will be described in detail below with reference to examples carried out to clarify the effects of the present invention, but the present invention is not limited to the following examples.

[0073] <Preparation of Silicon Nitride Particles> Si powder (D50 = 5 μm) and silicon nitride powder (D50 = 1 μm) prepared separately as a diluent were mixed in a tumbling ball mill. The amount of diluent added was 5 to 8 mass% of the total raw material (including diluent). The mixed powder was filled into a carbonaceous, heat-resistant container with a layer of powder 1 mm to 80 mm thick on the bottom and sides, so that the raw material layer was thicker than 100 mm and not more than 150 mm, and the raw material layer was further covered with a layer of powder 1 mm to 80 mm thick. A lid made of a carbonaceous, heat-resistant material was then placed, and synthesis was carried out under a nitrogen atmosphere at 0.9 MPa. After synthesis, the mixture was coarsely pulverized (crushed) in a mortar until it passed through a 500 μm sieve.

[0074] The obtained coarsely pulverized powder was subjected to fine pulverization in a ball mill. The obtained finely pulverized powder was sieved using a vibrating sieve and then wet-classified to obtain the following silicon nitride particles A to D. When sieved using a 150 μm sieve, silicon nitride particles A remained on the sieve (D50 is 192.0 μm). When sieved using a 150 μm sieve, the powder remaining below the sieve was further sieved using a 106 μm sieve, and silicon nitride particles B remained on the sieve (D50 is 118.0 μm). When sieved using a 106 μm sieve, the powder remaining below the sieve was further sieved using a 75 μm sieve, and silicon nitride particles C remained on the sieve (D50 is 83.0 μm). - When sieving using a sieve with 75 μm openings, the powder remaining below the sieve was further sieved using a 63 μm sieve, and silicon nitride particles D (D50 was 58.0 μm) remained on the sieve. - When sieving using a sieve with 63 μm openings, silicon nitride particles E (D50 was 22.0 μm) remained below the sieve. In addition, as a comparative example, a commercially available silicon nitride powder (manufactured by Aldrich, silicon nitride (predominantly β-phase, ≦10 micron primary particle size, product code 248622); hereinafter referred to as "silicon nitride particles Z") was used.

[0075] <Preparation of Alumina Particles> Three types of alumina particles were prepared. As the first alumina particles, DAW-05 manufactured by Denka (Sample Nos. A1 to A6, 1 to 6) or DAW-45 manufactured by Denka (Sample Nos. A7, 7) was used. As the second alumina particles, AA-04 manufactured by Sumitomo Chemical Co., Ltd. was used (Sample Nos. A1 to A6, 1 to 6). Mixed alumina particles obtained by mixing the first alumina particles and the second alumina particles at a predetermined ratio were used as "alumina particles."

[0076] Various measurements were carried out on the silicon nitride particles A to E and Z, the first alumina particles, and the second alumina particles.

[0077] <Measurement of D50 of each particle> The particle size distribution of silicon nitride particles and alumina particles was measured to determine the D50 of each particle. The particle size distribution of each particle was measured by laser diffraction. A sample dispersed in water was irradiated with a laser beam, and the diffraction was measured to determine the particle size. The measuring device used was a CILAS 1090L model. The particle diameter was taken as the circle-equivalent particle diameter. The circle-equivalent particle diameter is the particle diameter of a perfect circle that has the same area as a projected particle image. The particle diameter D50 was measured based on volume.

[0078] The measurement results of D50 for each particle are shown in Tables 1 and 3. The D50 of the mixed alumina particles (a mixture of first alumina particles and second alumina particles) was not measured. However, from the D50 (6.0 μm) of the first alumina particles before mixing and the D50 (0.5 μm) of the second alumina particles, it can be said that the D50 of the mixed alumina particles was 6.0 μm or less. In other words, the D50 of the alumina particles (mixed alumina particles) used in the examples was less than 6.0 μm.

[0079] <Measurement of aspect ratio of each particle> SEM images were taken for each of the silicon nitride particles, the first alumina particles, and the second alumina particles. The following equipment was used for the images. Equipment used: Scanning electron microscope: Helios G4 UX (manufactured by FEI Japan Co., Ltd.) The imaging conditions were as follows: Acceleration voltage: 5.0 kV Signal: BSE Probe current: 0.1 nA Magnification: 250x (particles with a D50 of more than 20 μm), 1000x (particles with a D50 of 20 μm or less), 100,000x (particles with a D50 of 1 μm or less)

[0080] The aspect ratios of all particles in the SEM images were determined using image processing software Image J (manufactured by the National Institute of Health). First, the longest particle diameter of each particle was defined as the longest diameter, and the particle diameter in the direction perpendicular to the longest diameter was defined as the shortest diameter. The longest and shortest diameters of each particle were then measured, and the ratio of the shortest diameter to the longest diameter (shortest diameter / longest diameter) was then determined. As a result, it was confirmed that the silicon nitride particles were amorphous particles 20 (aspect ratio less than 0.90), and that the first alumina particles and the second alumina particles were both spherical particles 30 (aspect ratios of 0.90 or more).

[0081] The average aspect ratio of each particle was determined as a reference for understanding the aspect ratio of each particle. The average aspect ratio of each particle was determined by randomly selecting 20 particles from the SEM image of each particle and calculating the arithmetic mean of the aspect ratios of those particles. Note that this average aspect ratio does not indicate the aspect ratio of each particle. Therefore, it should be noted that the average aspect ratio cannot be used to determine whether each particle is an amorphous particle or a spherical particle. The measurement results of the average aspect ratio of the silicon nitride particles are shown in Table 4. The average aspect ratio of the first alumina particles (Denka DAW-05 and Denka DAW-45) was 0.97, and the average aspect ratio of the second alumina particles was 0.91.

[0082] The average aspect ratio of the silicon nitride particles is preferably 0.50 or more and less than 0.90, more preferably 0.55 or more and 0.86 or less, and particularly preferably 0.60 or more and 0.85 or less. This makes it easier for the amorphous silicon nitride particles to form a skeletal structure in the resin composition, thereby further improving the thermal conductivity of the resin composition. Furthermore, adjusting the average aspect ratio of the silicon nitride particles makes it easier to produce a resin composition that satisfies formula (1). Furthermore, from the viewpoint of improving the filling and dispersibility of silicon nitride in the resin composition and improving thermal conductivity, the average aspect ratio of the silicon nitride particles may be 0.77 or more and 0.86 or less.

[0083] The average aspect ratio of the alumina particles is preferably 0.90 or more and 1.00 or less, and more preferably 0.91 or more and 1.00 or less. This makes it easier for the alumina particles to disperse in the gaps in the skeletal structure formed in the resin composition by the silicon nitride particles, and can further improve the thermal conductivity of the resin composition. Furthermore, adjusting the average aspect ratio of the alumina particles makes it easier to produce a resin composition that satisfies formula (1).

[0084] <Measurement of the β-phase ratio of silicon nitride particles> The diffraction pattern of the silicon nitride particles was obtained using a powder X-ray diffractometer (manufactured by Rigaku Denki). The measurement conditions were as follows: X-ray source: CuKα radiation; X-ray output: 45 kV, 200 mA; graphite monochromator; diffraction angle (2θ): step scan in 0.02° increments over the range of 2 to 90°; scanning speed: 21.7 deg / min.

[0085] When the silicon nitride particles contained components other than silicon nitride, the peaks of those components were compared with the corresponding peaks of standard samples of those components to determine the proportions of those components. The obtained powder X-ray diffraction patterns confirmed that all silicon nitride particles were composed exclusively of α-type silicon nitride and β-type silicon nitride. The proportion of β-type silicon nitride in the sample (β-conversion ratio) was then calculated using the Gazzara & Messier method. The calculation results are shown in Table 4.

[0086] <Measurement of specific surface area of ​​silicon nitride particles> The specific surface area of ​​powder (solid) by gas adsorption was measured in accordance with JIS Z 8830:2013, using krypton as the adsorption gas. In the measurement, 1 g of silicon nitride particles was placed in a sample tube, and an adsorption / desorption isotherm was obtained. The specific surface area (m ２ The results are shown in Table 4.

[0087] <Maximum particle filling rate FR in resin composition ｍａｘ Identification of Particles> Particles (silicon nitride particles, first alumina particles, second alumina particles) were blended into a silicone resin (base: DOWSIL (trademark) CY 52-276 A manufactured by Dow Chemical; curing agent: DOWSIL (trademark) CY 52-276 B manufactured by Dow Chemical). The blending ratio of each particle is shown in Table 1. Note that, in Sample No. A7, no second alumina particles were blended. For Samples No. A1 to No. A5, the total content of all particles was increased in 1 vol% increments from 75 vol% to 85 vol%, and multiple resin compositions were prepared. For Samples No. A6 and No. A7, the total content of all particles was increased in 1 vol% increments from 60 vol% to 75 vol%, and multiple resin compositions were prepared.

[0088]

[0089] A 1 mm thick aluminum plate with a 1 cm x 10 cm rectangular hole was prepared as a mold frame. A transparent PET film (backside film) coated with a release agent was attached to the back side of the mold frame so as to cover the rectangular hole, with the release agent-coated surface facing the mold frame. 3 g of liquid resin composition (gray) was poured into the rectangular hole in the mold frame, and then a transparent PET film (frontside film) coated with a release agent was attached on top of it, with the release agent-coated surface facing the mold frame and resin composition. Furthermore, light pressure was applied from above the frontside film with a metal roller to fit the resin composition into the rectangular hole in the mold frame and form it into a 1 cm x 10 cm strip. Another aluminum plate was then placed on top of it, heated at 120 °C for 12 hours, and allowed to stand to harden the resin. After curing was complete, the aluminum plate was allowed to cool, and when the temperature had dropped to about room temperature, the two PET films were peeled off from both sides of the cured resin composition to obtain a sheet-shaped resin composition for measurement.

[0090] The thermal diffusivity, specific heat, and density of the obtained sheet-shaped resin composition were measured to determine the thermal conductivity. A measurement sample piece measuring 10 mm long x 10 mm wide x 0.5 mm thick was prepared from the above-mentioned sheet-shaped resin composition, and the thermal diffusivity was measured at room temperature using temperature wave thermal analysis (TWA). An iPhase Mobile manufactured by iPhase Corporation was used as the measuring device. The thermal diffusivity was measured at three arbitrary points on the measurement sample piece, and the average of the measurement results was used as the thermal diffusivity of the resin composition.

[0091] The specific heat was calculated from the compounding ratio of the resin and each particle. The specific heat values ​​of the resin and each particle are shown in Table 2.

[0092]

[0093] The density was measured using an electronic hydrometer MDS-300 (Alpha Mirage Co., Ltd.). The density was calculated using the Archimedes method (solid density measurement) based on the following formula. The specific gravity was also calculated from the density: ρ = A ÷ (A - B) × (ρ ０ -ρ Ｌ ) + ρ Ｌwhere, ρ: density of the sheet-shaped resin composition, A: weight of the sheet-shaped resin composition measured in the air, and B: weight of the sheet-shaped resin composition measured in the displacement liquid (water). ０ : Density of the replacement liquid (water) (1.0000 g / cm ３ ) ρ Ｌ : air density (0.0012 g / cm ３ )

[0094] The measured results of thermal diffusivity, specific heat, and density were substituted into the following formula to calculate the thermal conductivity: Thermal conductivity = Thermal diffusivity × Specific heat × Density For Samples A1 to A7, the total content of all particles (silicon nitride particles, first alumina particles, and second alumina particles) contained in the resin composition that gave the highest thermal conductivity of the sheet-shaped resin composition was defined as the maximum filling rate FR. ｍａｘ It was decided.

[0095] <Measurement of Line Segment Ratio and Number of Line Segments in Resin Composition> Each particle (silicon nitride particles, first alumina particles, second alumina particles) was blended into a silicone resin (main agent: DOWSIL™ CY 52-276 A manufactured by Dow Chemical; curing agent: DOWSIL™ CY 52-276 B manufactured by Dow Chemical). The blending ratio of each particle is shown in Table 3. Note that in Sample No. 7, no second alumina particles were blended. The blending ratio of the silicone resin to all particles was adjusted so that the total content of all particles was the "maximum filling rate" in Table 3. The silicone resin and each particle blended at the predetermined blending ratio were stirred and mixed using a foam mixer (manufactured by Thinky Corporation) to obtain a liquid resin composition.

[0096] A 1 mm thick aluminum plate with a 1 cm x 10 cm rectangular hole was prepared as a mold frame. A transparent PET film (backside film) coated with a release agent was attached to the back side of the mold frame so as to cover the rectangular hole, with the release agent-coated surface facing the mold frame. 3 g of liquid resin composition (gray) was poured into the rectangular hole in the mold frame, and then a transparent PET film (frontside film) coated with a release agent was attached on top of it, with the release agent-coated surface facing the mold frame and resin composition. Furthermore, light pressure was applied from above the frontside film with a metal roller to fit the resin composition into the rectangular hole in the mold frame and form it into a 1 cm x 10 cm strip. Another aluminum plate was then placed on top of it, heated at 120 °C for 12 hours, and allowed to stand to harden the resin. After curing was complete, the aluminum plate was allowed to cool, and when the temperature had dropped to about room temperature, the two PET films were peeled off from both sides of the cured resin composition to obtain a sheet-shaped resin composition for measurement.

[0097] A cross section of the sheet-shaped resin composition in the thickness direction was exposed, and an SEM image of the cross section was taken. The SEM device and measurement conditions were the same as those in "Measurement of the aspect ratio of each particle," except that the magnification was 250 times.

[0098] A straight line LN with a length of 500 μm was drawn on the cross-sectional SEM image in the thickness direction of the sheet-shaped resin composition (direction T in FIG. 1 ). Furthermore, irregular particles 20 (line-measured particles) with an overlap length Lov of 8 μm or more with the line LN were identified, and the "line segments" where the line LN and the line-measured particles overlapped were further identified. For example, FIG. 1 shows a portion of a cross-sectional SEM image of a sheet-shaped resin composition prepared under the conditions of Sample No. 3, illustrating the line LN (shown as a white dashed line) and the line segments (shown as black solid lines). The length of each line segment (X21 to X29 in FIG. 1 ) and the number of line segments were then measured.

[0099] Furthermore, two more straight lines LN, each 500 μm long, were drawn at 100 μm intervals parallel to the straight line LN in FIG. 1 at different positions on the cross-sectional SEM image, and the same operation was carried out for each of the straight lines LN.

[0100] The total length of the three straight lines LN was 1,500 μm. The lengths of each of the line segments determined for the three straight lines LN were all added together to determine the total length X2 of the line segments. The ratio of the total length X2 of the line segments to the total length X1 (= 1,500 μm) of the line segments (line segment ratio) was then calculated and is shown in Table 4. The number of line segments determined from the three straight lines LN (corresponding to the sum of the number of line segments determined for each straight line LN) is also shown in Table 4.

[0101] A large number of line segments correlates with a large number of interfaces where silicon nitride particles come into contact with resin or alumina particles. Having many interfaces along the heat conduction path can lead to reduced thermal conductivity. On the other hand, a high line segment ratio correlates with the presence of many relatively large silicon nitride particles along the heat conduction path (i.e., high thermal conductivity).

[0102] <Measurement of Thermal Conductivity of Resin Composition> Each particle (silicon nitride particles, first alumina particles, second alumina particles) was blended at a predetermined blending ratio with a silicone resin (main agent: DOWSIL (trademark) CY 52-276 A manufactured by Dow Chemical; curing agent: DOWSIL (trademark) CY 52-276 B manufactured by Dow Chemical). The blending ratio of each particle is shown in Table 3. Note that in Sample No. 7, no second alumina particles were blended. The blending ratio of the silicone resin to all particles was adjusted to two types: "Blending Ratio 1," which was adjusted so that the total content of all particles was the "maximum filling rate" in Table 3, and "Blending Ratio 2," which was adjusted so that the total content of all particles was "maximum filling rate - 5 (vol %)." The silicone resin and each particle blended at the predetermined blending ratio were stirred and mixed using a WAWATORI MIXER (manufactured by THINKY CORPORATION) to obtain a liquid resin composition.

[0103] Using the same procedure as in "Measurement of the line segment ratio and number of line segments of a resin composition," sheet-shaped resin compositions for measurement were prepared from each of the liquid resin compositions of blending ratios 1 and 2.

[0104] The obtained sheet-shaped resin composition was subjected to the "maximum particle filling rate FR in the resin composition" ｍａｘ The thermal diffusivity, specific heat, and density were measured and the thermal conductivity was calculated using the same procedures as those described in "Identification of the properties of the material."

[0105] Table 5 shows the thermal conductivity A of the sheet-shaped resin composition prepared at blend ratio 1, the thermal conductivity B of the sheet-shaped resin composition prepared at blend ratio 2, and the difference therebetween (A−B).

[0106] A resin composition having a thermal conductivity A of 3.0 or more was rated as passing, and a resin composition having a thermal conductivity A of less than 3.0 was rated as failing.

[0107] A large difference in thermal conductivity (A-B) means that the thermal conductivity increased significantly when the particles were filled at the maximum filling rate. In other words, when the particles were filled at the maximum filling rate, the number of contact points / contact surfaces between the particles increased significantly, resulting in an increased thermal conduction path, compared to when the particles were filled at a rate slightly less than the maximum filling rate. Because the particles are in contact with each other, they are less likely to move within the resin composition, and even when an external force is applied, the particles are less likely to move from their original positions, ensuring stable contact between the particles. Therefore, when the resin composition is used as a heat dissipation material filling the gap between an electronic component and a heat sink, it can be said that it exhibits a stable, high thermal conductivity regardless of the presence or absence of external force from the electronic component and / or the heat sink.

[0108]

[0109]

[0110]

[0111] The resin compositions of samples 1 to 5 had a linear segment ratio of 30.0% or more, resulting in a high thermal conductivity A. On the other hand, the resin compositions of samples 6 and 7 had a linear segment ratio of less than 30.0%, resulting in a low thermal conductivity A. In these resin compositions, the silicon nitride had a D50 of 4.0 μm, but the particle size distribution contained silicon nitride with a particle diameter exceeding 8.0 μm. Therefore, when the linear segment ratio of the resin composition was measured, silicon nitride with an overlap length Lov of 8 μm or more was present, and the linear segment ratio was not 0%.

[0112] This application claims priority from Japanese Patent Application No. 2024-024838, filed February 21, 2024. Japanese Patent Application No. 2024-024838 is incorporated herein by reference.

[0113] 10 Resin composition 20 Irregular particle 30 Spherical particle 40 Resin LN Straight line X1 Total length of straight line LN X2 Total length of line segments X21 to X29 Length of each line segment

Claims

1. A resin composition containing amorphous particles with an aspect ratio of less than 0.90, spherical particles with an aspect ratio of 0.90 or more, and a resin, wherein three parallel lines, each 500 μm long, are drawn on an SEM image of a cross section of the resin composition taken at 250x magnification, and for the amorphous particles that overlap with at least one of the lines and whose overlapping length is 8 μm or more, the total length X2, calculated by adding up all of the overlapping lengths of 8 μm or more, exceeds 30.0% of the total length X1 of the lines.

2. The resin composition according to claim 1, wherein the irregular particles are silicon nitride particles and the spherical particles are alumina particles.

3. The specific surface area of ​​the silicon nitride particles is 2.66 m ２ The resin composition according to claim 2, wherein the viscosity is less than 1 / g.

4. The resin composition according to claim 2, wherein the silicon nitride particles have a particle diameter D50 of 50% from the finest particle side in the volume-based cumulative particle size distribution of more than 15 μm.

5. A resin composition according to claim 2, wherein the particle diameter D50 of the alumina particles at 50% cumulative size from the fine side of the volume-based cumulative particle size distribution is 70% or less of the particle diameter D50 of the silicon nitride particles at 50% cumulative size from the fine side of the volume-based cumulative particle size distribution.

6. The resin composition according to claim 2, wherein the silicon nitride particles have a beta-phase ratio of 65% or more.

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