JP5867047B2 - Filler, composition for forming an insulating layer, film for forming an insulating layer, and substrate - Google Patents

Description

  The present invention relates to a filler, a composition for forming an insulating layer, a film for forming an insulating layer, and a substrate.

  A substrate is known in which wiring is formed on a metal plate made of a metal material via an insulating layer (see, for example, Patent Document 1).

  Such a substrate can efficiently release heat from an electronic component such as a semiconductor element or a light-emitting element mounted on the substrate as compared with a substrate mainly composed of a resin material and a fiber base material.

In such a substrate, the insulating layer includes a resin material and an inorganic filler. Thereby, the heat from an electronic component can be efficiently transmitted to a metal plate through an insulating layer.
Moreover, such a board | substrate is manufactured as follows, for example.

  That is, first, a metal plate and a conductor plate for forming wiring are prepared, and a varnish containing an inorganic filler and a resin material is supplied between them to form a laminate. Next, the laminate is pressurized and heated so that the metal plate and the conductor plate come close to each other, thereby solidifying or curing the varnish to form an insulating layer. Next, by patterning the conductor plate into a predetermined shape, a wiring is formed on the insulating layer to obtain a substrate.

  Incidentally, in recent years, with the increase in the amount of heat from electronic components, such a substrate is required to further improve heat dissipation. Therefore, it is necessary to increase the content of the inorganic filler in the insulating layer.

  However, in this case, when the substrate is manufactured by the method as described above, when the laminate is pressed, a large amount of inorganic filler is contained in the varnish, resulting in a gap between the metal plate and the conductor plate. The flow rate of the inorganic filler is reduced. As a result, since voids remain in the formed insulating layer, there has been a problem that the effect of increasing the content of the inorganic filler cannot be obtained sufficiently. That is, there is a problem that an insulating layer having excellent thermal conductivity and insulating properties cannot be formed.

JP 2001-196495 A

  The objective of this invention provides the filler used for the composition for insulating layer formation which can form the insulating layer which has the outstanding heat conductivity and insulation, the composition for insulating layer formation, and the film for insulating layer formation. Another object of the present invention is to provide a substrate having excellent heat dissipation and reliability.

Such an object is achieved by the present invention described in the following (1) to ( 11 ).
(1) A filler used in an insulating layer forming composition for forming an insulating layer,
A filler characterized by being a granular body mainly composed of aluminum oxide and having an absolute value of zeta potential measured in a methyl ethyl ketone solvent of 5.0 mV or less.

  (2) The filler according to (1), wherein the granular body is configured by at least one of primary particles of the aluminum oxide and aggregates of the primary particles.

( 3 ) A composition for forming an insulating layer, which contains the filler according to (1) or (2) and a resin material, and is used for forming the insulating layer.

( 4 ) The composition for forming an insulating layer according to ( 3 ), wherein the content of the filler is 30% by volume or more and 70% by volume or less of the whole.

( 5 ) Content of the said resin material is a composition for insulating layer formation as described in said ( 3 ) or ( 4 ) which is 30 volume% or more and 70 volume% or less of the whole.

( 6 ) The composition for forming an insulating layer according to any one of ( 3 ) to ( 5 ), wherein the resin material is a thermosetting resin.

( 7 ) The composition for forming an insulating layer according to any one of ( 3 ) to ( 6 ), wherein the resin material is a hydrophobic resin.

( 8 ) An insulating layer forming film comprising an insulating layer forming layer formed by layering the insulating layer forming composition according to any one of ( 3 ) to ( 7 ) above.

( 9 ) The film for forming an insulating layer according to the above ( 8 ), which has a support layer for supporting the insulating layer forming layer.
( 10 ) The insulating layer forming film according to ( 9 ), wherein the support layer is a metal foil.

( 11 ) a metal plate made of a metal material;
An insulating layer provided on the metal plate and made of a cured product or a solidified product obtained by forming the insulating layer forming composition according to any one of ( 3 ) to ( 7 ) into a layer;
And a conductive layer provided on a surface of the insulating layer opposite to the metal plate.

  According to the filler of the present invention, the composition for forming an insulating layer obtained using the filler can have a desired flow property even if the filler content is increased. Therefore, it is possible to make this insulating layer excellent in thermal conductivity while preventing generation of voids in the insulating layer formed of the composition for forming an insulating layer containing such a filler. That is, an insulating layer having excellent thermal conductivity and insulating properties can be formed.

  Moreover, according to the insulating layer forming film of the present invention, an insulating layer having excellent thermal conductivity and insulating properties can be formed relatively easily.

Moreover, according to the board | substrate of this invention, since it has the insulating layer which has the outstanding heat conductivity and insulation, it is excellent in heat dissipation and reliability.

It is sectional drawing which shows embodiment of the board | substrate of this invention. It is a partial expanded sectional view which shows typically the insulating layer of the board | substrate shown in FIG. It is a figure for demonstrating the manufacturing method of the board | substrate shown in FIG. It is the schematic which shows an example of the electronic circuit using the board | substrate shown in FIG.

  Hereinafter, the filler, the composition for forming an insulating layer, the film for forming an insulating layer, and the substrate of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

  1 is a sectional view showing an embodiment of the substrate of the present invention, FIG. 2 is a partially enlarged sectional view schematically showing an insulating layer of the substrate shown in FIG. 1, and FIG. 3 is a method for manufacturing the substrate shown in FIG. FIG. 4 is a schematic view showing an example of an electronic circuit using the substrate shown in FIG. In the following, for convenience of explanation, the upper side in FIGS. 1 to 4 is also referred to as “upper” and the lower side is also referred to as “lower”. In each drawing, for convenience of explanation, the substrate and its respective parts are schematically shown exaggeratedly, and the size and ratio of the substrate and its respective parts are greatly different from actual ones.

First, the substrate of the present invention will be described.
(substrate)
A substrate 1 shown in FIG. 1 includes a metal plate 2, a conductor layer 3, and an insulating layer 4, and the metal plate 2 and the conductor layer 3 are joined via the insulating layer 4. That is, the substrate 1 has a metal plate 2, an insulating layer 4, and a conductor layer 3 laminated in this order.

  Such a substrate 1 can transmit heat from the conductor layer 3 side to the metal plate 2 through the insulating layer 4, and can radiate heat by the metal plate 2.

Hereinafter, each part which comprises the board | substrate 1 is demonstrated in detail sequentially.
The metal plate 2 has a function of supporting the conductor layer 3. In addition, the metal plate 2 also has a function as a heat radiating part that releases heat from the electronic components mounted on the substrate 1 when the substrate 1 is used in an electronic circuit as will be described later.
Such a metal plate 2 is made of a metal material.

  Although it does not specifically limit as this metal material, It is preferable to use aluminum or aluminum alloy. By constituting the metal plate 2 with aluminum or an alloy thereof, the thermal conductivity of the metal plate 2 can be made excellent. As a result, the heat dissipation of the substrate 1 can be made excellent.

The thickness of the metal plate 2 is not particularly limited as long as the conductor layer 3 can be supported. For example, the thickness is preferably 1 to 5 mm, and more preferably 1 to 2 mm. By setting the thickness of the metal plate 2 in such a numerical range, it is possible to reduce the thickness of the substrate 1 while ensuring the necessary mechanical strength of the substrate 1.
A conductor layer 3 is bonded to one surface of such a metal plate 2 via an insulating layer 4.

  The conductor layer 3 is provided on the surface of the insulating layer 4 opposite to the metal plate 2 and is patterned into a predetermined shape by processing such as etching when the substrate 1 is used for an electronic circuit as will be described later. It becomes wiring, an electrode, etc. That is, the conductor layer 3 is a conductor foil formed uniformly over the entire surface of the insulating layer 4, and becomes a conductor pattern by being patterned.

  Such a conductor layer 3 is made of a conductive material. Specifically, the constituent material of the conductor layer 3 is not particularly limited. For example, a metal material is preferably used, and in particular, copper or a copper alloy because of its low electrical resistance and low cost. Is preferably used.

  Moreover, although the thickness of the conductor layer 3 is not specifically limited, For example, it is preferable that it is 10-200 micrometers, and it is more preferable that it is 18-70 micrometers.

  The insulating layer 4 is provided between the metal plate 2 and the conductor layer 3 and has a function of bonding (bonding) these. The insulating layer 4 has an insulating property. Thereby, the insulation state of the metal plate 2 and the conductor layer 3 is ensured.

  Furthermore, in this invention, the insulating layer 4 is comprised so that the outstanding thermal conductivity may be exhibited. Thereby, the insulating layer 4 can transfer the heat on the conductor layer 3 side to the metal plate 2. The higher the thermal conductivity of the insulating layer 4 is, the better. Specifically, it is preferably 1 W / m · K or more, and more preferably 3 W / m · K or more. Thereby, the insulating layer 4 can efficiently transfer the heat on the conductor layer 3 side to the metal plate 2.

  The thickness (average thickness) of the insulating layer 4 is not particularly limited, but is preferably about 10 μm to 200 μm, and more preferably about 20 μm to 150 μm. Thereby, the thermal conductivity of the insulating layer 4 can be improved while ensuring the insulating property of the insulating layer 4.

  As shown in FIG. 2, the insulating layer 4 having the above-described function has a configuration in which fillers 42 are dispersed in a resin portion 41 composed of a resin material as a main material.

  The resin part 41 has a function as a binder for bonding the fillers 42 together. The filler 42 has a thermal conductivity higher than that of the resin portion 41. As described above, the insulating layer 4 includes the resin portion 41 and the filler 42, whereby the thermal conductivity of the insulating layer 4 can be increased.

  As will be described later, such an insulating layer 4 is formed by curing or solidifying an insulating layer forming composition containing a resin material (binder) and the filler of the present invention. That is, the insulating layer 4 is composed of a cured product or a solidified product obtained by forming the insulating layer forming composition into a layer shape.

  The filler and the insulating layer forming composition of the present invention will be described in detail in the following description of the method for manufacturing the substrate 1.

(Substrate manufacturing method)
Next, a method for manufacturing the substrate 1 as described above will be described with reference to FIG.

[1]
First, as shown in FIG. 3A, a conductor layer 3 is prepared. More specifically, for example, a conductor foil such as a copper foil is prepared as the conductor layer 3.

[2]
Next, as shown in FIG. 3B, an insulating layer forming layer 4 </ b> A is formed on the conductor layer 3. Thereby, the film for insulating layer formation (film for insulating layer formation of this invention) 10 is obtained.

  This insulating layer forming layer 4A is obtained by forming an insulating layer forming composition into a layer shape. And this insulating layer formation layer 4A turns into the insulating layer 4 by hardening or solidifying in process [3] mentioned later.

  Here, the conductor layer 3 constitutes a support layer that supports the insulating layer forming layer 4 </ b> A in the insulating layer forming film 10. Thus, by supporting the insulating layer forming layer 4A with the conductor layer 3, the handleability of the insulating layer forming film 10 can be improved.

  Moreover, it is preferable that the conductor layer 3 which comprises a support layer in this way is conductor foil (metal foil) like the copper foil mentioned above. Thereby, the insulating layer forming layer 4 </ b> A can be stably supported by the conductor layer 3. Therefore, the handleability of the insulating layer forming film 10 can be improved. Further, the conductivity and workability of the conductor layer 3 can be made excellent. Therefore, a conductor pattern having excellent characteristics can be obtained by processing the conductor layer 3.

  Such an insulating layer forming composition mainly includes a resin material and the filler of the present invention.

  The resin material contained in the composition for forming an insulating layer is not particularly limited, and various resin materials such as a thermoplastic resin and a thermosetting resin can be used.

  Examples of the thermoplastic resin include polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer, modified polyolefins, polyamides (eg, nylon 6, nylon 46, nylon 66, nylon 610, nylon 612, nylon 11, nylon 12). , Nylon 6-12, nylon 6-66), thermoplastic polyimide, aromatic polyester and other liquid crystal polymers, polyphenylene oxide, polyphenylene sulfide, polycarbonate, polymethyl methacrylate, polyether, polyetheretherketone, poly, such as phenoxy resin Hydroxy polyether, polyetherimide, polyacetal, styrene, polyolefin, polyvinyl chloride, polyurethane, polyester, polyamide, polybutadiene Various thermoplastic elastomers such as styrene-based, trans-polyisoprene-based, fluororubber-based, chlorinated polyethylene, and the like, and copolymers, blends, polymer alloys, etc. mainly composed of these, and one of these Or 2 or more types can be mixed and used.

  On the other hand, examples of the thermosetting resin include epoxy resin, phenol resin, urea resin, melamine resin, polyester (unsaturated polyester) resin, polyimide resin, silicone resin, polyurethane resin, and the like. Or 2 or more types can be mixed and used.

  Among these, as the resin material used for the composition for forming an insulating layer, it is preferable to use a thermosetting resin, and it is more preferable to use an epoxy resin from the viewpoint of availability. Thereby, the heat resistance of the insulating layer 4 obtained can be made excellent. Further, the metal plate 2 and the conductor layer 3 can be firmly bonded via the insulating layer 4. Therefore, the durability and reliability of the obtained substrate 1 can be made excellent.

  Examples of the epoxy resin include bisphenol A, bisphenol F, bisphenol AD, hydroquinone, methylhydroquinone, dimethylhydroquinone, dibutylhydroquinone, resorcin, methylresorcin, biphenol, tetramethylbiphenol, dihydroxynaphthalene, dihydroxydiphenyl ether, phenol novolak resin, cresol novolak. Various epoxy resins such as resin, bisphenol A novolak resin, dicyclopentadiene phenol resin, terpene phenol resin, phenol aralkyl resin, and naphthol novolak resin can be used.

  As will be described later, in the present invention, a filler having an absolute value of zeta potential measured in a methyl ethyl ketone solvent of 5.0 mV or less, that is, a material having a small absolute value of zeta potential is used. In view of such a configuration, the resin material is preferably a hydrophobic resin. Thereby, since the dispersibility of the filler in the composition for insulating layer formation improves, it can suppress or prevent exactly that the flow rate of the composition for insulating layer formation falls.

  The hydrophobic resin is not particularly limited, but for example, phenoxy resin, epoxy resin, silicone resin, ester resin, polyurethane resin, polyamide resin, vinyl chloride resin, styrene resin, polyethylene, fluorine resin, alkyd resin, polybutadiene resin, These can be used, and one or more of these can be used in combination.

  Further, the content of the resin material is preferably 30% by volume or more and 70% by volume or less, and preferably 40% by volume or more and 60% by volume or less of the entire composition for forming an insulating layer (excluding the solvent). More preferred. Thereby, the mechanical strength and thermal conductivity of the insulating layer 4 obtained can be made excellent.

  On the other hand, when the content is less than the lower limit value, the resin material cannot sufficiently exhibit the function as a binder for bonding fillers, and the mechanical strength of the insulating layer 4 to be obtained is lowered. Show the trend. In addition, depending on the constituent material of the insulating layer forming composition, the viscosity of the insulating layer forming composition becomes too high, and it becomes difficult to perform filtration work and layer forming (coating) of the insulating layer forming composition (varnish). In some cases, the flow of the composition for forming an insulating layer becomes too small, and voids are generated in the resulting insulating layer 4.

  On the other hand, when the content exceeds the upper limit, it is difficult to ensure the thermal conductivity of the insulating layer 4 while ensuring the insulating properties of the insulating layer 4 to be obtained.

  Further, the insulating layer forming composition contains a curing agent as necessary depending on the kind of the resin material described above.

  The curing agent is not particularly limited, and examples thereof include amide curing agents such as dicyandiamide and aliphatic polyamide, amine curing agents such as diaminodiphenylmethane, methanephenylenediamine, ammonia, triethylamine, and diethylamine, bisphenol A, and bisphenol F. And phenolic curing agents such as phenol novolac resin, cresol novolak resin, p-xylene-novolak resin, and acid anhydrides.

  In addition, the composition for forming an insulating layer may further contain a curing catalyst (curing accelerator). Thereby, the sclerosis | hardenability of the composition for insulating layer formation can be improved.

  Examples of the curing catalyst include amine catalysts such as imidazoles, 1,8-diazabicyclo (5,4,0) undecene, phosphorus catalysts such as triphenylphosphine, and the like. Of these, imidazoles are preferred. Thereby, especially the quick-hardening property and the preservability of the composition for insulating layer formation can be made compatible.

  Examples of imidazoles include 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 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 isocyanuric acid adduct, 2-phenylimidazole Null acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino -6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-s-triazine, 2,4-diamino-6-methacryloyloxyethyl-s-triazine isocyanuric acid adduct, etc. Can be mentioned. Among these, 2-phenyl-4,5-dihydroxymethylimidazole or 2-phenyl-4-methyl-5-hydroxymethylimidazole is preferable. Thereby, especially the preservability of the composition for insulating layer formation can be improved.

  Moreover, the content of the curing catalyst is not particularly limited, but is preferably about 0.01 to 30 parts by mass, more preferably about 0.5 to 10 parts by mass with respect to 100 parts by mass of the resin material. preferable. When the content is less than the lower limit, the curability of the composition for forming an insulating layer may be insufficient. On the other hand, when the content exceeds the upper limit, the composition for forming an insulating layer It shows a tendency to decrease the storage stability.

  The average particle diameter of the curing catalyst is not particularly limited, but is preferably 10 μm or less, and more preferably 1 to 5 μm. When the average particle size is within the above range, the reactivity of the curing catalyst is particularly excellent.

  Moreover, it is preferable that the composition for insulating layer formation contains a coupling agent further. Thereby, the adhesiveness of the resin material with respect to a filler, the conductor layer 3, and the metal plate 2 can be improved more.

  Examples of such coupling agents include silane coupling agents, titanium coupling agents, aluminum coupling agents, and the like. Of these, silane coupling agents are preferred. Thereby, the heat resistance of the composition for insulating layer formation can be improved more.

  Among these, as the silane coupling agent, for example, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, N-β (aminoethyl) γ-aminopropylmethyl Dimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysila N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, bis (3 -Triethoxysilylpropyl) tetrasulfane and the like.

  Although content of a coupling agent is not specifically limited, It is preferable that it is about 0.01-10 mass parts with respect to 100 mass parts of resin materials, and it is more preferable that it is especially about 0.5-10 mass parts. . When the content is less than the lower limit, the effect of improving the adhesion as described above may be insufficient. On the other hand, when the content exceeds the upper limit, the insulating layer 4 is formed. May cause outgassing and voids.

Further, the filler (filler of the present invention) in the composition for forming an insulating layer is a granular body mainly composed of aluminum oxide (alumina, Al ₂ O ₃ ), and the absolute value of the zeta potential measured in a methyl ethyl ketone solvent. Is 5.0 mV or less.

  The point that the absolute value of the zeta potential measured in a methyl ethyl ketone solvent is 5.0 mV or less will be described later in detail as the filler used in the insulating layer forming composition.

  The filler (filler 42) having such a configuration has a thermal conductivity higher than that of the resin portion 41. When this filler is dispersed in the composition for forming an insulating layer, the thermal conductivity of the insulating layer 4 can be increased.

  The content of the filler is preferably 30% by volume or more and 70% by volume or less, and more preferably 40% by volume or more and 60% by volume or less of the entire insulating resin composition (excluding the solvent). By increasing the filler content in the insulating resin composition within such a range, the thermal conductivity of the resulting insulating layer 4 can be made excellent.

  On the other hand, when the content is less than the lower limit, it is difficult to make the insulating layer 4 excellent in thermal conductivity while securing the insulating property of the insulating layer 4 to be obtained. On the other hand, if the content exceeds the upper limit, depending on the constituent material of the insulating layer forming composition, the viscosity of the insulating layer forming composition becomes too high, and the varnish is filtered or formed into a layer (coating). ) May be difficult, or the flow of the insulating layer forming composition may be too small, and voids may be generated in the resulting insulating layer 4.

  The absolute value of the zeta potential measured in a methyl ethyl ketone solvent as a filler contained in the composition for forming an insulating layer, even if the filler content in the composition for forming an insulating layer is set high as in the above range. By using what becomes 5.0 mV or less, the viscosity and flow property of the composition for insulating layer formation (varnish) can be made appropriate.

  The water content of the filler is preferably 0.10% by mass to 0.30% by mass, more preferably 0.10% by mass to 0.25% by mass, and 0.12% by mass. % Or more and 0.20% by mass or less is more preferable. Thereby, even if the content of the filler is increased, it has a more appropriate viscosity and flowability. Therefore, it is possible to form the insulating layer 4 having excellent thermal conductivity while preventing generation of voids in the obtained insulating layer 4. That is, the insulating layer 4 having excellent thermal conductivity and insulating properties can be formed.

  Here, since aluminum oxide (alumina) is a material having hygroscopicity, the present inventor pays attention to such a point, and appropriately applies moisture absorption treatment and drying treatment to the filler composed of aluminum oxide, Plural kinds of fillers having different moisture contents were prepared, and the relationship between the filler moisture content and the flowability of the insulating layer forming composition was examined. As a result, it has been found that as the moisture content of the filler increases, the flowability of the composition for forming an insulating layer increases and the voltage resistance of the resulting insulating layer 4 increases. In addition, it is thought that generation | occurrence | production of the void in the insulating layer 4 is prevented when the withstand voltage property of the insulating layer 4 obtained increases because the flow property of the composition for insulating layer formation increases.

  On the other hand, when the water content is too low, the flowability of the composition for forming an insulating layer is lowered, voids in the insulating layer 4 are generated, and the voltage resistance of the insulating layer 4 tends to be lowered. On the other hand, when the water content is excessively high, the flowability of the composition for forming an insulating layer becomes excessively high, and it becomes difficult to secure a desired thickness of the insulating layer 4. The voltage characteristic may be lowered. If the water content is too high, the moisture adversely affects the curability of the resin material in the insulating layer forming composition, and the insulating layer 4 is formed by heating and pressurizing the insulating layer forming composition. Moreover, the tendency for the void in the insulating layer 4 obtained to increase by water vapor | steam dissipating in the composition for insulating layer formation is shown.

  In addition, the moisture content of the filler in the composition for insulating layer formation before hardening or solidifying is substantially equal to the moisture content of the cured product or solidified product of the composition for insulating layer formation, that is, the filler in the insulating layer 4.

  Aluminum oxide is usually obtained by firing aluminum hydroxide. The obtained aluminum oxide granules are composed of a plurality of primary particles, and the average particle size of the primary particles can be set according to the firing conditions.

  Moreover, the aluminum oxide which has not been treated at all after the firing is composed of aggregates (secondary particles) in which primary particles are aggregated due to fixation.

  Therefore, the final filler can be obtained by solving the aggregation of the primary particles as necessary by pulverization. The average particle diameter of the final filler can be set according to the pulverization conditions (for example, time).

  During the pulverization, the aluminum oxide has a very high hardness, so the primary particles themselves are hardly broken, and the average particle size of the primary particles is almost maintained even after pulverization. The Rukoto.

  Therefore, as the grinding time becomes longer, the average particle size of the filler approaches the average particle size of the primary particles. And when grinding | pulverization time becomes more than predetermined time, the average particle diameter of a filler will become equal to the average particle diameter of a primary particle. That is, the filler is mainly composed of secondary particles when the grinding time is shortened, and the content of primary particles increases as the grinding time is lengthened. It will be.

  Further, for example, primary particles of aluminum oxide obtained by firing aluminum hydroxide as described above have a shape having a flat surface such as a scaly shape instead of a spherical shape. Therefore, the contact area between fillers can be increased. As a result, the thermal conductivity of the obtained insulating layer 4 can be increased.

  The average particle size of the filler 42 is not particularly limited, but is preferably about 0.1 μm to 25 μm, and more preferably about 0.25 μm to 20 μm. Thereby, the viscosity and flow property of the composition for insulating layer formation can be made moderate, and the heat conductivity and insulating property of the insulating layer 4 obtained can be made excellent.

  Further, the coefficient of variation (that is, narrow particle size distribution; CV value) of the particle size of the filler 42 is not particularly limited, but is preferably 30% or less, more preferably 20% or less, and more preferably 10%. More preferably, it is as follows.

Further, the specific surface area (BET specific surface area) of the filler is preferably 0.5 m ² / g or more and 3.0 m ² / g or less, and is 0.7 m ² / g or more and 2.5 m ² / g or less. Is more preferable.

  The larger the average particle size of the filler, the smaller the specific surface area of the filler. On the other hand, the smaller the average particle size of the filler, the larger the specific surface area of the filler. Moreover, the larger the average particle size of the primary particles of the filler, the smaller the specific surface area of the filler. On the other hand, the smaller the average particle size of the primary particles of the filler, the larger the specific surface area of the filler.

  Thus, the average particle diameter of the filler and the average particle diameter of the primary particles and the specific surface area of the filler have a correlation with each other.

  In addition to the components described above, the insulating layer forming composition may contain additives such as a leveling agent and an antifoaming agent as long as the object of the present invention is not impaired.

  Moreover, the composition for insulating layer formation contains solvents, such as methyl ethyl ketone, acetone, toluene, a dimethylformaldehyde, for example. Thereby, the composition for insulating layer formation will be in a varnish state, when resin material etc. melt | dissolve in a solvent.

  Such an insulating layer forming composition in a varnish state is coated on the conductor layer 3 by using a comma coater, a die coater, a gravure coater or the like, and dried to obtain the insulating layer forming layer 4A.

  Under the present circumstances, it is preferable that the viscosity of the composition for insulating layer formation of a varnish state is 3.0 Pa * s or less, and it is more preferable that it is 2.0 Pa * s or less. Thereby, the filtration operation | work and coating of the composition for insulating layer formation are attained.

  In the present invention, as described above, the filler used in the composition for forming an insulating layer is a granule mainly composed of aluminum oxide, and the absolute value of the zeta potential measured in a methyl ethyl ketone solvent (pKa 14.7). A value of 5.0 mV or less is used.

  Here, as a result of the inventor's investigation, when a filler having a large absolute value of zeta potential measured in a methyl ethyl ketone solvent is used for the composition for forming an insulating layer, the flowability of the composition for forming an insulating layer is reduced. It has been found that voids are generated in the insulating layer, and that the thermal conductivity and voltage resistance of the insulating layer 4 tend to decrease due to this.

  This is presumed to be due to a change in the dispersibility of the filler in the insulating layer forming composition (resin material) due to the increase in the absolute value of the zeta potential measured in the methyl ethyl ketone solvent. .

  As a result of further investigation, the present inventors paid attention to this point, and as a result, by using a filler having an absolute value of zeta potential in the methyl ethyl ketone solvent of 5.0 mV or less, dispersion of the filler in the composition for forming an insulating layer is achieved. As a result, the present inventors have found that the above problems can be solved, and have completed the present invention.

  In general, zeta potential is measured by a method combining electrophoresis and light scattering. Specifically, the particle is moved (electrophoresis) by applying an electric field to the particle (filler), and the moving particle is irradiated with a laser, and the electrophoretic velocity is calculated from changes in the frequency of the irradiated light and scattered light. By doing so, the zeta potential can be calculated.

  By the way, the absolute value of the zeta potential measured in the methyl ethyl ketone solvent of the filler which is a granular body mainly composed of aluminum oxide is usually more than 5.0 mV. This is considered due to the fact that sodium hydroxide is adhered to the filler having such a configuration. As described above, this is because particles (secondary particles or primary particles) mainly composed of aluminum oxide are usually obtained by firing aluminum hydroxide, and therefore, in the process of producing aluminum hydroxide, It is considered that sodium hydroxide adheres to aluminum hydroxide, and as a result, adheres to the granular material obtained by firing.

  Therefore, in the present invention, the absolute value of the zeta potential measured in a methyl ethyl ketone solvent is set to 5.0 mV or less, and a granular material mainly composed of aluminum oxide in which the adhesion of sodium hydroxide is accurately suppressed or prevented is used. And By using such a granular material as a filler, the flowability of the composition for forming an insulating layer can be improved, and as a result, the thermal conductivity and voltage resistance of the insulating layer 4 to be obtained are increased.

  In addition, although it does not specifically limit as a method of making the absolute value of the zeta potential measured in the methyl ethyl ketone solvent into the granular material mainly composed of aluminum oxide is 5.0 mV or less, for example, I: A method of washing with water, II: a method of neutralizing the granular material with a weakly acidic aqueous solution and then washing with water, III: a method of reacting sodium hydroxide adhering to the granular material with carbon dioxide, and IV: 1400 of the granular material. Examples of the method include heating at a temperature of 0 ° C. or higher to remove the attached sodium hydroxide, and the methods I and II are preferable. According to this method, the absolute value of the zeta potential of the filler measured in a methyl ethyl ketone solvent can be set within the above range easily and reliably.

  Therefore, in the following, a method for obtaining a composition for forming an insulating layer using the filler of the present invention obtained using the methods I and II will be described as an example.

  That is, the manufacturing method of the composition for forming an insulating layer described below includes preparing a granular body mainly composed of aluminum oxide, washing the granular body with water to obtain the filler, the filler and the resin. A mixing step of mixing the material to obtain the composition for forming an insulating layer.

(Washing process)
First, in this step, a granular material mainly composed of aluminum oxide is prepared, and the granular material is washed with water.

  Thereby, the absolute value of the zeta potential measured in the methyl ethyl ketone solvent of the granular material is set to 5.0 mV or less. When the absolute value of the zeta potential is within such a range, the composition for forming an insulating layer obtained in the next step can have excellent flow properties. Therefore, it is possible to reliably prevent generation of voids in the obtained insulating layer 4 and to form the insulating layer 4 having excellent thermal conductivity.

  When the method I is used, the liquid used for washing is not particularly limited, but in particular, pure water such as RO water, deionized water, and distilled water is preferably used. According to pure water, sodium hydroxide can be reliably removed from the granular material without other impurities adhering to the granular material.

  When the method II is used, a weakly acidic aqueous solution is used as the liquid in order to reduce the number of cleaning steps (number of times of cleaning) and to perform efficient cleaning. The acid contained in the weakly acidic aqueous solution is not particularly limited. Caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, salicylic acid, gallic acid, benzoic acid, phthalic acid, cinnamic acid, melicic acid, oxalic acid, citric acid Organic acids such as succinic acid, maleic acid, fumaric acid, lactic acid, malic acid, malonic acid, tartaric acid, aconitic acid, adipic acid, glutaric acid, etc., and one or more of these are used in combination be able to.

  When the method II was used, that is, when a weakly acidic aqueous solution was used as the liquid, pure water was further used as the liquid after washing with the weakly acidic aqueous solution (after weakly acidic water washing). Wash with water (replacement water) until the pH of the supernatant reaches 6.0. That is, the granular material is neutralized (washed) with a weakly acidic aqueous solution and then washed with pure water.

  Moreover, although it does not limit in order to make the replacement water washing using pure water as said liquid easy, it is preferable to use it as 1.0 mass% or less aqueous solution even if it uses any acid. Furthermore, as the acid contained in the weakly acidic aqueous solution, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, and enanthic acid, which are short-chain fatty acids with good solubility in water, are more preferable.

  Moreover, it does not specifically limit as a method to wash with water, For example, I.I. A method of stirring the liquid after supplying the liquid into a container in which the granular material is stored, and then removing the supernatant after standing for a predetermined time, II. Examples thereof include a method in which the granular material is packed in a column equipped with a filter, and then the liquid is brought into contact with (passed through) the granular material through the filter.

  In addition, although the water washing of the granular material by such a method may be performed singly, it is preferable to perform it multiple times. Thereby, sodium hydroxide can be more reliably removed from the granular material.

  The absolute value of the zeta potential measured in a methyl ethyl ketone solvent may be 5.0 mV or less, but is preferably 3.0 mV or less. Thereby, the flow property of the composition for insulating layer formation can be improved more reliably.

(Mixing process)
Next, in this step, the insulating layer forming composition is obtained by mixing the filler obtained through the water washing step and the resin material.

  The mixing of the filler and the resin material can be performed, for example, by previously dissolving the resin material in the aforementioned solvent to form a varnish, and then mixing the filler in the varnish.

  The mixer used for mixing is not particularly limited, and examples thereof include a disperser, a composite blade type stirrer, a bead mill, and a homogenizer.

In addition, although the temperature at the time of mixing a filler in a varnish changes a little with the structural material of a resin material, it is preferable that it is about 25-80 degreeC, and it is more preferable that it is about 40-60 degreeC. Thereby, the viscosity of a varnish can be reduced reliably and the dispersion rate of the filler in the composition for insulating layer formation can be improved more reliably. Further, it is possible to prevent a curing reaction from occurring in the resin material due to heat generated by stirring.
As described above, a composition for forming an insulating layer can be produced.

  According to such a composition for forming an insulating layer, even if the filler content is increased as in the above-described range, the composition for forming an insulating layer having excellent flow properties can be obtained. Therefore, it is possible to reliably prevent generation of voids in the obtained insulating layer 4 and to form the insulating layer 4 having excellent thermal conductivity.

[3]
Next, after the insulating layer forming layer 4A and the metal plate 2 are bonded together, the metal plate 2 and the conductor layer 3 are pressurized and heated so as to approach each other.

  Thus, the insulating layer forming layer 4A is cured or solidified to become the insulating layer 4, and the substrate 1 in which the metal plate 2 and the conductor layer 3 are bonded via the insulating layer 4 as shown in FIG. Is obtained.

  The heating and pressurizing conditions in this step are not particularly limited, but are set as follows, for example. That is, the heating temperature is preferably set to about 80 to 200 ° C, more preferably about 170 to 190 ° C.

  Moreover, the pressure which pressurizes the metal plate 2 and the conductor layer 3 becomes like this. Preferably it is about 2-14 MPa, More preferably, it is set to about 6-12 MPa.

Further, the heating and pressurizing time is preferably about 30 to 240 minutes, more preferably about 60 to 120 minutes.
The substrate 1 is manufactured through the steps as described above.

(Application examples of substrates)
Next, an application example of the substrate 1 described above will be described with reference to FIG.

  A control device 100 shown in FIG. 4 is mounted on the automobile 20 and controls driving of a headlight (light source) 201 that emits light toward the front thereof. In the present embodiment, the headlight 201 is one in which a plurality of light emitting diode elements (LEDs) 202 are arranged.

  The control device 100 includes a substrate 1A, semiconductor elements 51 and 52 and a connector 53 provided on the substrate 1A.

  The substrate 1 </ b> A has a metal plate 2, a conductor layer 3 </ b> A, and an insulating layer 4, and the metal plate 2 and the conductor layer 3 </ b> A are joined via the insulating layer 4.

  Here, the conductor layer 3A is a conductor pattern formed by patterning the conductor layer 3 of the substrate 1 described above by etching or the like. That is, the substrate 1 </ b> A is obtained by patterning the conductor layer 3 of the substrate 1.

  On the conductor layer 3A of the substrate 1A, semiconductor elements 51 and 52, a connector 53, and the like are provided, and these form a circuit 6.

  In the present embodiment, a coating layer (solder resist layer) 7 is provided on the upper surface of the insulating layer 4 to cover a portion where the conductor layer 3A is not formed. Thereby, the conductor layer 3 can be protected, and the deterioration and short circuit of the circuit 6 can be prevented. The constituent material of the coating layer 7 is not particularly limited as long as it has insulating properties. For example, various resin materials such as epoxy resin, cyanate resin, and phenol resin can be used. The covering layer 7 may be omitted.

  The semiconductor elements 51 and 52 are provided with a wiring pattern made of a conductive metal material such as copper. This wiring pattern is electrically connected to a plurality of terminals protruding from the lower surface. Each terminal is joined to the conductor layer 3A, whereby the semiconductor elements 51 and 52 are electrically connected to the conductor layer 3A. Each terminal can be composed mainly of various brazing materials such as solder, silver brazing, copper brazing, and phosphor copper brazing.

  In addition, the mold parts 512 and 522 which comprise the exterior part of the semiconductor elements 51 and 52 are comprised by thermosetting resins, such as an epoxy resin and a phenol resin, for example.

  The connector 53 is connected to the headlight 201 via the relay cable 204. A connector 205 connected to the connector 53 is installed at the end of the relay cable 204 opposite to the headlight 201.

  The connector 53 is a so-called “male side” connector, and includes a plurality of pins (terminals) 531 and a housing 532 that collectively stores these pins 531. Each pin 531 is made of a conductive metal material such as copper, and is electrically connected to the conductor layer 3A. Each pin 531 is connected to each terminal (not shown) of the so-called “female side” connector 205 by fitting.

  The housing 532 is formed of a cylindrical body and is erected with respect to the substrate 1A. Each pin 531 accommodated in the housing 532 is also erected vertically with respect to the substrate 1A, that is, vertically upward. Accordingly, when connecting the connector 205 of the relay cable 204 to the connector 53, the connector 205 can be inserted from above, and the connection work can be easily performed.

  Although it does not specifically limit as a constituent material of the housing 532, For example, the thermosetting resin similar to the constituent material of the mold parts 512 and 522 of the semiconductor elements 51 and 52 can be used.

  Further, the control device 100 includes a protective member 8 that covers the conductor layer 3 and the semiconductor elements 51 and 52, particularly the connection portion between the conductor layer 3 and the semiconductor elements 51 and 52.

  The protection member 8 is made of a hard resin material, and is provided in a layer shape. Thereby, the semiconductor elements 51 and 52 and the connector 53 can be fixed collectively. Therefore, even if the vibration is transmitted to the control device 100 when the automobile 20 is traveling, it is possible to reliably prevent the semiconductor elements 51 and 52 and the connector 53 from being detached due to the vibration. Further, for example, the semiconductor elements 51 and 52 can be protected without covering the control device 100 with a casing. Further, since the semiconductor elements 51, 52 and the like are embedded in the protective member 8, a waterproof / dustproof function for these can be exhibited.

  The hard resin material constituting the protective member 8 is not particularly limited, but for example, a thermosetting resin similar to the material constituting the mold parts 512 and 522 of the semiconductor elements 51 and 52 and the housing 532 can be used. Particularly preferred are epoxy resins and phenol resins.

  Here, the resin material constituting the protective member 8 is preferably filled with a metal oxide such as alumina, and an electrically insulating and highly thermally conductive filler typified by a nitride such as boron nitride. Thereby, heat dissipation of the heat generated by the semiconductor elements 51, 52 and the like by energization is promoted through the protective member 8. And this heat dissipation and heat dissipation through the metal plate 2 combine, and the control apparatus 100 becomes the thing which was extremely excellent in heat dissipation as a whole.

  As mentioned above, although the filler, the composition for insulating layer formation, the film for insulating layer formation, and the board | substrate of this invention were demonstrated about embodiment of illustration, this invention is not limited to these.

  For example, each part which comprises the filler of this invention, the composition for insulating layer formation, the film for insulating layer formation, and a board | substrate can be substituted with the thing of the arbitrary structures which can exhibit the same function. Moreover, arbitrary components may be added.

  Furthermore, it is needless to say that the use of the substrate to which the substrate manufacturing method of the present invention is applied is not limited to that of the above-described embodiment, and is suitably used as a substrate used in various devices that require heat dissipation. be able to. For example, the substrate can be used as a substrate on which an LED light emitting element is mounted.

  Hereinafter, specific examples of the present invention will be described. Note that the present invention is not limited to this.

1. Production of substrate A substrate was produced as follows.

Example 1
[1] First, 40.0 parts by mass of bisphenol F / bisphenol A phenoxy resin (Mitsubishi Chemical, 4275, weight average molecular weight 6.0 × 10 ⁴ , ratio of bisphenol F skeleton to bisphenol A skeleton = 75: 25), bisphenol Type A epoxy resin (DIC, 850S, epoxy equivalent 190) 55.0 parts by mass, 2-phenylimidazole (Shikoku Chemicals 2PZ) 3.0 parts by mass, γ-glycidoxypropyltrimethoxysilane as silane coupling agent 2.0 parts by weight of KBM-403 (Shin-Etsu Silicone) were weighed, dissolved and mixed in 400 parts by weight of cyclohexanone, and stirred using a high-speed stirrer to obtain a varnish containing a resin material.

  [2] Next, 800 g of alumina (manufactured by Nippon Light Metal, average particle size A 3.2 μm, primary particle size B 3.6 μm, average particle size A / primary particle size B = 0.9 (Lot No. Z401)) Were weighed and put into a plastic container in which 1300 mL of pure water was stored, and then using a disperser equipped with a blade having a diameter of 50 mm (“Special Number R94077”, manufactured by Tokushu Kika Kogyo Co., Ltd.), the rotational speed was 5000 rpm × The alumina was washed with water by stirring under conditions of a stirring time of 15 minutes.

  Then, after collecting a part of alumina and drying at 180 ° C. for 300 minutes, the zeta potential was measured using a zeta potential measuring device (Malvern, “Zetasizer Nano ZS90”) in a methyl ethyl ketone solvent. The supernatant was removed by decantation until the measured value was −0.8 mV, and then the water washing was performed several times.

[3] Next, after the washed alumina is left for 20 minutes, the supernatant is removed by decantation, and then 1000 mL of acetone is added, and the rotational speed is 800 rpm × using the disperser. Stirring was performed under the condition of stirring time of 5 minutes.
And after standing for 12 hours, the supernatant was removed.

  [4] Next, the alumina after the supernatant was removed was spread on a stainless steel vat, and this was subjected to a fully exhausted box dryer (“PHH-200” manufactured by Tabai Co., Ltd.) at a drying temperature of 40 ° C. × drying. Washed alumina (filler) was obtained by drying under conditions of 1 hour.

  Thereafter, the washed alumina was dried under the conditions of 200 ° C. × 24 hours and then left under the conditions of 85 ° C. × 85% RH, so that the moisture content of the washed alumina was 0.18% by mass.

  The water content of the alumina was calculated from the difference in mass between 25 ° C. and 500 ° C. measured using a differential thermal balance apparatus (TG-DTA).

  [5] Next, to the varnish containing the resin material prepared in advance in the step [1], washed alumina (505.0 parts by mass) and a disperser (made by Tokushu Kika Kogyo Co., Ltd. R94077 ") and mixing under conditions of a rotational speed of 1000 rpm and a stirring time of 120 minutes, an insulating layer forming composition having a resin solid content ratio of alumina of 83.5 wt% (60.0 vol%) is obtained. It was.

1.2 Production of Film for Forming Insulating Layer As a metal foil (conductor layer), a copper foil of 500 mm in length x 250 mm in width x 35 μm in thickness (manufactured by Furukawa Circuit Foil, GTSMP) is used on the roughened surface of the copper foil. The composition for forming an insulating layer obtained in 1.1 above is applied with a comma coater, dried by heating at 100 ° C. for 3 minutes and at 150 ° C. for 3 minutes, and the insulating layer forming composition has a thickness of 100 μm. A forming film (a copper foil with a composition for forming an insulating layer) was obtained.

1.3 Fabrication of Substrate The insulating layer forming film obtained in 1.2 above and an aluminum plate having a length of 530 mm × width of 300 mm × thickness of 1 mm are laminated as a metal plate, and a press pressure of 9.7 MPa is used using a vacuum press. Were pressed under the conditions of 80 ° C. for 30 minutes and 200 ° C. for 90 minutes to obtain a substrate.

(Examples 2 and 3)
In the step [2], the same procedure as in Example 1 was performed except that the alumina was washed with water several times until the zeta potential of the washed alumina became −3.0 mV and −4.9 mV, respectively. Thus, an insulating layer forming composition and a substrate were obtained.

Example 4
In the step [2], 800 g of the same alumina used in Example 1 was weighed in the same manner and put into a plastic container containing 1300 mL of a 0.1% by mass acetic acid aqueous solution. The alumina was washed with water by using a disperser provided (particularly, “R94077” manufactured by Kikai Kagaku Kogyo Co., Ltd.) under the conditions of a rotational speed of 5000 rpm and a stirring time of 15 minutes.

Thereafter, the solution was allowed to stand for 15 minutes, and the pH of 50 mL of the supernatant collected with a dropper was measured. After removing the supernatant by decantation until the pH reached 6.0 or more, pure water The replacement water was washed several times.
Other steps were the same as in Example 1, and an insulating layer forming composition and a substrate were obtained.

(Example 5)
The insulating layer forming composition and the composition were the same as in Example 1 except that the amount of washed alumina was changed to 787.0 parts by mass and the resin solid content ratio of alumina was 88.7% by weight (70.0% by volume). A substrate was obtained.

(Comparative Example 1)
An insulating layer forming composition and a substrate were obtained in the same manner as in Example 1 except that the alumina washing in the steps [2] to [4] was omitted.

(Comparative Example 2)
An insulating layer forming composition and a substrate were obtained in the same manner as in Example 5 except that the alumina washing in the steps [2] to [4] was omitted.

2. Evaluation The following evaluation was performed about the composition for insulating layer formation and board | substrate which were obtained by each Example and each comparative example.

2.1 Viscosity of composition for insulating layer formation About the composition for insulating layer formation of each Example and each comparative example, a viscosity is measured on 25 degreeC and shear rate 5.0rpm conditions using an E-type viscosity meter. did.

2.2 Flow Rate of Composition for Forming Insulating Layer For each composition for forming an insulating layer in each example and each comparative example, a copper foil (Furukawa Circuit Foil, 500 mm long × 250 mm wide × 35 μm thick) was used as the metal foil. Two, and a composition for forming an insulating layer is supplied between them using a comma coater, and then the metal foils are subjected to 190 at a press pressure of 9.7 MPa using a vacuum press. The sample was pressed under the condition of ° C. × 5 minutes to obtain a sample for measuring the flow rate.

  And after measuring the weight A about the sample obtained from the composition for insulating layer formation of each Example and each comparative example, respectively, after removing the insulating layer which protrudes from the edge part of metal foil The flow rate was calculated by measuring the weight B of the sample and obtaining B / A × 100 (%).

2.3 Appearance For the substrates of each Example and each Comparative Example, the copper foil (conductor layer) was removed by etching, the appearance of the insulating layer was visually observed, and the presence or absence of voids or scum was evaluated.

2.4 Solder heat resistance About the board | substrate of each Example and each comparative example, after cutting with a grinder saw to 50 mm x 50 mm, the sample was produced by removing the copper foil by etching so that only 1/4 may be left. The solder heat resistance was evaluated in accordance with JIS C 6481. This evaluation is based on whether or not there is an abnormality in the appearance after immersion in a solder bath at 288 ° C. for 30 seconds in the case where pretreatment is not performed and in the case where 121 ° C., 100%, (PCT treatment) is performed for 4 hours. Based on the following evaluation criteria.

Evaluation criteria: No abnormality (no bulges)
: Swelled (there is a bulge on the whole)

2.5 Dielectric breakdown voltage After cutting the substrate of each example and each comparative example to 100 mm × 100 mm with a grinder saw, the copper foil in the outer portion is removed by etching from a position of about 30 mm from the edge portion. Samples were prepared and dielectric breakdown voltage was evaluated. Such evaluation is performed by using a withstand voltage tester (MODEL7473, manufactured by EXTECH Electronics), bringing the electrode into contact with the copper foil and the metal plate, and increasing the voltage to both electrodes at a rate of 1 kV / sec. Was applied, and the voltage when the insulating layer was broken was defined as a dielectric breakdown voltage.

2.6 Thermal conductivity Two films for insulating layer formation (copper foil with composition for forming an insulating layer) of each example and each comparative example were stacked so that the insulating layers face each other, and a press pressure of 9 was used using a vacuum press. Pressing at 7 MPa under conditions of 190 ° C. × 5 minutes, an insulating plate with double-sided metal foil was obtained. Both surfaces of the obtained insulating plate with double-sided metal foil were etched, the C-stage state insulating layer was taken out, and the thermal conductivity was determined according to JIS R 1611 by the laser flash method.
These evaluation results are shown in Table 1.

  As is clear from the evaluation results shown in Table 1, in each Example, the absolute value of the zeta potential when measured in a methyl ethyl ketone solvent can be set to 5.0 mV or less by washing the granular material with water. As a result, the flow rate of the composition for forming a resin layer is improved, and as a result, an excellent solder heat resistance, a sufficiently high dielectric breakdown voltage value, and a product having a high thermal conductivity can be obtained. It became.

  On the other hand, in each comparative example, the absolute value of the zeta potential measured in the methyl ethyl ketone solvent is more than 5.0 mV, so that the appearance, solder heat resistance, or dielectric breakdown voltage is compared with each example. The result was inferior to the value.

1, 1A Substrate 2 Metal plate 3, 3A Conductor layer 4 Insulating layer 4A Insulating layer forming layer 41 Resin part 42 Filler 51, 52 Semiconductor element 512, 522 Mold part 53 Connector 531 Pin (terminal)
532 Housing 6 Circuit 7 Covering layer 8 Protective member 10 Insulating layer forming film 20 Automobile 100 Control device 201 Headlight 202 Light emitting diode element 204 Relay cable 205 Connector

Claims (11)

A filler used in an insulating layer forming composition for forming an insulating layer,
A filler characterized by being a granular body mainly composed of aluminum oxide and having an absolute value of zeta potential measured in a methyl ethyl ketone solvent of 5.0 mV or less.   The filler according to claim 1, wherein the granular material is composed of at least one of primary particles of the aluminum oxide and aggregates of the primary particles. An insulating layer-forming composition comprising the filler according to claim 1 or 2 and a resin material, wherein the insulating layer-forming composition is used to form the insulating layer. The composition for forming an insulating layer according to claim 3 , wherein the content of the filler is 30% by volume or more and 70% by volume or less of the whole. The content of the resin material, the entire 30% by volume or more, the insulating layer forming composition according to claim 3 or 4 is 70% by volume or less. The resin material, the insulating layer forming composition according to any one of claims 3 to 5, which is a thermosetting resin. The resin material, the insulating layer forming composition according to any one of claims 3 to 6 is a hydrophobic resin. Insulating layer forming film characterized by having an insulating layer formation layer an insulating layer-forming composition was molded into a layer according to any one of claims 3 to 7. The film for forming an insulating layer according to claim 8 , further comprising a support layer for supporting the insulating layer forming layer. The film for forming an insulating layer according to claim 9 , wherein the support layer is a metal foil. A metal plate made of a metal material;
Provided on the metal plate, and claims 3 to 7 insulating layer the insulating layer forming composition composed of a cured product or solidified product was formed into a layer of any one of,
And a conductive layer provided on a surface of the insulating layer opposite to the metal plate.

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