JP2015193704A - High heat conductive ceramic powder-containing resin composition and cured article thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high heat conductive resin cured article, a high heat conductive semi-cured resin film, and high heat conductive resin composition having both of excellent heat conductivity and excellent voltage resistance.SOLUTION: There is provided a high heat conductive alumina powder-containing resin composition containing a resin (A) and a high density spherical alumina powder (B), satisfying that: the high density spherical alumina powder (B) has an average particle diameter of 50 μm or less, sphericity of 0.9 or more, and true specific gravity of 3.9 or more; a cumulative water content exposed amount by 200°C in a heating discharge gas analysis is 40% or less than of a total discharge water content by 1000°C; the cumulative water content exposed amount by 550°C is 90% or less than of the total discharge water content by 1000°C; and the cumulative water content exposed amount by 600 to 1000°C is 10% or less than of the total discharge water content by 1000°C.

Description

  The present invention relates to a highly thermally conductive resin cured product, a highly thermally conductive semi-cured resin film, and a highly thermally conductive resin composition, which are useful for applications such as forming an insulating layer in a circuit board or an electronic component.

  In recent years, heat generation of electrical equipment due to high integration of semiconductors and increased handling power has increased, and heat dissipation has become an urgent issue. Conventionally, heat dissipation of devices has been performed using a ceramic substrate produced mainly by sintering alumina or the like. However, the ceramic substrate has problems that it is not only productive but also expensive, brittle and heavy. In order to solve this, a metal base substrate using a thick metal plate such as aluminum as a heat sink has been devised, and the market is now expanding.

  A metal base substrate has a resin insulating layer disposed on a thick metal plate, a circuit is formed thereon, and a semiconductor is mounted. The insulating layer is required to have a property of releasing heat well. For this reason, the insulating layer of the metal base substrate is provided with thermal conductivity while ensuring insulation by highly filling the resin with a thermally conductive filler.

  In order to increase the thermal conductivity of the insulating resin layer, there are three independent approaches: 1) high thermal conductivity of the resin, 2) high thermal conductivity of the filler or 3) high packing of the filler.

  Alumina is widely studied as a useful heat conductive material because it is relatively inexpensive but chemically stable and relatively high in heat conductivity. There are various types of fillers, but there have been many reports on the fact that the characteristics greatly change depending on the shape.

  The thermal conductivity of the material is better as the number of crystals is smaller and the true specific gravity and purity are higher. For example, with regard to alumina, α alumina single crystal with the highest true specific gravity shows the highest thermal conductivity, but since spherical alumina is generally produced by the flame melting method, it includes crystal systems other than α alumina. It becomes a polycrystal. Since all crystal systems other than α-alumina eventually transition to α-alumina at high temperatures, re-firing spherical alumina at high temperatures increases the α-alumina ratio while maintaining the spherical shape, which is higher than that of normal alumina. Thermal conductivity can also be increased. However, when the high specific gravity spherical alumina obtained by firing ordinary alumina is actually kneaded with the resin, there is a problem that the physical properties of the cured product are deteriorated as compared with ordinary alumina. This is thought to be due to the loss of hydroxyl groups on the surface of the alumina due to the firing. The resin is deteriorated in wettability with the resin compared to ordinary spherical alumina powder and the reaction point with the silane coupling agent is reduced. It is thought that a chemical bond cannot be formed.

  As a general method for improving the surface condition, for example, Patent Document 1 proposes a method of improving the kneadability by increasing the surface energy of the particle surface by irradiating boron nitride and aluminum nitride particles with ultraviolet rays. Yes. However, alumina has a problem that it is difficult to modify the surface by ultraviolet irradiation because it has better chemical stability than boron nitride.

  Patent Document 2 discloses an alumina powder obtained by heat-treating spherical alumina having an average particle diameter of 1 to 10 μm at 1100 to 1500 ° C. to increase an alpha conversion rate of 80% and a specific gravity of 3.85 or more, and a high thermal conductive insulating material using the same Resin compositions for use are disclosed. This method is to improve the thermal conductivity by increasing the alpha conversion rate by post-treatment, but due to the heat treatment at high temperature, the hydroxyl group on the particle surface is lost and the affinity with the resin is reduced, In particular, there was a problem that the mechanical properties and dielectric breakdown voltage of the cured product of the resin composition were lowered.

  Patent Documents 3 and 4 disclose a method of producing a spherical alumina powder having many isolated OH groups by flame melting an alumina raw material at 2200 to 2400 ° C. and quenching with an aqueous spray of 40 to 120 L / hr. Yes. However, the spherical alumina powder produced by rapid cooling tends to be a polycrystal having a higher proportion of crystal system other than α-alumina than the conventional one, and the produced spherical alumina powder has a proportion of crystal system other than α-alumina than the conventional one. There was a problem that many polycrystals were easily formed, and the thermal conductivity was not different from that of the conventional spherical alumina powder, and the thermal conductivity was lowered.

WO2013 / 046784 JP 2014-9140 A JP 2011-98841 A JP 2011-102215 A

  An object of the present invention is to provide a highly thermally conductive resin cured product, a highly thermally conductive semi-cured resin film, and a highly thermally conductive resin composition having both excellent thermal conductivity and excellent withstand voltage characteristics.

  The present invention is a resin composition comprising a resin (A) and a high specific gravity spherical alumina powder (B), wherein the high specific gravity spherical alumina powder (B) has an average particle diameter of 50 μm or less and a sphericity of 0.9. As described above, the true specific gravity is 3.9 or more, and the accumulated moisture expression up to 200 ° C. is 40% or less of the total released moisture amount up to 1000 ° C. in the heat release gas analysis, and the accumulated moisture up to 550 ° C. The discharge amount is 90% or more of the total released water amount up to 1000 ° C., and the cumulative water release amount up to 600 to 1000 ° C. is 10% or less of the total released water amount up to 1000 ° C. This is a resin composition containing a high thermal conductivity alumina powder.

  The content of the high specific gravity spherical alumina powder (B) is preferably 40% by weight or more based on the resin composition. The resin (A) is preferably a heat or photocurable resin, and more preferably an epoxy resin.

  Further, the present invention is a semi-cured resin film obtained by film-molding the above-mentioned highly thermally conductive alumina powder-containing resin composition and semi-cured, and a cured film obtained by curing the semi-cured resin film. Furthermore, this invention is a hardened | cured material obtained by hardening | curing said highly heat conductive alumina powder containing resin composition.

  Since the resin composition of the present invention contains a specific high specific gravity spherical alumina powder whose surface has been modified, the cured product and cured film obtained therefrom have both high thermal conductivity and insulation, excellent heat dissipation characteristics and high It has a withstand voltage characteristic. Therefore, the resin composition, cured product, and cured film of the present invention can be preferably applied to, for example, the formation of a heat-dissipating insulating layer in a circuit board, an electronic component, or an adhesive layer having both heat dissipating properties and insulating properties.

  Next, an embodiment of the present invention will be described.

  The high thermal conductivity alumina powder-containing resin composition of the present invention (hereinafter sometimes referred to as a resin composition) contains a resin (A) and a high thermal conductivity alumina powder (B).

  Resin (A) is not specifically limited, A thermoplastic resin and a thermosetting resin can be used. For example, use epoxy resin, phenol resin, polyimide resin, cresol resin, melamine resin, unsaturated polyester resin, isocyanate resin, polyurethane resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polyphenylene sulfide resin, fluorine resin, polyphenylene oxide resin Can do. Preferred is a light or thermosetting resin, and more preferred is an epoxy resin having a low coefficient of thermal expansion and excellent heat resistance and adhesiveness.

The high thermal conductivity alumina powder (B) has an average particle diameter of 50 μm or less, a sphericity of 0.9 or more, and a true specific gravity of 3.9 or more, and satisfies the following characteristics.
a) Cumulative water release amount A up to 200 ° C. is 40% or less of the total water release amount D up to 1000 ° C.,
b) Cumulative water release amount B up to 550 ° C. is 90% or more of the total water release amount D up to 1000 ° C., and
c) The cumulative water release amount C up to 600-1000 ° C. is 10% or less of the total water release amount D up to 1000 ° C.
The ratio of the cumulative water release amount A to the total water release amount D is 40% or less, preferably in the range of 23 to 38%. The ratio of the cumulative water release amount B to the total water release amount D is 90% or more, but is preferably in the range of 90 to 95%. The ratio of the cumulative water release amount C to the total water release amount D is 40% or less, but is preferably in the range of 5 to 8%.

  Here, the conditions of the heat release gas analysis follow the conditions described in the examples. In addition, the high specific gravity spherical alumina powder in the initial state subjected to the heat release gas analysis is left to stand for 24 hours or more at room temperature of 25 ° C. and relative humidity of RH 30%. In the cumulative water release amount and the total water release amount, when the initial temperature is not described, it is understood as the cumulative water release amount and the total water release amount from the room temperature of 25 ° C.

  Examples of the type of alumina powder include crystalline alumina and fused alumina. From the viewpoint of achieving high thermal conductivity by close-packing, either crystalline alumina or fused alumina may be used, but it is necessary to satisfy the above characteristics.

  General spherical alumina powder is a polycrystal because it is produced by a flame melting method, and also includes transition alumina such as γ-alumina and δ-alumina other than α-alumina. Since α-alumina has the highest specific gravity among the crystal systems of alumina and high thermal conductivity, the closer the specific gravity of the alumina powder is to 3.98, the better the thermal conductivity. Since some voids may be included inside, the specific gravity of the high specific gravity spherical alumina powder may be 3.9 or more. The method for obtaining high specific gravity alumina powder includes pulverization of bulk α-alumina, decomposition of aluminum alkoxide, re-firing of alumina powder, etc., but post-firing normal spherical alumina powder as commercially available Is preferred. The pulverization of massive α-alumina has an irregular particle shape, so that the specific surface area is increased and the kneadability is lowered. In addition, it is difficult to produce a sphere with high sphericity by chemicals or heat treatment. In addition, it is difficult to obtain spherical fillers and it is also difficult to obtain particles having a large particle diameter by a method using aluminum alkoxide decomposition.

  As described above, ordinary spherical alumina powder contains crystalline alumina (transition alumina) other than α-alumina, and these transition aluminas all transition to α-alumina crystals at a high temperature of 1100 ° C. or higher. Therefore, it is possible to obtain alumina powder having a high specific gravity while maintaining the spherical shape by refiring at a temperature of 1100 ° C. or higher under conditions that suppress sintering of alumina particles and deterioration of shape due to melting. . High specific gravity alumina powder with a true specific gravity of 3.9 or more is composed of α-alumina alone, but α-alumina has fewer surface hydroxyl groups than other transition aluminas, so it has affinity for resin and reaction with silane coupling agents. The properties are usually lower than spherical alumina powder. For this reason, the physical properties of the resin composition filled with the high specific gravity alumina powder are lower than those using the conventional ordinary spherical alumina, and therefore the filling amount cannot be increased, and the high thermal conductivity is effectively utilized. I couldn't. However, by setting the amount of water released in a specific temperature range in the above-mentioned heat release gas analysis to be above or below a certain value, it has affinity for high specific gravity spherical alumina powder resin and reactivity with silane coupling agent. The electrode withstand voltage and the thermal conductivity of the resin composition highly filled with high specific gravity spherical alumina can be improved.

The high specific gravity spherical alumina powder that satisfies the moisture release amount in a specific temperature region in the heat release gas analysis can be obtained by wet or dry surface modification treatment. Treatment is preferred, and it can be obtained, for example, by stirring with hot water for 20 minutes or more.
The water temperature at this time is preferably 70 ° C. or higher, more preferably 80 ° C. or higher. Furthermore, since alumina dissolves in a small amount in an alkaline aqueous solution, it is more preferable to add an alkaline substance to hot water because the surface modification effect of high specific gravity spherical alumina is enhanced.
When adding an alkaline substance to hot water, an alkali metal hydroxide exhibiting strong alkalinity such as sodium hydroxide or potassium hydroxide is preferred, and its concentration is preferably 0.1 M or more, more preferably 0.5 to 5 M. preferable. In addition, when a water-soluble alkaline substance is added to the treated water, it is preferable to perform washing several times with pure water after dehydrating the treated water. If neutralization is performed with an acid at this time, the effect of surface modification is reduced, which is not preferable.

  The high specific gravity spherical alumina powder after the surface modification treatment is filtered from treated water using a filter such as a non-woven fabric, dried by a hot air drier etc. at a temperature of 100 ° C. or more for 8 hours or more to remove moisture. preferable.

  The resin composition of the present invention contains the high specific gravity spherical alumina powder (B) as a filler, but other high heat conductive ceramic powders may be used together with the high specific gravity spherical alumina powder (B). Other high thermal conductive ceramic powders having a thermal conductivity of 5 W / m · K or more are suitable. Examples of such other high thermal conductive ceramic powders include alumina, aluminum nitride, crystalline silica, boron nitride, silicon nitride, etc., and aluminum nitride, boron nitride, silicon nitride, etc. are preferable because of their price, chemical stability, and powder particle shape. It is done. The other high thermal conductive ceramic powder is preferably in the range of 0 to 70 wt%, more preferably in the range of 0 to 50 wt%, based on the total of the high specific gravity spherical alumina powder (B) and the high specific gravity spherical alumina powder (B). .

  The particle size distribution of the high specific gravity spherical alumina powder (B) or other high thermal conductive ceramic powder blended as the filler is preferably blended as follows. Hereinafter, the term “filler” refers to the high specific gravity spherical alumina powder (B) when used alone, and other high heat conductive ceramic powders are used in combination unless otherwise specified. Sometimes understood to mean both.

i) A small particle size filler having an average particle diameter D50 of 0.1 to 1.0 μm is 15 to 25 wt%, preferably 18 to 22 wt%, based on the total amount of filler,
ii) A medium particle size filler having an average particle diameter D50 in the range of 3 to 20 μm is 15 to 45 wt%, preferably 18 to 42 wt%, based on the total amount of filler,
iii) 40 to 70 wt%, preferably 45 to 65 wt% of a large particle size filler having an average particle size D50 in the range of 30 to 60 [mu] m with respect to the total amount of filler.
Here, the total of the above-mentioned small particle size filler, medium particle size filler and large particle size filler is 100 wt%, and D50 as a whole filler is 50 μm or less.

  If the particle size distribution of the filler is out of the above range, it becomes difficult to achieve both high thermal conductivity and insulating properties, and sufficient heat dissipation characteristics and withstand voltage characteristics cannot be obtained in a cured product obtained by curing the resin composition. In addition, if the particle size distribution of the filler is out of the above range, the viscosity when used as a varnish or the melt viscosity when used as a resin film is increased. For example, workability and adhesion when an insulating adhesive layer is used. In some cases, the surface properties may deteriorate or the surface condition may deteriorate. The average particle diameter D50 means the particle diameter when 50% is accumulated in the cumulative curve of the volume fraction of the particle diameter when the total volume of the filler is 100%.

Among the fillers, use of high specific gravity spherical alumina powder (B) is particularly effective for large particle size fillers and / or medium particle size fillers in order to improve thermal conductivity, and 40 wt% or more of the total weight of the fillers. Is preferably a high specific gravity spherical alumina powder (B), more preferably the total weight of the large particle size filler is the high specific gravity spherical alumina powder (B). However, D50 of the large particle size filler in this case is preferably 50 μm or less.
Further, by setting the blending amount of the large particle size filler to 50 wt% or more with respect to the total amount of the filler, the large particle size filler is densely packed in the thickness direction of the cured product, and the heat conduction in the thickness direction is increased. The number of paths increases and the heat dissipation characteristics can be improved. On the other hand, if the blending amount of the large particle size filler is too small, the adjacent large particle size fillers are opened in the thickness direction of the cured product, the heat conduction path is reduced, and the heat dissipation characteristics tend to be deteriorated.

  Further, in addition to the large particle size filler, the medium particle size filler and the small particle size filler are blended as specified in the above i) and ii), so that the gap between the large particle size filler is filled with the medium particle size filler and the small particle size filler. It becomes possible to fill with, and it becomes a close-packed state, and can improve a thermal radiation characteristic. On the other hand, if the medium particle size filler and the small particle size filler are less than 30 wt% in total, the gap between the large particle size filler cannot be filled with the medium particle size filler and the small particle size filler, Filling failure results in deterioration of heat dissipation characteristics.

In the resin composition of the present invention, the high specific gravity spherical alumina powder (B) content is preferably 40 wt% or more of the resin composition. Moreover, as the whole filler containing high specific gravity spherical alumina powder (B), the content is in the range of 70 to 90 wt%, and more preferably in the range of 75 to 85 wt%. Here, content of a filler means content per solid content in a resin composition.
As the content of the filler in the resin composition increases, the heat dissipation characteristics can be improved. If the filler content in the solid content of the resin composition is 70 wt% or more, heat conduction is sufficient and sufficient heat dissipation characteristics are exhibited. On the other hand, if it exceeds 90 wt%, the withstand voltage characteristic is lowered, and the viscosity when used as a varnish increases, the melt viscosity increases when used as a resin film, and the workability and adhesiveness decrease. The surface condition may deteriorate.

  The solid content of the resin composition means, for example, when the resin composition is a varnish containing a predetermined solvent, in the process of forming a cured product such as an insulating layer or an adhesive layer using the varnish, by drying or curing. It means the solid content finally remaining after the solvent is removed. Here, the varnish contains a solvent for the purpose of reducing the viscosity of the resin composition and improving processability, but finally formed a cured product such as an insulating layer or an adhesive layer. Later, the solvent is removed by drying and heat treatment. Therefore, the content of the component in the resin composition is defined using the component content relative to the solid content of the resin composition. In addition, although arbitrary components may be mix | blended with the resin composition of this invention as needed, the solid content should just be calculated also including the arbitrary component mix | blended separately in that case.

  Next, as a preferred embodiment of the resin raw material that is the component (A) in the resin composition of the present invention, a case where an epoxy resin material is used will be described as an example. The epoxy resin-based material contains, for example, (a) an epoxy resin, (b) a curing agent, and (c) a phenoxy resin.

  (A) As an epoxy resin, when an insulating adhesive layer or a resin film is produced from a resin composition, sufficient insulation, adhesion, heat resistance, mechanical strength, workability, and the like are imparted. This epoxy resin can be used without any particular limitation. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, phenol novolac type epoxy resin, o -Epoxy having two or more epoxy groups in the molecule such as cresol novolac type epoxy resin, biphenyl novolac type epoxy resin, triphenylmethane type epoxy resin, dicyclopentadiene type epoxy resin, alicyclic epoxy resin, brominated epoxy resin, etc. Resins can be exemplified. These epoxy resins can be used alone or in combination of two or more. In addition, the purity of the epoxy resin is preferably low in ionic impurities and hydrolyzable chlorine from the standpoint of improving withstand voltage characteristics and moisture resistance reliability. Furthermore, from the viewpoint of preventing cracking when the resin film is in a B stage state (semi-cured state), the liquid epoxy resin is preferably 30 parts by weight or more, more preferably 100 parts by weight of the epoxy resin. It is preferable to blend 50 parts by weight or more. Here, the liquid state means a liquid having fluidity at 25 ° C., specifically, a liquid having a viscosity of 20000 Pa · s or less. By blending a liquid epoxy resin as the epoxy resin, the softening point of the resin film in the B-stage state can be lowered, and surface cracking can be suppressed.

  In addition, (i) the epoxy resin is an epoxy resin having an epoxy equivalent in the range of 150 to 220, preferably in the range of 150 to 200, and is 50% by weight or more, preferably 60% by weight with respect to the total amount of the epoxy resin It is good to contain above. The epoxy resin having an epoxy equivalent in the range of 150 to 220 may be a combination of two or more epoxy resins. When the average epoxy equivalent of all the epoxy resins is less than 150, the crystallinity of the epoxy resin is increased, the solvent solubility is lowered, and it becomes difficult to produce a B-stage resin film and the B-stage crack is likely to occur. On the other hand, when the average epoxy equivalent of all epoxy resins exceeds 220, the glass transition temperature (Tg) after curing of the resin composition tends to decrease.

  The glass transition temperature of the cured product of the present invention obtained by curing the resin composition is preferably 100 ° C. or higher, more preferably 100 to 180 ° C. When the glass transition temperature of the cured product after curing is less than 100 ° C., the temperature becomes lower than the actual use temperature of the circuit board, and the action of suppressing the generation of metal ions from the metal wiring (migration resistance) tends to decrease. In addition, the measurement of the glass transition temperature of hardened | cured material can be implemented as follows, for example. First, the resin composition was dissolved in a methyl ethyl ketone solvent to form a 90% by weight resin solution, which was then applied on a fluororesin sheet of length × width × thickness = 50 × 150 × 1 mm and dried at 135 ° C. for 5 minutes. Evaporate the solvent. Thereafter, another fluororesin sheet having the same shape is stacked on the coated surface, and vacuum heating press is performed at 170 ° C. for 1 hour to prepare a cured film as a sample. The temperature dispersion tan δ curve of the sample thus prepared was measured using a dynamic viscoelasticity measuring device under the conditions of a frequency of 10 Hz, a temperature range of −150 to 200 ° C., and a temperature increase rate of 2 ° C./min. The peak temperature of the −tan δ curve can be set as the glass transition temperature (Tg).

  B) The content of the epoxy resin is, for example, preferably in the range of 20 to 90 parts by weight, more preferably in the range of 40 to 80 parts by weight with respect to 100 parts by weight of the solid content of the epoxy resin raw material. When the content of the epoxy resin is more than 90 parts by weight with respect to 100 parts by weight of the solid content, the workability in the B-stage state of the resin composition and the cured product become brittle, the adhesive strength is reduced, and the heat resistance And temperature cycle resistance may decrease. On the other hand, when the content of the epoxy resin is less than 20 parts by weight with respect to 100 parts by weight of the solid content, the resin composition may be insufficiently cured, resulting in a decrease in adhesive strength and a decrease in heat resistance.

  (B) The curing agent is blended for the purpose of curing the epoxy resin. When an insulating layer, an adhesive layer or a resin film is produced from the resin composition, sufficient insulation, adhesion, and heat resistance are obtained. These are those that impart mechanical strength and can be used as long as they are curing agents for general epoxy resins such as amines, phenols, and acid anhydrides. Among them, imidazole compounds are preferably used. Since the imidazole compound does not liberate ammonium ions even when heated, for example, during heat treatment during curing, the amount of ammonium ions in the cured product obtained by curing the resin composition can be reduced by using the imidazole compound as a curing agent. It can be easily suppressed to 50 ppm by weight or less.

  Examples of the imidazole compound include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-methyl-2-phenylimidazole, and 2-phenyl. Examples include -4,5-dihydroxymethylimidazole and 2-phenyl-4-methyl-5-hydroxymethylimidazole. Among the imidazole compounds, 2-phenyl-4,5-dihydroxymethylimidazole is most preferably used. In general, when an imidazole compound is used as a curing agent for an epoxy resin, the curing reaction is likely to proceed because the activity of the imidazole compound is high, and it is difficult to control the curing reaction. 2-Phenyl-4,5-dihydroxymethylimidazole has two highly reactive hydroxyl groups in the molecule, but also has a phenyl group that acts to suppress reactivity with a bulky functional group. Therefore, it is possible to moderately suppress the activity as a curing agent, and it is easy to moderately control the curing reaction. Further, by using 2-phenyl-4,5-dihydroxymethylimidazole as a curing agent, for example, the temperature at the time of coating the resin composition can be set higher.

  In general, an imidazole compound is often blended as a curing accelerator in a resin composition mainly composed of an epoxy resin. However, in the resin composition of the present embodiment, a substance other than an imidazole compound is used as a curing agent. Since it is not used, the resin composition can be cured by a condensation reaction between epoxy resins. In this case, the imidazole compound is bonded to the end of the epoxy resin (or between the cross-linking points in the condensation reaction between the epoxy resins), and this bonding site exerts a catalytic function, thereby promoting the condensation reaction between the epoxy resins. Conceivable. From such reaction characteristics, the imidazole compound can function as a curing agent, and the blending amount as the curing agent can be kept low as compared with a reaction system in which an addition type curing agent component is blended. Thus, since the imidazole compound is a catalyst type curing agent, for example, if an addition type curing agent component such as dicyandiamide or phenol novolac resin exists, the addition type curing agent component and the epoxy resin react preferentially. The condensation reaction with an epoxy resin alone hardly occurs.

  (B) The content of the curing agent is preferably in the range of 2 to 10 parts by weight, and more preferably in the range of 3 to 8 parts by weight with respect to 100 parts by weight of the solid content of the epoxy resin raw material. When the content of the curing agent is more than 10 parts by weight, there is a risk of inducing a halogen element derived from the epoxy resin as a halogen ion. On the other hand, when the content of the curing agent is less than 2 parts by weight, the curing reaction does not proceed sufficiently, and the adhesive strength may be reduced, or the curing time may be prolonged and the usability may be reduced. Moreover, a resin composition having sufficient mechanical strength cannot be obtained, which is not preferable.

  (C) A phenoxy resin is a component that improves the flexibility when an insulating layer, an adhesive layer, or a resin film is produced from a resin composition. Examples of the phenoxy resin include bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, bisphenol AF type phenoxy resin, bisphenol S type phenoxy resin, brominated bisphenol A type phenoxy resin, brominated bisphenol F type phenoxy resin, and phosphorus-containing phenoxy. Examples thereof include resins. The weight average molecular weight of the phenoxy resin used is preferably in the range of 10,000 to 200,000, for example, and more preferably in the range of 20,000 to 100,000. When the weight average molecular weight of the phenoxy resin is less than 10,000, the heat resistance, mechanical strength, and flexibility of the epoxy resin composition may be reduced. Conversely, if the weight average molecular weight of the phenoxy resin is greater than 200,000, in addition to causing a decrease in solubility in an organic solvent and compatibility with an epoxy resin and a curing agent, the viscosity when used as a varnish, or When the resin film is used, the melt viscosity increases, and the workability and adhesiveness as the insulating layer and the adhesive layer are lowered, or the surface state is deteriorated. In addition, the weight average molecular weight here is a value in terms of polystyrene by GPC (gel permeation chromatography) measurement.

  (C) The content of the phenoxy resin is preferably 90 parts by weight or less, and more preferably in the range of 15 to 70 parts by weight with respect to 100 parts by weight of the solid content of the epoxy resin raw material, for example. When the content of the phenoxy resin is more than 90 parts by weight, the solubility in an organic solvent may be reduced, or the compatibility with (i) an epoxy resin or (b) a curing agent may be reduced. In addition, the viscosity in the case of varnish and the melt viscosity in the case of a resin film may increase, and the workability and adhesiveness as an insulating layer and an adhesive layer may decrease, or the surface state may deteriorate. In addition, the heat resistance may be reduced.

  In the resin composition of the present invention, it is preferable that (b) the epoxy resin contains an epoxy resin having an epoxy equivalent in the range of 150 to 220 in an amount of 50% by weight or more based on the total amount of the epoxy resin. By combining (ep) phenoxy resin in combination with this epoxy resin, it is possible to improve the flexibility when an insulating layer, an adhesive layer and a resin film are produced. It can compensate for the decline in sex.

  In the resin composition, (i) epoxy resin having an epoxy equivalent in the range of 150 to 220 (ii) bisphenol A type epoxy resin (bifunctional), bisphenol F type epoxy resin, Using a cresol novolac type epoxy resin (polyfunctional) or a triphenylmethane type epoxy resin (polyfunctional), (b) a combination using (b ') 2-phenyl-4,5-dihydroxymethylimidazole as a curing agent In addition, a combination using (ha ′) bisphenol A-type phenoxy resin as (ha) phenoxy resin is most preferable. By the combination of (A ') to (C'), it is possible to form an insulating layer and an adhesive layer that are less likely to deteriorate the adhesive strength and insulating properties over a long period of time and have excellent withstand voltage characteristics. Moreover, in the hardened | cured material which hardened the resin composition, while being excellent in heat conductivity, in a B stage molded article, a softness | flexibility and a flexibility are improved and it can prevent a surface crack. Furthermore, even in the state of a varnish containing a filler, the viscosity is preferably maintained in the range of 1000 to 20000 Pa · s, more preferably in the range of 2000 to 10000 Pa · s, and the sedimentation of the filler can be suppressed for a long period of time. Become. In addition, in the (a) epoxy resin, it is particularly preferable to use a bifunctional epoxy resin having an epoxy equivalent in the range of 150 to 220 and a polyfunctional epoxy resin having an epoxy equivalent in the range of 150 to 220 in combination. preferable.

  In addition to the above components, the resin composition of the present invention can contain, for example, a solvent, a rubber component, a fluorine-based or silicone-based antifoaming agent, a leveling agent, and the like as necessary. Moreover, from the viewpoint of improving the adhesion to members such as a metal substrate and copper wiring, for example, an adhesion imparting agent such as a silane coupling agent or a thermoplastic oligomer can be added. Furthermore, other inorganic fillers and organic fillers may be added to the resin composition as needed other than the high thermal conductive ceramic powder as long as the effects of the present invention are not impaired. Examples of the inorganic filler include silica, calcium carbonate, magnesium carbonate and the like. Examples of the organic filler include silicon powder, nylon powder, acrylonitrile-butadiene-based crosslinked rubber, and the like. About these fillers, the 1 type (s) or 2 or more types can be used. Moreover, colorants, such as phthalocyanine green, phthalocyanine blue, and carbon black, can be blended in the resin composition as necessary.

  The resin composition of the present invention can be prepared by mixing the above essential components and optional components. In this case, it is preferable to use a varnish containing a solvent. That is, the resin composition may be dissolved or dispersed in a predetermined solvent to form a varnish. Examples of solvents that can be used here include amide solvents such as N, N-dimethylformamide (DMF), N, N-dimethylacetamide, N-methyl-2-pyrrolidone (NMP), and 1-methoxy-2-propano- A mixture of one or more of ether solvents such as methyl ether, methyl ethyl ketone, methyl isobutyl ketone (MIBK), ketone solvents such as cyclohexanone and cyclopentanone, aromatic solvents such as toluene and xylene, etc. it can. Among curing agents, fillers, and optional components added as necessary, inorganic fillers, organic fillers, colorants, etc., are not necessarily dissolved in the solvent as long as they are uniformly dispersed in the solvent. Good.

  A varnish can be prepared according to the procedure shown below, for example. First, (c) phenoxy resin is dissolved in a suitable solvent while stirring in a container with a stirrer. Next, (a) an epoxy resin, (b) a curing agent, and optional components are mixed in this solution, and the mixture is stirred and dissolved. In addition, (a) Depending on the kind of epoxy resin, the thing of the state which dissolved the epoxy resin in the solvent may be prepared separately, and you may make it mix it. Next, a varnish of the resin composition can be prepared by blending a filler into the mixed solution, stirring, and uniformly dispersing the filler.

  The varnish preferably has a viscosity in the range of 1000 to 20000 Pa · s, and more preferably in the range of 2000 to 10000 Pa · s. When the viscosity of the varnish is less than 1000 Pa · s, the filler tends to settle out, and unevenness or repellency during coating tends to occur. On the other hand, when the viscosity of the varnish is larger than 20000 Pa · s, the coating property is lowered due to the decrease in fluidity, and it becomes difficult to produce a uniform coating film.

  Moreover, in the resin composition of this invention, it is preferable that the boiling extraction water sodium ion per solid content of a resin composition is 20 ppm or less, Preferably it is 5 ppm or less. The resin composition is preferably one in which impurity metals are reduced as much as possible from the viewpoint of improving withstand voltage characteristics. In the alumina powder, there is a possibility that sodium remains in the alumina for manufacturing reasons, and these may have a great influence on the withstand voltage characteristics. Therefore, it is preferable that the amount of sodium ions be within the above range. In order to keep the amount of sodium ions within the above range, it is preferable to use a high-purity grade having a small amount of sodium ions among commercially available aluminas.

  Next, a resin film according to an embodiment of the present invention will be described. This resin film contains a semi-cured resin and a filler. The particle diameter of the filler in the resin film of the present embodiment, the blending ratio thereof, the maximum particle diameter, the average particle diameter, the content thereof, the film thickness of the resin film, the sodium ion concentration, and the like in the resin composition The contents are the same as described.

  The semi-cured resin film of the present invention is a B-stage resin film, which can be obtained by applying the varnish on a base film as a support material and drying it. Moreover, the copper foil with a resin film can also be formed by apply | coating the said varnish on copper foil, and making it dry. Here, the thickness of the resin film is not particularly limited, but for example, a resin in a B stage state in consideration of pressure conditions at the time of curing and film thickness variation after curing due to a difference in the dimensions of the resin film The film thickness of the film can be in the range of 1.06 to 1.33 times the film thickness of the cured product. From another viewpoint, in order to set the film thickness of the cured product within the range of 150 to 200 μm, the film thickness of the B-stage resin film can be set within the range of 159 to 266 μm. When a resin film in a B-stage state (copper foil with a resin film) is bent, the value as a product is impaired when the surface is cracked. Such surface cracks in the B-stage state are likely to occur when a large amount of a solid resin component is blended at room temperature. From the viewpoint of reducing the content of ammonium ions in the cured product, it may be possible to use a phenol novolac-based curing agent, but since it is generally solid, surface cracking is likely to occur. However, the use of an imidazole compound as a curing agent is preferred because the proportion of the solid resin component in the epoxy resin raw material can be kept low. In addition, since the imidazole compound can suppress the blending amount as a curing agent as compared with the case where, for example, a phenol novolac-based curing agent component is blended, more liquid or semi-solid components are blended at room temperature. Therefore, the flexibility and flexibility in the B-stage state are improved, and surface cracking can be prevented, which is preferable.

  Moreover, about the softness | flexibility of the film of a resin film or a copper foil with a resin film (before hardening), it exists in the tendency for the softness | flexibility of a film to be so favorable that a solvent residual rate is high. However, if the solvent residual ratio is too high, the resin film or the copper foil with resin film (before curing) may be tacked or foamed during curing. Therefore, the solvent residual ratio is preferably 1% by weight or less. In addition, a solvent residual rate is the value calculated | required by the measurement of the net weight reduction rate of the resin film part at the time of drying for 60 minutes in 180 degreeC atmosphere.

  In addition, the resin film and the copper foil with a resin film may be obtained by applying a resin composition not containing a solvent on a base film as a support material in a heated and melted state and then cooling.

Examples of the support material used when forming the resin film or the copper foil with a resin film include polyethylene terephthalate (PET), polyethylene, copper foil, aluminum foil, release paper, and the like. The thickness of the support material can be set to, for example, 10 to 100 μm. When using metal foil, such as copper foil and aluminum foil, as the support material, the metal foil may be manufactured by, for example, an electrolytic method, a rolling method, or the like. In these metal foils, the surface on the side in contact with the insulating layer is preferably roughened from the viewpoint of enhancing the adhesion to the insulating layer.
In addition, the resin film or the copper foil with a resin film is laminated on a base film as a support material, and then the other surface not in contact with the copper foil is covered with a film as a protective material and wound into a roll. Can also be saved. Examples of the protective material used at this time include polyethylene terephthalate, polyethylene, release paper, and the like. In this case, the thickness of the protective material can be set to 10 to 100 μm, for example.

Next, the cured product of the present invention will be described. The cured product contains a resin and a filler. The particle diameter of the filler in the cured product, the blending ratio thereof, the maximum particle diameter, the average particle diameter, the content thereof, the film thickness of the cured product, and the like are the same as those described in the resin composition.
This cured product is prepared by, for example, preparing the B-stage resin film (or copper foil with resin film) from the resin composition and then curing it by heating to a temperature in the range of 150 ° C. to 250 ° C., for example. Can be manufactured. The cured product thus obtained preferably has a thermal conductivity of, for example, 10 W / mK or more, and more preferably 11 W / mK or more. When the cured product has a thermal conductivity of 10 W / mK or more, it has excellent heat dissipation characteristics and can be applied to a circuit board or the like used in a high temperature environment. Thus, the outstanding heat conductivity is attained by using the said high specific gravity spherical alumina powder (B), and adjusting the compounding quantity of a filler in the said range.

  The cured product of the present invention preferably has a dielectric breakdown voltage of 5 kV or higher. Since the dielectric breakdown voltage of the cured product is 5 kV or more, sufficient insulation can be ensured, so that it can be applied to circuit boards, electronic components, and the like. Thus, the outstanding withstand voltage characteristic becomes possible by using high specific gravity spherical alumina powder (B) and adjusting a compounding quantity in the said range.

  Next, an example of a method for manufacturing a metal base circuit board according to an embodiment of the present invention will be described. Here, an aluminum base circuit board using an aluminum substrate is illustrated. First, after obtaining said copper foil with a resin film from a resin composition, this copper foil with a resin film is used for temperature 150-250 degreeC, pressure 1. for example using a batch type vacuum press on an aluminum substrate. Bonding is performed under conditions of 0 to 30 MPa. At this time, the resin film surface is brought into contact with the aluminum substrate surface, and the epoxy resin is cured by applying heat and pressure in a state where the copper foil as a support material is the upper surface, thereby being attached to the aluminum substrate. In this way, a laminate in which the resin film is used as an insulating adhesive layer and interposed between the copper foil layer and the aluminum substrate can be obtained. Next, by removing the copper foil at a predetermined location by etching, circuit wiring can be formed, and finally an aluminum base circuit board can be obtained. In addition, although there is no restriction | limiting in particular about the thickness of an aluminum substrate, Generally, it can be 0.5-3.0 mm, for example.

  In order to obtain an aluminum base circuit board comprising a conductor layer made of copper, an insulating adhesive layer, and an aluminum layer using the resin composition of the present invention, in addition to the above method, an adhesive layer is provided on the aluminum substrate surface. After forming the copper foil on the adhesive layer and curing it while heating and pressing, or after forming and curing an insulating adhesive layer on the aluminum substrate surface, You may employ | adopt the method of forming a conductor layer. In addition, regarding the formation of the adhesive layer at this time, any of a method of volatilizing the solvent by heating after applying the varnish, a method of applying a solvent-free paste, or a method of bonding the resin film may be used.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In the following examples, various measurements and evaluations are as follows unless otherwise specified.

[Thermal conductivity]
A predetermined amount of B-stage resin film was heated at 180 ° C. for 10 minutes in a compression press molding machine, taken out of the press, and further heated at 180 ° C. for 50 minutes in a dryer to give a diameter of 50 mm. A disk-shaped test piece having a thickness of 5 mm was obtained. The thermal conductivity [W / m · K] of this test piece was measured by a steady method using a thermal conductivity measuring device HC-110 manufactured by Eiko Seiki.

[Electrode breakdown voltage]
Withstand voltage characteristics were evaluated by dielectric breakdown voltage. First, a copper foil with a film-like resin was pressed and cured on an aluminum substrate having a thickness of 1.5 mm using a batch type vacuum press in a temperature profile maintained at a pressure of 10 MPa and a maximum temperature of 180 ° C. for 1 hour. At that time, the film-like resin surface was brought into contact with the aluminum substrate surface, and the copper foil was pressed and applied to the aluminum substrate with the copper foil as the upper surface. Then, this test piece was cut into 180 × 180 mm, and a circular measuring electrode having a diameter of 20 mm per location in the area on the copper foil side was etched at an equal interval in a total of 4 locations in 2 rows and 2 rows in total. Was formed. At this time, the four measurement electrodes must be insulated from each other. A plurality of the test pieces thus obtained were measured per sample by a short time destructive test method in an insulating oil at 23 ° C. using TP-516UZ manufactured by Tama Denshoku. And the average value of the measured dielectric breakdown voltage value of a plurality of the same samples was adopted as the value of the dielectric breakdown voltage of each sample.
[Electric reliability]
The electrical reliability was evaluated by a constant temperature and humidity bias test. First, on both sides of an uncured resin sheet (165 mm square) peeled off from a PET film with a release layer as a coating substrate, a roughened surface of 70 μm thick electrolytic copper foil (170 mm square) is placed on the resin sheet side. After lamination, a double-sided copper-clad laminate was produced by thermocompression bonding using a batch type vacuum press in a temperature profile maintained at a pressure of 10 MPa and a maximum temperature of 180 ° C. for 1 hour. The prepared double-sided copper-clad laminate is angled to 160 x 160 mm, and then circular electrodes with a diameter of 20 mm per location are arranged at equal intervals in two vertical rows and two horizontal rows on the copper foil surface peeled from the PET film. A total of four locations were formed by etching. Further, the four measurement electrodes were cut into individual pieces each having a size capable of securing an insulating layer of 10 mm or more from the electrodes, and used as test pieces for a constant temperature and humidity bias test. The test piece obtained in this way was soldered to the circular measuring electrode and the copper foil on the backside of the wiring for bias application, and then SIR series insulation degradation and characteristics evaluation by Enomoto Kasei Co., Ltd. equipped with a constant temperature and humidity chamber Using a system apparatus, a DC 1 kV bias was continuously applied in an atmosphere of 85 ° C. and 85% RH, and the insulation resistance value of the test piece was continuously measured for 250 hours. The quality of the test piece was determined as to whether or not the insulation was maintained, and the criterion was NG when the insulation resistance value of the test piece was below 1.0 × 10 ⁶ Ω. In addition, the test results were ◎ if all four test pieces used in the test were alive (not NG) after 250 hours, ◯ if two or more were alive, only one was alive A case was marked with Δ, and a case where all were NG was marked with ×.

[Void amount]
The density of the resin sheet in the B-stage state at a liquid temperature of 23 ° C and the cured resin for thermal conductivity measurement was measured by the Archimedes method using an electric hydrometer EW-300SG manufactured by Alpha Mirage, and the resin film in the B-stage state From the density measurement result of the cured product, the amount of voids in the resin film was calculated by the following formula.
V (void) vol% = (1 / ρ (resin film) -1 / ρ (cured product)) * ρ (resin sheet) * 100vol%
Strictly speaking, in the above formula, minute voids remaining after pressing and curing shrinkage due to curing should be considered, but this calculation is an approximation that does not consider this.

[Method of making a three-point bending specimen and its measurement]
The B-stage resin film was folded and placed in a mold opened in the form of 10 mm wide, 100 mm long and 4 mm thick, and pressed under conditions of 180 ° C., 15 MPa, 10 minutes. The obtained test piece was post-cured at 180 ° C. for 1 hour. The obtained test piece was polished to remove the surrounding protrusions. The three-point bending test was measured according to JIS K-7171. As the apparatus, AUTOGRAPH AGS-X 10kN manufactured by Shimadzu Corporation was used.

[Sodium ion content]
Using a predetermined amount of film-like resin, heating at 180 ° C. for 10 minutes in a compression press molding machine, taking out from the press, and further heating at 180 ° C. for 50 minutes in a dryer, a cured product test piece Got. 1 g of the cured product thus obtained was extracted in 50 cc of pure water at 121 ° C. for 20 hours. About this extracted water, the sodium ion density | concentration was measured using the ion chromatography measuring apparatus DX-300 made from DIONEX. The content of sodium ions was expressed as a weight fraction (ppm) of sodium ions relative to the cured product.

The raw materials used for producing the high thermal conductive resin composition and the resin film and their abbreviations are as follows.
(I) Epoxy resin / Epototo 8125: Bisphenol A type epoxy resin (manufactured by Nippon Steel & Sumikin Chemical, Epototo 8125 (trade name), epoxy equivalent 175, liquid)
EPPN-501H; triphenylmethane type epoxy resin (manufactured by Nippon Kayaku, EPPN-501H (trade name), epoxy equivalent 170, semi-solid)
(B) Curing agent 2-phenyl-4,5-dihydroxymethylimidazole (manufactured by Shikoku Kasei Kogyo Co., Ltd., Curazole 2PHz-PW (trade name))
(C) Phenoxy resin / bisphenol A type phenoxy resin (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., YP-50 (trade name))
(D) Silane coupling agent, Sila Ace S-510 (manufactured by Chisso)

Alumina powder (1): Normal spherical alumina powder, manufactured by Micron, trade name: AL35-75R, spherical, crystalline, average particle diameter D50: 35 μm
Alumina powder (2): high specific gravity spherical alumina powder, manufactured by Micron, trade name: TA22B, spherical, crystallinity, average particle diameter D50: 35 μm
Alumina powder (3): manufactured by Micron, trade name: AL10-75R, spherical, crystallinity, average particle diameter D50: 10 μm, specific gravity: 3.83
Alumina powder (4): manufactured by Admatechs, trade name: AO-802, spherical, crystalline, average particle diameter D50: 0.7 μm, specific gravity: 3.75

Reference example 1
The surface-modified high specific gravity spherical alumina powder was obtained by the following treatment.
The high specific gravity spherical alumina powder (2) was suspended in pure water at 25 ° C. and stirred for 5 hours. Thereafter, the alumina powder was separated by a filter using a non-woven fabric and dried for 8 hours in a hot air drier set at 100 ° C. to obtain a surface-modified high specific gravity alumina powder (2A).

Reference example 2
After suspending the high specific gravity spherical alumina powder (2) in pure water, the water temperature of the suspension was heated to 100 ° C. and stirred for 20 minutes. Thereafter, the alumina powder was separated by a filter using a non-woven fabric and dried for 8 hours in a hot air dryer set at 100 ° C. to obtain a surface-modified high specific gravity alumina powder (2B).

Reference example 3
The high specific gravity spherical alumina powder (2) was suspended in a 1M aqueous sodium hydroxide solution, and the suspension was heated to 80 ° C. and stirred for 10 hours. Thereafter, the alumina powder was filtered off with a filter using a non-woven fabric, and water washing and filtration were repeated until the pH of the washing water after the filtration became 7. The washed alumina powder was dried in a hot air dryer set at 100 ° C. for 8 hours to obtain a surface-modified high specific gravity alumina powder (2C).

Reference Examples 4-5
The obtained surface-modified high specific gravity alumina powders (2A to 2C) and the alumina powders (1) and (2) used as raw materials were subjected to particle size distribution measurement, true specific gravity measurement, specific surface area measurement, and then released by heating. Gas analysis and oil absorption test were performed. The results are summarized in Table 1.

[Average particle diameter (D50)]
Alumina powder was weighed and mixed in a 0.2 wt% sodium hexametaphosphate solution as a dispersion medium so that the sample concentration was 0.04 wt%, and dispersed using an ultrasonic homogenizer for 3 minutes. The particle size distribution of the filler dispersion was measured from the scattered light obtained by irradiation with a semiconductor laser having a wavelength of 780 nm, using a particle size distribution measuring device Microtrac MT3300EX (manufactured by Nikkiso). The average particle diameter D50 indicates the particle diameter when the particle volume distribution obtained by the measurement method is 50% cumulative in the cumulative curve of the volume fraction of the particle diameter when the total volume of the particles is 100%. .

[True specific gravity measurement]
The true specific gravity of the alumina powder was confirmed based on the method described in JIS R9301-2-1 alumina powder physical property measurement method-true density by pycnometer method.

[Sphericality measurement]
For the circularity of the alumina powder, a wet flow type particle size / shape analyzer FPIA-3000 manufactured by Sysmex Corporation was used. The measurement was performed by irradiating a predetermined amount of alumina powder weighed in a beaker with ultrasonic waves for 3 minutes while stirring in distilled water, and then stirring it with a magnetic stirrer and using a suction pipette. The obtained data was 75 μm. Analysis was performed in the following particle diameter range, and the sphericity of each alumina powder was calculated.

[Specific surface area measurement]
The specific surface area of the alumina powder was measured by BET one-point method measurement using a fully automatic BET specific surface area measuring apparatus Massorb HM-1201 manufactured by Mountec Co., Ltd.

[Heat release gas analysis]
Spherical alumina powder is analyzed with a heated emission gas analyzer consisting of a TE-360S vacuum heated gas extraction / mass spectrometer manufactured by Nippon Steel & Sumikin Technology Co., Ltd. and a quadrupole mass spectrometer M201QA-TDM manufactured by Anelva. went.
Prior to measurement, a predetermined amount of the sample was precisely weighed and inserted into the apparatus, and after evacuation for 2 hours, the sample was heated at a constant rate from room temperature to 1000 ° C. at a rate of 10 ° C. per minute in vacuum. In the meantime, the release curve of H ₂ O gas generated from the sample was determined as temperature and mass spectral intensity per unit mass.
When calculating the release amount of H ₂ O, the hydrogen release curve obtained by analyzing the hydrogen analysis control sample JSS GS-7a sold by the Japan Iron and Steel Federation as a measurement sample was converted based on The coefficient was obtained and calculated.
The unit of heat release gas analysis in the table is × 10 ³ ml / g.

[Oil absorption]
The amount of oil absorption of the high specific gravity spherical alumina powder was carried out based on the method described in JIS K 5101-13-2 pigment test method-oil absorption. In addition, as the oil, the following epoxy resin varnish and polyimide resin varnish were used in place of the boiled oil.

・ Varnish a: Resin solution obtained by diluting bisphenol A type epoxy resin (manufactured by NS Resin solution and varnish c containing 1 wt% of Silaace S-510 (3-glycidoxypropyltrimethoxysilane, manufactured by Chisso) as a silane coupling agent to a; pyromellitic anhydride (PMDA) and 2,2-bis N, N-dimethylacetamide solution of polyamic acid which is a copolymer of [4- (4-aminophenoxy) phenyl] propane (BAPP) (solid content concentration 10 wt%)

The higher the true specific gravity of the alumina powder, the better the thermal conductivity, and the smaller the oil absorption, the better the affinity with the resin. Although the alumina powder (1) has a low true specific gravity, the oil absorption of various resin varnishes is small and the affinity with the resin is excellent. On the other hand, the high specific gravity alumina powder (2) has a high true specific gravity, but the oil absorption is low. In many cases, the affinity with the resin is usually lower than that of spherical alumina. At this time, the total H ₂ O gas release amount of the cumulative moisture release amount up to 200 ° C. was 40% or more. On the other hand, the surface modified high specific gravity alumina powder (2A to 2C) subjected to the surface modification treatment has a total water release amount of up to 550 ° C. The total H ₂ O gas release amount is 90% or higher, which is higher than that of the untreated product. In particular, alumina powder (2B to 2C) had a total H ₂ O gas release amount of up to 40% up to 200 ° C. The alumina powder (2B to 2C) showed a decrease in oil absorption, that is, an improvement in affinity with the resin.
The release of H ₂ O gas in these specific temperature ranges seems to originate mainly from the adsorbed water on the powder surface in the temperature range up to 200 ° C. In addition, cumulative H ₂ O gas release up to 550 ° C is due to the generation of hydroxyl groups derived from alumina hydrates such as aluminum hydroxide and boehmite that do not dissociate at high temperatures on the surface of high specific gravity spherical alumina powder due to surface modification treatment. it is conceivable that. The presence of these hydroxyl groups has been shown to be more compatible with resin varnish than alumina powder having no hydrophilic group. This is clear from the result that the oil absorption is further reduced by adding a silane coupling agent to the epoxy resin varnish a (epoxy resin varnish b).

Examples 1-2 and Comparative Examples 1-3
The above raw materials were blended in the proportions shown in Table 2. First, only the phenoxy resin was stirred and dissolved in methyl isobutyl ketone (MIBK) in a container equipped with a stirrer. Next, an epoxy resin, a curing agent, and a silane coupling agent were added to the MIBK solution, and the mixture was stirred and dissolved. Thereafter, alumina powder was blended in this mixed solution, and stirred and dispersed to prepare varnishes of high thermal conductive resin compositions of Comparative Examples 1 to 3 and Examples 1 and 2.
This varnish was applied to a release-treated PET film (MR-50, manufactured by Mitsubishi Chemical Corporation) having a thickness of 50 μm so that the thickness of the cured product was 150 μm, and dried at 110 ° C. for 5 minutes to obtain a B-stage state. Then, it was cured at 180 ° C. to obtain cured products of Comparative Examples 1 to 3 and Examples 1 and 2. About the obtained hardened | cured material, the dielectric breakdown voltage was measured and the withstand voltage characteristic was evaluated. The results are also shown in Table 2. In Table 2, the compounding amount of the epoxy resin raw material a is shown by mass% with respect to the total solid content of the high thermal conductive resin composition, and the compounding amount of each alumina powder is the total solid content of the high thermal conductive resin composition. The mass% with respect to was described.

From Table 2, the cured product of the resin composition using alumina powder (2B) and (2C) has a smaller amount of voids than the cured product of the resin composition using high specific gravity spherical alumina that was not subjected to surface treatment. The withstand voltage, flexural modulus, and flexural strength were also improved to the same or better than the cured product of the resin composition that usually uses spherical alumina. On the other hand, the total H ₂ O gas release amount of accumulated water release up to 200 ° C. was 40% or more for surface-modified high specific gravity alumina (2A) than for high specific gravity spherical alumina without surface modification treatment. The physical properties of the cured product were further reduced.
In this way, by adjusting the surface of the high specific gravity spherical alumina powder so as to have a specific total H ₂ O gas release amount, while maintaining the high thermal conductivity characteristic of the high specific gravity spherical alumina, it has good physical properties. It became possible to produce a cured product of the resin composition shown.

Claims (7)

  A resin composition comprising a resin (A) and a high specific gravity spherical alumina powder (B), wherein the high specific gravity spherical alumina powder (B) has an average particle diameter of 50 μm or less, a sphericity of 0.9 or more, and a true specific gravity. Is not less than 3.9, and the accumulated water release amount up to 200 ° C. in the heat release gas analysis is 40% or less of the total released water amount up to 1000 ° C., and the cumulative water release amount up to 550 ° C. is 1000 ° C. High thermal conductivity alumina powder, characterized in that it is 90% or more of the total amount of released water up to and the cumulative amount of released water up to 600-1000 ° C. is 10% or less of the total amount of released water up to 1000 ° C. Containing resin composition.   The high specific gravity spherical alumina powder (B) is contained in an amount of 40% by weight or more based on the resin composition.   The resin composition (A) is a heat or photocurable resin, and the highly heat conductive alumina powder-containing resin composition according to claim 1 or 2.   Resin (A) is an epoxy resin, The highly heat conductive alumina powder containing resin composition of Claim 1 or 2 characterized by the above-mentioned.   The semi-hardened resin film which shape | molded the highly heat conductive alumina powder containing resin composition in any one of Claims 1-4, and was semi-hardened.   Hardened | cured material obtained by hardening | curing the highly heat conductive alumina powder containing resin composition in any one of Claims 1-4.   A cured film obtained by curing the semi-cured resin film according to claim 5.