WO2024013858A1

WO2024013858A1 - Heat dissipation member, heat dissipation member with base material, and power module

Info

Publication number: WO2024013858A1
Application number: PCT/JP2022/027452
Authority: WO
Inventors: 元基正木
Original assignee: 三菱電機株式会社
Priority date: 2022-07-12
Filing date: 2022-07-12
Publication date: 2024-01-18
Also published as: JP7330419B1

Abstract

Provided is a heat dissipation member including a ceramic filler, a non-magnetic and flat metal filler, and a retention material.

Description

Heat dissipation components, heat dissipation components with base materials, and power modules

The present disclosure relates to a heat dissipation member, a heat dissipation member with a base material, and a power module.

In electrical and electronic equipment equipped with heat generating components such as LED elements and ICs, the importance of heat dissipation technology is increasing due to the increase in heat generation due to higher output. Particularly, in-vehicle electrical components used in sealed casings for dust-proofing and waterproofing, space equipment used in vacuum, and the like have a problem in that heat dissipation through air convection is difficult. Therefore, conventional heat dissipation techniques such as natural air cooling using an aluminum heat sink and forced air cooling using an electric fan cannot provide a sufficient heat dissipation effect. In addition, information devices, including notebook computers, whose heat output tends to increase due to higher performance CPUs, are becoming smaller and more densely packaged, and there is a problem that there is no space to install large aluminum heat sinks. be. Furthermore, since conventional aluminum heat sinks are made of metal, there is a problem in that they generate electromagnetic noise, leading to malfunctions of electrical and electronic equipment. Therefore, in recent years, ceramic heat sinks that utilize infrared heat radiation have been attracting attention for electrical and electronic devices that are difficult to dissipate using conventional heat dissipation techniques.

In Japanese Patent No. 4404855 (Patent Document 1), a coating agent made by mixing scholl tourmaline powder with a particle size ranging from a minimum of 3 μm to a maximum of 325 mesh and a fluid fixative is applied to a base made of copper or aluminum. Disclosed is a heat dissipating member characterized in that it has a tourmaline layer formed by applying and solidifying shawl tourmaline powder to the surface of the material at an areal density of 0.025 to 0.05 g per square cm. ing.

Patent No. 4404855

However, since the heat radiating member disclosed in Patent Document 1 contains a resin-based fixing agent with low thermal conductivity, the thermal resistance of the heat radiating member becomes too large. Therefore, the heat from the heat source may not be sufficiently transmitted to the surface of the heat radiating member, and the radiation performance of the surface of the heat radiating member may deteriorate.

The present disclosure has been made to solve the above problems, and aims to provide a heat dissipation member and a base material-attached heat dissipation member that have high thermal conductivity and excellent radiation performance.
Another purpose is to provide a power module with excellent heat dissipation performance.

As a result of extensive studies to solve the above problems, the present inventors have developed a material that combines a ceramic filler with high emissivity and a non-magnetic metal filler with high thermal conductivity. It was discovered that by making the shape of the filler flat, it is possible to efficiently obtain contact between the metal fillers that serve as a heat path, resulting in a heat dissipation member with high thermal conductivity and excellent radiation performance. . We have also discovered that by applying this ceramic filler to a heat dissipating member, the radiation performance of the heat dissipating member can be improved.
The present disclosure relates to the following heat radiating member, heat radiating member with a base material, and power module.

A heat dissipation member that includes a ceramic filler, a non-magnetic and flat metal filler, and a holding material.

Comprising a base material and a heat dissipation member,
The heat dissipation member is a heat dissipation member with a base material, which is a coating layer coated on the surface of the base material.

A power semiconductor element, a heat radiation member or a heat radiation member with a base material capable of radiating heat generated by the power semiconductor element to the outside, and a lead frame electrically connected to the outside,
The lead frame has an external connection part,
At least a part of the surface of the external connection part is covered with the heat radiating member or the heat radiating member with a base material.

According to the present disclosure, it is possible to provide a heat dissipation member and a base material-attached heat dissipation member that have high thermal conductivity and excellent radiation performance. Furthermore, a power module with excellent heat dissipation performance can be provided.

FIG. 1 is a schematic cross-sectional view showing an example of a heat dissipation member in the first embodiment. FIG. 2 is a schematic cross-sectional view showing an example in which the heat dissipation member in Embodiment 1 is installed on a heat source. FIG. 3 is a schematic cross-sectional view showing the state of contact between spherical fillers. FIG. 4 is a schematic cross-sectional view showing a contact situation between flat fillers. FIG. 5 is a schematic cross-sectional view showing another example of the heat dissipation member in the first embodiment. FIG. 6 is a schematic cross-sectional view showing another example of the heat dissipation member in the first embodiment. FIG. 7 is a schematic cross-sectional view showing another example of the heat dissipation member in the first embodiment. FIG. 8(a) is a schematic cross-sectional view of a ceramic filler, and FIG. 8(b) is a schematic cross-sectional view of a metal filler. FIG. 9 is a schematic cross-sectional view showing an example of a heat dissipating member with a base material according to the second embodiment. FIG. 10 is a schematic cross-sectional view of a power module in Embodiment 3.

Hereinafter, embodiments of the present disclosure will be described.

Embodiment 1.
<Heat dissipation member>
FIG. 1 is a schematic cross-sectional view showing an example of a heat dissipation member according to the first embodiment. Hereinafter, a heat dissipating member 1 according to the present embodiment will be described using FIG. 1. The heat dissipation member 1 according to the present embodiment includes a ceramic filler 2, a non-magnetic flat metal filler 3, and a holding material 4. As shown in FIG. 2, the heat dissipation member 1 according to the present embodiment exhibits a heat dissipation effect by discharging heat generated from a heat source 5 such as a semiconductor element to the outside through infrared radiation from the surface of the heat dissipation member 1. do. Moreover, the higher the surface temperature of the heat dissipation member 1, the more infrared rays are radiated from the surface (the surface opposite to the surface in contact with the heat source in FIG. 2), and the heat dissipation effect improves. Therefore, in order to enhance the heat dissipation effect of the heat dissipation member 1, it is necessary to efficiently transfer the heat from the heat source to the surface and raise the surface temperature as much as possible.

However, in general, ceramic fillers and holding materials do not have high thermal conductivity compared to metal fillers, so they tend to have high thermal resistance, making it difficult to efficiently transfer heat. Therefore, in the heat dissipating member 1 of the present embodiment, the thermal conductivity of the heat dissipating member 1 is improved by containing the non-magnetic metal filler 3 having high thermal conductivity. At this time, by making the shape of the non-magnetic metal filler 3 flat, the non-magnetic metal fillers 3 can more easily come into contact with each other, so even if the content of the non-magnetic metal filler 3 is small, the heat dissipation member 1 improves thermal conductivity. Therefore, the heat dissipation member 1 of this embodiment has high thermal conductivity and excellent radiation performance.

(ceramic filler)
The heat dissipation member 1 of this embodiment includes a ceramic filler 2. By including the ceramic filler 2, radiation performance can be improved.

The ceramic filler 2 is not particularly limited, but preferably has a high emissivity, such as industrial ceramic materials such as alumina, zinc oxide, silica, zirconia, silicon carbide, aluminum nitride, silicon nitride, boron nitride, etc. Mineral ceramic materials such as silicate minerals such as tourmaline, clay, and pumice, aluminosilicate minerals such as pearlite and zeolite, and magnesium silicate minerals such as talc and cordierite. Can be mentioned. These ceramic fillers 2 may be used alone or in combination of two or more. When using two or more types in combination, the combination is not particularly limited.

Among these ceramic fillers 2, alumina and tourmaline are preferred, and tourmaline, which is a type of polar crystal that has a high emissivity of infrared rays with a wavelength of 3 μm or more and 25 μm or less, which is important for heat dissipation in electronic devices, is particularly preferred. In addition, from the viewpoint of increasing the thermal conductivity of the heat dissipation member, nitride-based ceramic materials such as aluminum nitride, silicon nitride, and boron nitride, which have relatively high thermal conductivity as well as emissivity, are preferable. Furthermore, by using a combination of a mineral ceramic material with high emissivity and a nitride ceramic material with high thermal conductivity, it is possible to further improve the radiation performance and thermal conductivity of the heat dissipation member. .

From the viewpoint of obtaining sufficient radiation performance, the content of the ceramic filler 2 is preferably 30 volume% or more and 80 volume% or less, and preferably 40 volume% or more and 70 volume% or less. If the content of the ceramic filler 2 is less than 30% by volume, the radiation performance of the heat radiation member 1 will not be sufficiently improved. When the content of the ceramic filler 2 exceeds 80% by volume, the content of the metal filler 3 and the retaining material 4, which are other constituent components, decreases, so from the viewpoint of the thermal conductivity improvement effect and moldability of the heat dissipation member 1. There is a risk that it will be inferior.

The average particle size (d ₁ ) of the ceramic filler 2 is not particularly limited, but is preferably 1.0 μm or more and 30 μm or less. Here, the average particle size of the ceramic filler 2 in this embodiment is determined by preparing a sample in which the ceramic filler 2 is embedded in an epoxy resin, polishing the cross section of the sample, and enlarging it with an SEM (scanning electron microscope). (for example, by a factor of 5000), then measuring the major axis of at least 20 particles, and averaging the measured values. The major axis is the length of the line segment (longest line segment) that has the maximum length among the line segments connecting two points on the outer circumference of the ceramic filler 2 (line segments between two points) in the cross section of the ceramic filler 2. (See Figure 8(a)).

The shape of the ceramic filler 2 is not particularly limited, but examples thereof include spherical or substantially spherical, scale-like, columnar, etc., and spherical or substantially spherical is preferable.

(metal filler)
The heat dissipation member 1 of this embodiment includes a non-magnetic and flat metal filler 3. By including the nonmagnetic and flat metal filler 3, thermal conductivity can be improved.

The metal filler 3 is a metal material with high thermal conductivity. In general, non-magnetic metals tend to have higher thermal conductivity than magnetic metals. Moreover, when the heat dissipation member 1 containing magnetic metal is used in an electronic device, there is a possibility that it may have an adverse effect on the circuit electromagnetically. Therefore, in the heat dissipation member 1 of this embodiment, a non-magnetic metal material is used as the metal filler 3.

The thermal conductivity of the non-magnetic metal filler 3 is preferably 100 W/(m・K) or more, more preferably 150 W/(m・K) or more, and 200 W/(m・K) or more. It is even more preferable that there be. Examples of the nonmagnetic metal filler 3 include metal materials with relatively high thermal conductivity, such as gold, silver, copper, copper alloy, aluminum, aluminum alloy, and tungsten. These non-magnetic metal fillers 3 may be used alone or in combination of two or more. When using two or more types in combination, the combination is not particularly limited. In particular, from the viewpoints of cost and thermal conductivity, it is preferable to use copper and copper alloys.

The shape of the metal filler 3 is flat. When the shape of the metal filler is, for example, spherical, as shown in FIG. 3, it is difficult for the spherical metal fillers to come into contact with each other in the heat dissipation member, making it difficult to form an effective heat path. Therefore, in order to improve the thermal conductivity of the heat dissipation member, it is necessary to contain a large amount of metal filler. As a result, there is a problem in that the content of the ceramic filler 2, which plays a role in radiation performance, becomes relatively small in the range of filler content that allows the production of a heat dissipating member. On the other hand, since the metal filler 3 of this embodiment has a flat shape, as shown in FIG. Even if the amount is relatively small, it is possible to form a heat path that is effective in improving the thermal conductivity of the heat dissipation member 1.

Furthermore, the term "metal filler 3 having a flat shape" includes a filler obtained by heating and compressing a metal filler used as a raw material, a raw material of a flat metal filler, and the like.

The aspect ratio of the non-magnetic and flat metal filler 3 is 3 or more and 30 or less, preferably 4 or more and 20 or less. Here, the aspect ratio of the nonmagnetic and flat metal filler 3 is determined by preparing a sample in which the nonmagnetic and flat metal filler 3 is embedded in epoxy resin, polishing the cross section of the sample, and using SEM (scanning). After magnifying (e.g., 5000 times) with a type electron microscope, the major axis and minor axis of the non-magnetic and flat metal filler 3 are measured for at least 20 particles, and the ratio of the major axis to the minor axis (major axis/short axis) is determined. It means the value obtained by calculating the diameter) and finding the average value. The major axis is the maximum length of the line segment connecting two points on the outer circumference of the non-magnetic and flat metal filler 3 (line segment between two points) in the cross section of the non-magnetic and flat metal filler 3. The short axis is the length of the line segment with the maximum length among the line segments between two points that intersect perpendicularly to the longest line segment. (See FIG. 8(b)).

If the aspect ratio of the non-magnetic and flat metal filler 3 is less than 3, the effect of making it easier for the metal fillers 3 to come into contact with each other due to the flat shape cannot be sufficiently obtained, and the There is a risk that a heat path will not be formed. When the aspect ratio of the non-magnetic and flat metal filler 3 exceeds 30, the short axis is short, that is, the thickness of the flat metal filler 3 is too thin, and the strength of the non-magnetic and flat metal filler 3 is reduced. It may become extremely weak and unable to maintain its flat shape.

The average major axis (d ₂ ) of the nonmagnetic and flat metal filler 3 preferably satisfies the following formula (1), where t is the thickness of the heat dissipation member 1.
2.0≦ _d2 ≦t/2...(1)
If the average major axis (d ₂ ) is less than 2 μm, the nonmagnetic and flat metal fillers 3 are unlikely to come into contact with each other, so although this does not impede practicality, it may be difficult to form an effective heat path. When the average major axis (d ₂ ) exceeds t/2 μm, the average major axis (d ₂ ) is too long with respect to the thickness (t) of the heat dissipating member 1, so the non-magnetic and flat metal filler 3 It becomes easy to fall down in the direction perpendicular to the thickness direction. Therefore, although it does not impede practicality, there is a possibility that the thermal conductivity in the thickness direction of the heat dissipating member 1 is difficult to improve. Note that, as described later, the thickness t of the heat dissipation member 1 is preferably 5 μm or more.

From the viewpoint of obtaining sufficient thermal conductivity, the content of the nonmagnetic and flat metal filler 3 is preferably 10 volume% or more and 60 volume% or less, and preferably 15 volume% or more and 50 volume% or less. If the content of the nonmagnetic and flat metal filler 3 is less than 10% by volume, the thermal conductivity of the heat dissipation member 1 will not be sufficiently improved. When the content of the non-magnetic and flat metal filler 3 exceeds 60% by volume, the content of the other components, the ceramic filler 2 and the holding material 4, decreases, so the effect of improving the radiation performance of the heat dissipation member 1 and There is a possibility that the moldability is inferior.

(Holding material)
The holding material 4 included in the heat dissipation member 1 of this embodiment is not particularly limited, and has a function of uniformly dispersing and fixing the ceramic filler 2 and the non-magnetic and flat metal filler 3 in the heat dissipation member 1. It is sufficient if it has the following. As the holding material 4, for example, an organic binder or an inorganic binder can be appropriately selected and used. Examples of indicators for selecting an organic binder or an inorganic binder include heat resistance, and depending on the temperature range in which the heat dissipation member 1 is used, an organic binder or an inorganic binder having the desired heat resistance may be selected as appropriate. Bye. Further, from the viewpoint of adhesion and ease of manufacturing the heat dissipating member 1, an organic binder is preferable.

Examples of organic binders include, but are not limited to, thermosetting resins such as epoxy resins, unsaturated polyester resins, phenol resins, melamine resins, silicone resins, and polyimide resins from the viewpoint of heat resistance and durability. From the viewpoint of adhesion, epoxy resin is preferred. Specific examples of epoxy resins include bisphenol A epoxy resin, bisphenol F epoxy resin, orthocresol novolac epoxy resin, phenol novolac epoxy resin, alicycloaliphatic epoxy resin, glycidyl-aminophenol epoxy resin, etc. It will be done. These organic binders may be used alone or in combination of two or more. When using two or more types in combination, the combination is not particularly limited.

When using the above-mentioned thermosetting resin as the organic binder, the heat dissipation member 1 may contain a curing agent. The curing agent is not particularly limited, and any known curing agent may be appropriately selected depending on the type of thermosetting resin used. Examples of the curing agent include amines, phenols, acid anhydrides, imidazoles, polymercaptan curing agents, polyamide resins, and the like.

In addition, as a curing agent when using an epoxy resin as an organic binder, for example, alicyclic acid anhydrides such as methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, hymic anhydride, dodecenylsuccinic anhydride, etc. Aliphatic acid anhydrides, aromatic acid anhydrides such as phthalic anhydride and trimellitic anhydride, organic dihydrazides such as dicyandiamide and adipic dihydrazide, 2-methylimidazole and its derivatives, 2-ethyl-4-methylimidazole, 2 Examples include imidazoles such as -phenylimidazole, tris(dimethylaminomethyl)phenol, dimethylbenzylamine, 1,8-diazabicyclo(5,4,0)undecene and its derivatives. These curing agents may be used alone or in combination of two or more. When using two or more types in combination, the combination is not particularly limited.

The content of the curing agent may be set as appropriate depending on the type of thermosetting resin and curing agent used, but generally it is 0.1 parts by mass or more per 100 parts by mass of the thermosetting resin. It is 200 parts by mass or less.

The heat dissipation member 1 of the present embodiment contains a coupling agent from the viewpoint of improving the adhesive force at the interface between the ceramic filler 2 and the non-magnetic and flat metal filler 3 and the cured product of the thermosetting resin. You can stay there. Examples of coupling agents include γ-glycidoxypropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, Examples include methoxysilane. These coupling agents may be used alone or in combination of two or more. When using two or more types in combination, the combination is not particularly limited.

The content of the coupling agent may be set as appropriate depending on the type of thermosetting resin and coupling agent used, but in general, it is 0.01 parts by mass per 100 parts by mass of the thermosetting resin. Part or more and no more than 1 part by mass.

The inorganic binder is not particularly limited, but a liquid inorganic binder that is compatible with the ceramic filler 2 and the non-magnetic and flat metal filler 3 and can be uniformly dispersed is preferred. Furthermore, the curing temperature of an inorganic binder is often higher than that of an organic binder. The temperature is 250°C or lower, preferably 200°C or lower, and more preferably 180°C or lower. By using an inorganic binder having such a curing temperature, it is possible to efficiently form a coating layer without causing thermal deterioration of the base material 8. Specific examples of the inorganic binder include sol-gel glass, organic-inorganic hybrid glass, water glass, one-component inorganic adhesive, two-component inorganic adhesive, and the like. These inorganic binders may be used alone or in combination of two or more. When using two or more types in combination, the combination is not particularly limited.

The content of the holding material 4 is 10 volume% or more and 60 volume% or less, and preferably 15 volume% or more and 50 volume% or less. When the content of the holding material 4 is less than 10% by volume, the force for holding the ceramic filler 2 and the non-magnetic and flat metal filler 3 may be insufficient, leading to poor moldability. When the content of the holding material 4 exceeds 60% by volume, the content of the other components, the ceramic filler 2 and the non-magnetic and flat metal filler 3, decreases, so the radiation performance and heat conduction of the heat dissipation member 1 are reduced. There is a risk that it will be inferior in terms of rate improvement effect.

(distributed structure)
In the heat dissipation member 1 of this embodiment, as shown in FIG. 1, the ceramic filler 2 and the nonmagnetic flat metal filler 3 may be uniformly dispersed throughout the heat dissipation member 1. By uniformly dispersing the ceramic filler 2 and the non-magnetic flat metal filler 3, the heat from the heat source 5 is easily transmitted evenly throughout the heat dissipation member 1, and the heat dissipation performance is further improved.

Furthermore, the ceramic filler 2 and the non-magnetic flat metal filler 3 may have a concentration gradient in their content in the thickness direction of the heat dissipation member 1. Specifically, as shown in FIG. 6, the content of the ceramic filler 2 may have a concentration gradient that decreases as it goes in the thickness direction of the heat dissipation member, and the content of the ceramic filler 2 may have a concentration gradient that decreases as it goes in the thickness direction of the heat dissipation member. The content may have a concentration gradient that increases in the thickness direction of the heat dissipation member. That is, in the thickness direction of the heat dissipation member 1, the area close to the surface in contact with the heat source 5 (lower side in FIG. 6) preferably contains a large amount of non-magnetic and flat metal filler 3, and the area is close to the surface in contact with the heat source 5. It is preferable that the region opposite to the contacting surface (the upper side in FIG. 6) contains a large amount of the ceramic filler 2. This is because the ceramic filler 2 has a function of improving radiation performance, and the non-magnetic and flat metal filler 3 has a function of improving thermal conductivity.

Furthermore, as shown in FIG. 7, the heat dissipation member 1 has a two-layer structure including a first layer 6 containing a large amount of ceramic filler 2 and a second layer 7 containing a large amount of non-magnetic and flat metal filler 3. It may have. In such a case as well, it is preferable that the second layer 7 near the surface in contact with the heat source 5 in the thickness direction of the heat dissipating member 1 contains a large amount of non-magnetic and flat metal filler 3, so that the second layer 7 is close to the surface in contact with the heat source 5. It is preferable that the first layer 6 on the opposite side to the contacting surface contains a large amount of the ceramic filler 2.

The distributed structure of the heat dissipation member 1 can be confirmed by cutting the heat dissipation member 1 and observing its cross section with an SEM magnification (for example, 5000 times).

(Orientation state)
The orientation state of the nonmagnetic and flat metal filler 3 in the heat dissipation member 1 of this embodiment is preferably isotropically distributed, as shown in FIG. Here, "distributed isotropically" means that the nonmagnetic and flat metal filler 3 has no orientation (or has little orientation) in its distribution. That is, in the heat dissipation member 1, the non-magnetic and flat metal fillers 3 are oriented in random directions. For example, as shown in FIG. 5, if the long axis direction of the nonmagnetic and flat metal filler 3 is oriented in the longitudinal direction of the heat dissipation member 1 (horizontal direction in FIG. 5), the heat in the thickness direction of the heat dissipation member 1 is Conductivity may be difficult to improve. On the other hand, when the nonmagnetic and flat metal filler 3 is isotropically dispersed, a thermal path is easily formed in the thickness direction of the heat dissipating member 1, and the thermal conductivity is further improved.

Physically, the non-magnetic and flat-shaped metal filler 3 is such that due to the presence of the ceramic filler 2 in the heat-radiating member 1, the long axis direction of the non-magnetic and flat-shaped metal filler 3 is oriented in the longitudinal direction of the heat-radiating member 1. is prevented and tends to disperse isotropically. Therefore, in order to isotropically disperse the nonmagnetic and flat metal filler 3 in the heat dissipation member 1, the average particle diameter (d ₁ ) of the ceramic filler 2 and the nonmagnetic and flat metal filler 3 must be adjusted. The ratio to the average major axis (d ₂ ) may be adjusted. The ratio (d ₁ /d ₂ ) of the average particle diameter (d ₁ ) of the ceramic filler 2 to the average major axis (d ₂ ) of the nonmagnetic and flat metal filler 3 preferably satisfies the following formula (2) .
0.5≦ _d1 / _d2 ≦5.0...(2)
When d ₁ /d ₂ is within the above range, the nonmagnetic and flat metal filler 3 is more likely to be isotropically dispersed. Note that the orientation state of the nonmagnetic and flat metal filler 3 in the heat dissipation member 1 can be confirmed by the same method as the dispersion structure of the heat dissipation member 1 described above.

(average emissivity)
The average emissivity of the heat dissipation member 1 of this embodiment is 70% or more. In general, the emissivity of the heat dissipation member 1 changes depending on the temperature, but in the temperature range of 200°C or less, preferably 150°C or less, which is usually used as the heat dissipation member 1 of electrical and electronic equipment, the emissivity of 70% or more When it has an average emissivity, sufficient cooling performance can be obtained as the heat dissipation member 1. The average emissivity of the heat dissipating member 1 is preferably 75% or more, more preferably 80% or more.

The average emissivity is determined by measuring each emissivity in the wavelength range of 3 μm or more and 25 μm or less using an emissivity measurement device, and calculating the average value of the emissivity in the entire wavelength range.

(Thermal conductivity)
The thermal conductivity of the heat dissipation member 1 of this embodiment is 3 W/(m·K) or more. When the thermal conductivity of the heat dissipation member 1 is 3 W/(m·K) or more, the heat generated from the heat source is efficiently transferred to the heat dissipation member 1, so that even higher heat dissipation performance can be expected. The thermal conductivity of the heat dissipating member 1 is preferably 5 W/(m·K) or more, more preferably 10 W/(m·K) or more. Note that the thermal conductivity of the heat dissipating member 1 in this embodiment means the thermal conductivity of the heat dissipating member 1 in the thickness direction.

Thermal conductivity is measured using the laser flash method.

(shape)
The shape of the heat dissipating member 1 of this embodiment is appropriately set depending on the application. The shape of the heat dissipating member 1 is not particularly limited, and examples thereof include a sheet, a film, a thin film, a molded body, and the like.

(thickness)
The thickness t of the heat dissipation member 1 is adjusted as appropriate depending on the shape of the heat dissipation member 1, the ceramic filler 2 used, and the non-magnetic and flat metal filler 3. However, in consideration of the average major axis (d ₂ ) of the nonmagnetic and flat metal filler 3, the thickness t of the heat dissipation member 1 is preferably 5 μm or more.

(others)
The heat dissipation member 1 of this embodiment may contain a solvent to the extent that the effects of the present disclosure are not impaired. The solvent is not particularly limited, and any known solvent may be appropriately selected depending on the type of ceramic filler 2 and non-magnetic and flat metal filler 3 to be used. Examples of the solvent include water, methanol, ethanol, propanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, dimethylsulfoxide, N -Methyl-2-pyrrolidone, ethyl acetate, butyl acetate, propylene carbonate, diethylene carbonate, toluene, xylene, pyridine, tetrahydrofuran, dichloromethane, chloroform, 1,1,1,3,3,3-hexafluoroisopropanol, formic acid, acetic acid etc. These solvents may be used alone or in combination of two or more. When using two or more types in combination, the combination is not particularly limited.

Embodiment 2.
FIG. 9 is a schematic cross-sectional view showing an example of a heat dissipating member with a base material according to the second embodiment. Hereinafter, the heat dissipating member with a base material according to the present embodiment will be described using FIG. 9. The heat dissipation member with a base material of this embodiment includes a base material 8 and a heat dissipation member 1, and the heat dissipation member 1 is a coating layer coated on the surface of the base material 8.

The base material 8 is not particularly limited, but from the viewpoint of efficiently transmitting heat from the heat source 5, it is preferably made of metal or ceramic with high thermal conductivity. Examples of the metal include aluminum, copper, stainless steel, iron, and other alloys. Examples of the ceramic include alumina, magnesia, zirconia, aluminum nitride, and silicon carbide. These may be used alone or in combination of two or more. When using two or more types in combination, the combination is not particularly limited.

In addition, the thickness of the coating layer is determined by the shape of the heat dissipating member 1, the average particle diameter (d ₁ ) of the ceramic filler 2 used, the average major axis (d 1 ) of the non-magnetic and flat metal filler 3, as well as the thickness of the heat dissipating member 1. _d2 ) is adjusted as appropriate. However, from the viewpoint of adhesion to the base material 8 and peeling resistance in long-term reliability tests such as heat cycles, the thickness is preferably 10 μm or more and 200 μm or less.

Embodiment 3.
The power module of this embodiment includes a power semiconductor element and the heat radiation member described in Embodiment 1 that can radiate heat generated by the power semiconductor element to the outside, or the heat radiation member with base material described in Embodiment 2. and a lead frame that is electrically connected to the outside. The lead frame has external connections. At least a portion of the surface of the external connection portion is covered with the heat radiating member described in Embodiment 1 or the heat radiating member with a base material described in Embodiment 2.

The power module of this embodiment will be described below with reference to the drawings.
FIG. 10 is a schematic cross-sectional view of the power module of this embodiment. In FIG. 10, the power module 9 includes a lead frame 10, a heat sink 11 which is a heat dissipation member, an insulating sheet 12 disposed between the lead frame 10 and the heat sink 11, and a power semiconductor element mounted on the lead frame 10. 13 and a control semiconductor element 14. Wire bonding is performed between the power semiconductor element 13 and the control semiconductor element 14 and between the power semiconductor element 13 and the lead frame 10 using metal wires 15. Further, the lead frame 10 has an external connection part, and the parts other than the external connection part of the lead frame 10 and the external heat dissipation part of the heat sink 11 are sealed with a sealing resin 16. Furthermore, at least a portion of the surface of the external connection portion of the lead frame 10 is covered with the heat radiating member 1 or the heat radiating member with a base material. The heat dissipation member 1 with a base material is preferable from the viewpoint of ease of construction. In the power module 9, at least a part of the surface of the external connection part of the lead frame 10 is covered with the heat dissipation member 1 or the heat dissipation member with a base material, so that the heat dissipation performance is improved by infrared radiation from the surface of the lead frame 10. improves. Furthermore, the more portions of the surface of the external connection portion of the lead frame 10 that are covered by the heat radiating member 1 or the heat radiating member with a base material, the more the heat radiating performance of the power module 9 improves.

In the power module of this embodiment, members other than the heat radiating member 1 are not particularly limited, and members known in the technical field can be used. For example, as the power semiconductor element 13, one formed of silicon can be used, but it is preferable to use one formed of a wide band gap semiconductor having a larger band gap than silicon. Examples of wide bandgap semiconductors include silicon carbide, gallium nitride materials, and diamond.

Since the power semiconductor element 13 formed of a wide bandgap semiconductor has high voltage resistance and high allowable current density, the power semiconductor element 13 can be miniaturized. By using the power semiconductor element 13 miniaturized in this way, it is also possible to miniaturize the power module 9 incorporating the power semiconductor element 13.

Furthermore, since the power semiconductor element 13 formed of a wide bandgap semiconductor has high heat resistance, it also leads to the miniaturization of heat dissipation members such as the lead frame 10 and the heat sink 11, making it possible to further miniaturize the power module 9. become.

Further, since the power semiconductor element 13 formed of a wide bandgap semiconductor has low power loss, it is possible to improve the efficiency of the element.

Hereinafter, the present disclosure will be described in detail with reference to Examples, but the present disclosure is not limited thereto.

<Example 1>
As a holding material, 100 parts by mass of a liquid bisphenol A type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., Epicoat 828), which is a thermosetting resin, and 1-cyanoethyl-2-methylimidazole (Shikoku Kasei Kogyo Co., Ltd.), which is a curing agent, were used as a retaining material. After mixing with 1 part by mass of Curesol 2PN-CN (manufactured by Nippon Express Co., Ltd.), 166 parts by mass of methyl ethyl ketone as a solvent was added and mixed and stirred. Next, 563 parts by mass of alumina filler (No. A) (shape: spherical, average particle size (d ₁ ): 1.2 μm) as a ceramic filler and copper filler as a nonmagnetic and flat metal filler were added to this mixture. (No. c) (average major axis (d ₂ ): 5.0 μm) and 505 parts by mass were added and premixed. Next, this premix was kneaded using a three-roll mill so that the ceramic filler and the non-magnetic and flat metal filler were uniformly dispersed.

Next, the prepared composition was applied onto a 2 mm thick base material (aluminum plate) using a coater, and then heated and dried at 110° C. for 15 minutes. Thereafter, the solvent was completely removed by heating at 120° C. for 1 hour and then at 160° C. for 3 hours, and the holding material was completely cured, thereby obtaining a heat dissipating member.

<Example 2>
A heat dissipation member was prepared in the same manner as in Example 1, except that alumina filler (No. B) (shape: spherical, average particle size (d ₁ ): 2.5 μm) was used instead of alumina filler (No. A). I got it.

<Example 3>
A heat dissipation member was obtained in the same manner as in Example 1, except that alumina filler (No. C) (shape: spherical, average particle size (d ₁ ): 10 μm) was used instead of alumina filler (No. A). Ta.

<Example 4>
A heat dissipation member was obtained in the same manner as in Example 1, except that alumina filler (No. E) (shape: spherical, average particle size (d ₁ ): 24 μm) was used instead of alumina filler (No. A). Ta.

<Example 5>
Alumina filler (No.D) (shape: spherical, average particle size (d ₁ ): 15 μm) was used instead of alumina filler (No.A), and copper was used instead of copper filler (No.c). A heat radiating member was obtained in the same manner as in Example 1, except that filler (No. b) (average major axis (d ₂ ): 2.1 μm) was used.

<Example 6>
Example except that alumina filler (No.E) was used instead of alumina filler (No.A) and copper filler (No.b) was used instead of copper filler (No.c). A heat dissipating member was obtained in the same manner as in Example 1.

<Example 7>
Alumina filler (No.B) was used instead of alumina filler (No.A), and copper filler (No.a) was used instead of copper filler (No.c) (average major axis (d ₂ ): 0 A heat dissipating member was obtained in the same manner as in Example 1, except that .8 μm) was used.

<Example 8>
Same method as Example 1 except that 436 parts by mass of tourmaline (No. F) (shape: spherical, average particle size (d ₁ ): 3.0 μm) was used instead of alumina filler (No. A). A heat dissipating member was obtained.

<Comparative example 1>
A heat dissipation member was prepared in the same manner as in Example 1, except that alumina filler (No. C) 610 mass was used instead of alumina filler (No. A), and non-magnetic and flat metal fillers were not used. Obtained.

<Comparative example 2>
Alumina filler (No.C) was used instead of alumina filler (No.A), and non-magnetic and spherical copper filler (average particle size: 2.5 μm) was used instead of copper filler (No.c). ) A heat dissipating member was obtained in the same manner as in Example 1, except that the material was used.

Note that the copper filler No. used in Examples 1 to 8 As a result of calculating the aspect ratios of a to c using the method described above, it was confirmed that all of them were 3 or more and 30 or less. In addition, as a result of observing the cross sections of the heat dissipating members of Examples 1 to 8 using the method described above, it was confirmed that the ceramic filler and the nonmagnetic and flat metal fillers were uniformly dispersed, as in the case of kneading. Ta.

<Evaluation method>
Evaluation was performed by the following method.

(1) Thermal conductivity The thermal conductivity in the thickness direction of the heat dissipating members obtained in Examples 1 to 8 and Comparative Examples 1 to 2 was measured by a laser flash method. The test pieces used were those cut out from each heat dissipation member to a diameter of 10 mm and a thickness of 1 mm. The thermal conductivity results are based on the thermal conductivity obtained with the heat dissipating member of Example 1, and the relative value of the thermal conductivity obtained with the heat dissipating member of each example or each comparative example ([each example Or the value of [thermal conductivity obtained with the heat dissipating member of each comparative example]/[thermal conductivity obtained with the heat dissipating member of Example 1]] is shown in Table 1.

(2) Cooling performance (heat dissipation performance)
A ceramic heater was attached to one surface of the heat dissipating member obtained in Examples 1 to 8 and Comparative Examples 1 to 2, which had a length of 100 mm, a width of 100 mm, and a thickness of 7 mm, and a power of 20 W was applied to the temperature of the heat dissipating member and the ceramic heater. It was left for several hours until it reached saturation temperature. Thereafter, the surface temperature of the ceramic heater was measured using a thermocouple. The results are shown in Table 1. The saturation temperature of the ceramic heater when a power of 20 W is applied is the cooling performance as a heat radiating member, and the lower the saturation temperature, the higher the cooling performance as the heat radiating member.

The heat dissipating members of Examples 1 to 8 had excellent thermal conductivity and cooling performance. In particular, Examples 2 to 4 satisfying 0.5≦d ₁ /d ₂ ≦5.0 had better thermal conductivity and cooling performance. Furthermore, Example 8, in which tourmaline with excellent radiation performance was used as the ceramic filler, had the best cooling performance.

On the other hand, Comparative Example 1 had poor thermal conductivity and cooling performance because it did not contain nonmagnetic and flat metal fillers. Although Comparative Example 2 was a non-magnetic metal filler, it used a spherical metal filler, so its thermal conductivity and cooling performance were poor.

The embodiments and examples disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the claims rather than the above description, and it is intended that equivalent meanings and all changes within the scope of the claims are included.

1 Heat dissipation member, 2 Ceramic filler, 3 Metal filler, 4 Holding material, 5 Heat source, 6 First layer, 7 Second layer, 8 Base material, 9 Power module, 10 Lead frame, 11 Heat sink, 12 Insulating sheet, 13 Electric power Semiconductor element, 14. Control semiconductor element, 15. Metal wire, 16. Sealing resin.

Claims

A heat dissipation member that includes a ceramic filler, a non-magnetic and flat metal filler, and a holding material.
The following formula (1):
0.5≦ d1 / d2 ≦5.0...(1)
satisfies the relationship, and in the above formula (1),
d1 indicates the average particle size of the ceramic filler,
The heat dissipation member according to claim 1, wherein d2 represents an average major axis of the metal filler.
The heat dissipation member according to claim 1 or 2, wherein the ceramic filler contains at least one selected from the group consisting of alumina and tourmaline.
The heat dissipation member according to any one of claims 1 to 3, wherein the ceramic filler and the metal filler are uniformly dispersed.
The heat dissipation member according to any one of claims 1 to 3, wherein the ceramic filler and the metal filler have a concentration gradient in content in the thickness direction of the heat dissipation member.
comprising a base material and the heat dissipation member according to any one of claims 1 to 5,
The heat dissipation member is a heat dissipation member with a base material, which is a coating layer coated on the surface of the base material.
A power semiconductor element, a heat radiating member according to any one of claims 1 to 5, or a heat radiating member with a base material according to claim 6, which is capable of radiating heat generated by the power semiconductor element to the outside; A lead frame that is electrically connected to the outside,
The lead frame has an external connection part,
At least a part of the surface of the external connection part is covered with the heat radiating member or the heat radiating member with a base material.
The power module according to claim 7, wherein the power semiconductor element is made of a wide bandgap semiconductor.
The power module according to claim 8, wherein the wide bandgap semiconductor is silicon carbide, gallium nitride-based material, or diamond.