Heat dissipation material and electronic device

Abstract

To provide a heat dissipation material superior in heat dissipation and low dielectric.SOLUTION: In insulating heat dissipation material using spherical filler, at least one of at least 20% or more of fillers with a particle size of 200 μm or more and 1000 μm or less, and 20% or more of fillers with a particle size of 1 nm or more and 10 μm or less for the total amount of filament.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a heat dissipation material and an electronic device using the heat dissipation material.

Background Art

[0002] As a technology related to a heat dissipation material for electronic components mounted on an electronic device, there is the technology described in Patent Document 1 below. Patent Document 1 describes "spherical AlN sintered powder... and a resin-based heat dissipation material characterized by containing a synthetic resin, which has a spherical shape, an average particle diameter of 10 to 500 μm, and a porosity of 0.3% or less", and also "due to the lower porosity of the spherical AlN sintered powder than that of conventional AlN powder, the amount of air remaining in the pore portion during dispersion is reduced, and thereby, higher thermal conductivity can be exhibited."

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, with the high functionality of electronic devices, for the heat dissipation material for electronic components mounted on the electronic device, in addition to heat dissipation performance, low dielectric constant is desired for the purpose of reducing noise of the electronic components. In response to such a demand, although the resin-based heat dissipation material described in Patent Document 1 is expected to improve heat dissipation performance due to its high thermal conductivity, there is no knowledge about reducing the dielectric constant.

[0005] Therefore, an object of the present invention is to provide a heat dissipation material excellent in heat dissipation and low dielectric properties, and an electronic device capable of realizing high functionality by using this heat dissipation material as a heat dissipation material for mounted electronic components.

Means for Solving the Problems

[0006] To solve the above-described problems, the present invention is configured as follows. This application includes a plurality of means for solving the above problems. For example, in an insulating heat dissipation material using spherical fillers, the ratio of fillers having a particle size of 200 μm or more and 1000 μm or less is 20% or more with respect to the total amount of the fillers, and / or the ratio of fillers having a particle size of 1 nm or more and 10 μm or less is 20% or more.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a heat dissipation material excellent in heat dissipation and low dielectric properties, and an electronic device capable of realizing high functionality by using this heat dissipation material as a heat dissipation material for mounted electronic components.

[0008] Regarding problems, configurations, and effects other than those described above, they will be clarified by the description of the following embodiments and examples.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the heat dissipation material and the electronic device of the present invention will be described in detail with reference to the drawings. In the following, first, an embodiment in which an in-vehicle electronic control device is exemplified as an example of the electronic device will be described with reference to the attached drawings, and then the configuration of the heat dissipation material used for this electronic device will be described. In each figure, the same reference numerals are given to common members.

[0011] ≪In-vehicle electronic control device (electronic device)≫ FIG. 1 is an external perspective view of the in-vehicle electronic control device 1 according to the embodiment. Further, FIG. 2 is an exploded perspective view of the in-vehicle electronic control device 1 according to the embodiment, and FIG. 3 is a perspective view of the exploded perspective view shown in FIG. 2 as viewed from the opposite side. Further, FIG. 4 is a partial cross-sectional view of the in-vehicle electronic control device 1 according to the embodiment.

[0012] The in-vehicle electronic control device 1 shown in FIGS. 1, 2, 3, and 4 is installed in the interior of an automobile and has an electronic circuit for controlling the automobile. As shown in FIGS. 2 to 4, the in-vehicle electronic control device 1 includes a heat-generating electronic component 2 such as a semiconductor element, a connector 3, a circuit board 4, and a base 5 and a cover 6 that constitute a housing. The electronic component 2 and the circuit board 4 are mounted on the circuit board 4 and housed in the base 5 and the cover 6.

[0013] Among these, the electronic component 2 is for in-vehicle use here, and is, for example, a semiconductor element that generates heat by high-speed operation, such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an SoC (System on a chip), a DDR (Double Data Rate) memory, etc. Such an electronic component 2 is electrically connected (mounted) to one or both sides of the circuit board 4 using solder or the like. As a specific example, the electronic component 2 in the embodiment is electrically connected to one surface of the circuit board 4 facing the cover 6 via an interposer 19 and solder bumps 18 (shown only in FIG. 4). In the in-vehicle electronic control device 1 of the present embodiment, the electronic component 2 may be mounted on at least one of both sides of the circuit board 4.

[0014] The connector 3 (illustrated only in FIGS. 2 and 3) connects the electronic component 2 mounted on the circuit board 4 to an external device. The connector 3 has a plurality of pin terminals. The connector 3 is mounted on the circuit board 4 by connecting the pin terminals to the circuit board 4 by press-fitting, soldering, or the like. The connector 3 is electrically connected to the circuit board 4 via the pin terminals.

[0015] The circuit board 4 is, for example, a general laminated wiring board made of a thermosetting resin, glass cloth, and a metal wiring on which a circuit pattern is formed, a wiring board made of ceramics and a metal wiring, a wiring board made of a flexible board such as polyimide and a metal wiring, or the like. Threaded holes are formed at the four corners of the circuit board 4. Then, the circuit board 4 is fixed to the base 5 and the cover 6 by fixing screws 8. The detailed configuration of the portion of the circuit board 4 where the electronic component 2 is mounted will be described later.

[0016] The base 5 is formed in a substantially flat plate shape. Threaded holes are formed at the four corners of the end portion of the base 5. The base 5 is disposed in a state of sandwiching the circuit board 4 between the cover 6 and is fixed integrally with the circuit board 4 and the cover 6 by fixing screws 8.

[0017] The cover 6 is a hollow box shape with one side open, and the bottom surface of the box shape is formed in a substantially rectangular shape. On the bottom surface of the cover 6 facing the opening surface, a plurality of convex portions, i.e., heat dissipation pedestals 10, are formed. The convex heat dissipation pedestals 10 protrude from the cover 6 toward the circuit board 4. The heat dissipation pedestals 10 are provided at positions facing the electronic components 2 mounted on the circuit board 4 when the circuit board 4 is placed in the hollow of the cover 6. Also, a plurality of electronic components 2 may face one heat dissipation pedestal 10. Further, threaded holes are formed at the four corners of the end portion of the cover 6 where the opening is formed. The cover 6 houses the circuit board 4 in the hollow and is installed so as to sandwich the circuit board 4 between the base 5. Then, by fastening the fixing screws 8 to the threaded holes of the base 5, the cover 6, and the circuit board 4, the circuit board 4, the base 5, and the cover 6 are fixed integrally.

[0018] Note that the base 5 and the cover 6 are formed, for example, by casting, pressing, cutting, injection molding, or the like. The materials constituting the base 5 and the cover 6 are preferably, for example, an alloy mainly composed of aluminum if made of metal, or may be formed of a high thermal conductivity resin in which a resin and a filler are mixed. The thermal conductivity of the high thermal conductivity resin is preferably 2 to 30 W / (m·K). Further, the base 5 and the cover 6 are not limited to composite materials, and the base 5 and the cover 6 may be formed of only a resin or a metal material.

[0019] Also, as the resin for forming the base 5 and the cover 6, it is preferable to use polybutylene terephthalate resin (PBT), polyphenylene sulfide resin (PPS), polyamide resin (PA6), or the like. As the filler, it is preferable to use any one of glass fiber, carbon fiber, alumina (Al2O3), or the like. And as the metal for forming the base 5 and the cover 6, in addition to aluminum (Al) and an alloy mainly composed of aluminum, magnesium or steel may also be used.

[0020] Next, with reference to FIG. 4, the detailed configuration of the location where the electronic component 2 in the in-vehicle electronic control device 1 is mounted will be described.

[0021] FIG. 4 is a partial cross-sectional view of the in-vehicle electronic control device 1 according to the embodiment, and is a cross-sectional view showing the circuit board 4 and the heat dissipation pedestal 10.

[0022] As shown in Fig. 4, a heat dissipation material 15 is sandwiched between an electronic component 2 and a cover 6 which is a housing, at the location on the circuit board 4 where the electronic component 2 is mounted. More specifically, the heat dissipation material 15 is filled in a state of covering the electronic component 2, between an interposer 19 for mounting the electronic component 2 on the circuit board 4 and a heat dissipation pedestal 10 provided on the cover 6. In this state, it is preferable that the heat dissipation material 15 is in direct contact with the heat dissipation pedestal 10 and the electronic component 2. Thereby, the heat dissipation material 15 thermally connects the heat dissipation pedestal 10, the electronic component 2, and further the circuit board 4 via the interposer 19 and solder bumps 18, and also adheres the heat dissipation pedestal 10 and the circuit board 4. Then, the heat generated by the electronic component 2 is dissipated to the outside via the interposer 19, the solder bumps 18, and the circuit board 4 by this heat dissipation material 15. Or, the heat generated by the electronic component 2 is dissipated to the outside from the heat dissipation pedestal 10 through the cover 6 by the heat dissipation material 15.

[0023] In addition, if the electronic component 2 is mounted on the side of the circuit board 4 facing the base 5, the heat dissipation pedestal 10 is formed on the base 5. That is, a heat dissipation pedestal 10 on which the heat dissipation material 15 is applied is formed on the facing surface of the housing having the base 5 and the cover 6 with the electronic component 2.

[0024] The heat dissipation material 15 has functions as a resin material adhesive and a grease (lubricant), and has a structure in which a sheet-shaped thermosetting resin is used as a base material and a filler with high thermal conductivity is dispersed in the resin which is the base material. The configuration of the heat dissipation material 15 will be described below.

[0025] ≪Heat Dissipation Material 15≫ Fig. 5 is a schematic diagram for explaining the configuration of the heat dissipation material 15 according to the embodiment. As shown in Fig. 5, the heat dissipation material 15 is obtained by mixing and dispersing a filler 151 in a resin 150, and is a mixture of the resin 150 and the filler 151.

[0026] Resin 150 is preferably a thermosetting resin. Thus, in the assembly of the electronic device 1 shown in FIG. 4, with the electronic components 2 and the heat dissipation material sandwiched between the circuit board 4 and the cover 6, the resin 150 can be activated by heating without depending on light irradiation. As an example of such a resin 150, a silicone resin is exemplified. The silicone resin is a synthetic polymer having a main skeleton composed of siloxane bonds (Si-O-Si). The silicone resin exhibits rubber-like properties and causes less stress on the heat dissipation device, so it is often used as the resin 150 for the base material of the heat dissipation material 15.

[0027] Filler 151 is made of, for example, aluminum nitride. Aluminum nitride is a solid compound composed of nitrogen and aluminum and has a shape such as a sphere close to a perfect sphere. The filler 151 made of aluminum nitride is excellent in thermal conductivity, heat resistance, corrosion resistance, electrical insulation, lubricity and mold release properties, and can be mixed with various resins. Since the spherical filler 151 has isotropic thermal conductivity, the heat conduction paths in the heat dissipation material 15 formed by the spherical filler 151 spread isotropically. Therefore, the heat dissipation material 15 in which the spherical filler 151 is dispersed in the resin 150 is superior in heat dissipation compared to a heat dissipation material in which a filler having anisotropic thermal conductivity due to its fibrous shape like carbon fiber is dispersed in the resin.

[0028] Also, the filler 151 made of aluminum nitride has a thermal conductivity of nearly 200 W / mK, and high thermal conductivity can be expected. Also, aluminum nitride has a certain degree of rigidity. For this reason, even during the kneading of the resin 150 and the filler 151, particularly large-sized fillers are likely to retain their original particle sizes, and in the heat dissipation material 15, it is possible to realize an ideal filling structure of the filler 151 as described hereinafter.

[0029] Note that as long as the thermal conductivity of the filler 151 is 1 to 200 W / mK, it is not limited to being made of aluminum nitride, and it may be composed of aluminum oxide, zinc oxide, magnesium oxide, or silicon dioxide. The filler 151 made of these materials also becomes spherical.

[0030] <Content of filler 151> The content of filler 151 in the heat dissipation material 15 is defined as the volume fraction of filler 151 when the volume of the heat dissipation material 15 is 100 vol%. Such a content of filler 151 is preferably 40 vol% or more, more preferably 30 vol% or more, from the viewpoint of ensuring the high thermal conductivity and low dielectric constant of the heat dissipation material 15. Furthermore, it is preferably 20 vol% or more. The upper limit value of the content of filler 151 is set within a range where it is possible to form the heat dissipation material 15 by mixing and integrating with the resin 150 as the base material, and is approximately 95 vol%. In such a heat dissipation material 15, the space between filler 151 and filler 151 is filled with resin 150 to an extent that filler 151 can be integrated as the heat dissipation material 15.

[0031] In the above content range of filler 151, even when the content of filler 151 is lowered for the purpose of reducing the dielectric constant of the heat dissipation material 15, high thermal conductivity can be achieved by optimizing the diameter of filler 151. Also, the lower the content of filler 151, the lower the dielectric constant of the entire heat dissipation material 15, and it becomes possible to reduce the noise of electronic components mounted on an electronic device using the heat dissipation material 15.

[0032] The method for calculating the content of filler 151 in the heat dissipation material 15 is not particularly limited, and for example, it can be examined by decomposing the heat dissipation material 15 which is a mixture of filler 151 and resin 150. As an example, in the case of a mixture (heat dissipation material 15) using a silicone resin, a certain volume of the mixture is exposed to n - hexane to dissolve the resin 150, and the component of filler 151 is separated by filtering the n - hexane solution in which the resin 150 has dissolved. The volume of the separated filler 151 is calculated based on the mass of filler 151 and the density of the material (for example, aluminum nitride) constituting filler 151, and the content of filler 151 in the mixture can be calculated from the calculated volume of filler 151 and the volume of the mixture.

[0033] <Particle size of filler 151> The diameter of the particles of filler 151 to be mixed into resin 150 (hereinafter also referred to as particle size) is the length of the particles of filler 151 measured according to rules determined by the shape of the particles of filler 151. When the shape of the particles of filler 151 is spherical, the diameter of the particles of filler 151 is defined as the particle size of the particles of filler 151. When the shape of the particles of filler 151 is irregular, the major axis diameter of the particles of filler 151 is defined as the particle size of filler 151.

[0034] The determination of the major axis of the particles of filler 151 is, for example, based on observations made with a device capable of directly observing the shape, such as a scanning electron microscope, and reflects the results of quantitatively measuring the shape and its length. Also, the length of the major axis of the particles of filler 151 at that time is measured using the length measurement function of a scanning electron microscope in addition to a particle size distribution measuring device.

[0035] <Particle size distribution of filler 151> As a result of the investigations shown in the following examples, it was confirmed that if the particle size distribution of filler 151 in heat dissipation material 15 is as follows, high thermal conductivity of heat dissipation material 15 can be achieved. Here, filler 151 with a particle size of 200 μm or more (denoted as 200 μm~) is referred to as large-diameter filler 151L. The upper limit value of the particle size of large-diameter filler 151L is the upper limit value in the manufacture of filler 151, and at present it is approximately 200 μm. Also, filler 151 with a particle size of 1 nm or more and 10 μm or less (denoted as 1 nm~10 μm) is referred to as small-diameter filler 151S. Filler 151 with a particle size exceeding 10 μm and less than 200 μm (denoted as 10 μm~200 μm), which is intermediate between these, is referred to as medium-diameter filler 151M.

[0036] For heat dissipation material 15, the proportion of large-diameter filler 151L is 20% or more, or the proportion of small-diameter filler 151S is 20% or more, or both, with respect to the total amount of filler 151. Note that this proportion is a volume ratio, and the same applies hereinafter. Also, when mixing filler 151 into resin 150, it is preferable that the filler 151 component includes large-diameter filler 151L with a particle size of 200 μm~ and small-diameter filler 151S with a particle size of 1 nm~10 μm.

[0037] The filler 151 dispersed in the resin 150 preferably has a proportion of large-diameter filler 151L of 20% or more, or a proportion of small-diameter filler 151S of 20% or more. Here, when the proportion of the large-diameter filler 151L is 20% or more, less than 80% of the filler 151 other than the large-diameter filler 151L is at least one of the small-diameter filler 151S and the medium-diameter filler 151M. Note that the upper limit value of the proportion of the large-diameter filler 151L with respect to the total amount of the filler 151 is the upper limit value in the production of the filler 151, similar to the upper limit value of the particle diameter of the filler 151, and is approximately 30% at present. Further, when the proportion of the small-diameter filler 151S is 20% or more, less than 80% of the filler 151 other than the small-diameter filler 151S is at least one of the large-diameter filler 151L and the medium-diameter filler 151M, but the filler 151 contained in the heat dissipation material 15 may be only the small-diameter filler 151S.

[0038] Moreover, it is more preferable that the particle size distribution of the filler 151 dispersed in the resin 150 has a proportion of the large-diameter filler 151L of 20% or more and a proportion of the small-diameter filler 151S of 20% or more. In this case, less than 60% of the filler 151 other than the large-diameter filler 151L and the small-diameter filler 151S with respect to the total amount of the filler 151 is the medium-diameter filler 151M, but the filler 151 contained in the heat dissipation material 15 may be only the large-diameter filler 151L and the small-diameter filler 151S.

[0039] The method for measuring the particle size distribution of the filler 151 dispersed in the resin 150 is not particularly limited, and for example, it can be examined by a laser diffraction / scattering type particle size distribution measuring device. The laser diffraction method is a method of irradiating a sample with laser light and obtaining the particle size distribution of the sample from the intensity pattern of the diffracted / scattered light.

[0040] The porosity between the fillers 151 in the heat dissipation material 15 is defined as the volume of the gaps between the fillers 151 in the unit volume of the space containing the fillers 151. The gaps between the fillers 151 in the heat dissipation material 15 are parts filled with the resin 150 or space parts.

[0041] For example, a mixture (heat dissipation material 15) in which filler 151 is dispersed in resin 150 is exposed to a solvent such as hexane to dissolve resin 150, and then the total ratio of the gaps present in the aggregated filler 151 is the porosity.

[0042] The lower the porosity, the closer the filling state of filler 151 in heat dissipation material 15, which is a mixture of resin 150 and filler 151, approaches the closest packing, the smaller the gaps between fillers 151, and a heat conduction path is formed, enabling high thermal conductivity. From the results of the following study, it can be seen that the porosity is preferably 22% or less, and more preferably 7% or less.

[0043] FIG. 6 is a graph showing the critical significance of the filler ratio and porosity. This FIG. 6 is a graph with the ratio of small-diameter filler 151S on the horizontal axis and the porosity between fillers 151 in heat dissipation material 15 on the vertical axis when the ratio of large-diameter filler 151L is fixed at 20% with respect to the total amount of filler 151 contained in heat dissipation material 15. Note that other than 20% large-diameter filler 151L and small-diameter filler 151S at each ratio, it is medium-diameter filler 151M. The porosity is the result of inputting data on the particle size distribution of filler 151 into porosity simulation software and calculating. As shown in this graph, the porosity is 22% when the large-diameter filler 151L is 20% and the small-diameter filler 151S is 0%, and it was confirmed that the porosity decreases as the ratio of the small-diameter filler 151S increases. Thus, it can be seen that even small-diameter filler 151S with a particle size of 1 nm to 10 μm contributes to the improvement of the thermal conductivity due to the decrease in porosity by being contained in heat dissipation material 15. And when the ratio of the large-diameter filler 151L is 20%, while the ratio of the small-diameter filler 151S increases to 20%, the porosity significantly decreases from 22% to 7%, and it can be seen that by setting the ratio of the small-diameter filler 151S to 20% or more, it is possible to reduce the porosity to 7% or less.

[0044] FIG. 7 is a graph showing the ratio of fillers of each diameter and the thermal conductivity in the heat dissipation material, and shows an example of the particle size distribution of filler 151 made of aluminum nitride and the measurement results of the thermal conductivity.

[0045] In Fig. 7, in the particle size distribution range [A1] where the proportion of the small-diameter filler 151S is less than 20% and the proportion of the large-diameter filler 151L is less than 20%, the thermal conductivity was 1 to 3 W / (m·K).

[0046] Also, in the particle size distribution range [A2] where the proportion of the small-diameter filler 151S is 20% or more or the proportion of the large-diameter filler 151L is 20% or more, the thermal conductivity was 3 to 8 W / (m·K).

[0047] Also, in the range [A3] where the proportion of the small-diameter filler 151S is 20% or more and the proportion of the large-diameter filler is 20% or more, the thermal conductivity was 8 to 10 W / (m·K).

[0048] From the experimental results shown in Fig. 7, it can be seen that from the viewpoint of thermal conductivity, the particle size distribution of the filler 151 made of aluminum nitride preferably has a proportion of the small-diameter filler 151S of 20% or more or a proportion of the large-diameter filler 151L of 20% or more, and it is more preferable that both are satisfied.

Example

[0049] Next, with reference to Fig. 5, each example of the heat dissipation material used in the in-vehicle electronic control device having the configuration described in the embodiment will be described together with the comparative examples. In each example and comparative example, a mixture serving as the heat dissipation material 15 was created using the filler 151 made of aluminum nitride and the resin 150 made of silicone.

[0050] (Example 1) Example 1 of the present invention will be described. Table 1 below shows the composition of the mixture that becomes the heat dissipation material 15 created in Example 1.

[0051] In Example 1, the content of filler 151 was adjusted to 70 vol%, and filler 151 and resin 150 were mixed. The particle size distribution of filler 151 was adjusted such that the proportion of small-diameter filler 151S with a particle size of 1 nm to 10 μm was 60%, the proportion of medium-diameter filler 151M with a particle size of 10 to 200 μm was 10%, and the proportion of large-diameter filler 151L with a particle size of 200 μm to 1000 μm was 30%.

[0052] The material mixed as described above was heated at 120°C for 90 minutes to cure it. Thus, a mixture within the range of the content and particle size distribution of filler 151 shown in the embodiment was created as the mixture of Example 1.

[0053] (Comparative Example 1) Next, Comparative Example 1 of the present invention will be described. Table 1 below shows the composition of the mixture created in Comparative Example 1.

[0054] In Comparative Example 1, the content of filler 151 was adjusted to 80 vol%, and filler 151 and resin 150 were mixed. The particle size distribution of filler 151 was adjusted such that the proportion of medium-diameter filler 151M was 100%.

[0055] The material mixed as described above was heated and cured under the same heating conditions as in Example 1 to create the mixture of Comparative Example 1.

[0056] (Comparative Example 2) Next, Comparative Example 2 of the present invention will be described. Table 1 below shows the composition of the mixture created in Comparative Example 2.

[0057] In Comparative Example 2, the content of filler 151 was adjusted to 94 vol%, and filler 151 and resin 150 were mixed. The particle size distribution of filler 151 was adjusted such that 100% of the particle size was 10 μm to 500 μm as described in Patent Document 1.

[0058] The material mixed as described above was heated and cured under the same heating conditions as in Example 1 to create the mixture of Comparative Example 2.

[0059]

Table 1

[0060] (Evaluation Results of Example 1 and Comparative Examples 1 and 2) Each mixture prepared in Example 1 and Comparative Examples 1 and 2 was processed to a thickness of 1 mm, and the thermal diffusivity was measured using a thermal diffusivity measuring device. For the measured thermal diffusivity, the density measured by the Archimedes method was multiplied by the specific heat measured by DSC (differential scanning calorimetry), a thermal analysis method, to obtain the thermal conductivity of each mixture. Also, the dielectric constant and the noise level of each mixture were measured. These results are shown in Table 1 above. The noise level is shown for the 1.6 GHz band as a representative value.

[0061] As shown in Table 1, the mixture prepared in Example 1 has a lower content of Filler 151 than the mixtures of Comparative Examples 1 and 2. However, it can be seen that the thermal conductivity of the mixture prepared in Example 1 is higher than that of the mixture of Comparative Example 1 and is also as high as that of the mixture of Comparative Example 2. Furthermore, the dielectric constant of the mixture prepared in Example 1 is Dielectric constant about the same as that of the mixture of Comparative Example 1 and lower than that of the mixture of Comparative Example 2.

[0062] From the above results, even when the content of Filler 151 is set low for the purpose of reducing the dielectric constant, it is possible to improve the thermal conductivity by optimizing the particle size distribution of Filler 151, and it is confirmed that it is possible to obtain a heat dissipation material with high thermal conductivity and low dielectric constant. Thereby, by mounting an electronic component using a heat dissipation material with an adjusted particle size distribution, it is possible to ensure the heat dissipation performance of the electronic component and keep the noise level low, and it is confirmed that an in-vehicle electronic control device with enhanced functionality can be obtained.

[0063] (Examples 2 to 7 and Comparative Example 3) Examples 2 to 7 of the present invention and Comparative Example 3 will be described. Table 2 below shows the composition of the mixture used as the heat dissipation material prepared in Examples 2 to 7 and Comparative Example 3. In Examples 2 to 7 and Comparative Example 3, the content of Filler 151 was adjusted so that the dielectric constant of each mixture was about 7 to 7.5, and Filler 151 and Resin 150 were mixed. The particle size distribution of Filler 151 in Examples 2 to 7 and Comparative Example 3 is as shown in Table 2. Also, in Examples 2 to 7 and Comparative Example 3, each of the mixed materials was heated and cured under the same conditions as the heating conditions of Example 1 to prepare each mixture.

[0064]

Table 2

[0065] (Evaluation Results of Examples 2 to 7 and Comparative Example 3) For each of the mixtures prepared in Examples 2 to 7 and Comparative Example 3, the thermal conductivity was determined in the same procedure as in Example 1 and Comparative Examples 1 and 2. The results are shown in conjunction with Table 2 above.

[0066] From Table 2, it can be seen that the thermal conductivity of the mixtures of Examples 2, 5 to 7 in which the proportion of the small-diameter Filler 151S is 20% or more is higher than that of the mixture of Comparative Example 3 in which the medium-diameter Filler 151M is 100%. Also, it can be seen that the thermal conductivity of the mixtures of Examples 3 and 4 in which the proportion of the large-diameter Filler 151L is 20% or more is higher than that of the mixture of Comparative Example 3 in which the medium-diameter Filler 151M is 100%.

[0067] From the above, it was confirmed that the mixtures of Examples 2 to 7 within the scope of the present invention in which the proportion of the small-diameter Filler 151S is 20% or more, or the proportion of the large-diameter Filler 151L is 20% or more, are heat dissipation materials with a high thermal conductivity while having a dielectric constant as low as that of the mixture of Comparative Example 3.

[0068] (Examples 8 to 12) Examples 8 to 12 of the present invention will be described. Table 3 below shows the composition of the mixture used as the heat dissipation material created in Examples 8 to 12. In Examples 8 to 12, the content of Filler 151 was adjusted so that the dielectric constant of each mixture was about 7 to 7.5, and Filler 151 and Resin 150 were mixed. The particle size distribution of Filler 151 in Examples 8 to 12 is as shown in Table 3. Also, in Examples 8 to 12, each of the mixed materials was heated and cured under the same heating conditions as in Example 1 to create each mixture.

[0069]

Table 3

[0070] (Evaluation Results of Examples 8 to 12) For each of the mixtures created in Examples 8 to 12, the thermal conductivity was determined in the same procedure as in Example 1 and Comparative Examples 1 and 2. The results are shown in accordance with Table 3 above.

[0071] From Table 3, it can be seen that the thermal conductivities of the mixtures of Examples 8, 9, and 12, which contain 20% or more of the small-diameter Filler 151S and medium-diameter Filler 151M and large-diameter Filler 151L with a particle size exceeding 10 μm, are higher than the thermal conductivities of the mixtures of Examples 2 to 7 shown in Table 2. Also, it can be seen that the thermal conductivities of the mixtures of Examples 10 and 11, which contain 20% or more of the large-diameter Filler 151L and medium-diameter Filler 151M and small-diameter Filler 151S with a particle size less than 200 μm, are higher than the thermal conductivities of the mixtures of Examples 2 to 7 shown in Table 2.

[0072] From the above, it was confirmed that by configuring the particle size distribution of Filler 151 in the heat dissipation material 15 to contain 20% or more of the small-diameter Filler 151S and a filler with a particle size exceeding 10 μm, or to contain 20% or more of the large-diameter Filler 151L and a filler with a particle size less than 200 μm, it is possible to achieve both further reduction of the dielectric constant and increase of the thermal conductivity.

[0073] (Examples 13 to 18) Examples 13 to 18 of the present invention will be described. Table 4 below shows the composition of the mixture that becomes the heat dissipation material created in Examples 13 to 18. In Examples 13 to 18, the content rate of filler 151 was adjusted so that the dielectric constant of each mixture would be about 8, and filler 151 and resin 150 were mixed. The particle size distribution of filler 151 in Examples 13 to 18 is as shown in Table 4. Also, in Examples 13 to 18, each of the mixed materials was heated and cured under the same conditions as the heating conditions of Example 1 to create each mixture.

[0074]

Table 4

[0075] (Evaluation Results of Examples 13 to 18) For each of the mixtures created in Examples 13 to 18, the thermal conductivity was determined in the same procedure as in Example 1 and Comparative Examples 1 and 2. The results are shown in accordance with Table 4 above.

[0076] From Table 4, it can be seen that the thermal conductivity of the mixtures of Examples 13 to 18, where the ratio of the small-diameter filler 151S is 20% or more and the ratio of the large-diameter filler 151L is 20% or more, is higher than the thermal conductivity of the mixtures of Examples 8 to 12 shown in Table 3. Also, in the comparison of the mixtures of Examples 13 to 15 and 17 where the ratio of the large-diameter filler 151L is 20%, the higher the ratio of the small-diameter filler 151S, the higher the thermal conductivity. Accordingly, it is predicted that the gaps between the large-diameter fillers 151L are filled with the small-diameter fillers 151S, the filling state of the fillers in the mixture is improved, and the thermal conductivity is increased.

[0077] From the above, it was confirmed that by configuring the particle size distribution of filler 151 in heat dissipation material 15 such that the ratio of the small-diameter filler 151S is 20% or more and the ratio of the large-diameter filler 151L is 20% or more, it is possible to achieve both further reduction of the dielectric constant and increase of the thermal conductivity.

[0078] Note that the present invention is not limited to the above-described embodiments and examples, and further includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, for a part of the configuration of each embodiment, addition, deletion, or replacement with other configurations is possible.

[0079] For example, the heat dissipation material according to the present invention is applicable not only to in-vehicle electronic control devices but also to heat dissipation materials used in inverters, converters, etc. other than in-vehicle ones.

Explanation of Reference Numerals

[0080] 1... In-vehicle control device, 2... Electronic component, 5... Base (housing), 6... Cover (housing), 10... Heat dissipation pedestal, 15... Heat dissipation material, 150... Resin, 151... Filler

Claims

1. In an insulating heat dissipating material using spherical fillers, the filler is aluminum nitride, wherein the proportion of fillers having a particle size of 200 μm or more and 1000 μm or less is 20% or more, and the proportion of fillers having a particle size of 1 nm or more and 10 μm or less is 20% or more with respect to the total amount of the fillers Heat dissipating material.

2. The filler is made of a material having a thermal conductivity of 1 W / mK to 200 W / mK The heat dissipating material according to Claim 1.

3. The content of the filler is 20 vol% or more and 95 vol% or less The heat dissipating material according to Claim 1.

4. The filler is dispersed in a resin The heat dissipating material according to Claim 1.

5. The resin is a thermosetting resin The heat dissipating material according to Claim 4.

6. The resin is a silicone resin The heat dissipating material according to Claim 4.

7. An electronic device including a circuit board on which an electronic component is mounted and a housing that houses the circuit board therein, wherein the heat dissipating material according to any one of Claims 1 to 6 is sandwiched between the electronic component and the housing Electronic device.

8. At a position of the housing facing the electronic component, there is a heat dissipation pedestal protruding toward the electronic component side, and the heat dissipating material is sandwiched between the electronic component and the heat dissipation pedestal The electronic device according to Claim 7.

9. The electronic component is at least one of a CPU, a GPU, a SoC, and a DDR memory The electronic device according to Claim 7.

10. The electronic component is an in-vehicle electronic component The electronic device according to Claim 7.

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