JP7176943B2 - Laminates, electronic components, and inverters - Google Patents

Description

The present invention relates to laminates used in electronic components, such as power semiconductor modules.

Conventionally, power semiconductor modules are used in industrial equipment such as inverters, elevators, and uninterruptible power supplies (UPS). A substrate used in a power semiconductor module is generally composed of a laminate of a ceramic substrate and a copper plate, but these have different coefficients of thermal expansion, so there is a problem of peeling and warping over time. Therefore, in recent years, the development of replacing the ceramic substrate with a resin sheet is underway.

As such a resin sheet, for example, as shown in Patent Document 1, a first insulating layer which is a semi-cured material or a cured material and an uncured material or a semi-cured material are placed on a heat conductor such as a copper plate. A laminate is known in which a second insulating layer, which is an object, is provided in this order. In general, a conductive layer such as a lead frame is attached on the substrate. By further curing the laminate to which the is attached, the adhesion to the conductive layer can be enhanced.

In the laminate of Patent Document 1, the first insulating layer contains 86% by weight or more and less than 97% by weight of the inorganic filler, and the second insulating layer contains 67% by weight or more and less than 95% by weight of the inorganic filler. Including, the content ratio of the inorganic filler in the first insulating layer is higher than the content ratio of the inorganic filler in the second insulating layer. In Patent Document 1, by adjusting the content ratio in this manner, high heat dissipation is ensured while ensuring adhesion to the conductive layer.

Japanese Patent No. 5346363

In power semiconductor module applications, the density of semiconductor circuits is increasing, and there is a need to further improve heat dissipation while ensuring the insulating properties of resin sheets for substrates. In order to improve heat dissipation, it is conceivable to use an inorganic filler with high thermal conductivity or to further increase the content of the inorganic filler. However, since a laminate having both high levels of insulation and heat dissipation has not been realized, improvement is required.
Then, this invention makes it a subject to provide the laminated body excellent in insulation and heat dissipation.

As a result of intensive studies, the inventors have found that the above problems can be solved by adjusting the porosity of the insulating resin layer of the laminate, and completed the present invention below. That is, the present invention provides the following [1] to [15].
[1] A laminate comprising a thermal conductor having a thermal conductivity of 10 W/m·K or more and an insulating resin layer provided on the surface of the thermal conductor and containing a thermally conductive filler, ,
A laminate having a porosity of 0.09% or less in terms of area ratio in a cross section of the insulating resin layer obtained by image analysis.
[2] The laminate according to [1] above, wherein the insulating resin layer has a region that melts at 50°C or higher and 175°C or lower and a region that does not melt at 50°C or higher and 175°C or lower.
[3] The laminate according to [2] above, wherein a region of the insulating resin layer on the side opposite to the surface on which the heat conductor is provided is a region that melts at 50°C or higher and 175°C or lower.
[4] The above [ 1] The laminate according to any one of [3].
[5] The insulating resin layer according to any one of [1] to [4], wherein at least a region on the side opposite to the surface on which the heat conductor is provided is an uncured material or a semi-cured material. Laminate as described.
[6] The laminate according to any one of [1] to [5] above, wherein the insulating resin layer has at least a semi-cured material or a cured material in a region on the side where the heat conductor is provided.
[7] The hardening rate of the region on the side where the heat conductor is provided is 50% or more,
The hardening rate of the region on the side opposite to the surface on which the heat conductor is provided is less than 80%,
Any one of the above [1] to [6], wherein the hardening rate of the area on the side where the heat conductor is provided is higher than the hardening rate of the area on the side opposite to the side on which the heat conductor is provided. The laminate according to the item.
[8] The thermally conductive filler contains boron nitride,
The laminate according to any one of the above [1] to [7], wherein the boron nitride is contained in at least a region of the insulating resin layer on the side where the heat conductor is provided.
[9] The thermally conductive filler contains alumina,
The laminate according to any one of [1] to [8] above, wherein the alumina is contained in a region of the insulating resin layer on the side opposite to the side on which the heat conductor is provided.
[10] The laminate according to [9] above, wherein the alumina has an aspect ratio of 2 or less.
[11] The thermally conductive filler contains boron nitride,
The laminate according to [9] or [10] above, wherein a region of the insulating resin layer on the side opposite to the surface on which the heat conductor is provided further contains boron nitride.
[12] The thermally conductive filler contains boron nitride,
Both the region on the side of the surface on which the thermal conductor is provided and the region on the side opposite to the surface on which the thermal conductor is provided both contain boron nitride,
In the insulating resin layer, the content of boron nitride in the region on the side where the heat conductor is provided is higher than the content of boron nitride in the region on the side opposite to the face on which the heat conductor is provided. The laminate according to any one of [1] to [11].
[13] The laminate according to any one of [1] to [12] above, wherein the heat conductor has a thickness of 0.03 mm or more and 3 mm or less.
[14] An electronic component comprising the laminate according to any one of [1] to [13] above.
[15] An inverter comprising the electronic component according to [14] above.

ADVANTAGE OF THE INVENTION According to this invention, the laminated body excellent in insulation and heat dissipation can be provided.

It is a typical sectional view showing a layered product of the present invention. It is a typical sectional view showing a layered product concerning one embodiment of the present invention.

Hereinafter, the present invention will be described using embodiments.
<Laminate>
The laminate 10 of the present invention includes a thermal conductor 11 having a thermal conductivity of 10 W/m·K or more, and an insulating resin layer 12 provided on the surface of the thermal conductor 11 and containing a thermally conductive filler. The porosity in the cross section of the insulating resin layer 12 obtained from image analysis is 0.09% or less in terms of area ratio.
Since the insulating resin layer 12 contains a thermally conductive filler, it is possible to increase the thermal conductivity. It is possible to obtain a laminate having both thermal conductivity and insulation.

[Insulating resin layer]
(Porosity)
The insulating resin layer 12 has a porosity of 0.09% or less in terms of area ratio in the cross section of the insulating resin layer, which is obtained by image analysis. If the porosity exceeds 0.09%, the ratio of air in the insulating resin layer increases, resulting in poor insulation. Moreover, since the insulating resin layer 12 tends to become brittle, the sheet strength is lowered.
From the viewpoint of improving insulation and sheet properties, the porosity of the insulating resin layer 12 is preferably 0.07% or less, more preferably 0.06% or less, and even more preferably 0.04% or less.
The porosity of the insulating resin layer 12 can be measured by the method described in Examples below.

The insulating resin layer 12 is formed by applying a resin composition diluted with a solvent and then drying the solvent used as the diluent, as will be described later in the manufacturing method. Then, the obtained insulating resin layer 12 is vacuum-pressed while being heated to obtain a laminate. Therefore, although not particularly limited, the porosity of the insulating resin layer 12 may be adjusted by appropriately changing these drying conditions, curing conditions, vacuum press conditions, and the like.

(relative permittivity)
In the insulating resin layer 12, the dielectric constant of the surface (one surface 12X) on which the heat conductor 11 is provided is the ratio of the surface opposite to the surface on which the heat conductor 11 is provided (the other surface 12Y). It is preferably lower than the dielectric constant. The laminate 10 is used for a semiconductor substrate or the like, and a conductive layer (not shown) such as a lead frame is formed on the other surface 12Y in a post-process or the like. When a voltage is applied to the laminate 10 on which the conductive layer is formed, if the dielectric constant of the other surface 12Y of the insulating resin layer 12 is high, generally at the end of the interface between the conductive layer and the insulating resin layer 12 Concentration of the electric field may cause dielectric breakdown, but the concentration of the electric field can be alleviated by lowering the dielectric constant of the one surface 12X of the insulating resin layer 12 . As a result, dielectric breakdown is less likely to occur, and the insulation of the laminate 10 can be improved.

In the insulating resin layer 12, when the dielectric constant on the one surface 12X side is lower than the dielectric constant on the other surface 12Y side, the difference between these dielectric constants is preferably 2 or more, and 3 or more. is more preferable. By setting the difference in relative permittivity to be equal to or more than these lower limits, electric field concentration can be alleviated, and the insulation of the laminate 10 can be easily ensured.
The difference in dielectric constant is not particularly limited, but is, for example, 10 or less, preferably 7 or less from the viewpoint of practicality.

In addition, from the viewpoint of enhancing insulation, the dielectric constant of the one surface 12X side is, for example, 2 or more and 10 or less, preferably 3 or more and 7 or less, and more preferably 3 or more and 5 or less. With respect to the entire thickness of the insulating resin layer 12, the insulating resin layer 12 may have a dielectric constant within the above range in a region of a certain thickness from the one surface 12X. The relative permittivity of the thick region may be within the above range, and it is preferable that the relative permittivity of at least the 20% thick region be within the above range.
The dielectric constant of the other surface 12Y is, for example, 4 or more and 11 or less, preferably 5 or more and 9 or less, more preferably 6 or more and 8 or less, from the viewpoint of enhancing insulation. With respect to the entire thickness of the insulating resin layer 12, the insulating resin layer 12 may have a dielectric constant within the above range in a region of a certain thickness from the other surface 12Y. The relative permittivity of the thick region may be within the above range, and it is preferable that the relative permittivity of at least the 20% thick region be within the above range.
In addition, in this specification, the dielectric constant means the dielectric constant at a frequency of 1 MHz. The dielectric constant can be measured by the method described in Examples below.

(Melting properties)
The insulating resin layer 12 preferably has a region that melts at 50° C. or higher and 175° C. or lower and a region that does not melt at 50° C. or higher and 175° C. or lower. It is preferable that the region on the other surface 12Y) side is a region that melts at a temperature of 50° C. or more and 175° C. or less. The laminate 10 is used for a semiconductor substrate or the like as described above, and a conductive layer such as a lead frame is formed on the other surface 12Y in a post-process or the like. Therefore, if the region on the side opposite to the surface on which the heat conductor 11 is provided is a region that melts at 50° C. or more and 175° C. or less, the adhesion between the insulating resin layer 12 and the conductive layer is improved.
In this specification, melting at 50° C. or higher and 175° C. or lower means having fluidity in the range of 50° C. or higher and 175° C. or lower, that is, the melting temperature is in the range of 50° C. or higher and 175° C. or lower. . Therefore, the insulating resin layer 12 may have a melting temperature within a range of 50° C. or more and 175° C. or less in a constant thickness region from the other surface 12Y with respect to the entire thickness of the insulating resin layer 12 . Specifically, the melting temperature of the region at least 10% thick from the other surface 12Y should be within the above range, and the melting temperature of the region at least 20% thick is preferably within the above range. The melting temperature can be measured by the method described in Examples.

From the viewpoint of improving the adhesion between the insulating resin layer 12 and the conductive layer, the melting temperature of the region on the side opposite to the surface on which the heat conductor 11 is provided (the other surface 12Y) is preferably 85° C. or higher. 170° C. or lower, more preferably 100° C. or higher and 170° C. or lower, still more preferably 120° C. or higher and 160° C. or lower.
In addition, the melt viscosity at 50° C. or higher and 175° C. or lower in the region on the side of the surface opposite to the surface on which the heat conductor 11 is provided (the other surface 12Y) is preferably 150 Pa s or less, more preferably 120 Pa s. Below, it is more preferably 70 Pa·s or less, still more preferably 50 Pa·s or less. When the melt viscosity is equal to or less than the upper limit, the adhesion between the insulating resin layer 12 and the conductive layer is improved. On the other hand, the lower limit of the melt viscosity at 50°C or higher and 175°C or lower is usually 1 Pa·s or higher.
The melt viscosity can be measured by the method described in Examples.

(curing properties)
The insulating resin layer 12 is preferably uncured or semi-cured at least in the region on the other surface 12Y side. As described above, a conductive layer or the like is laminated on the other surface 12Y of the insulating resin layer 12 in a post-process. In addition, when the other surface 12Y side of the insulating resin layer 12 is cured after laminating the conductive layer, the adhesiveness between the conductive layer and the insulating resin layer 12 is enhanced.

Further, it is more preferable that the insulating resin layer 12 has at least an uncured or semi-cured region on the other surface 12Y side and a semi-cured or cured region on the one surface 12X side. When the region on the one surface 12X side is a semi-cured material or a cured material, various performances such as thermal conductivity and insulation of the laminate 10 can be stably ensured.

Here, the fact that at least the area on the other surface 12Y side is an uncured material or a semi-cured material means that the area of a certain thickness from the other surface 12Y is an uncured material or a semi-cured material, Specifically, the hardening rate of the region of constant thickness should be less than 80%. By setting the curing rate to less than 80%, it becomes easier to increase the adhesiveness to the conductive layer. Also, the curing rate is preferably less than 70%, more preferably less than 60%, and even more preferably less than 50%.
Also, the hardening rate of the region of constant thickness from the other surface 12Y is preferably 1% or more, more preferably 5% or more, and even more preferably 10% or more.
Note that the insulating resin layer 12 may have a curing rate within the above range for a certain thickness region from the other surface 12Y with respect to the total thickness of the insulating resin layer 12. Specifically, it is at least 10%. It suffices that the hardening rate of the region having a thickness of 20% is within the above range, and the hardening rate of the region having a thickness of at least 20% is preferably within the above range.

In addition, the fact that the region on the side of one surface 12X is a semi-cured material or a cured material means that the area having a constant thickness from the one surface 12X is a semi-cured material or a cured material. , the curing rate of the region of constant thickness may be, for example, 50% or more. By setting the curing rate to 50% or more, the adhesiveness to the heat conductor 11 can be easily increased. In addition, it becomes easier to improve the insulation and thermal conductivity of the laminate 10 . From these viewpoints, the curing rate is preferably 65% or more, more preferably 75% or more, and even more preferably 85% or more.
Moreover, the curing rate of the region having a constant thickness from the one surface 12X may be 100% or less, but may be 95% or less, for example.
Note that the insulating resin layer 12 may have a curing rate within the above range in a region of a certain thickness from the one surface 12X with respect to the total thickness of the insulating resin layer 12, but specifically at least 10%. It suffices that the hardening rate of the region having a thickness of is within the above range, and the hardening rate of at least 20% of the thickness is preferably within the above range.

The hardening rate of the region on the one surface 12X side described above is typically higher than the hardening rate of the region on the other surface 12Y side. Here, the curing rate of the region on the one surface 12X side is preferably 5% or more, more preferably 10% or more, and 30% or more than the curing rate of the other surface 12Y side. It is more preferable to be In addition, the curing rate of the region on the one surface 12X side is preferably higher than the curing rate of the region on the other surface 12Y side by a difference of 100% or less, preferably by a difference of 90% or less. % or less is more preferable. By setting the difference in the curing rate within these ranges, it becomes easy to improve the insulation properties, the thermal conductivity, the adhesion to the thermal conductor 11, the adhesion to the conductive layer, and the like in a well-balanced manner.
The above curing rate can be adjusted by appropriately setting the curing conditions such as the curing temperature and the curing time of the first insulating layer 12A and the second insulating layer 12B, as will be described later. It can also be adjusted by making the content of the thermosetting agent in the first insulating layer 12A larger than the content of the thermosetting agent in the second insulating layer 12B.

In a preferred embodiment, the insulating resin layer 12 comprises a first insulating layer 12A and a second insulating layer 12B, as shown in FIG. 12 A of 1st insulating layers and the 2nd insulating layer 12B are provided in this order on the surface of the heat conductor 11, as shown in FIG. In this case, the region having a constant thickness from the side of the one surface 12X mentioned in the explanation of the dielectric constant and the hardening rate is the region constituted by the first insulating layer 12A. Further, the region having a constant thickness from the other surface 12Y side is a region composed of the second insulating layer 12B.
Therefore, the dielectric constant of the first insulating layer 12A is lower than the dielectric constant of the second insulating layer 12B, and the dielectric constant of the first insulating layer 12A and the dielectric constant of the second insulating layer 12B Specific values of the coefficients are as described above for the dielectric constant of the region on the one surface 12X side and the dielectric constant of the region on the other surface 12Y side.

Further, in the insulating resin layer 12, the second insulating layer 12B is preferably an uncured or semi-cured material, more preferably the second insulating layer 12B is an uncured or semi-cured material and the first is a semi-cured material or a cured material.
The specific values of the hardening rate of the first insulating layer 12A, the hardening rate of the second insulating layer 12B, and the difference between these hardening rates are the hardening rate of the region on the one surface 12X side described above, The hardening rate of the area on the side of the other surface 12Y and the difference between these hardening rates are as follows.
In the present invention, by providing the two insulating layers 12A and 12B, it becomes possible to easily adjust the relative permittivity and curing characteristics of the insulating resin layer 12 within the predetermined ranges described above.

(Thermal conductive filler)
The insulating resin layer 12 contains a thermally conductive filler. Since the insulating resin layer 12 contains a thermally conductive filler, the thermal conductivity of the insulating resin layer 12 is increased, and the heat dissipation property of the laminate 10 is improved. The thermally conductive filler is an inorganic filler having a thermal conductivity of 10 W/m·K or more. Although only one type of thermally conductive filler may be used, it is preferable to use two or more types in combination.
From the viewpoint of further increasing the thermal conductivity of the laminate 10, the thermal conductivity of the thermally conductive filler is preferably 15 W/m·K or more, more preferably 20 W/m·K or more. The upper limit of the thermal conductivity of the thermally conductive filler is not particularly limited, but inorganic fillers with a thermal conductivity of about 300 W/m K are widely known, and the thermal conductivity is about 200 W/m K. Inorganic fillers are readily available.

The thermally conductive filler is, for example, at least one selected from alumina, synthetic magnesite, silica, boron nitride, aluminum nitride, silicon nitride, silicon carbide, zinc oxide, magnesium oxide, talc, mica, and hydrotalcite. be. More preferably, the thermally conductive filler is at least one selected from alumina, silica, boron nitride and aluminum nitride. The use of these inorganic fillers increases the thermal conductivity of the laminate.

More preferably, the thermally conductive filler is at least one selected from alumina and boron nitride, and more preferably both. Since boron nitride is a material with a low relative dielectric constant, as will be described later, when boron nitride is contained in the first insulating layer 12A (the region on the side of the one surface 12X), the ratio of the region on the side of the surface 12X becomes It becomes easier to lower the dielectric constant. On the other hand, by including alumina in the second insulating layer 12B (the region on the other surface 12Y side), the dielectric constant on the one surface 12X side is made lower than that on the other surface 12Y side. easier.
Boron nitride may be contained in both the first insulating layer 12A (region on the one surface 12X side) and the second insulating layer 12B (region on the other surface 12Y side). In that case, as will be described in detail below, in order to lower the dielectric constant of the region on the one surface 12X side, the boron nitride content in the region on the one surface 12X side is reduced to the other surface 12Y side. is preferably higher than the boron nitride content in the region.
The shapes and the like of boron nitride and alumina are as described in more detail with respect to the first filler and second filler described later.

The shape of the thermally conductive filler is not particularly limited, and may be plate-like, spherical, irregular, crushed, polygonal, or the like. Further, the thermally conductive filler may be aggregated particles in which primary particles such as plate-like fillers are aggregated.

(first filler)
The thermally conductive filler of the present invention preferably contains a plate-like filler (also referred to as "first filler"). By containing the plate-like filler, the thermal conductivity tends to be good. The material of the first filler may be appropriately selected from those described above, preferably boron nitride. By using boron nitride, it becomes easier to improve thermal conductivity and insulation, and to lower the dielectric constant. Also, the first filler preferably has a lower dielectric constant than the second filler described later. Also, the first filler preferably constitutes agglomerated particles.

Boron nitride used as the first filler is hexagonal boron nitride, cubic boron nitride, boron nitride produced by a reduction nitriding method using a boron compound and ammonia, and a nitrogen-containing compound such as a boron compound and melamine. and boron nitride prepared from sodium borohydride and ammonium chloride. The boron nitride is preferably hexagonal boron nitride from the viewpoint of more effectively increasing thermal conductivity.

The aspect ratio of the plate-like filler (first filler) is preferably greater than 2, more preferably 3 or more, and even more preferably 4 or more. Also, it is preferably 25 or less, more preferably 22 or less, and even more preferably 20 or less. When it is 4 or more, the major diameter (maximum length) of the primary particles of the plate-like filler becomes long, and the thermal conductivity of the laminate can be easily increased. Moreover, by making it 20 or less, it becomes easy to improve sheet property.
In the present invention, the aspect ratio means maximum length/minimum length in each filler (primary particle). The minimum length is the thickness of the plate-like filler. In the present specification, the aspect ratio is the average aspect ratio. Specifically, 50 arbitrarily selected particles are observed with an electron microscope or an optical microscope, and the average value of the maximum length/minimum length of each particle It is obtained by calculating

In addition, in the plate-like filler primary particles, the average major diameter, which is the average of the major diameters (maximum length of each particle), is preferably 1 μm or more, more preferably 2 μm or more, from the viewpoint of suitably increasing thermal conductivity. , preferably 40 μm or less, more preferably 38 μm or less. In addition, the average major axis refers to the average of 100 major axis obtained in the measurement of the aspect ratio described above.

As noted above, the first filler may be agglomerated particles. Aggregated particles are secondary particles obtained by aggregating the primary particles of the plate-like filler described above. By using aggregated particles as the first filler, it is possible to further effectively increase thermal conductivity while ensuring insulation. The plate-like filler is preferably boron nitride as described above, that is, the aggregated particles are preferably boron nitride aggregated particles.

The method for producing aggregated particles is not particularly limited, and examples thereof include a spray drying method and a fluidized bed granulation method. Preferably, the method for producing agglomerated particles is a spray drying (also called spray drying) method. The spray drying method can be classified into a two-fluid nozzle method, a disk method (also called a rotary method), an ultrasonic nozzle method, and the like, and any of these methods can be applied. An ultrasonic nozzle system is preferable from the viewpoint of being able to control the total pore volume more easily.

The aggregated particles are preferably boron nitride aggregated particles as described above, and the boron nitride aggregated particles are preferably produced using the primary particles of boron nitride as a raw material. The boron nitride used as the raw material for the boron nitride aggregated particles is not particularly limited, and includes hexagonal boron nitride, cubic boron nitride, boron nitride produced by a reduction nitriding method using a boron compound and ammonia, a boron compound and melamine, and the like. boron nitride made from a nitrogen compound, boron nitride made from sodium borohydride and ammonium chloride, and the like. From the viewpoint of more effectively increasing the thermal conductivity of the aggregated boron nitride particles, the boron nitride used as the material for the aggregated boron nitride particles is preferably hexagonal boron nitride.

In addition, a granulation step is not necessarily required as a method for producing aggregated particles. For example, the aggregated boron nitride particles may be aggregated boron nitride particles formed by spontaneous aggregation of primary particles of boron nitride as the crystals of boron nitride grow. Further, the aggregated particles may be pulverized aggregated particles in order to make the particle size of the aggregated particles uniform.

From the viewpoint of effectively improving insulation and thermal conductivity, the average particle size of the aggregated particles is preferably 12 μm or more, preferably 15 μm or more, and preferably 200 μm or less. It is more preferably 150 μm or less.
The average particle size can be measured using a "laser diffraction particle size distribution analyzer" manufactured by Horiba, Ltd. Regarding the method for calculating the average particle size, the particle size (d50) of the thermally conductive filler when the cumulative volume is 50% is adopted as the average particle size.

The compressive strength of the aggregated particles when compressed by 20% is preferably 0.8 to 2.5 N/mm ² , more preferably 1.0 to 2.0 N/mm ² . With 0.8 to 2.5 N / mm ² , it can be easily crushed during pressing and the shape can be deformed so that the air present at the filler interface can be pushed out, so when aggregated particles are used. Even if it is, it becomes easy to adjust the porosity of the insulating resin layer 12 . That is, since the compressive strength of the agglomerated particles is relatively small, they are crushed by the press treatment during the production of the insulating resin layer 12, but by adjusting the pressure during the press treatment, the porosity can be kept low, and the thermal conductivity and insulation can be improved. can improve the quality.

Compressive strength in the present invention can be measured as follows.
First, using a micro-compression tester, a square column made of diamond is used as a compression member, and the smooth end face of the compression member is lowered toward the aggregated particles to compress the aggregated particles. As a measurement result, the relationship between the compressive load value and the compressive displacement can be obtained. strength. Also, the compressibility is calculated from the compression displacement and the particle diameter of the aggregated particles, and the relationship between the compressive strength and the compressibility is obtained. Aggregated particles to be measured are observed using a microscope, and aggregated particles having a particle diameter of ±10% are selected and measured. In addition, the compressive strength at each compressibility is calculated as an average compressive strength obtained by averaging 20 measurement results. As the micro-compression tester, for example, "Micro-compression tester HM2000" manufactured by Fisher Instruments Co., Ltd. is used. Also, the compressibility can be calculated by (compressibility=compressive displacement/average particle diameter×100).

(second filler)
The thermally conductive filler of the present invention may contain thermally conductive fillers other than the plate-like fillers described above. Examples of such fillers include thermally conductive fillers having an aspect ratio of 2 or less (hereinafter also referred to as "second fillers").
The aspect ratio of the second filler is preferably 1.8 or less, more preferably 1.5 or less. By using a thermally conductive filler having a low aspect ratio in this way, it is possible to increase the thermal conductivity without deteriorating the sheet properties, the insulating properties, and the like. The aspect ratio of the second filler may be 1 or more.
The shape of the second filler is not particularly limited, but examples thereof include a spherical shape and a crushed shape. Further, the material of the second filler may be appropriately selected from those described above, and the second filler is preferably alumina.

The average particle size of the second filler is preferably 0.1 µm or more, more preferably 0.5 µm or more, and preferably 1 µm or more. Moreover, it is preferably 20 μm or less, preferably 15 μm or less, and more preferably 10 μm or less. When the average particle size is set to these lower limit values or more, the second filler can be highly filled in the insulating resin layer. Moreover, when it is below the upper limit, it becomes easy to improve insulation. Furthermore, when the second filler having an average particle size within these ranges is used together in the same region as the first filler (for example, the first insulating layer 12A), can easily enter into the gaps between the layers to effectively increase the thermal conductivity of the laminate.

In the present invention, the dielectric constant of the insulating resin layer 12 is adjusted by the thermally conductive filler contained in the insulating resin layer 12 . Specifically, it is preferable to adjust the dielectric constant according to the type of thermally conductive filler used. For example, the thermally conductive filler contained in the region on the one surface 12X side (that is, the first insulating layer 12A) contains a filler with a low relative dielectric constant (also referred to as a “low dielectric constant filler”), and the other A filler with a high relative dielectric constant (also referred to as a “high dielectric constant filler”) may be used as the thermally conductive filler contained in the region on the side of the surface 12Y of (that is, the second insulating layer 12B).
Furthermore, both the region on the side of one surface 12X (that is, the first insulating layer 12A) and the region on the side of the other surface 12Y (that is, the second insulating layer 12B) contain a low dielectric constant filler, The low dielectric constant filler content in the region on the one surface 12X side may be higher than the low dielectric constant filler content in the region on the other surface 12Y side. The low dielectric constant filler content here means the ratio of the low dielectric constant filler content to the mass of the region (for example, each insulating layer) containing each filler.
The low dielectric constant filler is, for example, the first filler described above, such as boron nitride. The high dielectric constant filler is, for example, the second filler described above, and may be any filler having a higher relative dielectric constant than the low dielectric constant filler, such as alumina.

In the insulating resin layer 12, the content of the thermally conductive filler is preferably 40% by mass or more and 96% by mass or less, more preferably 55% by mass or more and 95% by mass or less, and 65% by mass or more and 93% by mass, based on the total amount of the insulating resin layer. % by mass or less is more preferable. By setting the thickness within these ranges, it becomes easy to improve all of sheet properties, insulation properties, and thermal conductivity.

As described above, the insulating resin layer 12 preferably has first and second insulating layers 12A and 12B. In this case, both the first and second insulating layers 12A and 12B preferably contain thermally conductive filler. That is, the first and second insulating layers 12A and 12B (that is, the region on the side of one surface 12X and the region on the side of the other surface 12Y) are, as will be described later, first and second insulating layers containing thermally conductive fillers, respectively. It is preferably formed from the curable composition of No. 2.
In the first insulating layer 12A (that is, the first curable composition), the content of the thermally conductive filler is preferably 40% by mass or more and 94% by mass or less, more preferably 55% by mass or more and 90% by mass or less. , more preferably 65 mass % to 87 mass %. By setting the thickness within these ranges, it becomes easier to improve the thermal conductivity of the first insulating layer 12A while ensuring insulation.

As the thermally conductive filler contained in the first insulating layer 12A, the first filler may be used alone, or the first filler and the second filler may be used in combination. In addition, as the first filler, it is preferable to use boron nitride or the like having a low dielectric constant, as described above. In particular, the use of agglomerated boron nitride is preferable in that the porosity of the insulating resin layer 12 can be easily adjusted. On the other hand, the second filler is a filler having a dielectric constant higher than that of the first filler, preferably alumina.
When the first filler is used alone in the first insulating layer 12A, it becomes easier to lower the dielectric constant on the side of the one surface 12X and to improve the insulating properties. In addition, when the first and second fillers are used together, it becomes easy to improve the insulation properties, the thermal conductivity, the adhesion to the thermal conductor 11, and the like in a well-balanced manner.

The content of the first filler in the first insulating layer 12A (that is, the first curable composition) is preferably 20% by mass or more and 84% by mass or less, more preferably 30% by mass or more and 80% by mass or less, 45% by mass or more and 75% by mass or less is more preferable. By setting the thickness within these ranges, it becomes easy to improve the thermal conductivity of the first insulating layer 12A while ensuring the adhesion with the thermal conductor 11 and the insulating properties. In addition, by using a filler (for example, boron nitride) having a low dielectric constant as described above as the first filler within these ranges, the dielectric constant of the region on the one surface 12X side of the insulating resin layer 12 is can be lowered. Further, by using, for example, aggregated boron nitride or the like in the above content, the porosity of the insulating resin layer 12 can be easily adjusted.

Also, the content of the second filler in the first insulating layer 12A (that is, the first curable composition) is, for example, 70% by mass or less. By making it 70% by mass or less, it is possible to allow the first insulating layer 12A to contain a certain amount or more of the first filler, and the dielectric constant of the region on the one surface 12X side of the insulating resin layer 12 is lowered. It becomes easy to improve the insulation by doing so. From the viewpoint of improving the insulation, thermal conductivity, and adhesion to the thermal conductor 11 in a well-balanced manner while lowering the dielectric constant, the first insulating layer 12A (that is, the region on the one surface 12X side) When containing the second filler, the content of the second filler is more preferably 10% by mass or more and 60% by mass or less, and further preferably 20% by mass or more and 50% by mass or less.

The mass ratio (A2/A1) of the content (A2) of the second filler to the content (A1) of the first filler in the first insulating layer 12A (that is, the first curable composition) is , is preferably 2 or less, more preferably 1.5 or less, still more preferably 1.2 or less, and even more preferably 0.8 or less. When the mass ratio (A2/A1) is set to a certain value or less, it becomes possible to allow the first insulating layer 12A to contain a certain amount or more of the first filler, and the area on the one surface 12X side of the insulating resin layer 12 is reduced. It becomes easy to improve insulation by lowering the dielectric constant.
In addition, from the viewpoint of improving the insulation, heat dissipation, adhesion to the heat conductor 11, etc. in a well-balanced manner while reducing the relative dielectric constant, the first insulating layer 12A (that is, the region on the one surface 12X side ) does not contain the second filler, but when the second filler is contained, the mass ratio (A2/A1) is preferably 0.2 or more, more preferably 0.3 or more, and 0.3 or more. 5 or more is more preferable.

In the second insulating layer 12B (that is, the second curable composition), the content of the thermally conductive filler is preferably 40% by mass or more and 96% by mass or less, more preferably 55% by mass or more and 95% by mass or less. , more preferably 70% by mass to 94% by mass. By setting the thickness within these ranges, it becomes easier to improve the thermal conductivity of the first insulating layer 12A while ensuring insulation.

A second filler is preferably used as the thermally conductive filler contained in the second insulating layer 12B (that is, the second curable composition). As the second filler, as described above, it is preferable to use a filler having a dielectric constant higher than that of the first filler such as alumina, thereby allowing the second filler to be contained in the second insulating layer 12B. Therefore, the relative dielectric constant of the region on the other surface 12Y side of the insulating resin layer 12 can be easily made higher than the relative dielectric constant of the region on the one surface 12X side, and the insulating property is improved.
In the second insulating layer 12B, the second filler may be used alone, or the second filler and the first filler may be used together. As the first filler, boron nitride or the like having a low dielectric constant is preferably used as described above.

The content of the second filler in the second insulating layer 12B (that is, the second curable composition) is preferably 25% by mass or more and 96% by mass or less, more preferably 40% by mass or more and 95% by mass or less, 50% by mass to 94% by mass is more preferable. By setting the thickness within these ranges, it becomes easier to improve the thermal conductivity of the laminate 10 while ensuring insulation.

The content of the first filler in the second insulating layer 12B (that is, the second curable composition) is, for example, less than 50% by mass. When the amount is less than 50% by mass, the dielectric constant of the second insulating layer 12B can be easily made higher than that of the first insulating layer 12B, and deterioration of sheet properties can be prevented.
From these viewpoints, when the second insulating layer 12B (that is, the second curable composition) contains the first filler, the content of the first filler is 10% by mass or more and 45% by mass or less. More preferably, 20% by mass to 40% by mass is even more preferable.

The mass ratio (A1/A2) of the content (A1) of the first filler to the content (A2) of the second filler in the second insulating layer 12B (that is, the second curable composition) is , is preferably less than 1.5, more preferably less than 1, and even more preferably less than 0.8. When the mass ratio (A1/A2) is set to a certain value or less, the first filler is not contained more than necessary in the second insulating layer 12B, and the sheet properties and the like are improved, while the ratio of the area on the one surface 12X side is It becomes easier to lower the dielectric constant. In addition, the adhesiveness to the conductive layer is less likely to deteriorate.
In addition, from the viewpoint of insulation and thermal conductivity, the second insulating layer 12B (that is, the second curable composition) may not contain the first filler, but the second insulating layer 12B does not need to contain the first filler. (That is, when the second curable composition) contains the first filler, the mass ratio (A1/A2) is preferably 0.1 or more, more preferably 0.3 or more, and 0.4 or more. is more preferred.

(Curable compound)
The insulating resin layer 12 is formed from a curable composition containing a curable compound and a thermally conductive filler. The curable compound constitutes the matrix resin of the insulating resin layer 12 by being thermally cured. Moreover, the curable compound is preferably cured with a thermosetting agent. That is, the curable composition preferably contains a thermosetting agent in addition to the curable compound and thermally conductive filler.
The insulating resin layer 12 preferably has the first and second insulating layers 12A, 12B formed from the first and second curable compositions, respectively, as described above. Each of the compositions comprises a curable compound and a thermally conductive filler, and preferably also contains a thermal curing agent in addition to the curable compound and thermally conductive filler.

In the present invention, a curable compound having an epoxy group is preferable as the curable compound, and specifically, it is preferable to use an epoxy resin, a phenoxy resin, or both of them. By using an epoxy resin, a phenoxy resin, or both of them, heat resistance, sheet properties, adhesion to the heat conductor 11, adhesion to the conductive layer, etc. are improved.

<Epoxy resin>
Epoxy resins include, for example, compounds containing two or more epoxy groups in the molecule. The epoxy resin has a weight average molecular weight of less than 5,000.
Specific examples of epoxy resins include styrene skeleton-containing epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol S-type epoxy resins, phenol novolac-type epoxy resins, biphenol-type epoxy resins, naphthalene-type epoxy resins, Fluorene type epoxy resin, phenol aralkyl type epoxy resin, naphthol aralkyl type epoxy resin, dicyclopentadiene type epoxy resin, anthracene type epoxy resin, epoxy resin having adamantane skeleton, epoxy resin having tricyclodecane skeleton, and triazine nucleus as skeleton epoxy resins and the like. Among these, bisphenol A type epoxy resins are preferred.

The epoxy equivalent of the epoxy resin is not particularly limited, but is, for example, 100 g/eq to 500 g/eq, preferably 120 g/eq to 400 g/eq, and more preferably 150 g/eq to 350 g/eq.
In addition, an epoxy equivalent can be measured according to the method prescribed|regulated to JISK7236, for example.

<Phenoxy resin>
A phenoxy resin is, for example, a resin obtained by reacting epihalohydrin with a divalent phenol compound, or a resin obtained by reacting a divalent epoxy compound with a divalent phenol compound. The phenoxy resin has a bisphenol A skeleton, a bisphenol F skeleton, a bisphenol A/F mixed skeleton, a naphthalene skeleton, a fluorene skeleton, a biphenyl skeleton, anthracene skeleton, a pyrene skeleton, a xanthene skeleton, an adamantane skeleton, or a dicyclopentadiene skeleton. is preferred. The phenoxy resin more preferably has a bisphenol A skeleton, a bisphenol F skeleton, a bisphenol A/F mixed skeleton, a naphthalene skeleton, a fluorene skeleton, or a biphenyl skeleton, and more preferably has a bisphenol A skeleton.

The phenoxy resin has a weight average molecular weight of 10,000 or more, preferably 20,000 or more, more preferably 30,000 or more, and preferably 1,000,000 or less, more preferably 250,000 or less. Even if a resin having such a high molecular weight is used as the resin, in the present invention, the insulating resin layer is formed by applying a diluted solution obtained by diluting the curable composition as described later, so that the laminate can be easily formed. can be formed. In addition, a weight average molecular weight is a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC). In gel permeation chromatography (GPC) measurement, tetrahydrofuran is preferably used as an eluent.
The epoxy equivalent of the phenoxy resin is not particularly limited, but is, for example, 2500 g/eq or more and 25000 g/eq or less, preferably 4000 g/eq or more and 18000 g/eq or less, more preferably 5000 g/eq or more and 13000 g/eq or less.

In the present invention, as described above, the insulating resin layer 12 preferably has the first and second insulating layers 12A, 12B made of the first and second curable compositions. In the first curable composition, the content of the curable compound is preferably 5% by mass or more and 55% by mass or less, more preferably 8% by mass or more and 40% by mass or less, and further 9% by mass or more and 30% by mass or less. preferable. Within these ranges, it becomes easier to ensure various performances such as sheet properties.
In the second curable composition, the content of the curable compound is preferably 3% by mass or more and 55% by mass or less, more preferably 4% by mass or more and 35% by mass or less, and 5% by mass to 25% by mass or less. is more preferred. Within these ranges, it becomes easier to ensure various performances such as sheet properties.

When both the epoxy resin and the phenoxy resin are contained in each of the first and second curable compositions, the content of the epoxy resin is 40% by mass or more and 90% by mass or less based on the total amount thereof, and the phenoxy resin is The resin content is preferably 10% by mass or more and 60% by mass or less. Further, the content of the epoxy resin is 50% by mass or more and 80% by mass or less, the content of the phenoxy resin is more preferably 20% by mass or more and 50% by mass or less, and the content of the epoxy resin is 55% by mass or more. It is 75% by mass or less, and the content of the phenoxy resin is more preferably 25% by mass or more and 45% by mass or less.

<Heat curing agent>
Examples of heat curing agents include phenol compounds (phenol heat curing agents), amine compounds (amine heat curing agents), imidazole compounds, acid anhydrides, and the like when the above epoxy resins and phenoxy resins are used. Among these, imidazole compounds are preferred.

Examples of phenol compounds include novolac-type phenol, biphenol-type phenol, naphthalene-type phenol, dicyclopentadiene-type phenol, aralkyl-type phenol, and dicyclopentadiene-type phenol.
Amine compounds include dicyandiamide, diaminodiphenylmethane, diaminodiphenylsulfone, and the like.

Examples of imidazole compounds include 2-undecylimidazole, 2-heptadecylimidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2 -methylimidazole, 1-benzyl-2-phenylimidazole, 1,2-dimethylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecyl imidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'- Methylimidazolyl-(1′)]-ethyl-s-triazine, 2,4-diamino-6-[2′-undecylimidazolyl-(1′)]-ethyl-s-triazine, 2,4-diamino-6 -[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s- triazine isocyanurate, 2-phenylimidazole isocyanurate, 2-methylimidazole isocyanurate, 2-phenyl-4,5-dihydroxymethylimidazole and 2-phenyl-4-methyl-5-dihydroxymethylimidazole, etc. is mentioned.

Acid anhydrides include styrene/maleic anhydride copolymer, benzophenonetetracarboxylic anhydride, pyromellitic anhydride, trimellitic anhydride, 4,4′-oxydiphthalic anhydride, phenylethynylphthalic anhydride, glycerol. Bis(anhydrotrimellitate) monoacetate, ethylene glycol bis(anhydrotrimellitate), methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride and the like.

In each of the first and second curable compositions for forming the first and second insulating layers 12A and 12B (that is, the region on the side of one surface 12X and the region on the side of the other surface 12Y), heat The content of the curing agent is, for example, 1 part by mass or more and 100 parts by mass or less, preferably 10 parts by mass or more and 90 parts by mass or less, more preferably 20 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the curable compound. is. However, the first insulating layer 12A is more preferably 40 parts by mass or more and 70 parts by mass or less, in order to increase the curing rate and improve the adhesion to the heat conductor 11 .
Moreover, the content (that is, the content ratio) of the thermosetting agent with respect to 100 parts by mass of the curable compound is preferably higher in the first insulating layer than in the second insulating layer. By increasing the content of the first insulating layer, it becomes easier to increase the hardening rate of the first insulating layer 12A (that is, the region on the one surface 12X side).

In the above description, the curable compound is a curable compound having an epoxy group, but is not limited to a curable compound having an epoxy group, and may be a melamine compound, an oxetanyl compound, an isocyanate compound, or the like. , the thermosetting agent may also be appropriately selected according to the curable compound.

(dispersant)
The curable compositions (ie, each of the first and second curable compositions) may contain dispersants. The dispersant makes it easier to disperse the thermally conductive filler in the resin component, improving the insulation and thermal conductivity of the laminate.
Alkoxysilanes, for example, are used as dispersants. Alkoxysilanes include alkoxysilanes with reactive groups and alkoxysilanes without reactive groups. Reactive groups in alkoxysilanes having reactive groups are selected from, for example, epoxy groups, (meth)acryloyl groups, amino groups, vinyl groups, ureido groups, mercapto groups, and isocyanate groups. Alkoxysilanes are preferably alkoxysilanes having a reactive group, more preferably alkoxysilanes having an epoxy group.
Alkoxysilanes having an epoxy group include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxysilane. and propyltriethoxysilane.
In each of the first and second curable compositions, the content of the dispersant is preferably 0.01% by mass or more and 2% by mass or less, more preferably 0.02% by mass or more and 1.5% by mass or less, and 0.05% by mass or more. % by mass or more and 1 mass % or less is more preferable. By making it more than these lower limits, it becomes easy to disperse|distribute a heat conductive filler in each insulating layer. Moreover, by setting the content to not more than these upper limits, it becomes easier to obtain an effect commensurate with the compounding amount.

The resin composition of the present invention contains flame retardants, antioxidants, ion scavengers, tackifiers, plasticizers, thixotropic agents, photosensitizers and colorants in addition to the above components. good too.

The thickness of the insulating resin layer 12 is, for example, 0.04 mm or more and 0.30 mm or less, preferably 0.06 mm or more and 0.25 mm or less. By making it more than these lower limits, it becomes easy to secure insulation and heat dissipation. In addition, by making the thickness equal to or less than these upper limits, it becomes easier to reduce the thickness of the electronic component.
Also, the ratio (T2/T1) of the thickness (T2) of the second resin layer to the thickness (T1) of the first insulating layer 12A is, for example, 1/9 or more and 9 or less, preferably 2/ It is 8 or more and 8/2 or less.

[Heat conductor]
The heat conductor 11 is not particularly limited as long as it is a heat conductor having a heat conductivity of 10 W/m·K or more. Examples include aluminum, copper, alumina, beryllia, silicon carbide, silicon nitride, aluminum nitride and graphite sheets. Among them, the heat conductor 11 is preferably made of copper or aluminum. Copper or aluminum has high thermal conductivity and is excellent in heat dissipation. In addition, the thermal conductivity of the thermal conductor 11 can be measured by, for example, a laser flash method.
The thickness of the heat conductor 11 is, for example, 0.03 mm or more and 3 mm or less, preferably 0.1 mm or more and 2.5 mm or less.

In the above description, as shown in FIG. 2, the insulating resin layer 12 is mainly composed of the first and second insulating layers 12A and 12B. The configuration is not limited to two layers. For example, a third insulating layer may be provided between the first and second insulating layers. The third insulating layer typically contains a thermally conductive filler as described above, and the thermally conductive filler may be appropriately selected from the thermally conductive fillers described above. In this case, the dielectric constant of the third insulating layer is preferably higher than that of the first insulating layer and lower than that of the second insulating layer.
Alternatively, the insulating resin layer 12 may be configured such that the dielectric constant gradually increases from one surface 12X toward the other surface 12Y. In this case, the insulating resin layer 12 may be formed by laminating four or more thin film insulating layers sufficiently thinner than the thickness of the entire insulating resin layer 12, for example. In this case, each dielectric constant of each thin film insulating layer may be adjusted by adjusting the type and content of filler, for example.

(Laminate manufacturing method)
In the present invention, a diluted solution of the curable composition for forming the insulating resin layer is prepared, and the insulating resin layer is formed with the diluted solution of the curable composition. Hereinafter, the method for manufacturing the laminate of the present invention will be described in detail for the case where the insulating resin layer is composed of the first and second insulating layers.

First, diluted solutions of the first and second curable compositions for forming the first and second insulating layers, respectively, are prepared. Specifically, a curable compound, a thermally conductive filler, and other optional heat curing agents and other additives are mixed with an organic solvent to form the first and second curable compounds. A dilution of the composition may be prepared.

Here, the solvent for diluting the resin composition liquid is not particularly limited, but n-pentane, n-hexane, n-heptane, aliphatic hydrocarbon solvents such as cyclohexane, and aromatic hydrocarbons such as toluene. ester solvents such as ethyl acetate and n-butyl acetate; and ketone solvents such as acetone, methyl ethyl ketone (MEK) and cyclohexanone. One of these organic solvents may be used alone, or two or more of them may be used as a mixed solvent. Among these, methyl ethyl ketone is preferred.
Further, the solid content concentration in each diluted solution of the first and second curable compositions is, for example, 60 to 96% by mass, preferably 65 to 95% by mass, more preferably 70 to 94% by mass. An insulating layer can be efficiently formed as solid content concentration is more than a lower limit. Further, by setting the solid content concentration to the upper limit or less, it becomes easier to adjust the viscosity of the diluted solution of the curable composition to an appropriate viscosity, so that problems in the process are less likely to occur.

Next, a diluted solution of the first curable composition is preferably applied to a release sheet or the like and dried to form the first insulating layer on the release sheet. Similarly, a diluted solution of the second curable composition may be applied to a release sheet or the like and dried to form the second insulating layer on the release sheet.

In the insulating resin layer 12, the organic solvent used for diluting the first and second curable compositions may remain in the insulating layers 12A and 12B in a very small amount (for example, 50 to 2000 ppm). The sheet property of the laminate 10 is improved by leaving a very small amount of the organic solvent in the insulating layers 12A and 12B.
In order to keep the solvent content in the insulating resin layer 12 within a certain range, the drying time and drying temperature in drying the diluted solutions of the first and second curable compositions should be relatively gentle. good.
Specifically, the drying temperature may be appropriately set depending on the type of solvent and the like. The drying time is, for example, 5 minutes or more and 60 minutes or less, preferably 10 minutes or more and 40 minutes or less. By adjusting the drying temperature and drying time within the above ranges, the insulating layers 12A and 12B are not excessively hardened. Since it becomes easy to push out outside, it becomes easy to adjust a porosity to a desired range.
Drying may be performed by hot air, or a release sheet or the like coated with a diluent of the curable composition may be placed in a drying furnace or oven for drying.

The first and second insulating layers produced as described above are successively laminated on a heat conductor, pressed, and cured as necessary to obtain a laminated body. Specifically, first, the first insulating layer peeled off from the release sheet is laminated on the heat conductor, and then, for example, the first insulating layer is vacuum-pressed to cure the first insulating layer ( first curing step). Next, after laminating the second insulating layer peeled off from the release sheet on the first insulating layer, then, if necessary, for example, while vacuum pressing the first and second insulating layers, the second insulating layer The first and second insulating layers or the second insulating layer may be cured (second curing step). Curing in the first and second curing steps is performed by heating. In this manufacturing method, by performing curing twice, it becomes easier to adjust the curing rates of the first insulating layer and the second insulating layer to different values.

The conditions for vacuum pressing the insulating layer in the first curing step are not particularly limited, but the press pressure during vacuum pressing is preferably 7 MPa or more, more preferably 8 MPa or more, preferably 20 MPa or less, more preferably 15 MPa. It is below. When the pressing pressure is 7 MPa or more, the porosity of the insulating resin layer becomes low, and the amount of air in the insulating resin layer becomes small, so that the insulating performance is improved. In addition, for example, even when a filler such as a plate-like filler or agglomerated particles that easily creates voids is used, and a large amount of filler is blended, voids are less likely to occur. On the other hand, if the pressing pressure is 20 MPa or less, the laminate will not be excessively compressed and the flexibility will be good.
The vacuum press conditions in the second curing step are not particularly limited, but the press pressure during vacuum pressing is preferably 0.1 MPa or more, more preferably 0.5 MPa or more, as in the first curing step. In addition, it may be 7 MPa or more, or 8 MPa or more. The second insulating layer is preferably an uncured material or a semi-cured material, but when it is an uncured material or a semi-cured material, voids are less likely to form even if the pressing pressure is not increased. The vacuum press pressure may be lowered as follows. Also, the press pressure in the second curing step is preferably 20 MPa or less, more preferably 15 MPa or less. When the pressing pressure is 20 MPa or less, the laminate is not excessively compressed and has good flexibility.

In the first and second curing steps, the heating temperature and heating time should be adjusted so that the first and second insulating layers have desired curing properties.
Specifically, the heating temperature in the first curing step is, for example, 100° C. or higher and 230° C. or lower, preferably 120° C. or higher and 210° C. or lower. The heating time within these temperature ranges is, for example, 30 minutes or more and 5 hours or less, preferably 1 hour or more and 3 hours or less.

The heating temperature in the second curing step is generally lower than the heating temperature in the first curing step. When the heating temperature in the second curing step is lowered, the curing rate of the second insulating layer is likely to be lower than that of the first insulating layer.
Specifically, the heating temperature in the second curing step is, for example, 80° C. or higher and 150° C. or lower, preferably 90° C. or higher and 130° C. or lower. The heating time within these temperature ranges is, for example, 1 minute or more and 1 hour or less, preferably 1 minute or more and 30 minutes or less. By setting the heating temperature and the heating temperature in the second curing step within the above range, it becomes easier to adjust the curing rate of the second insulating layer to a desired range.
However, if the second insulating layer is not cured, the second curing step may be omitted.

Further, in the above description, the curing process is divided into the first process of curing the first insulating layer and the second curing process of mainly curing the second insulating layer. The two insulating layers may be done together in the same curing step. Specifically, for example, after sequentially laminating a first insulating layer and a second insulating layer on the heat conductor, the first and second insulating layers may be cured by heating.
In this case, the curing rates of the first insulating layer and the second insulating layer can be appropriately adjusted by, for example, the content of the thermosetting agent contained in each layer.

In the manufacturing method described above, the first insulating layer and the second insulating layer formed on the release sheet are sequentially transferred to the heat conductor, but the release sheet may not be used. In such cases, the first insulating layer may be applied directly to the thermal conductor and dried. Also, the second insulating layer may be formed by applying directly onto the first insulating layer formed on the heat conductor and drying.

In the above description, the method for manufacturing the laminate in which the insulating resin layer is composed of the first and second insulating layers has been described, but the insulating resin layer having another configuration can also be manufactured by the same method. For example, when the insulating resin layer is composed of three or more insulating layers, a plurality of insulating layers may be sequentially laminated on the heat conductor. Further, the curing of each insulating layer may be performed by heating each time one layer is laminated on the heat conductor, but may be performed by heating each time a plurality of layers are laminated, for example.

(Use of laminate)
The laminated body 10 is used, for example, as one component of an electronic component, specifically used as a substrate on which a circuit or the like is attached, and preferably used as a substrate in a power semiconductor module. That is, the present invention also provides an electronic component including the laminate described above and a power semiconductor module including the electronic component.
Power semiconductor modules are used, for example, in industrial equipment such as inverters, elevators, uninterruptible power supplies (UPS), and are preferably inverters.

A conductive layer such as a lead frame is attached to the surface of the other surface 12Y of the laminate 10 . More specifically, the laminated body 10 is formed by placing a conductive layer (not shown) on the other surface 12Y of the insulating resin layer 12, and then curing the insulating resin layer 12 by heating. A conductive layer may be attached to the laminate 10 . In the present invention, the region (for example, the second insulating layer 12B) on the other surface 12Y side of the insulating resin layer 12 is semi-cured or uncured as described above. The conductive layer and the insulating resin layer 12 are firmly adhered.
Alternatively, after arranging the conductive layer on the other surface 12Y, the laminated body 10 having the conductive layer laminated thereon may be embedded in a mold resin or the like. In this case, the molding resin may be embedded after the insulating resin layer 12 is cured or before it is cured.

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these.

In addition, the measuring method of each physical property is as follows.
[Dielectric constant]
The first and second insulating layers produced in each example and comparative example were peeled off from the release PET sheet, and both sides were sandwiched between copper foil (40 μm thick) and aluminum plate (1.0 mm thick). A sample sheet was obtained by curing under the same conditions as in Examples and Comparative Examples. The obtained sample sheet was cut into a size of 40 mm×40 mm, and a pattern of φ20 mm was processed by etching. After that, the relative permittivity is measured at room temperature in the air with an LCR (impedance) analyzer "PSM3750" manufactured by Iwasaki Tsushin Co., Ltd., at 33 points divided by a log scale from 100 mHz to 10 MHz, one cycle, and the waveform obtained. was obtained to obtain the dielectric constant at a frequency of 1 MHz.

[Curing rate]
The cure rate is determined by measuring heat generated during curing when the corresponding region of the insulating resin layer is heated. A differential scanning calorimeter (DSC) device (“DSC7020” manufactured by SII Nano Technology Co., Ltd.) is used to measure the curing rate. Specifically, the curing rate is measured as follows.
At a measurement start temperature of 30° C. and a temperature increase rate of 8° C./min, a component in the corresponding region of the insulating resin layer is taken as a sample (sample weight: 20 to 30 mg), heated to 180° C. and held for 1 hour. The amount of heat generated when the sample is cured at this elevated temperature (hereinafter referred to as "heat amount A") is measured. In addition, a curable composition for forming each region was coated on a release PET (polyethylene terephthalate) sheet with a thickness of 50 μm so as to have a thickness of 80 μm, and was placed under vacuum at room temperature at 23 ° C. and 0.01 atm. An uncured insulating resin layer that has been dried without heating is prepared in the same manner as the insulating resin layer in the corresponding region, except that the insulating resin layer is dried for a certain period of time. Using this insulating resin layer, the amount of heat (hereinafter referred to as "the amount of heat B") generated when the insulating resin layer is heated and cured is measured in the same manner as the measurement of the amount of heat A described above. From the obtained heat quantity A and heat quantity B, the curing rate is obtained by the following formula.
Curing rate (%) = [1-(calorie A/calorie B)] × 100

[Porosity]
After each laminate of Examples and Comparative Examples was held at 285 ° C. for 5 minutes, it was cut into 10 × 10 mm, the surface of the obtained sample cross section was smoothed with abrasive paper, and a cross section polisher (manufactured by JEOL Ltd.) "IB-19520CCP") was used to prepare an observation surface. After that, the observation surface obtained by sputtering the cross section with Pt ion sputtering (E-1045, manufactured by Hitachi High-Technologies) was scanned with a scanning electron microscope (SEM) at a magnification of 500 and a pixel size of 198 so that the entire sheet could be included. 0.4 and cross-sectional images were obtained.
Image processing and analysis were then performed on this image. Median filter processing (1 pixel) was performed using "Avizo 9.2" (manufactured by Thermo Fisher Scientific), and the area below the threshold value of 75 among the 256 gradations was regarded as a crack, and the ratio of the area below the threshold value of 75 was calculated. A porosity was determined.

[Melting temperature/Melt viscosity]
For the first insulating layer and the second insulating layer, 1.5 cm-square cut samples were prepared and measured using a rheometer measuring device (manufactured by TA instruments, "ARES") at a frequency of 6.28 Hz and a strain of 21.5 cm. The melting temperature and the melt viscosity at the melting temperature were measured under the conditions of 8%, temperature of 30 to 195°C, and heating rate of 8°C/min. In addition, when the insulating layer does not melt in this measurement, it is indicated by "-" in Table 1.

The laminates obtained in Examples and Comparative Examples were evaluated by the following methods.
[Insulation evaluation]
A test sample was obtained by patterning a circular copper foil with a diameter of 2 cm on the other side of the obtained laminate on which the heat conductor was not provided. Using a withstand voltage tester ("MODEL7473" manufactured by ETECH Electronics), an alternating voltage was applied between test samples at 25°C so that the voltage increased at a rate of 0.33 kV/sec. The voltage at which a current of 10 mA was applied to the test sample was taken as the dielectric breakdown voltage. The dielectric breakdown voltage was normalized by dividing the dielectric breakdown voltage by the sample thickness to calculate the dielectric breakdown strength. Dielectric breakdown strength was determined according to the following criteria.
A: 60 kV/mm or more B: 50 kV/mm or more and less than 60 kV/mm C: less than 50 kV/mm

[Heat dissipation evaluation]
After cutting the laminates obtained in Examples and Comparative Examples into 1 cm squares, carbon black was sprayed on both sides of the measurement samples. Thermal conductivity was measured by laser flash method. Based on the thermal conductivity, the heat dissipation was evaluated according to the following criteria.
A: 7 W/m·K or more B: Less than 7 W/m·K

Components used in Examples and Comparative Examples are as follows.
Epoxy resin: bisphenol A type epoxy resin, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., trade name "YD-127", epoxy equivalent: 180 to 190 g / eq
Phenoxy resin: Mitsubishi Chemical Corporation, trade name "jER1256", epoxy equivalent: 7,500 to 8,500 g / eq, weight average molecular weight: about 50,000 Dispersant: 3-glycidoxypropyltriethoxysilane, Shin-Etsu Chemical Company product, trade name "KBM403"
Thermosetting agent (1): imidazole compound, manufactured by Shikoku Kasei Kogyo Co., Ltd., trade name "2P4MZ"
Thermosetting agent (2): Dicyandiamide pulverized product, Mitsubishi Chemical Corporation, trade name "DICY7"
First filler: boron nitride, plate-like filler, agglomerated particles, "HP-40" manufactured by Mizushima Allometal Co., Ltd., aspect ratio 6, average major diameter of primary particles 7 μm, average particle diameter of agglomerated particles 40 μm, at 20% compression Compressive strength 1.7 N/mm ²
Second filler: alumina, aspect ratio 1, manufactured by Micron, trade name "AZ-4", average particle size 5 μm

[Example 1]
According to the formulations in Table 1, first and second curable compositions for forming first and second insulating layers were prepared. The first and second curable compositions were prepared as diluted solutions of each composition diluted with an organic solvent (MEK) so that the solid content was 75% by mass and 90% by mass, respectively.
A diluted solution of the first curable composition was applied onto a release PET sheet (thickness: 40 µm) so that the thickness after drying was 200 µm. In addition, a diluted solution of the second curable composition was applied onto another release PET sheet (thickness 40 μm) so that the thickness after drying was 80 μm, and these were dried in an oven according to the drying conditions described in Table 1. Then, the first and second insulating layers were formed on each release PET sheet.

Next, the first insulating layer formed on the release PET sheet was laminated on a copper plate (thickness: 0.4 mm) while peeling off the release PET sheet. The obtained laminate before curing was vacuum-pressed for 80 minutes at a temperature of 195° C. and a pressure of 8 MPa to cure the first insulating layer (first curing step). Next, the second insulating layer formed on the release PET sheet is laminated on the first insulating layer while peeling off the release PET sheet, and vacuum is applied for 3 minutes at a temperature of 110° C. and a pressure of 8 MPa. By pressing, a laminate in which the second insulating layer was semi-cured was obtained (second curing step). In this laminate, the thickness of the first insulating layer was 0.1 mm, and the thickness of the second insulating layer was 0.08 mm.

[Examples 2 to 5, Comparative Examples 1 to 3]
Example 1 was repeated except that the formulations of the first and second curable compositions were changed as shown in Table 1 and the vacuum press pressure was changed as shown in Table 1. The vacuum press pressure described in the column for the first insulating layer is the press pressure in the first curing step, and the vacuum press pressure described in the column for the second insulating layer is the press in the second curing step. pressure.

As is clear from the results in Table 1, in each example, by setting the porosity to a specific amount or less, it was possible to improve heat dissipation and insulation.

10 Laminated body 11 Thermal conductor 12 Insulating resin layer 12A First insulating layer 12B Second insulating layer 12X One surface 12Y The other surface

Claims (14)

A laminate comprising a thermal conductor having a thermal conductivity of 10 W/m·K or more and an insulating resin layer provided on the surface of the thermal conductor and containing a thermally conductive filler,
The insulating resin layer has a region that melts at 50° C. or higher and 175° C. or lower and a region that does not melt at 50° C. or higher and 175° C. or lower,
A laminate having a porosity of 0.09% or less in terms of area ratio in a cross section of the insulating resin layer obtained by image analysis. 2. The laminate according to claim 1 , wherein a region of the insulating resin layer opposite to the surface on which the heat conductor is provided is a region that melts at 50[deg.] C. or higher and 175[deg.] C. or lower. 3. The dielectric constant of the side of the insulating resin layer on which the heat conductor is provided is lower than the dielectric constant of the side opposite to the side of the insulating resin layer on which the heat conductor is provided. The laminate according to . 4. The laminate according to any one of claims 1 to 3 , wherein at least a region of the insulating resin layer on the side opposite to the surface on which the heat conductor is provided is an uncured material or a semi-cured material. 5. The laminate according to any one of claims 1 to 4 , wherein the insulating resin layer has at least a semi-cured material or a cured material in a region on the side where the heat conductor is provided. The hardening rate of the region on the side where the heat conductor is provided is 50% or more,
The hardening rate of the region on the side opposite to the surface on which the heat conductor is provided is less than 80%,
6. The hardening rate of the area on the side where the heat conductor is provided is higher than the hardening rate of the area on the side opposite to the side on which the heat conductor is provided. laminate. the thermally conductive filler comprises boron nitride;
7. The laminate according to any one of claims 1 to 6 , wherein the boron nitride is contained in at least a region of the insulating resin layer on the side where the heat conductor is provided. the thermally conductive filler comprises alumina,
The laminate according to any one of claims 1 to 7 , wherein the alumina is contained in a region of the insulating resin layer on the side opposite to the surface on which the heat conductor is provided. 9. The laminate according to claim 8 , wherein the alumina has an aspect ratio of 2 or less. the thermally conductive filler comprises boron nitride;
10. The laminate according to claim 8 , wherein a region of the insulating resin layer on the side opposite to the surface on which the heat conductor is provided further contains boron nitride. the thermally conductive filler comprises boron nitride;
Both the region on the side of the surface on which the thermal conductor is provided and the region on the side opposite to the surface on which the thermal conductor is provided both contain boron nitride,
In the insulating resin layer, the content of boron nitride in the region on the side where the heat conductor is provided is higher than the content of boron nitride in the region on the side opposite to the side on which the heat conductor is provided. Item 11. The laminate according to any one of items 1 to 10 . The laminate according to any one of claims 1 to 11 , wherein the heat conductor has a thickness of 0.03 mm or more and 3 mm or less. An electronic component comprising the laminate according to any one of claims 1 to 12 . An inverter comprising the electronic component according to claim 13 .

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