JP2022007554A - Insulating heat radiation material, insulating film and method for producing insulating film - Google Patents

Abstract

To provide an insulating heat radiation material and an insulating film which improve both voltage resistance and thermal conductivity in a balanced manner.SOLUTION: An insulating heat radiation material contains a resin and a filler, in which the filler contains aluminum nitride particles having an average particle diameter of 1.0 μm or more and 3.0 μm or less, alumina particles having a particle diameter of 1.0 μm or less, and alumina particles having a particle diameter of 0.3 μm or less, a content of the aluminum nitride particles is within a range of 25 vol.% or more and 40 vol.% or less of volume concentration in the insulating heat radiation material, a content of the alumina particles having the particle diameter of 1.0 μm or less is within a range of 20 vol.% or more and 40 vol.% or less of volume concentration in the insulating heat radiation material, and a content of the alumina particles having the particle diameter of 0.3 μm or less μm is within a range of 10 vol.% or more and 20 vol.% or less of volume concentration in the insulating heat radiation material.SELECTED DRAWING: Figure 1

Description

The present invention relates to an insulating heat radiating material, an insulating film, and a method for manufacturing the insulating film.

The insulating heat radiating material is used, for example, as a material for an insulating film of a metal base substrate. The metal base substrate is one of the substrates for mounting electronic components such as semiconductor elements and LEDs. The metal base substrate is a laminate in which a metal substrate, an insulating film, and a circuit layer are laminated in this order. Electronic components are mounted on the circuit layer via solder. In the metal-based substrate having such a configuration, the heat generated in the electronic component is transferred to the metal substrate via the insulating film and dissipated from the metal substrate to the outside. Therefore, the insulating film is required to have excellent withstand voltage resistance and high thermal conductivity. The insulating heat radiating material used as the material of such an insulating film generally includes a resin having excellent insulating property and withstand voltage resistance and a filler having excellent thermal conductivity.

As the filler contained in the insulating heat radiating material, inorganic particles such as alumina, aluminum nitride, magnesia, silicon carbide, and crystalline silica are used. Further, it has been studied to use inorganic particles having different average particle diameters contained in the insulating heat radiating material (Patent Documents 1 to 3).

Japanese Unexamined Patent Publication No. 2012-31402 Japanese Unexamined Patent Publication No. 2014-189701 JP-A-2015-207669

By the way, with the recent increase in integration and miniaturization of electronic devices, it is desired that the metal base substrate has further improved withstand voltage and thermal conductivity. Therefore, further improvement of withstand voltage and thermal conductivity is required for the insulating heat radiating material used as the material of the insulating film of the metal base substrate. However, although the filler is effective for improving the thermal conductivity of the insulating heat-dissipating material, if the filler content is increased and the resin content is decreased, the withstand voltage in the insulating heat-dissipating material becomes higher. May decrease. Therefore, it is difficult to improve both withstand voltage and thermal conductivity in a well-balanced manner.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an insulating heat radiating material and an insulating film having both withstand voltage resistance and thermal conductivity improved in a well-balanced manner. It is also an object of the present invention to provide a method for producing an insulating film having both withstand voltage resistance and thermal conductivity improved in a well-balanced manner.

In order to solve the above problems, the insulating heat radiating material of the present invention is an insulating heat radiating material containing a resin and a filler, and the filler has an average particle size in the range of 1.0 μm or more and 3.0 μm or less. It contains aluminum nitride particles inside, alumina particles having a particle size of 1.0 μm or less, and alumina particles having a particle size of 0.3 μm or less, and the content of the aluminum nitride particles is the volume in the insulating heat dissipation material. The content of alumina particles having a concentration within the range of 25% by volume or more and 40% by volume or less and having a particle size of 1.0 μm or less is 20% by volume or more and 40% by volume or less in terms of volume concentration in the insulating heat dissipation material. The content of alumina particles having a particle size of 0.3 μm or less is in the range of 10% by volume or more and 20% by volume or less in terms of volume concentration in the insulating heat radiating material.

According to the insulating heat radiating material of the present invention, the aluminum nitride particles having an average particle size in the range of 1.0 μm or more and 3.0 μm or less, the alumina particles having a particle size of 1.0 μm or less, and the particle size of 0. It contains alumina particles of 3 μm or less, and fine alumina particles can be efficiently interposed between the aluminum nitride particles. Therefore, it is possible to improve the thermal conductivity of the insulating heat radiating material while suppressing the decrease in withstand voltage due to the addition of inorganic particles. In particular, according to the insulating heat-dissipating material of the present invention, the content of the aluminum nitride particles is within the above range, the alumina particles having a particle size of 1.0 μm or less and the finer particle diameters of 0.3 μm or less. Since the content of the alumina particles in the above range is within the above range, the thermal conductivity can be further improved without lowering the withstand voltage.

Here, in the insulating heat radiating material of the present invention, it is preferable that the filler has at least two peaks in the particle size distribution of the filler within the range of 0.01 μm or more and less than 1.0 μm.
In this case, since the difference between the alumina particles having a relatively large particle size and the alumina particles having a relatively small particle size becomes clear, the particle size is relatively large between the particles of the alumina particles having a relatively large particle size. Alumina particles with a small diameter can be intervened more efficiently. Therefore, the thermal conductivity of the insulating heat radiating material can be further improved. The particle size distribution is a volume-based frequency distribution. The volume-based frequency distribution can be measured by a particle size distribution measuring device or the like using a laser diffraction / scattering method.

Further, in the insulating heat radiating material of the present invention, the resin is preferably polyimide, polyamide-imide, or a mixture thereof.
In this case, the insulating property, withstand voltage property, chemical resistance and mechanical properties of the insulating heat radiating material can be improved.

Further, in the insulating heat radiating material of the present invention, it is preferable that the volume concentration of the aluminum nitride particles is higher than the volume concentration of the alumina particles having a particle size of 1.0 μm or less.
In this case, in order to suppress the generation of voids (pores) by filling the space between the particles of the aluminum nitride particles having a relatively large particle size contained in the filler with the alumina particles having a relatively small particle size of 1.0 μm or less. , Thermal conductivity and insulation can be further improved.

The insulating film of the present invention includes the above-mentioned insulating heat radiating material.
Since the insulating film of the present invention contains the above-mentioned insulating heat radiating material, both withstand voltage resistance and thermal conductivity can be improved in a well-balanced manner.

In the method for producing an insulating film of the present invention, aluminum nitride particles having an average particle size in the range of 1.0 μm or more and 3.0 μm or less are contained in a volume concentration of 25% by volume or more and 40% by volume or less in the solid content. Solid content containing alumina particles with an average particle size of 0.01 μm or more and less than 1.0 μm in a volume concentration of 20% by volume or more and 40% by volume or less in the solid content, with the balance being a resin. A liquid composition containing the above and a solvent, wherein the content of the aluminum nitride particles is in the range of 25% by volume or more and 40% by volume or less in terms of volume concentration in the solid content, and the particle size is 1.0 μm or less. The content of alumina particles in the solid content is in the range of 20% by volume or more and 40% by volume or less in terms of volume concentration in the solid content, and the content of alumina particles having a particle size of 0.3 μm or less is 10 in volume concentration in solid content. A step of forming a wet insulating composition film on a substrate using a liquid composition in the range of 50% by volume or more and 20% by volume or less, and heating the wet insulating composition film to form an insulating film. It has a step of forming.

According to the above-mentioned method for producing an insulating film of the present invention, aluminum nitride particles having a relatively large average particle size and alumina particles having a relatively small average particle size have a volume concentration in the solid content within the above range. Since it is used in such a proportion, alumina particles having a relatively small particle size can be efficiently interposed between the particles of aluminum nitride particles having a relatively large particle size. Therefore, it is possible to manufacture an insulating film having both withstand voltage resistance and thermal conductivity improved in a well-balanced manner. The average particle size means a volume average particle size. The volume average particle size is a particle size at a point corresponding to a volume of 50% in a volume-based cumulative frequency distribution curve with the total volume of particles as 100%. The volume-based cumulative frequency distribution curve can be measured by a particle size distribution measuring device using a laser diffraction / scattering method.

Further, in the method for producing an insulating film of the present invention, aluminum nitride particles having an average particle size in the range of 1.0 μm or more and 3.0 μm or less are contained in a volume concentration in the solid content of 25% by volume or more and 40% by volume or less. 1. Alumina particles having an average particle size in the range of 0.01 μm or more and less than 0.3 μm are contained in a volume concentration of 10% by volume or more and 20% by volume or less in the solid content, and the average particle size is 0.3 μm or more. A liquid composition containing a solid content containing alumina particles in the range of less than 0 μm in a volume concentration of 10% by volume or more and 20% by volume or less in the volume concentration of the solid content, with the balance being a resin, and a solvent. The content of the aluminum nitride particles is in the range of 25% by volume or more and 40% by volume or less in terms of volume concentration in the solid content, and the content of alumina particles having a particle size of 1.0 μm or less is in the solid content. The content of alumina particles with a particle size of 0.3 μm or less is within the range of 10% by volume or more and 20% by volume or less in terms of volume concentration in the solid content. It has a step of forming a wet insulating composition film on a substrate by using the liquid composition in the above, and a step of heating the wet insulating composition film to form an insulating film.

According to the above-mentioned method of the insulating film of the present invention, two types of alumina particles having different average particle sizes are used at a ratio in which the volume concentration in the solid content is within the above range, so that the particle size is relatively large. Alumina particles having a relatively small particle size can be efficiently interposed between the particles of the large aluminum nitride particles. Therefore, it is possible to manufacture an insulating film having both withstand voltage resistance and thermal conductivity improved in a well-balanced manner.

According to the present invention, it is possible to provide an insulating heat radiating material and an insulating film having both withstand voltage and thermal conductivity improved in a well-balanced manner. Further, according to the present invention, it is also possible to provide a method for manufacturing an insulating film having both withstand voltage resistance and thermal conductivity improved in a well-balanced manner.

It is a schematic sectional drawing of the insulating heat dissipation material which concerns on one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings.
FIG. 1 is a schematic cross-sectional view of an insulating heat radiating material according to an embodiment of the present invention.
In FIG. 1, the insulating heat radiating material 1 contains a resin 2 and a filler 3.

The resin 2 preferably contains a polyimide resin, a polyamide-imide resin, or a mixture thereof. Since these resins are excellent in properties such as insulation, withstand voltage, chemical resistance, and mechanical properties, these properties of the insulating heat dissipation material 1 are improved.

The filler 3 is dispersed in the resin 2. The filler 3 includes aluminum nitride particles having an average particle size in the range of 1.0 μm or more and 3.0 μm or less, alumina particles having a particle size of 1.0 μm or less, and alumina particles having a particle size of 0.3 μm or less. include. That is, the filler 3 includes aluminum nitride particles 4, medium-diameter alumina particles 5a having a particle size of 1.0 μm or less and exceeding 0.3 μm, and small-diameter alumina particles 5b having a particle size of 0.3 μm or less. Medium-diameter alumina particles 5a and small-diameter alumina particles 5b are interposed between the particles of the aluminum nitride particles 4, and small-diameter alumina particles 5b are formed between the aluminum nitride particles 4 and the medium-diameter alumina particles 5a and between the particles of the medium-diameter alumina particles 5a. Intervene. By interposing the particles having a relatively small particle size between the particles having a relatively large particle size, the thermal conductivity between the particles is improved.

The aluminum nitride particles 4 are not particularly limited in particle shape. The aluminum nitride particles 4 may have, for example, a spherical shape, an elliptical spherical shape, a columnar shape, a plate shape, or the like, or may have an amorphous shape that does not have a uniform shape.

The medium-diameter alumina particles 5a and the small-diameter alumina particles 5b may have a shape such as a spherical shape, an elliptical spherical shape, a columnar shape, or a plate shape, or may have an irregular shape having no uniform shape. The medium-diameter alumina particles 5a and the small-diameter alumina particles 5b are preferably spherical or elliptical spheres from the viewpoints of dispersibility with respect to the resin 2, difficulty in agglomeration, ease of filling, and the like.

The content of the aluminum nitride particles 4 is in the range of 25% by volume or more and 40% by volume or less in terms of volume concentration in the insulating heat radiating material 1. The content of alumina particles with a particle size of 1.0 μm or less (total of medium-diameter alumina particles 5a and small-diameter alumina particles 5b) is within the range of 20% by volume or more and 40% by volume or less in terms of volume concentration in the insulating heat-dissipating material 1. be. The content of alumina particles (small diameter alumina particles 5b) having a particle size of 0.3 μm or less is within the range of 10% by volume or more and 20% by volume or less in terms of volume concentration in the insulating heat radiating material 1. That is, the content of the medium-diameter alumina particles 5a is in the range of 10% by volume or more and 20% by volume or less. The content of the filler 3 (total amount of aluminum nitride particles 4, medium-diameter alumina particles 5a, and small-diameter alumina particles 5b) is in the range of 50% by volume or more and 80% by volume or less in terms of volume concentration in the insulating heat-dissipating material 1. Is preferable.

When the contents of the aluminum nitride particles 4, the medium-diameter alumina particles 5a and the small-diameter alumina particles 5b are within the above ranges, the heat conduction of the insulating heat-dissipating material 1 is suppressed while suppressing the deterioration of the withstand voltage of the insulating heat-dissipating material 1. It is possible to improve the sex. The filler 3 may contain coarse alumina particles having a particle size of more than 1.0 μm. It is preferable that the coarse alumina particles having a particle size of more than 1.0 μm do not contain 5% by volume or more in volume concentration in the insulating heat radiating material 1.

When the contents of the medium-diameter alumina particles 5a and the small-diameter alumina particles 5b are within the above ranges, the medium-diameter alumina particles 5a and the small-diameter alumina particles 5b can be sufficiently interposed between the particles of the aluminum nitride particles 4. Therefore, it is possible to improve the thermal conductivity of the insulating heat radiating material 1 while maintaining the withstand voltage of the insulating heat radiating material 1.

The average particle size of the aluminum nitride particles 4 of the insulating heat radiating material 1 and the content (volume concentration) of the aluminum nitride particles 4 and the alumina particles (medium-diameter alumina particles 5a and small-diameter alumina particles 5b) are determined as follows. be able to.
The insulating heat radiating material 1 is heated in the atmosphere to remove the resin 2 and the remaining filler 3 is recovered. The heating temperature is not particularly limited as long as the resin 2 is thermally decomposed and the filler 3 is not thermally decomposed. The heating time is, for example, 12 hours. The weight of the recovered filler 3 is measured, and the weight-based content (weight concentration) of the filler 3 is calculated from the weight of the insulating heat radiating material 1 before heating.

Specifically, the weight of the filler 3 recovered by heating is Wa (g), the weight of the insulating heat radiating material 1 before heating is Wf (g), the density of the filler 3 is Da (g / cm ³ ), and the resin. The content (% by weight) of the filler 3 is calculated from the following formula, where the density of 2 is Dr (g / cm ³ ).
Content of filler 3 (% by weight) = Wa / Wf × 100
= Wa / {Wa + (Wf-Wa)} x 100

Next, the particle size distribution of the alumina particles and the aluminum nitride particles of the filler 3 is measured.
Element mapping is performed on the heat-recovered filler 3 using SEM-EDX (scanning electron microscope-energy dispersive X-ray spectroscope) to discriminate between alumina particles and aluminum nitride particles. Next, the particle sizes of the alumina particles and the aluminum nitride particles are measured using the SEM image. The volume-based particle size distribution is obtained by spherically approximating the alumina particles whose particle size has been measured and the aluminum nitride particles. The average particle size of the aluminum nitride particles is calculated from the particle size distribution of the aluminum nitride particles. Further, from the particle size distribution of the alumina particles, the volume concentration (volume%) of the particles having a particle size of 1.0 μm or less is calculated as Vx, and the volume concentration (volume%) of the particles having a particle size of 0.2 μm or less is calculated as Vy.

The oxygen and nitrogen contents of the filler 3 are measured using an oxygen / nitrogen analyzer. The obtained nitrogen content is converted into the aluminum nitride particle amount, and the oxygen content is converted into the alumina particle, and the mass ratio of the alumina particle to the aluminum nitride particle (alumina particle / aluminum nitride particle) is calculated as C. From the above particle size distribution, the mass ratio of the alumina particles to the aluminum nitride particles (alumina particles / aluminum nitride particles) is calculated as C'. It is confirmed that the difference [(XY) / X × 100] between the mass ratio C obtained by using the oxygen / nitrogen analyzer and the mass ratio C'determined from the particle size distribution is less than 3%. When the difference between the mass ratio C and the mass ratio C'is 3% or more, the particle size distribution of the alumina particles and the aluminum nitride particles is weighted so that the difference is less than 3%.

The density Da of the filler 3 is calculated by the following formula using the mass ratio C, the density Dn (g / cm ³ ) of the aluminum nitride particles, and the density Dо (g / cm ³ ) of the alumina particles.
Da (g / cm ³ ) = Dn × {1 / (1 + C)} + Do × {C / (1 + C)}

Next, the content Va (% by volume) of the filler 3 was measured by the weight Wa (g) of the filler 3 recovered by heating, the density Da (g / cm ³ ) of the filler 3, and the insulating heat radiating material 1 before heating. It is calculated from the following formula using the weight Wf (g) and the density Dr (g / cm ³ ) of the resin 2.
Va (% by volume) = (Wa / Da) / {(Wa / Da) + (Wf-Wa) / Dr} × 100

The volume concentration Vn (volume%) of the aluminum nitride particles is calculated from the following formula.
Vn (% by volume) = Va × {1 / (1 + C × Dn / Dо)

The volume concentration Vo _1.0 (volume%) of the alumina particles having a particle size of 1.0 μm or less is calculated from the following formula.
Vo _1.0 (% by volume) = (Va-Vn) x Vx / 100

The volume concentration Vo _0.2 (volume%) of the alumina particles having a particle size of 0.2 μm or less is calculated from the following formula.
Vo _0.2 (% by volume) = (Va-Vn) × Vy / 100

The filler 3 may have at least two peaks in the range where the particle size distribution of the filler 3 is 0.01 μm or more and less than 1.0 μm.
The peak having a relatively large particle size is preferably in the range of 0.5 μm or more and 0.9 μm or less. The peak having a relatively small particle size is preferably in the range of 0.05 μm or more and less than 0.3 μm. The difference between the peak on the large diameter side and the peak on the small diameter side is preferably in the range of 0.2 μm or more and 0.8 μm or less, and more preferably in the range of 0.3 μm or more and 0.7 μm or less.

The insulating heat radiating material 1 of the present embodiment can be used as an insulating film arranged between the metal foil (circuit pattern) and the substrate in a circuit board such as a metal base substrate. It can also be used as a protective film that protects the surface of electronic components and circuit boards. Further, it can be used as a single sheet or film, for example, as an insulating film for a circuit board such as a flexible printed circuit board. Furthermore, it can be used as an insulating film for an insulating conductor used in a coil or a motor, such as an enamel film for an enamel wire.

Next, a method of manufacturing an insulating film containing the insulating heat radiating material 1 of the present embodiment will be described.
The method for producing an insulating film of the present embodiment includes, for example, a step of forming a wet insulating composition film on a substrate using a liquid composition containing a solid content and a solvent, and the obtained wet insulating property. It comprises a step of heating a composition film to form an insulating film.

The solid content contained in the liquid composition is a component that remains as a solid when the liquid composition is heated to remove the solvent. The solid content is aluminum nitride particles, alumina particles and a resin. The resin in the liquid composition may be dissolved in a solvent.

The aluminum nitride particles have an average particle size in the range of 1.0 μm or more and 3.0 μm or less. The content of the aluminum nitride particles having a particle size of less than 1.0 μm is preferably 40% by volume or less, and the content of particles having a particle size of 3.0 μm or more is preferably 5% by volume or less.

Alumina particles include one type of alumina particles or two types of alumina particles having different average particle sizes. When the alumina particles are a kind of alumina particles, the average particle size of the alumina particles is in the range of 0.01 μm or more and less than 1.0 μm, more preferably in the range of 0.01 μm or more and 0.8 μm or less. The difference in the average particle size between the aluminum nitride particles and the alumina particles is preferably in the range of 0.5 μm or more and 1.3 μm or less, and more preferably in the range of 0.5 μm or more and 1.0 μm or less. The alumina particles preferably have a particle content of more than 1.0 μm of 5% by volume or less.

The mixing ratio of the solid content of the liquid composition is within the range of 25% by volume or more and 40% by volume or less for the aluminum nitride particles and 20% by volume or more and 40% by volume or less for the alumina particles. It is the ratio that the balance becomes resin. Further, the composition of the solid content of the liquid composition is such that the content of aluminum nitride particles is in the range of 25% by volume or more and 40% by volume or less in volume concentration, and the content of alumina particles having a particle size of 1.0 μm or less. Is in the range of 20% by volume or more and 40% by volume or less in volume concentration, and the content of alumina particles having a particle size of 0.3 μm or less is in the range of 10% by volume or more and 20% by volume or less in volume concentration.

The method of mixing the aluminum nitride particles, the alumina particles, and the resin is not particularly limited. For example, a particle mixture dispersion containing aluminum nitride particles, alumina particles, and a solvent may be mixed with a resin solution. Further, the aluminum nitride particle dispersion, the alumina particle dispersion, and the resin solution may be mixed at the same time.

When the alumina particles include two types of alumina particles, the first alumina particles having a relatively small average particle size are in the range of 0.01 μm or more and less than 0.3 μm. The content of the first alumina particles is preferably 1% by volume or less, and the content of particles having a particle size of 0.3 μm or more is 20% by volume or less. preferable. Further, the second alumina particles having a relatively large average particle size are in the range where the average particle size is 0.3 μm or more and less than 1.0 μm. The content of the second alumina particles having a particle size of less than 0.3 μm is preferably 3% by volume or less, and the content of particles having a particle size of more than 1.0 μm is preferably 30% by volume or less.

The mixing ratio of the solid content of the liquid composition is such that the aluminum nitride particles are in the range of 25% by volume or more and 40% by volume or less in terms of the volume concentration in the solid content, and the first alumina particles are 10 in volume concentration in the solid content. It is in the range of 10% by volume or more and 20% by volume or less, the second alumina particles are in the range of 10% by volume or more and 20% by volume or less in terms of volume concentration in the solid content, and the balance is the ratio of resin. Further, the composition of the solid content of the liquid composition is such that the content of aluminum nitride particles is in the range of 25% by volume or more and 40% by volume or less in volume concentration, and the content of alumina particles having a particle size of 1.0 μm or less. Is in the range of 20% by volume or more and 40% by volume or less in volume concentration, and the content of alumina particles having a particle size of 0.3 μm or less is in the range of 10% by volume or more and 20% by volume or less in volume concentration.

The method of mixing the aluminum nitride particles, the first alumina particles, the second alumina particles, and the resin is not particularly limited. For example, a particle mixture dispersion containing aluminum nitride particles, first alumina particles, second alumina particles, and a solvent may be mixed with a resin solution. Further, the aluminum nitride particle dispersion, the first alumina particle dispersion, the second alumina particle dispersion, and the resin solution may be mixed at the same time.

As a method for forming a wet insulating composition film on a substrate by using the above liquid composition, a coating method or an electrodeposition method can be used.

The coating method is a method of coating a liquid composition on a substrate to form a coating layer. As a method for applying the liquid composition, a spin coating method, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, a dip coating method and the like can be used.

In the electrodeposition method, a metal substrate is immersed in a liquid composition (electrodeposition liquid) containing resin particles and inorganic particles, and the resin particles and the inorganic particles are electrodeposited on the surface of the metal substrate to form an electrodeposition layer. How to do it. The electrodeposition solution is an inorganic particle dispersion resin solution obtained by mixing a dispersion in which an inorganic particle mixture is dispersed and a resin solution in which a resin is dissolved, and a poor solvent for the resin is added to precipitate the resin as particles. It is possible to use the prepared product.

The method for forming the insulating film by heating the wet insulating composition film is not particularly limited, and may be heated at a temperature equal to or higher than the volatilization temperature of the solvent. The heating temperature is usually 200 ° C. or higher, preferably 250 ° C. or higher.

According to the insulating heat radiating material 1 of the present embodiment having the above configuration, the aluminum nitride particles 4 having an average particle size in the range of 1.0 μm or more and 3.0 μm or less and the particle size of 1.0 μm. Below, medium-diameter alumina particles 5a having a particle size of more than 0.3 μm and small-diameter alumina particles 5b having a particle size of 0.3 μm or less are included, and fine alumina particles (medium-diameter alumina particles 5a and small diameters) are included between the particles of the aluminum nitride particles 4. Alumina particles 5b) can be efficiently interposed. Therefore, it is possible to improve the thermal conductivity of the insulating heat radiating material while suppressing the decrease in withstand voltage due to the addition of inorganic particles. In particular, according to the insulating heat radiating material 1 of the present embodiment, the contents of the aluminum nitride particles 4, the medium-diameter alumina particles 5a, and the small-diameter alumina particles 5b are each within the above ranges, so that the withstand voltage resistance is lowered. It is possible to further improve the thermal conductivity without causing it.

In the insulating heat radiating material 1 of the present embodiment, when the particle size distribution of the filler 3 has at least two peaks within the range of 0.01 μm or more and less than 1.0 μm, the alumina particles have a relatively large particle size. Since the difference from the alumina particles having a relatively small particle size becomes clear, the alumina particles having a relatively small particle size can be more efficiently interposed between the particles of the alumina particles having a relatively large particle size. .. Therefore, the thermal conductivity of the insulating heat radiating material can be further improved. Further, in the insulating heat radiating material 1 of the present embodiment, when the resin 2 is polyimide, polyamideimide, or a mixture thereof, the insulating heat insulating material 1 has insulating properties, withstand voltage properties, chemical resistance, and mechanical properties. Can be improved. Further, in the insulating heat radiating material 1 of the present embodiment, the volume concentration of the aluminum nitride particles 4 having a relatively large particle size contained in the filler 3 is such that the particle size having a relatively small particle size is 1.0 μm or less. When the volume concentration of the particles (total of medium-diameter alumina particles 5a and small-diameter alumina particles 5b) is higher, the thermal resistance at the interface between the filler 3 and the resin 2 can be lowered, so that the thermal conductivity can be further improved. can.

Further, since the insulating film of the present embodiment contains the above-mentioned insulating heat radiating material, both withstand voltage resistance and thermal conductivity can be improved in a well-balanced manner.

Further, according to the method for producing an insulating film of the present embodiment, the volume concentration in the solid content of the aluminum nitride particles having a relatively large average particle size and the alumina particles having a relatively small average particle size is in the above range. Since it is used in the inner ratio, the inorganic particles having a relatively small particle size can be efficiently interposed between the particles of the inorganic particles having a relatively large particle size. Therefore, it is possible to manufacture an insulating film having both withstand voltage resistance and thermal conductivity improved in a well-balanced manner.

Although the embodiments of the present invention have been described above, the present invention is not limited to this, and can be appropriately changed without departing from the technical idea of the invention.

In the examples, polyimide (PI), polyamide-imide (PAI), and a mixture (PI + PAI) containing polyamide-imide and polyimide in a mass ratio of 50:50 are used as the resin, and the average particle size is 5.0 μm as the filler. , 1.5 μm aluminum nitride particles and alumina particles having an average particle size of 0.7 μm and 0.1 μm were used. The content of particles of 2.5 μm or less contained in alumina particles with an average particle size of 0.7 μm is 100% by volume, the content of particles of 0.6 μm or less is 43% by volume, and the content of alumina particles with an average particle size of 0.1 μm is The content of the particles of 0.6 μm or less contained was 100% by volume, and the content of the particles of 0.2 μm or less was 79% by volume.

[Example 1 of the present invention]
The resin is 33% by volume, the aluminum nitride particles having an average particle size of 1.5 μm are 35% by volume, the alumina particles having an average particle size of 0.7 μm are 20% by volume, and the average particle size is. A filler-dispersed resin solution containing 0.1 μm alumina particles at a volume concentration of 12% by volume was prepared as follows. Polyamideimide was used as the resin.

First, aluminum nitride particles having an average particle size of 1.5 μm, alumina particles having an average particle size of 0.7 μm, and alumina particles having an average particle size of 0.1 μm are mixed at the above ratios to prepare a filler mixture. did. 1.0 g of the obtained filler mixture, 62.5 g of NMP (N-methyl-2-pyrrolidone), 10 g of 1M2P (1-methoxy-2-propanol), and 0.22 g of AE (amino ether). It was put into a mixed solvent containing the mixture and subjected to ultrasonic treatment for 30 minutes to prepare a filler dispersion. In addition, polyamide-imide was dissolved in NMP to prepare a resin solution.
The above filler dispersion and the above resin solution are mixed so that the content of the resin and the filler is the above ratio and the concentration of the resin is 5% by mass to prepare a filler dispersion resin solution. did. Using this filler-dispersed resin solution, an insulating film made of an insulating resin material was formed into a film by an electrodeposition method as follows to prepare a copper substrate with an insulating film.

While stirring the above filler-dispersed resin solution at a rotation speed of 5000 rpm, 21 g of water was added dropwise to the filler-dispersed resin solution to precipitate the resin, thereby preparing a filler-dispersed electrodeposition solution. A copper substrate having a thickness of 0.3 mm and a thickness of 30 mm × 20 mm and a stainless electrode were immersed in the obtained filler dispersion electrodeposition liquid, and a DC voltage of 100 V was applied with the copper substrate as the positive electrode and the stainless electrode as the negative electrode. An electrodeposition film was formed on the surface of the copper substrate. A protective tape was attached to the back surface of the copper substrate to protect it from forming an electrodeposition film. The film thickness of the electrodeposition film was set so that the film thickness of the insulating film generated by heating was 20 μm. Next, the copper substrate on which the electrodeposition film was formed was heated at 250 ° C. for 3 minutes in an atmospheric atmosphere to dry the electrodeposition film, thereby producing a copper substrate with an insulating film.

[Example 2 of the present invention, Comparative Examples 1 and 2]
A copper substrate with an insulating film was produced in the same manner as in Example 1 of the present invention, except that the type of resin and the composition of the filler-dispersed resin solution were changed as shown in Table 1 below. In Table 1, PI indicates polyimide and PAI indicates polyamide-imide in the resin types.

[Example 3 of the present invention]
42% by volume of resin, 27% by volume of aluminum nitride particles with an average particle size of 1.5μm, 18% by volume of alumina particles with an average particle size of 0.7μm, average particle size A filler-dispersed resin solution containing 0.1 μm alumina particles at a volume concentration of 13% by volume was prepared as follows. As the resin, a mixture of polyamide-imide and polyimide was used.

First, aluminum nitride particles having an average particle size of 1.5 μm, alumina particles having an average particle size of 0.7 μm, and alumina particles having an average particle size of 0.1 μm are mixed at the above ratios to prepare a filler mixture. did. 1.0 g of the obtained filler mixture was added to 10 g of cyclohexane and sonicated for 30 minutes to prepare a filler dispersion. In addition, polyamide-imide was dissolved in cyclohexane to prepare a resin solution of the resin.
The above filler dispersion and the above resin solution are mixed so that the content of the resin and the filler is the above ratio and the concentration of the resin is 5% by mass to prepare a filler dispersion resin solution. did.

The obtained filler-dispersed resin solution was dispersed by repeating a high-pressure injection treatment at a pressure of 50 MPa 10 times using a starburst manufactured by Sugino Machine Limited to prepare a filler-dispersed resin coating liquid. The obtained filler dispersion resin coating liquid was applied to the surface of a copper substrate having a thickness of 0.3 mm and a thickness of 30 mm × 20 mm so that the film thickness after heating was 20 μm to form a coating film. Next, the copper substrate on which the coating film was formed was placed on a hot plate, the temperature was raised from room temperature to 60 ° C. at a heating rate of 3 ° C./min, heated at 60 ° C. for 100 minutes, and then further 1 ° C./min. The temperature was raised to 120 ° C. at a heating rate, heated at 120 ° C. for 100 minutes, and dried to obtain a dry film. Then, the dry film was heated at 250 ° C. for 1 minute and then at 400 ° C. for 1 minute to prepare a copper substrate with an insulating film.

[Examples 4 to 5 of the present invention, Comparative Examples 3 to 5]
A copper substrate with an insulating film was produced in the same manner as in Example 3 of the present invention, except that the type of resin and the composition of the filler-dispersed resin solution were changed as shown in Table 1 below.

[evaluation]
The copper substrates with an insulating film obtained in Examples 1 to 5 of the present invention and Comparative Examples 1 to 5 were evaluated as follows. The results are shown in Table 2 below.

(Volume concentration of aluminum nitride particles and alumina particles in the insulating film)
The copper substrate with an insulating film and the insulating film were separated by energizing the copper substrate with an insulating film in an aqueous sodium chloride solution to generate gas from the copper substrate. Using the obtained insulating film, the volume concentrations of the aluminum nitride particles and the alumina particles in the insulating film were measured by the above-mentioned method. Then, the volume concentration of the alumina particles having a particle size of 1.0 μm or less and the alumina particles having a particle size of 0.3 μm or less was measured by the above-mentioned method.

(Withstand voltage per film thickness)
The withstand voltage was measured using a multifunctional safety tester 7440 of Measurement Technology Laboratory Co., Ltd. An electrode (φ6 mm) was placed on the surface of the insulating film of the copper substrate with an insulating film. The copper substrate of the copper substrate with an insulating film and the electrodes arranged on the surface of the insulating film were connected to each power source, and the voltage was increased to 6000 V in 30 seconds. The voltage at the time when the current value flowing between the copper substrate and the electrode reached 5000 μA was defined as the withstand voltage of the insulating film.

(Thermal conductivity of the insulating film)
The thermal conductivity (thermal conductivity in the thickness direction of the insulating film) was measured by a laser flash method using LFA477 Nanoflash manufactured by NETZSCH-Geratebau GmbH. The thermal conductivity was calculated using a two-layer model that does not consider the interfacial thermal resistance. As described above, the thickness of the copper substrate was 0.3 mm, and the thermal diffusivity of the copper substrate was 117.2 mm ² / sec. To calculate the thermal conductivity of the insulating film, the density of the aluminum nitride particles is 3.40 g / cm ³ , the specific heat of the aluminum nitride particles is 0.72 J / gK, the density of the alumina particles is 3.89 g / cm ³ , and the specific heat of the alumina particles is 0. The specific heat of .78 J / gK, the density of the polyamideimide resin 1.41 g / cm ³ , the specific heat of the polyamideimide resin 1.09 J / gK, the density of the polyimide 1.4 g / cm ³ , and the specific heat of the polyimide 1.13 J / gK were used.

(Performance value)
The value obtained from the following formula was used as the performance value.
Performance value = Withstand voltage per film thickness (kW / mm) x Thermal conductivity of insulating film (W / mK)

(Presence / absence of voids)
A copper substrate with an insulating film was embedded in resin, and the cross section was exposed by mechanical polishing. Next, the cross section of the insulating film of the exposed copper substrate with the insulating film was observed using an SEM (scanning electron microscope). The case where one or more voids (pores) having a maximum diameter of 0.3 μm or more were found with respect to the cross-sectional area of 100 μm ² of the insulating film was considered to have voids.

In Examples 1 to 5 of the present invention in which the particle size and volume concentration of the aluminum nitride particles and the alumina particles are within the range of the present invention, the performance values are both high, so that the withstand voltage and the thermal conductivity are improved in a well-balanced manner. It was confirmed that it was done. In particular, the performance values of Examples 1 to 2, 4 to 5 of the present invention, in which the volume concentration of the aluminum nitride particles is higher than the volume concentration of the alumina particles having a particle size of 1.0 μm or less, are particularly improved.

In Comparative Example 1 in which the average particle size of the aluminum nitride particles exceeds the range of the present invention, the withstand voltage tends to decrease. This is because dielectric breakdown tends to proceed at the interface, and if particles having a relatively large particle size are used, a dielectric breakdown path along the interface is likely to be formed.

In Comparative Example 2 in which the volume concentration of the aluminum nitride particles exceeded the range of the present invention, the withstand voltage tended to decrease. This is because there were not enough alumina particles to fill the spaces between the aluminum nitride particles, and voids (pores) were formed in the insulating film.

In Comparative Example 3 in which the volume concentration of the alumina particles having a particle size of 1.0 μm or less (particularly, the particle size is 0.3 μm or less) exceeds the range of the present invention, the withstand voltage tended to decrease. This is because the thermal resistance at the interface between the filler and the resin has increased due to the increase in the proportion of alumina particles having a relatively small particle size.

In Comparative Example 4 in which the volume concentration of the alumina particles having a particle size of 1.0 μm or less was smaller than the range of the present invention, the thermal conductivity tended to decrease. This is because the amount of alumina particles having a particle size of 0.3 μm or less intervening between the aluminum nitride particles is reduced, so that voids are formed between the particles of the aluminum nitride particles.

In Comparative Example 5 in which the volume concentration of the aluminum nitride particles was lower than the range of the present invention, the thermal conductivity tended to be low. This is because the content of the aluminum nitride particles in the insulating film is too low, so that a path for transferring heat is not sufficiently formed.

1 Insulating heat dissipation material 2 Resin 3 Filler 4 Aluminum nitride particles 5a Medium diameter alumina particles 5b Small diameter alumina particles

Claims (7)

An insulating heat-dissipating material containing a resin and a filler.
The filler includes aluminum nitride particles having an average particle size in the range of 1.0 μm or more and 3.0 μm or less, alumina particles having a particle size of 1.0 μm or less, and alumina particles having a particle size of 0.3 μm or less. Including,
The content of the aluminum nitride particles is within the range of 25% by volume or more and 40% by volume or less in terms of volume concentration in the insulating heat dissipation material, and the content of the alumina particles having a particle size of 1.0 μm or less is the insulation. The content of alumina particles having a volume concentration of 20% by volume or more and 40% by volume or less in the heat-dissipating material and having a particle size of 0.3 μm or less is 10% by volume in the insulating heat-dissipating material. Insulating heat dissipation material within the range of 20% by volume or more. The insulating heat-dissipating material according to claim 1, wherein the filler has at least two peaks in a particle size distribution of the filler of 0.01 μm or more and less than 1.0 μm. The insulating heat-dissipating material according to claim 1 or 2, wherein the resin is polyimide, polyamide-imide, or a mixture thereof. The insulating heat-dissipating material according to any one of claims 1 to 3, wherein the volume concentration of the aluminum nitride particles is higher than the volume concentration of the alumina particles having a particle size of 1.0 μm or less. An insulating film containing the insulating heat radiating material according to any one of claims 1 to 4. 1. The volume concentration of aluminum nitride particles in the range of 1.0 μm or more and 3.0 μm or less in the solid content is in the range of 25% by volume or more and 40% by volume or less, and the average particle size is 0.01 μm or more. A liquid composition containing a solid content containing alumina particles in the range of less than 0 μm in a volume concentration of 20% by volume or more and 40% by volume or less in the volume concentration of the solid content, with the balance being a resin, and a solvent. The content of the aluminum nitride particles is in the range of 25% by volume or more and 40% by volume or less in terms of volume concentration in the solid content, and the content of alumina particles having a particle size of 1.0 μm or less is in the solid content. The content of alumina particles with a particle size of 0.3 μm or less is within the range of 10% by volume or more and 20% by volume or less in terms of volume concentration in the solid content. A step of forming a wet insulating composition film on a substrate using the liquid composition in
A method for producing an insulating film, comprising a step of heating the wet insulating composition film to form an insulating film. Aluminum nitride particles having an average particle size in the range of 1.0 μm or more and 3.0 μm or less are contained in a volume concentration in the solid content of 25% by volume or more and 40% by volume or less, and the average particle size is 0.01 μm or more and 0.3 μm. Alumina particles in the range of less than 10% by volume or more and 20% by volume or less in volume concentration in the solid content, and alumina particles having an average particle size in the range of 0.3 μm or more and less than 1.0 μm are solid content. It is a liquid composition containing a solid content and a solvent contained in a volume concentration of 10% by volume or more and 20% by volume or less in a ratio in which the balance becomes a resin, and the content of the aluminum nitride particles is solid. The content of alumina particles having a particle size of 1.0 μm or less in the range of 25% by volume or more and 40% by volume or less in the volume concentration in the minute is 20% by volume or more and 40% by volume or less in the volume concentration in the solid content. On the substrate using a liquid composition in which the content of alumina particles having a particle size of 0.3 μm or less is in the range of 10% by volume or more and 20% by volume or less in terms of volume concentration in the solid content. In the process of forming a wet insulating composition film,
A method for producing an insulating film, comprising a step of heating the wet insulating composition film to form an insulating film.

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