JP2012253167A - Thermally conductive insulation sheet, metal base substrate and circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermally conductive insulation sheet exhibiting excellent insulation and heat dissipation, and to provide a metal base substrate and a circuit board.SOLUTION: On one or a plurality of longitudinally oriented sheets 4 where hexagonal boron nitrides 2 are oriented in the thickness direction, one or a plurality of laterally oriented sheets 3 where hexagonal boron nitrides 2 are oriented in the width direction or the length direction are laminated to produce a thermally conductive insulation sheet 1. Total thickness of the longitudinally oriented sheets 4 is set thicker than the total thickness of the laterally oriented sheets 3. In addition, the thermally conductive insulation sheet 1 and a conductive layer are laminated, in this order, on a metal base material so that the laterally oriented sheet 3 is disposed on the conductor layer side thus obtaining a metal base substrate. Furthermore, a metal base circuit board is produced by processing the conductor layer of the metal base substrate.

Description

  The present invention relates to a heat conductive insulating sheet, a metal base substrate, and a circuit board. More specifically, the present invention relates to a heat conductive insulating sheet used for heat dissipation of electronic components, a metal base substrate provided with a heat conductive insulating layer, and a circuit board.

  In recent years, with the increase in density, integration, and output of electronic components such as semiconductor elements, countermeasures for heat generation from these electronic components have become important, and metal base substrates having excellent heat dissipation have attracted attention. . In particular, since power semiconductors such as LEDs (Light Emitting Diodes) generate a large amount of heat, studies have been made to improve the heat dissipation performance of metal base substrates (see, for example, Patent Documents 1 to 3).

  In the insulating substrate described in Patent Document 1, a plurality of heat transfer layers in which an inorganic filler is dispersed in a resin are formed on a metal plate, and a measurement electrode is provided therebetween, thereby achieving both insulation and heat dissipation. Yes. In addition, in the high thermal conductive insulating substrate described in Patent Document 2, insulation is achieved by an organic polymer compound containing magnesium and / or calcium borate particles (non-oriented BN powder) coated with hexagonal boron nitride. Forming a layer.

  Furthermore, in Patent Document 3, an insulating layer made of a resin composition containing an epoxy resin, a curing agent, and hexagonal boron nitride is laminated on a metal base plate, and a metal foil is laminated on the insulating layer. A circuit board in which a circuit is formed by being cut out is disclosed. In the circuit board described in Patent Document 3, the heat dissipation direction is improved by orienting the hexagonal boron nitride in the insulating layer in one direction to improve the heat dissipation characteristics.

JP 2009-004731 A JP 2000-223807 A JP 2011-012193 A

  However, the conventional techniques described above have the following problems. That is, in the insulating substrate described in Patent Document 1, the electrode provided in the intermediate layer plays a role of heat diffusion, but the heat conductivity of the insulating layer itself is low, so that sufficient heat dissipation cannot be obtained. There is a point. In addition, since the insulating substrate described in Patent Document 2 uses non-oriented BN powder as an inorganic filler, the maximum anisotropic thermal conductivity (200 W / mK) of BN powder cannot be utilized. However, there is a problem that sufficiently high heat dissipation cannot be obtained. On the other hand, the circuit board described in Patent Document 3 has excellent thermal conductivity and excellent insulation reliability, but is required to have improved insulation and heat dissipation properties for various applications. ing.

  Therefore, the main object of the present invention is to provide a thermally conductive insulating sheet, a metal base substrate, and a circuit board that are excellent in insulation and heat dissipation.

The thermally conductive insulating sheet according to the present invention is laminated on one or a plurality of longitudinally oriented sheets in which hexagonal boron nitride is oriented in the thickness direction, and the hexagonal boron nitride is oriented in the width direction or 1 or a laterally oriented sheet oriented in the length direction, and the total thickness of the longitudinally oriented sheet is thicker than the total thickness of the laterally oriented sheet.
The thermally conductive insulating sheet includes the longitudinally oriented sheet and the laterally oriented sheet, at least containing an epoxy resin, a curing agent, and hexagonal boron nitride, and at least one of the epoxy resin and the curing agent is polycyclic. It can be formed of a cured product of a resin composition having an aromatic structure.
In that case, at least one of the epoxy resin and the curing agent may have a naphthalene structure.
Further, the longitudinally oriented sheet can be constituted by an aggregate of prismatic oriented bodies formed by laminating the laterally oriented sheets and cutting in the laminating direction.
Furthermore, after laminating a B-staged horizontally oriented sheet on a B-staged vertically oriented sheet, it may be heated to a C-staged state.
Furthermore, this heat conductive insulating sheet is arrange | positioned so that a horizontal orientation sheet | seat may become the component side which heat | fever-generates, for example.

  The metal base substrate according to the present invention is a metal base substrate in which an insulating layer and a conductor layer are laminated in this order on a metal base material, wherein the insulating layer is the above-described thermally conductive insulating sheet, and the conductor layer Is formed on the laterally oriented sheet.

  The circuit board according to the present invention is a metal base circuit board in which an insulating layer is formed on a metal base material and a conductor circuit is formed on the insulating layer, and the insulating layer is the conductive insulating sheet described above. And the conductor circuit is formed on the laterally oriented sheet.

  According to the present invention, since it has a structure in which a horizontally oriented sheet is laminated on a vertically oriented sheet, it is possible to realize a heat conductive insulating sheet, a metal base substrate, and a circuit board that have improved heat dissipation efficiency and excellent heat dissipation characteristics. .

It is a figure which shows typically the structure of the heat conductive insulating sheet of the 1st Embodiment of this invention. (A)-(e) is a schematic diagram which shows an example of the manufacturing method of the heat conductive insulating sheet 1 of the 1st Embodiment of this invention in the order of the process. It is a figure which shows typically the structure of the heat conductive insulating sheet of the modification of the 1st Embodiment of this invention. It is a figure which shows typically the structure of the metal base substrate of the 2nd Embodiment of this invention. (A)-(c) is a schematic diagram which shows an example of the manufacturing method of the metal base substrate of the 2nd Embodiment of this invention in the order of the process.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below.

(First embodiment)
The thermally conductive insulating sheet according to the first embodiment of the present invention will be described. FIG. 1 is a diagram schematically showing the configuration of the thermally conductive insulating sheet of the present embodiment. As shown in FIG. 1, the thermally conductive insulating sheet 1 of the present embodiment has a hexagonal boron nitride 2 in the width direction or a longitudinally oriented sheet 4 in which the hexagonal boron nitride 2 is oriented in the thickness direction. The laterally oriented sheet 3 oriented in the length direction is laminated. And this heat conductive insulating sheet 1 is arrange | positioned so that the horizontal orientation sheet | seat 3 may become the component side which generate | occur | produces heat.

[Horizontal orientation sheet 3]
The laterally oriented sheet 3 is formed by curing a resin composition having at least an epoxy resin, a curing agent, and hexagonal boron nitride, and the hexagonal boron nitride 2 is oriented in the width direction or the length direction thereof. is doing. Moreover, in the resin composition which forms this horizontal orientation sheet | seat 3, at least one of an epoxy resin and a hardening | curing agent has a naphthalene structure.

(Epoxy resin)
The epoxy resin used for the heat conductive insulating sheet 1 of the present embodiment may be an epoxy compound having two or more epoxy groups in one molecule, and in particular, there are many such as naphthalene structure and anthracene structure in the molecule. Those having a ring aromatic structure are preferred. Among them, the naphthalene structure is liquid at normal temperature and has good wettability with the hexagonal boron nitride 2. Therefore, by using an epoxy resin having a naphthalene structure in the molecule, the filling of the hexagonal boron nitride 2 can be achieved. The rate can be increased, and heat dissipation and heat resistance can be improved.

  The compounding amount of the epoxy resin with respect to the resin composition forming the laterally oriented sheet 3 is not particularly limited, but from the viewpoint of the properties of the obtained cured product, in particular, insulation and adhesion to a metal material. The total amount is preferably 7.5 to 33.0% by mass, and more preferably 8.8 to 31.7% by mass.

(Curing agent)
The curing agent used in the thermally conductive insulating sheet 1 of the present embodiment is the epoxy resin curing agent described above, and specifically uses phenol novolac resin, acid anhydride resin, amino resin, imidazoles, and the like. can do. Also about this hardening | curing agent, what has a polycyclic aromatic structure is preferable, and what has a naphthalene structure is especially preferable. Thereby, the filling rate of the hexagonal boron nitride 2 can be increased, and heat dissipation and heat resistance can be improved.

  The blending amount of the curing agent with respect to the resin composition forming the laterally oriented sheet 3 is not particularly limited, but from the viewpoint of characteristics of the obtained cured body, particularly insulation and adhesion to a metal material, the resin composition. The total amount is preferably 0.5 to 8.0% by mass, more preferably 0.9 to 6.55% by mass. In particular, when the curing agent is a phenol novolac resin, an acid anhydride resin or an amino resin, the equivalent ratio to the epoxy resin is preferably 0.75 to 1.25, and more preferably an equivalent ratio of 0.8. ~ 1.2. In addition, about what hardens | cures by ion polymerization like imidazoles etc., an equivalent ratio is not specifically limited.

(Hexagonal boron nitride 2)
Hexagonal boron nitride 2 is a tabular grain having a flake-like crystal structure similar to graphite and excellent in thermal conductivity, heat resistance and electrical insulation. For this reason, the heat conductive insulating sheet excellent in heat dissipation is obtained by highly filling the hexagonal boron nitride 2. On the other hand, when the hexagonal boron nitride 2 is highly filled, there is a problem that moldability is lowered. Therefore, in the thermally conductive insulating sheet of the present embodiment, high filling of the hexagonal boron nitride 2 is realized by using an epoxy resin having a naphthalene structure and / or a curing agent.

  Specifically, the content of hexagonal boron nitride 2 in the laterally oriented sheet 3 is 50 to 85% by volume. When the content of hexagonal boron nitride 2 is less than 50% by volume, the thermal conductivity is lowered and sufficient heat dissipation performance cannot be obtained. On the other hand, if the content of hexagonal boron nitride 2 exceeds 85% by volume, voids are likely to occur during molding, and insulation and mechanical strength are reduced. In addition, it is preferable that content of the hexagonal boron nitride 2 in the laterally oriented sheet 3 is 65 to 83 volume% from the viewpoint of heat dissipation and moldability.

  The hexagonal boron nitride 2 is desirably a coarse powder having an average particle size of 10 to 400 μm. Thereby, a highly oriented alignment sheet can be formed without reducing the fluidity of the resin composition. In this case, the GI (Graphitization: graphitization index) value of the hexagonal boron nitride 2 is preferably 1.5 or less.

  Here, the “GI value” is represented by a ratio of the area [Area (002)] of (002) diffraction lines measured by X-ray diffraction and the area [Area (100)] of (100) diffraction lines. , Which is a value obtained by the following mathematical formula 1. That is, the lower the GI value is, the more crystallization proceeds. The hexagonal boron nitride having a low degree of crystallinity does not have a sufficiently grown particle and has a low thermal conductivity. Therefore, in the thermally conductive insulating sheet 1 of the present embodiment, the GI value is 1.5 or less. It is desirable to use hexagonal boron nitride which has been crystallized.

Furthermore, the hexagonal boron nitride 2 desirably has a tap density of 0.5 g / cm ³ or more. Thereby, the filling rate and dispersibility of the inorganic filler in the oriented sheet can be improved. Here, the “tap density” represents the bulk density of the filler, and is the mass per unit volume of the powder in the vibrated container as defined in JIS Z 2500 (2045).

(Inorganic filler)
Furthermore, it is desirable that the resin composition forming the laterally oriented sheet 3 is blended with fine powder of an inorganic filler having an average particle diameter of 0.5 to 4.0 μm together with the hexagonal boron nitride 2 described above. By blending the fine powder of the inorganic filler together with the coarse powder of the hexagonal boron nitride 2, the fine powder is filled between the coarse powders, and the filling rate as a whole can be increased.

  Examples of the fine powder material include silicon oxide, aluminum oxide, magnesium oxide, boron nitride, aluminum nitride, silicon nitride, and nitrogen carbide. Among these, hexagonal boron nitride is particularly suitable. By blending hexagonal boron nitride fine powder, an oriented sheet having low dielectric constant, high insulation, and high thermal conductivity can be obtained. Moreover, when spherical alumina is used, an oriented sheet having high insulation and high thermal conductivity can be obtained.

  In addition, when using together the coarse powder of the hexagonal boron nitride 2 and the fine powder of the inorganic filler, it is preferable that the blending ratio of the coarse powder is 70% by mass or more, and 75% by mass or more with respect to the total amount of these. More preferably. Thereby, there can be formed an orientation sheet with no voids and densely filled.

(Other ingredients)
In addition to the components described above, an organic solvent, a coupling agent, a surfactant, and the like may be blended in the resin composition that forms the laterally oriented sheet 3.

(Degree of orientation)
The laterally oriented sheet 3 has an orientation index determined by the following formula 2 of O.D. It is preferable that I << 1.0. Thereby, since heat can be diffused in a wide range, the heat transfer area is increased and the heat dissipation performance is further improved. Moreover, insulation can also be improved by the shielding effect of BN particles.

[Vertical orientation sheet 4]
The laterally oriented sheet 4 is formed by curing a resin composition having at least an epoxy resin, a curing agent, and hexagonal boron nitride, like the laterally oriented sheet 3 described above. The hexagonal boron nitride 2 is oriented in the thickness direction. Also in the resin composition forming the longitudinally oriented sheet 4, it is desirable that at least one of the epoxy resin and the curing agent has a polycyclic aromatic structure, particularly a naphthalene structure.

  The configuration of the resin composition forming the longitudinally oriented sheet 4 is the same as that of the laterally oriented sheet 3 described above. In addition, although the horizontal alignment sheet 3 and the vertical alignment sheet 4 may be formed with a resin composition having the same composition, they may be formed with resin compositions having different compositions.

(Degree of orientation)
The longitudinally oriented sheet 4 has an orientation index determined by the above formula 2 of O.D. It is preferable that I> 0.5. Thereby, since the heat conductivity of the vertical direction (thickness direction) can be improved, the heat dissipation efficiency is further improved.

[Thickness of each sheet]
The thicknesses of the laterally oriented sheet 3 and the longitudinally oriented sheet 4 are not particularly limited and can be set as appropriate according to the application, but the thickness of the longitudinally oriented sheet 4 is made thicker than that of the laterally oriented sheet 3. It is desirable. Thereby, the effect of diffusing the heat by the lateral sheet 3 and the effect of efficiently transferring the heat by the longitudinally oriented sheet 4 to the outside of the sheet, such as a heat sink or a metal base material, can be obtained efficiently and synergistically. Can do. As a result, the heat dissipation performance can be further improved.

  In addition, since the horizontal alignment sheet 3 has low heat transfer performance in the vertical direction (thickness direction), the thickness of the horizontal alignment sheet 3 is preferably 20 μm or less from the viewpoint of improving heat dissipation.

[Production method]
Next, the manufacturing method of the heat conductive insulating sheet 1 of the structure mentioned above is demonstrated. Drawing 2 (a)-(e) is a mimetic diagram showing an example of a manufacturing method of heat conductive insulating sheet 1 of this embodiment in the order of the process. The thermally conductive insulating sheet 1 of this embodiment includes a laterally oriented sheet 3 in which hexagonal boron nitride 2 is oriented in the width direction or length direction, and a longitudinal direction in which hexagonal boron nitride 2 is oriented in the thickness direction. Although it can also laminate | stack after producing the orientation sheet 4 separately, you may cut out the horizontal orientation sheet 3 and the longitudinal orientation sheet 4 from one molded object.

  In that case, the laterally oriented sheet 3 and the longitudinally oriented sheet 4 can be formed by extrusion molding or press molding using the resin composition described above. At that time, the horizontally oriented sheet 3a and the vertically oriented sheet 4a before lamination are desirably in a B-stage state. Here, the “B stage state” means a state in which the resin composition is dried at room temperature and melts again when heated to a high temperature. More precisely, DSC (Differential Scanning Calorimetry) ), The degree of cure is less than 70% with a value calculated from the amount of heat generated during curing.

  Then, it is desirable that the B-stage state horizontal alignment sheet 3a is arranged on the B-stage state vertical alignment sheet 4a, and these are brought into the C-stage state by, for example, heating while pressing from the vertical direction or the entire periphery. . Thereby, the horizontal alignment sheet 3 and the vertical alignment sheet 4 can be integrated easily. Here, the “C stage state” means a state where the curing of the resin composition is almost completed and does not melt again even when heated to a high temperature, and means a state where the curing degree is 70% or more.

  Also, as shown in FIGS. 2 (a) to (e), a plurality of laterally oriented sheets 3 a obtained by molding with an extrusion molding apparatus 10 or the like are laminated to form a molded body 5, and this is broken by a breaking blade 11. The longitudinally oriented sheet 4a may be formed by cutting in the thickness direction of the laterally oriented sheet 3a, that is, in a direction perpendicular to the orientation direction of the hexagonal boron nitride 2. In this case, the longitudinal sheet 4a has a configuration in which a plurality of prismatic alignment bodies 6 are arranged in one direction. Also in the manufacturing method shown in FIG. 2, it is desirable that the laterally oriented sheet 3a and the longitudinally oriented sheet 4a before lamination are in the B stage state and are in the C stage state after lamination.

  The thermally conductive insulating sheet 1 of the present embodiment has a configuration in which the laterally oriented sheet 3 and the longitudinally oriented sheet 4 are laminated. Therefore, in the laterally oriented sheet 3, heat generated by electronic components and the like is diffused laterally. Further, the diffused heat is released out of the sheet by the longitudinal sheet 4. Thereby, it becomes possible to radiate heat efficiently.

  In addition, although the heat conductive insulating sheet 1 shown in FIG. 1 has a configuration in which the laterally oriented sheet 3 and the longitudinally oriented sheet 4 are laminated one by one, the present invention is not limited to this, A plurality of laterally oriented sheets 3 and / or longitudinally oriented sheets 4 may be laminated. FIG. 3 is a diagram schematically showing a configuration of a thermally conductive insulating sheet according to a modification of the present embodiment. In FIG. 3, the same components as those of the heat conductive insulating sheet 1 shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 3, in the heat conductive insulating sheet 21 of this modification, the laterally oriented sheet 3 is laminated on two longitudinally oriented sheets 22 and 23 having the same or different thickness. In this way, by laminating a plurality of laterally oriented sheets and / or longitudinally oriented sheets, by changing the number of sheets laminated and the width of the oriented body in a single sheeting process respectively for lateral orientation and longitudinal orientation, A thermally conductive insulating sheet having an arbitrary size and thickness can be obtained. In addition, the structure and effect other than the above in the heat conductive insulating sheet 21 of this modification are the same as that of 1st Embodiment mentioned above.

(Second Embodiment)
A metal base substrate according to a second embodiment of the present invention will be described. FIG. 4 is a diagram schematically showing the configuration of the metal base substrate of the present embodiment. In FIG. 4, the same components as those of the thermally conductive insulating sheet 1 shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 4, the metal base substrate 30 of this embodiment has a C-stage heat conductive insulating layer 32 formed on a metal base material 31, and a conductor foil 33 is laminated thereon. Yes.

[Metal base material 31]
The material of the metal base material 31 is not particularly limited, but is preferably aluminum, iron, copper, stainless steel, or an alloy thereof, and particularly in terms of heat dissipation, price, lightness, and workability. In view of this, aluminum is preferable. Further, the metal base material 31 has alumite treatment, degreasing treatment, sand blasting, etching, various plating treatments, cups on the adhesive surface with the heat conductive insulating layer 32 in order to improve adhesion with the heat conductive insulating layer 32. It is desirable that various surface treatments such as primer treatment using a ring agent or the like are performed.

[Thermal conductive insulating layer 32]
The heat conductive insulating layer 32 is configured by the heat conductive insulating sheet of the first embodiment described above or its modification. That is, the heat conductive insulating layer 32 is formed on the one or more longitudinally oriented sheets 4 in which the hexagonal boron nitride 2 is oriented in the thickness direction, and the hexagonal boron nitride 2 is arranged in the width direction or the length direction. It has a configuration in which one or two or more horizontally oriented sheets 3 are laminated.

  The thickness of the thermally conductive insulating layer 32 in the C-stage state is preferably 80 to 300 μm from the viewpoint of insulation strength and heat dissipation characteristics. When the thickness of the heat conductive insulating layer 32 is less than 80 μm, it may be difficult to obtain a desired insulation strength, and when the thickness of the insulating adhesive layer 2b exceeds 300 μm, the thermal resistance increases. The heat dissipation characteristics may deteriorate.

  On the other hand, the insulation strength of the thermally conductive insulating layer 32 in the C-stage state is preferably 30 kV / mm or more, and more preferably 35 kV / mm or more. Thereby, a metal base circuit board with higher quality and higher heat dissipation can be realized.

[Conductor foil 33]
For the conductor foil 33, for example, a foil material or a clad foil made of aluminum, iron, copper, stainless steel or an alloy thereof can be used, and in particular, a copper foil is used from the viewpoint of electrical conductivity and heat dissipation. Is preferred. In addition, in order to improve adhesion to the heat conductive insulating layer 32, primer treatment using a degreasing process, sand blasting, etching, various plating processes, a coupling agent, etc. on the adhesive surface with the heat conductive insulating layer 32 It is desirable that various surface treatments such as are applied.

[Thermal resistance]
The thermal resistance of the metal base substrate including the thermally conductive insulating layer 32 in the C stage state is preferably 1.0 ° C./W or less, and more preferably 0.9 ° C./W or less. Thereby, a metal base circuit board with higher quality and higher heat dissipation can be realized.

[Production method]
Next, the manufacturing method of the metal base substrate 30 of this embodiment is demonstrated. FIGS. 5A to 5C are schematic views showing an example of a method for manufacturing a metal base substrate according to this embodiment in the order of the steps. As shown in FIG. 5A, when manufacturing the metal base substrate 30 of this embodiment, first, the longitudinally oriented sheet 4 a is disposed on the metal base 31. In that case, the longitudinally oriented sheet 4a is desirably in a B-stage state. Further, the longitudinally oriented sheet 4a may have a configuration in which a plurality of prismatic oriented bodies 6 manufactured by the steps shown in FIGS. 2A to 2D are arranged in one direction.

  Next, as shown in FIG. 5B, a laterally oriented sheet 3a in which the hexagonal boron nitride 2 is oriented in the width direction or the length direction is laminated on the longitudinally oriented sheet 4a. At that time, it is desirable that the laterally oriented sheet 3a is also in the B stage state.

  Next, the conductor foil 33 is laminated on the laterally oriented sheet 3a, and heated while being pressed to obtain the metal base substrate 30. Thereby, for example, when the horizontally oriented sheet 3a and the vertically oriented sheet 4a are in the B stage state, the thermally conductive insulating layer 32 composed of the horizontally oriented sheet 3 and the vertically oriented sheet 4 in the C stage state is formed.

  As described in detail above, in the metal base substrate 30 of the present embodiment, the heat conductive insulating layer 32 is configured by laminating the horizontally oriented sheet 3 and the vertically oriented sheet 4, and electronic components such as semiconductors are provided. The laterally oriented sheet 3 is disposed on the side to be mounted, and the longitudinally oriented sheet 4 is disposed on the side of the metal base material 31 that contributes to heat dissipation. With this configuration, the heat generated in the electronic component can be diffused in the lateral direction, and the diffused heat can be transmitted to the metal base material 31 by the longitudinal sheet 4, thereby improving the heat dissipation efficiency and having excellent heat dissipation characteristics. can get. In addition, due to the shielding effect of the horizontally oriented particles, the metal base substrate 30 can be provided with high insulation performance.

(Third embodiment)
A metal base circuit board according to a third embodiment of the present invention will be described. The circuit board of this embodiment is obtained by processing the conductor foil 33 of the metal base substrate 30 of the second embodiment described above to form a predetermined conductor circuit on the heat conductive insulating layer 32.

  The formation method of the conductor circuit in the metal base circuit board of this embodiment is not specifically limited, A well-known method is applicable. For example, an etching resist is formed on the conductor foil 33 of the metal base substrate 30 by a screen printing method or a photographic development method, and a predetermined position on the surface of the conductor foil 33 is masked. In this state, a part of the conductor foil 33 is corroded and dissolved with a ferric chloride etching solution, a cupric chloride etching solution, a hydrogen peroxide / sulfuric acid etching solution, an alkali etching solution, etc., and then the etching resist is peeled off. Thereby, a conductor circuit is formed in the heat conductive insulating layer 32.

  In the metal base circuit board of the present embodiment, since the conductor circuit is formed on the laterally oriented sheet 3, even when an electronic component with a large calorific value such as a power semiconductor is mounted, the heat is transmitted in the lateral direction. Can diffuse. And since the heat | fever diffused to the horizontal direction is transmitted to the metal base material 31 via the vertical direction sheet | seat 4, heat dissipation efficiency improves and the outstanding heat dissipation characteristic is acquired.

  Hereinafter, the effects of the present invention will be specifically described with reference to Examples and Comparative Examples of the present invention. In this example, a heat conductive insulating sheet having a configuration shown in Table 1 below was produced and its characteristics were evaluated.

<The manufacturing method of a heat conductive insulating sheet>
A laterally oriented resin sheet and a longitudinally oriented resin sheet were prepared and laminated using the resin compositions having the compositions shown in Tables 1 and 2 below. At that time, a naphthalene type epoxy resin (manufactured by DIC, HP4032) containing a naphthalene structure was used as the epoxy resin, and an imidazole (manufactured by Shikoku Kasei Co., Ltd., 2E4MZ-CN) was used as the curing agent. Moreover, the silane coupling agent (the Toray Dow Corning company make, Z-0640N) was used for the coupling agent. Further, spherical aluminum oxide (ASFP-20, manufactured by Denki Kagaku Kogyo Co., Ltd.) was used as the fine powder of the inorganic filler. This aluminum oxide contained 90% by volume of particles having a particle size of 3.0 μm or less, and the average particle size was 0.5 μm.

  In Tables 1 and 2 below, “BN” is hexagonal boron nitride. The average particle diameters of hexagonal boron nitride (BN) and inorganic filler fine powder shown in Tables 1 and 2 below were measured using “Laser Diffraction Particle Size Analyzer SALD-200” manufactured by Shimadzu Corporation. Specifically, first, pure water: 50 cc and hexagonal boron nitride: 5 g were put into a glass beaker, stirred with a spatula, and then subjected to dispersion treatment for 10 minutes with an ultrasonic cleaner.

  Next, the dispersion-treated hexagonal boron nitride solution was added drop by drop to the sampler portion of the apparatus using a dropper, and measurement was performed when the absorbance was stabilized. In the laser diffraction particle size distribution analyzer, the particle size distribution is calculated from the data of the light intensity distribution of the diffracted / scattered light by the particles detected by the sensor. The average particle size was determined by multiplying the value of the measured particle size by the relative particle amount (difference%) and dividing by the total relative particle amount (100%). The average particle diameter is the average diameter of the particles.

Moreover, each heat conductive insulating sheet of an Example and a comparative example shape | molds the resin composition shown in following Table 1 in the thin plate shape of 1.0 mm thickness using an extrusion molding apparatus, Furthermore, 10.0 kgf / cm ^In a state where the upper and lower surfaces were pressed with a pressure of ² (0.98 MPa), it was semi-cured by heating at 100 ° C. for 5 minutes to obtain a B-staged horizontally oriented sheet 3a. Further, 50 plate-like bodies after the extrusion molding were laminated, and the upper and lower sides and the both sides were pressed isotropically at a pressure of 50.0 kgf / cm ² (4.90 MPa) for 10 minutes at 100 ° C. After being semi-cured by heating, it was cut in the thickness direction to obtain a B-staged longitudinally oriented sheet 4a.

And after laminating the horizontal alignment sheet 3a on the vertical alignment sheet 4a, it heated for 120 minutes on 150 degreeC temperature conditions in the state which pressed both upper and lower surfaces with the pressure of 1.0 kgf / cm < ² > (98.1 kPa). And cured to obtain a thermally conductive insulating sheet 1 in a C-stage state.

<Heat dissipation characteristics>
The heat conductive insulating sheets of Examples and Comparative Examples prepared by the above-described method were laminated on an aluminum plate having a thickness of 1.5 mm and then heated to a semi-cured state. Were bonded together and completely cured to produce a metal base substrate. Next, each substrate was cut out to a size of 3 cm in length and 4 cm in width, and the copper foil was removed by etching except for a 15 mm square to obtain a sample for evaluating heat dissipation characteristics.

  In the evaluation, each sample was soldered with a TO-220 type transistor on a copper foil, and then fixed on a heat radiation fin whose temperature was controlled at 15 ° C. via heat radiation grease. Then, the transistor mounted on each sample was energized to generate heat (heat flow W = 20 W), and the difference between the surface temperature (Tj) of the transistor and the temperature on the radiation fin (Ti = 15 ° C.) was measured.

  Based on the measurement result, the thermal resistance (A) of the test piece was obtained by the following mathematical formula 3. Note that the surface temperature (Tj) of the transistor and the surface temperature of the insulating layer (thermally conductive insulating sheet) were measured using an infrared thermography (H2640 manufactured by NEC Avio Infrared Technology Co., Ltd.).

<Insulation strength>
After laminating the copper foil having a thickness of 0.1 mm on the aluminum conductive sheet having the thickness of 1.5 mm laminated on the heat conductive insulating sheet of the example and the comparative example prepared by the method described above, at 150 ° C. By heating for 2.0 hours, the thermally conductive insulating sheet was completely cured to produce a substrate for evaluating the insulation strength.

  Next, the copper foil of this evaluation board, which was etched leaving a circular portion with a diameter of 20 mm, was immersed in insulating oil, and an AC voltage was applied between the copper foil and the aluminum plate at room temperature, and JIS The initial withstand voltage was measured based on C2110. At that time, TOS-8700 manufactured by Kikusui Electric Co., Ltd. was used as a measuring instrument. The initial withstand voltage is required to be 20 kV / mm or more.

<Stripping strength>
The copper foil of the substrate for evaluating heat radiation characteristics described above was left in a strip shape having a width of 10 mm, and the other portions were removed by etching to obtain a peel strength measurement sample. Then, using a Tensilon tester U-1160 manufactured by Toyo Baldwin Co., Ltd. (Orientec Co., Ltd.), the angle between the copper foil and the substrate was 90 °, the tensile speed was 50 mm / min, and other conditions were based on JIS C6481. Then, the load when the sample was peeled was measured.

  The above results are summarized in Tables 1 and 2 below. In addition, “determination” shown in Tables 1 and 2 below indicates that the thermal resistance is 0.9 ° C./W or less, the insulation strength is 35 kV / mm or less, and the peel strength is 5.0 N / cm or more. Except for x.

  As shown in Table 2 above, the sheets of Comparative Examples 2 and 3 composed only of the laterally oriented sheet were inferior in heat dissipation characteristics and insulation characteristics. Moreover, the sheet | seat of the comparative example 1 whose thickness of the horizontal orientation sheet | seat and the longitudinal orientation sheet | seat was the same was also inferior in the thermal radiation characteristic.

  On the other hand, the sheet | seat of Examples 1-7 produced within the scope of the present invention was excellent in both heat dissipation characteristics and insulation characteristics. Thereby, according to this invention, it was confirmed that the heat conductive insulating sheet, metal base board | substrate, and circuit board which were excellent in the thermal radiation characteristic are realizable.

DESCRIPTION OF SYMBOLS 1,21 Thermal conductive insulating sheet 2 Inorganic filler 3 Horizontally oriented sheet in C stage state 3a Horizontally oriented sheet in B stage state 4, 22, 23 Vertically oriented sheet in C stage state 4a Vertically oriented sheet in B stage state 5 Laminate 6 prismatic oriented body 10 extrusion molding machine 11 cutting blade 30 metal base substrate 31 metal base material 32 heat conductive insulating layer 33 conductor foil

Claims (8)

One or a plurality of longitudinally oriented sheets in which hexagonal boron nitride is oriented in the thickness direction, and laminated on the longitudinally oriented sheet, the hexagonal boron nitride is oriented in the width direction or the length direction. An orientation sheet,
A thermally conductive insulating sheet in which the total thickness of the longitudinally oriented sheet is thicker than the total thickness of the laterally oriented sheet.   The longitudinally oriented sheet and the laterally oriented sheet contain at least an epoxy resin, a curing agent, and hexagonal boron nitride, and at least one of the epoxy resin and the curing agent has a polycyclic aromatic structure. The thermally conductive insulating sheet according to claim 1, wherein the thermally conductive insulating sheet is a cured product.   The thermally conductive insulating sheet according to claim 2, wherein at least one of the epoxy resin and the curing agent has a naphthalene structure.   The said vertical orientation sheet | seat is an aggregate | assembly of the prismatic oriented body formed by laminating | stacking the said horizontal orientation sheet | seat and cut | disconnecting in the lamination direction, The said any one of Claim 1 thru | or 3 characterized by the above-mentioned. Thermally conductive insulating sheet.   The thermally conductive insulation according to any one of claims 1 to 4, wherein a B-staged horizontally oriented sheet is laminated on a B-staged vertically oriented sheet and then heated to a C-staged state. Sheet.   The thermally conductive insulating sheet according to any one of claims 1 to 5, wherein the laterally oriented sheet is arranged so as to be on a component side that generates heat. A metal base substrate in which an insulating layer and a conductor layer are laminated in this order on a metal base material,
The metal base substrate in which the said insulating layer is a heat conductive insulating sheet of any one of Claims 1 thru | or 6, and the said conductor layer is formed on the said horizontal orientation sheet | seat. A metal base circuit board in which an insulating layer is formed on a metal base material, and a conductor circuit is formed on the insulating layer,
The circuit board in which the insulating layer is the thermally conductive insulating sheet according to any one of claims 1 to 6, and the conductor circuit is formed on the laterally oriented sheet.

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