JP2012077123A - Adhesive resin composition, cured product of the same, and adhesive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive resin composition having excellent thermal conductivity in a cured product of the composition and hardly causing deterioration in adhesive power or insulating properties.SOLUTION: The adhesive resin composition contains an epoxy resin, a curing agent comprising a liquid phenol novolac having a hydroxyl group equivalent ranging from 130 to 200, a curing accelerator, a phenoxy resin and an alumina powder, and contains 50 ppm by weight or less of ammonium ion in a cured product of the adhesive resin composition. The alumina powder has the maximum particle diameter of 120 μm or less, and contains crystalline spherical alumina in an amount of 90 wt.% or more in the whole alumina powder. The crystalline spherical alumina includes: (i) particles having an average particle diameter Dof 35 to 50 μm and having a [volume average particle diameter]/[number average particle diameter] in the range from 1.2 to 2.0, of 30 to 50 wt.%; (ii) particles having an average particle diameter Dof 5 to 15 μm and having a [volume average particle diameter]/[number average particle diameter] in the range from 2.0 to 3.5, of 30 to 50 wt.%; and (iii) particles having an average particle diameter Dof 0.1 to 2 μm, of 10 to 30 wt.%.

Description

  The present invention relates to an adhesive resin composition used for forming an insulating adhesive layer in a circuit board or an electronic component, a cured product thereof, and an adhesive film, for example.

  Epoxy resin is excellent in adhesiveness, mechanical strength, and electrical insulation, and can have a function suitable for various applications by a combination of a resin, a curing agent, a modifier and the like. Therefore, epoxy resins are frequently used as circuit board materials, adhesives for electronic components, sealants, and the like. In recent years, higher performance and higher density of electric / electronic devices have been developed, and accordingly, countermeasures against heat generation from electronic components mounted on circuit boards are required. Then, as a technique for improving the heat dissipation of a circuit board, a proposal has been made to fill an epoxy resin composition for a circuit board with a highly thermally conductive inorganic filler whose particle size distribution is controlled (for example, Patent Document 1, 2).

  By the way, in the epoxy resin composition for the electric / electronic material field, a latent curing agent that is preliminarily dispersed in the composition and starts to cure by heating and dissolving is generally used. Dicyandiamide is widely used as such a latent curing agent. Dicyandiamide has a long pot life and excellent potential, but on the other hand, since the curing temperature is high and the curing rate during heating is slow, a curing accelerator is usually used in combination. As curing accelerators, amines, imidazole compounds and the like are generally used (for example, see Patent Document 2).

JP 2001-348488 A JP 2007-246861 A

  As described above, dicyandiamide is frequently used as a latent curing agent in epoxy resin compositions. However, in circuit boards and electronic parts that use an epoxy resin composition containing dicyandiamide and have an insulating adhesive layer in contact with a metal layer such as wiring, the adhesive strength of the adhesive layer is reduced or the insulating property is reduced. In some cases, this causes a decrease in insulation and causes insulation failure.

  An object of the present invention is to provide an adhesive resin composition in which a cured product has excellent thermal conductivity and is less likely to cause a decrease in adhesive strength or insulation.

  The present inventors have obtained knowledge that ammonium ions derived from dicyandiamide serve as a migration-related factor in an adhesive layer of an epoxy resin using dicyandiamide as a curing agent, and adversely affect the insulating properties of circuit boards and the like. It was. Then, the curing agent in the adhesive resin composition is selected from liquid phenol novolak, and the above problem can be solved by suppressing the amount of ammonium ions in the cured product to a certain level or less, thereby completing the present invention. It came to.

That is, the adhesive resin composition of the present invention is an adhesive resin composition containing the following components (A) and (B), and ammonium ions in the cured product obtained by curing the adhesive resin composition are The adhesive resin composition is 50 ppm by weight or less.
(A): Epoxy adhesive resin raw material containing the following components (A) to (D).
(A) epoxy resin,
(B) a curing agent comprising a liquid phenol novolac having a hydroxyl group equivalent in the range of 130 to 200;
(C) a curing accelerator; and (d) a phenoxy resin (B): an alumina powder that satisfies the following conditions a) to c).
a) The maximum particle size is 120 μm or less,
b) The proportion of crystalline spherical alumina in the total alumina powder is 90% by weight or more, and
c) The crystalline spherical alumina particle size distribution satisfies the following conditions i) to iii).
i) An average particle diameter D50 of 35 to ₅₀ μm and a [volume average particle diameter] / [number average particle diameter] in the range of 1.2 to 2.0 is 30 in crystalline spherical alumina. Present in the range of ~ 50% by weight,
ii) An average particle diameter D50 of ₅ to 15 μm and a [volume average particle diameter] / [number average particle diameter] in the range of 2.0 to 3.5 is 30 in crystalline spherical alumina. Present in the range of ~ 50 wt%, and
iii) Those having an average particle diameter D ₅₀ in the range of 0.1 to 2 μm are present in the crystalline spherical alumina in the range of 10 to 30% by weight.

  In the adhesive resin composition of the present invention, the content of the component (B) may be in the range of 86 to 95 parts by weight with respect to 100 parts by weight of the solid content of the adhesive resin composition.

  The cured product of the present invention is obtained by curing the above adhesive resin composition.

  The adhesive film of the present invention is formed by molding the adhesive resin composition into a film in a semi-cured state.

  The adhesive resin composition of the present invention is less likely to deteriorate the adhesive strength and insulation over a long period of time, and can maintain the withstand voltage characteristics. In addition, the adhesive resin composition of the present invention has excellent thermal conductivity, and the flexibility and flexibility of the B-stage molded product are improved, so that surface cracks can be prevented. Therefore, the adhesive resin composition of the present invention can be preferably applied to an insulating adhesive layer in, for example, a circuit board, an electronic component and the like.

  Embodiments of the present invention will be described below. The adhesive resin composition of this invention contains said epoxy-type adhesive resin raw material of (A) component, and the alumina powder of (B) component. The component (A) contains (a) an epoxy resin, (b) a curing agent, (c) a curing accelerator, and (d) ammonium in a cured product obtained by curing the adhesive resin composition. Ion is 50 ppm by weight or less.

[(A) Component Epoxy Resin]
(A) The component epoxy resin has sufficient insulation, adhesion, heat resistance, mechanical strength, workability, etc. when an insulating adhesive layer or adhesive film is produced from the adhesive resin composition. Give. As the epoxy resin of component (a), bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, phenol novolak type epoxy resin, o-cresol novolak type Examples of epoxy resins having two or more epoxy groups in the molecule such as epoxy resins, biphenyl novolac type epoxy resins, triphenylmethane type epoxy resins, dicyclopentadiene type epoxy resins, alicyclic epoxy resins, brominated epoxy resins, etc. be able to. 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 adhesive film is in a B-stage state, the liquid epoxy resin is preferably 30 parts by weight or more, more preferably 100 parts by weight of the epoxy resin of component (a). It is preferable to blend 50 parts by weight or more. Here, “liquid” means a liquid having fluidity at 25 ° C., specifically, a liquid having a viscosity of 20000 Pa · s or less. (A) By mix | blending a liquid epoxy resin as an epoxy resin of a component, the softening point of the adhesive film of a B stage state can be reduced, and the crack of a surface can be suppressed.

  The content of the component (a) epoxy resin is preferably, for example, in the range of 20 to 60 parts by weight with respect to 100 parts by weight of the solid content of the component (A) epoxy-based adhesive resin material, and 25 to 50 parts by weight. Within the range of parts is more preferable. When the content of the epoxy resin is more than 60 parts by weight, the workability of the adhesive resin composition in the B-stage state is lowered, the cured product becomes brittle, the adhesive force is lowered, the heat resistance is lowered, and the temperature cycle resistance is increased. May decrease. On the other hand, when the content of the epoxy resin is less than 20 parts by weight, the adhesive resin composition may be insufficiently cured, resulting in a decrease in adhesive strength and a decrease in heat resistance.

[(B) Component curing agent]
(B) The component curing agent is blended for the purpose of curing the epoxy resin. When an insulating adhesive layer or adhesive film is produced from the adhesive resin composition, sufficient insulation, Provides adhesion, heat resistance, mechanical strength, etc. In this invention, a hardening | curing agent is comprised only from the liquid phenol novolak in the range whose hydroxyl equivalent is 130-200. Phenol novolac, for example, does not liberate ammonium ions even when heated in a heat treatment during curing. Therefore, by using only phenol novolac as a curing agent, ammonium ions in a cured product obtained by curing an adhesive resin composition are used. Can be easily suppressed to 50 ppm by weight or less.

  Phenol novolac is usually blended as a curing agent in a resin composition mainly composed of an epoxy resin, but in the adhesive resin composition of the present invention, a substance other than liquid phenol novolac is used as the curing agent. do not use. Here, “liquid” means a liquid having fluidity at 25 ° C., specifically, a liquid having a viscosity of 10,000 Pa · s or less. That is, a solid at 25 ° C. is not included. In general, a resin composition containing phenol novolak as a curing agent has a high softening point and is liable to cause surface cracking as an adhesive film in a B-stage state, but the softening point is lowered by using liquid phenol novolac. And the surface crack as an adhesive film of a B stage state can be prevented.

  In the adhesive resin composition of the present invention, a liquid phenol novolac having a hydroxyl group equivalent within the range of 130 to 200, preferably within the range of 130 to 165 is used. By setting the hydroxyl equivalent within this range, the flexibility and flexibility of the molded product in the B stage state can be improved, and cracking can be prevented. When the hydroxyl equivalent of phenol novolac is less than 130, the phenol novolac becomes solid and cracks occur in the molded product in the B stage state. On the other hand, when the hydroxyl equivalent exceeds 200, the adhesive strength of the cured product is lowered, or the insulating property is lowered.

  As the (B) component curing agent, for example, Meiwa Kasei's liquid phenol novolak MEH-8000H (hydroxyl equivalent 141), MEH-8005 (hydroxyl equivalent 135, liquid), and the like can be preferably used.

  (B) The content of the curing agent of the component is preferably in the range of 10 to 45 parts by weight with respect to 100 parts by weight of the solid content of the epoxy adhesive resin raw material of the component (A), for example. Within the range of parts is more preferable. If the content of the curing agent is more than 45 parts by weight, the water absorption of the cured product is increased, the solder heat resistance is lowered, and the curing reaction is insufficient so that sufficient adhesive force cannot be obtained. Arise. On the other hand, when the content of the curing agent is less than 10 parts by weight, the curing reaction does not proceed sufficiently, and the adhesive strength and heat resistance may be lowered.

  Moreover, it is preferable that the equivalent ratio of the epoxy resin of (a) component and the hardening | curing agent of (b) component is 0.5-1.5, for example, and the equivalent ratio of an epoxy resin / hardening agent is 0.7- More preferably, 1.2. Outside this range, a resin composition having sufficient mechanical strength cannot be obtained.

[(C) Component curing accelerator]
In the adhesive resin composition of the present invention, the component (c) curing accelerator is blended from the viewpoint of imparting sufficient curing reaction rate, heat resistance, mechanical strength and the like to the epoxy resin. Examples of the curing accelerator include imidazole compounds, organic phosphines, amines and the like. Specifically, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-ethyl- 4-methylimidazole, 2-phenylimidazole, 4-methyl-2-phenylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,4-diamino -6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine, 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-s-triazine isocyanuric Acid adduct, triphenylphosphine, tetraphenylphosphonium tetraphenylborate 1,8-diazabicyclo [5,4,0] can be exemplified undecene -7 (DBU) and the like. Moreover, what microcapsulated these can be used. These curing accelerators can be used alone or in combination of two or more. Among the curing accelerators, it is preferable to use an imidazole compound or an organic phosphine from the viewpoint of reducing the content of ammonium ions in the cured product.

  About the compounding quantity of a hardening accelerator, it is preferable that it is the range of 0.05-1.0 weight part with respect to 100 weight part of total amounts of the epoxy resin of (A) component, and the hardening agent of (B) component. . In this case, if the blending amount of the curing accelerator is less than 0.05 parts by weight, the curing promoting effect is not sufficient, and if it is more than 1.0 part by weight, the curing promoting effect is not increased, but rather the resin composition. As a result.

[(D) Component Phenoxy Resin]
The component (d) phenoxy resin is a component that improves the flexibility when an insulating adhesive layer or adhesive film is produced from the adhesive 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 smaller than 10,000, the heat resistance, mechanical strength, and flexibility of the epoxy resin composition are lowered. When the weight average molecular weight is larger than 200,000, the solubility in an organic solvent is increased. In addition to causing a decrease in compatibility with epoxy resin and curing agent, the viscosity when used as a varnish or the melt viscosity when used as an adhesive film is increased, and the processability as an insulating adhesive layer is increased. And adhesiveness may deteriorate, or the surface condition may deteriorate. In addition, the weight average molecular weight here is a value in terms of polystyrene by GPC (gel permeation chromatography) measurement.

  The content of the component (d) phenoxy resin is preferably 90 parts by weight or less, for example, within a range of 15 to 70 parts by weight with respect to 100 parts by weight of the solid content of the component (A) epoxy adhesive resin raw material. Is more preferable. If the content of phenoxy resin exceeds 90 parts by weight, the solubility in organic solvents may decrease, or the compatibility with (i) component epoxy resins and (b) component curing agents may decrease. There is. In addition, the viscosity when used as a varnish and the melt viscosity when used as an adhesive film are increased, and the workability and adhesiveness as an insulating adhesive layer may be reduced or the surface state may be deteriorated. In addition, the heat resistance may be reduced.

[Alumina powder of component (B)]
The component (B) alumina powder blended in the adhesive resin composition of the present invention has the following characteristics a) to c).

  a) The maximum particle size of the alumina powder is 120 μm or less, preferably 100 μm or less. If the maximum particle diameter is larger than 120 μm, the processability as an insulating adhesive layer is not sufficient, and the surface state of the insulating layer may be deteriorated. Here, the maximum particle diameter is the particle diameter when the distribution probability of the particle diameter is equal to or greater than a certain particle diameter in the distribution curve of the volume fraction of the particle diameter when the total volume of the alumina particles is 100%. Indicates the minimum value of. The lower limit value of the maximum particle diameter of the alumina powder is preferably 55 μm, for example, because alumina powder having a large particle diameter is advantageous from the viewpoint of achieving high thermal conductivity.

  b) 90% by weight or more of the total alumina powder is crystalline spherical alumina, and preferably 95% by weight or more is crystalline spherical alumina. Examples of the type of alumina powder include crystalline alumina and fused alumina. Examples of the shape of the alumina powder include spherical and crushed shapes. In the adhesive resin composition of the present invention, crystalline spherical alumina is most suitable from the viewpoint of achieving high thermal conductivity by closest packing. By using crystalline alumina, there is an effect of increasing the thermal conductivity compared to fused alumina, and by using spherical alumina, the viscosity or adhesion when used as a varnish compared to crushed alumina When used as an agent film, there is an effect of lowering the melt viscosity. When the content of crystalline spherical alumina in the total alumina powder is less than 90% by weight, the viscosity when used as a varnish or the melt viscosity when used as an adhesive film increases, and an insulating adhesive The processability, withstand voltage characteristics, and adhesion as a layer may be deteriorated or the surface state may be deteriorated.

c) The particle size distribution of crystalline spherical alumina satisfies the following conditions i) to iii).
i) The average particle diameter D50 is 35 to ₅₀ μm, and the volume average particle diameter / number average particle diameter is in the range of 1.2 to 2.0 and in the range of 30 to 50% by weight. Exists.
ii) An average particle diameter D50 of ₅ to 15 μm and a [volume average particle diameter] / [number average particle diameter] within a range of 2.0 to 3.5 is within a range of 30 to 50% by weight. Exists.
iii) an average particle diameter _{D 50} in the range of 0.1~2μm is present in the range of 10 to 30 wt%.

Here, [volume average particle size] / [number average particle size] is used as an index representing the particle size distribution, and is generally [volume average particle size] / [number average particle size] ≧ 1. The smaller the value, the sharper the particle size distribution, and the larger the value, the broader the particle size distribution. When the particle size distribution of the crystalline spherical alumina is out of the above range, the high thermal conductivity is not sufficient, and in addition to not exhibiting sufficient heat dissipation, the viscosity when used as a varnish, or the case when used as an adhesive film As the melt viscosity increases, the workability, withstand voltage characteristics, and adhesiveness of the insulating adhesive layer are lowered, and the surface state is deteriorated. Incidentally, the average particle diameter D _50, when the total volume of the alumina particles is 100%, meaning the particle size at which the 50% cumulative in cumulative curve of the volume fraction of the particle size.

  In addition to the features a) to c), in the present embodiment, the content of the alumina powder of the component (B) per solid content of the adhesive resin composition is preferably 86 to 95% by weight. More preferably, it is 88 to 93% by weight. The higher the content of alumina powder in the adhesive resin composition, the higher the thermal conductivity and the lower the thermal expansion. If the content of the alumina powder of the component (B) in the solid content of the adhesive resin composition is less than 86% by weight, the thermal conductivity may be insufficient and sufficient heat dissipation may not be exhibited. Further, the low thermal expansion property becomes insufficient, and the solder heat resistance may be lowered. On the other hand, when the content of the alumina powder of the component (B) is more than 95% by weight, the viscosity when used as a varnish increases, or the melt viscosity when used as an adhesive film increases, resulting in an insulating adhesive. The processability, withstand voltage characteristics, and adhesion as a layer may be deteriorated or the surface state may be deteriorated.

  The solid content of the adhesive resin composition is, for example, in the process of forming a cured product such as an insulating adhesive layer using the varnish when the adhesive resin composition is a varnish containing a predetermined solvent. The solid content finally remaining after the solvent is removed by drying or curing. Here, the varnish contains a solvent for the purpose of reducing the viscosity of the adhesive resin composition and improving processability, but finally a cured product such as an insulating adhesive layer is used. After formation, the solvent is removed by drying and heat treatment. Therefore, the content rate of the component in the adhesive resin composition of this invention was prescribed | regulated using the component content rate with respect to solid content of an adhesive resin composition. In addition to the components (A) and (B), which are essential components, optional components may be blended as necessary in the adhesive resin composition of the present invention. What is necessary is just to calculate solid content including an arbitrary component.

  The adhesive resin composition of the present embodiment can contain, for example, a solvent, a rubber component, and other optional components in addition to the essential components (A) and (B) described above.

[Rubber component]
In addition, the adhesive resin composition in the present invention is necessary from the viewpoint of improving film support and reducing the elasticity as an insulating adhesive layer when the adhesive film or the copper foil with an adhesive film is used. Accordingly, a rubber component can be added. Examples of such a rubber component include polybutadiene rubber, acrylonitrile-butadiene rubber, modified acrylonitrile-butadiene rubber, and acrylic rubber. These rubbers can be used alone or in combination of two or more. The weight average molecular weight of the rubber used can be, for example, 10,000 to 1,000,000, preferably 20,000 to 500,000. Here, the weight average molecular weight is a value in terms of polystyrene by GPC measurement. If the weight average molecular weight of the rubber component is less than 10,000, the heat resistance, mechanical strength, and flexibility of the cured product (adhesive layer) may be reduced, and the film support in the pre-curing stage In some cases, this may lead to a decrease. If the weight average molecular weight is greater than 1,000,000, solubility in organic solvents, compatibility with epoxy resins and curing agents may be reduced, and workability may be reduced. Viscosity or melt viscosity in the case of an adhesive film increases, and the workability and adhesiveness as an insulating adhesive layer are lowered, or the surface state is deteriorated. In addition, the purity of the rubber used as the rubber component should be low in ionic impurities from the viewpoint of improving the withstand voltage characteristics and moisture resistance reliability.

[Other optional ingredients]
In addition, from the viewpoint of reducing voids and improving smoothness, the adhesive resin composition of the present invention may be added with an antifoaming agent such as a fluorine type or a silicone type, a leveling agent, or the like, if necessary. it can. 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, an inorganic filler other than alumina and an organic filler other than alumina may be added to the adhesive resin composition of the present invention, as necessary, as a filler other than the alumina powder of component (E). Examples of the inorganic filler include silica, boron nitride, aluminum nitride, silicon nitride, 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. Further, the adhesive resin composition of the present invention can be blended with a colorant such as phthalocyanine / green, phthalocyanine / blue, or carbon black, if necessary.

  Among the above optional components, from the viewpoint of reducing the content of ammonium ions in the cured product, it is preferable to use those having no amino group or few amino groups in the molecular structure.

[Composition / Varnish]
The adhesive 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 adhesive resin composition of the present invention comprises a predetermined solvent, for example, an amide solvent such as N, N-dimethylformamide (DMF), N, N-dimethylacetamide, N-methyl-2-pyrrolidone (NMP), One or two ether solvents such as 1-methoxy-2-propanol, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone (MIBK), cyclohexanone and cyclopentanone, and aromatic solvents such as toluene and xylene The varnish may be formed by dissolving or dispersing in a mixture of seeds or more. Among the (b) component curing agent, (c) component curing accelerator, (B) component alumina powder, and optional additional optional components, inorganic filler, organic filler, colorant, etc. As long as it is uniformly dispersed in the solvent, it is not necessarily dissolved in the solvent.

  A varnish can be prepared according to the procedure shown below, for example. First, the phenoxy resin of component (d) is dissolved in an appropriate solvent while stirring in a container with a stirrer. Next, the epoxy resin of component (a), the curing agent of component (b), the curing accelerator of component (c), and optional components are mixed in this solution, and stirred and dissolved. Depending on the type of component (a) epoxy resin, an epoxy resin may be separately prepared in a solvent and mixed. Next, the varnish of the adhesive resin composition can be produced by blending the alumina powder of the component (B) into this mixed solution, stirring and uniformly dispersing.

  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 alumina powder is likely to settle, and unevenness and repellency are likely to occur during coating. When the viscosity is greater than 20000 Pa · s, the fluidity decreases. The coatability is lowered and it is difficult to produce a uniform coating film. When the alumina powder of the component (B) has the characteristics a) to c), it becomes easy to adjust the viscosity of the varnish within the above range.

[Adhesive film / copper foil with adhesive film]
In this invention, the adhesive film of a B stage state can be formed by apply | coating the said varnish on the base film as a support material, and making it dry. Moreover, the copper foil with an adhesive film can also be formed by apply | coating the said varnish on copper foil, and making it dry. Here, although the thickness of an adhesive film is not specifically limited, For example, it can be in the range of 100-300 micrometers. The B-stage adhesive film (copper foil with adhesive film) loses its value as a product if it is bent when its 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. However, in the adhesive film of the present invention (copper foil with adhesive film), the use of only a liquid phenol novolac having a hydroxyl group equivalent in the range of 130 to 200 as a curing agent allows flexibility in the B-stage state. Flexibility is improved and surface cracks can be prevented. This is because the hydroxyl group equivalent of phenol novolac used as a curing agent is in the range of 130 to 200, it becomes liquid and lowers the softening point in the B stage state, which gives the B stage resin flexibility and flexibility. It is thought to be for granting.

  In addition, regarding the film supportability of the adhesive film or the copper foil with adhesive film (before curing), the higher the solvent residual ratio, the better the film supportability, but if the solvent residual ratio is too high, The adhesive film or the copper foil with an adhesive film (before curing) is tacked or foamed during curing. Therefore, the solvent residual ratio is preferably 5% 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 an adhesive film part at the time of drying for 60 minutes in 180 degreeC atmosphere.

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

  Examples of the support material used when forming the adhesive film or the copper foil with the adhesive 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 adhesive film or the copper foil with the adhesive film is laminated on the 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 rolled. It can also be wound and stored. 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.

[Cured product]
The cured product of the present invention is prepared by, for example, preparing the above-mentioned B-staged adhesive film (or copper foil with an adhesive film) from the adhesive resin composition, and then heating to a temperature in the range of 150 ° C. to 250 ° C. And cured. The cured product thus obtained is one in which the content of ammonium ions (NH ₄ ⁺ ) is suppressed. That is, the content of ammonium ions in the cured product of the present invention is 50 ppm by weight or less, and more preferably 25 ppm by weight or less. By suppressing the ammonium ions to 50 ppm by weight or less, even when the cured product is used as an adhesive layer in contact with the metal wiring, generation of metal ions is not induced, resulting in adhesion failure or insulation failure. Migration can be effectively suppressed.

  In addition, content of the ammonium ion in hardened | cured material can be measured by heat-extracting what grind | pulverized hardened | cured material in pure water, and attaching | subjecting the ammonium ion density | concentration of the obtained extracted water to ion chromatography. The content of ammonium ions was expressed as a weight fraction (weight ppm) of ammonium ions with respect to the cured product.

  Moreover, the cured product of the present invention preferably has a thermal conductivity of, for example, 7 W / mK or more, and more preferably 10 W / mK or more. Generally, when the thermal conductivity of the cured product is less than 7 W / mK, it is necessary to devise such as forming a thermal via on the substrate for heat dissipation, but the thermal conductivity of the cured product is more than 7 W / mK. By being large, it has excellent heat dissipation characteristics, and can be applied to circuit boards and the like used in high temperature environments. Thus excellent thermal conductivity is obtained by controlling the particle size distribution and content of the (B) component alumina powder so as to satisfy the above a) to c).

[Metal-based circuit board manufacturing method]
Next, an example of a method for producing a metal base circuit board using the adhesive resin composition 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 an adhesive film from an adhesive resin composition, this copper foil with an adhesive film is temperature-150-250 degreeC using a batch type vacuum press on an aluminum substrate, for example. And bonding under conditions of pressure 1.0-30 MPa. At this time, the adhesive film surface is brought into contact with the aluminum substrate surface, and the epoxy resin is cured by heating and pressing in a state where the copper foil as the support material is the upper surface, thereby being attached to the aluminum substrate. In this way, a laminate in which the adhesive 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 adhesive resin composition of the present invention, in addition to the above method, an adhesive is applied to the aluminum substrate surface. After forming a layer and placing a copper foil on this adhesive layer and curing it while heating and pressurizing, or forming an insulating adhesive layer on the aluminum substrate surface and curing it, by copper plating A method of forming a copper conductor layer may be employed. 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 adhesive film may be used. .

  In the metal base circuit board manufactured as described above, the peel strength between the adhesive layer and the copper foil is, for example, preferably 0.5 kN / m or more, and more preferably 1.0 kN / m or more. . Such a high peel strength can be obtained by including all of the above-mentioned conditions (a) to c) regarding the content of the curing agent of the component (b) and the alumina powder of the component (B). (B) When the content of the curing agent of the component and the conditions (a) to c) of the alumina powder of the component (B) are not satisfied, the peel strength with the copper foil is less than 0.5 kN / m As a result, the adhesion required for the use of a circuit board or the like is insufficient.

[Action]
Conventionally, dicyandiamide, which has been widely used as a latent curing agent in epoxy resin compositions, has the property that, for example, the —NH ₂ group in the molecule is liberated due to heat generated by the element during actual use, and ammonium ions are easily generated. Yes. Therefore, when dicyandiamide is used as a curing agent for the epoxy resin composition to form an adhesive layer for circuit boards or electronic components, ammonium ions generated from dicyandiamide remain in the adhesive layer. When ammonium ions have an opportunity to come into contact with an anion (for example, sulfate ion SO ₄ ²⁻ ) in the course of use of the product, an anion and an ammonium salt are formed and the anion is taken into the adhesive layer. In this way, the anion taken into the adhesive layer in the form of ammonium salt is released little by little in the use environment where high temperature and high humidity are repeated, inducing generation of metal ions from the metal wiring, and poor insulation. It is thought to cause the migration that causes the problem.

  In the adhesive resin composition of the present invention, by using only a liquid phenol novolac having a hydroxyl group equivalent within the range of 130 to 200 as a curing agent, the amount of ammonium ions that become a migration-related factor in the cured product is 50 ppm by weight. Since it suppresses below, even when it uses as an adhesive layer which contacts metal wiring, generation | occurrence | production of a metal ion is not induced and the migration which causes the insulation defect can be suppressed effectively.

  In the adhesive resin composition of the present invention, the resin composition is obtained by using a liquid phenol novolak having a hydroxyl group equivalent within the range of 130 to 200 as a curing agent in a system containing alumina powder with a controlled particle size distribution. By lowering the softening point of the product, the flexibility and flexibility of the semi-cured (B stage) molded product can be improved, and the occurrence of surface cracks can be prevented.

  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.

[Varnish viscosity]
The varnish viscosity is a measured value (Pa · s) when the viscosity of the varnish of the obtained adhesive resin composition is measured at 23 ° C. and 6 rpm using a B-type viscometer No. 4 rotor.

[Settling in varnish]
For varnish sedimentation, 400 g of the adhesive resin composition varnish is left in a 500 ml Erlenmeyer flask at 23 ° C. for 7 days, and the presence of sedimentation of alumina powder at the bottom of the Erlenmeyer flask is confirmed. The case where there was a sediment was evaluated as “Yes”, and the case where there was less than 10 mm was evaluated as “No”. However, even if it was less than 10 mm, the precipitate was hard, and even when stirring did not return to the original state, it was determined as “Yes”.

[Ammonium ion (NH ₄ ⁺ )]
The B-stage adhesive film was cured by heating at 180 ° C. for 1 hour using a compression press molding machine to obtain a cured product. 1 g of the pulverized cured product was extracted at a heating temperature of 121 ° C. for 20 hours while being pressurized in 50 cc of pure water. The extracted water was processed with an ion chromatograph DX-300 manufactured by DIONEX, and the ammonium ion concentration was measured. The content of ammonium ions was the weight fraction (weight ppm) of ammonium ions with respect to the cured product.

[Coating properties]
The adhesive resin composition varnish was coated on a PET film with a knife coater so that the thickness after drying was 100 μm, and the case where the coated surface was uniform was evaluated as “good”, streaks or unevenness, etc. The case where the appearance defect was caused was evaluated as “bad”.

[Thermal conductivity]
Using a predetermined amount of the B-stage adhesive film, heated at 180 ° C. for 10 minutes in a compression press molding machine, removed from the press, and further heated in a dryer at 180 ° C. for 50 minutes to obtain a diameter. A disc-shaped test piece having a thickness of 50 mm and 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 Eihiro Seiki.

[Peel strength]
Peel strength was obtained by superposing a B-stage adhesive film on a copper foil and using a batch-type vacuum press on a 1.5 mm thick aluminum substrate in a temperature profile maintained at a pressure of 10 MPa and a maximum temperature of 180 ° C. for 1 hour. Pressed and cured. At that time, the adhesive film surface was brought into contact with the aluminum substrate surface, and pressure was applied to the aluminum substrate with the copper foil as the upper surface. And the test was implemented based on JIS C 6481 (peeling strength). That is, the test piece prepared as described above was cut into a shape based on the standard, and using a Tensilon tester (Orientec RTA-250), the copper foil was rotated in the direction of 90 degrees at a speed of 50 mm / min. By pulling, 90 degree copper foil peel strength (kN / m) was measured.

[B stage crack]
When the B-stage adhesive film was bent 180 ° along a 5 mm diameter round bar, the case where there was no abnormality on the surface of the film was evaluated as “none”, and the occurrence of cracks was confirmed as “ The crack was evaluated.

[Moisture resistance reliability]
As a test substrate, copper foil was laminated on both sides of the adhesive film of the B stage, and thermocompression bonding was performed 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. A laminate was prepared. A grid pattern having a line width of 200 microns and an interval of 200 microns was formed on one side of this laminate by etching. After this laminate was cut into 2 cm square, bias application wiring was attached to the upper and lower copper foil portions. The test substrate was subjected to a voltage application of DC 50V for 72 hours in a pressure cooker tester at 122 ° C., 2 atm and 100% humidity. Based on the initial resistance value, the case where the resistance value after the test was reduced by 20% or more was evaluated as “bad”, and the case where the resistance value decrease after the test was less than 20% was evaluated as “good”.

[Examples 1 to 6 and Comparative Examples 1 to 12]
The raw materials used for producing the adhesive resin composition and the adhesive film and their abbreviations are as follows.

(A) Epoxy adhesive resin raw material (a) Epoxy resin Epoxy resin (1): Bisphenol A type epoxy resin (YD128 manufactured by Tohto Kasei, epoxy equivalent 189, liquid)
Epoxy resin (2): Bisphenol F type epoxy resin (YDF-170 manufactured by Tohto Kasei, epoxy equivalent 170, liquid)
Epoxy resin (3): o-cresol novolac epoxy resin (EOCN-1020-55 manufactured by Nippon Kayaku, epoxy equivalent 200, softening point 55 ° C.)

(B) Curing agent curing agent (1): MEH Kasei, MEH-8000H (hydroxyl group equivalent 141, liquid)
Curing agent (2): Meiwa Kasei, MEH-8005 (hydroxyl equivalent: 135, liquid)
Curing agent (3): manufactured by Gunei Chemical Industry Co., Ltd., PSM-4324 (hydroxyl equivalent 105, softening point 100 ° C. solid)
Curing agent (4): manufactured by Gunei Chemical Industry Co., Ltd., PSM-4261 (hydroxyl equivalent: 105, softening point: 80 ° C. solid)
Curing agent (5): Dicyanamide (hydroxyl equivalent 21)

(C) Curing accelerator Curing accelerator (1): 2-ethyl-4-methylimidazole

(D) Phenoxy resin Phenoxy resin (1): Bisphenol A type phenoxy resin (YP-50 manufactured by Tohto Kasei)
Phenoxy resin (2): Bisphenol AF type phenoxy resin (YP-70 manufactured by Tohto Kasei)

(B) Alumina powder Alumina powder (1):
Spherical, crystallinity, maximum particle size: 100 μm, average particle size D ₅₀ ; 45 μm, volume average particle size MV; 49 μm, number average particle size MN; 38 μm, MV / MN; 1.3
Alumina powder (2):
Spherical, crystallinity, maximum particle size: 68 μm, average particle size D ₅₀ ; 11 μm, volume average particle size MV: 12 μm, number average particle size MN; 4.3 μm, MV / MN; 2.8
Alumina powder (3):
Spherical shape, crystallinity, maximum particle size: 7 μm, average particle size D ₅₀ ; 0.4 μm, volume average particle size MV: 0.7 μm, number average particle size MN: 0.1 μm, MV / MN; 6.7

[Particle size distribution parameter of alumina powder] The alumina powder to be measured is weighed and mixed in a 0.2 wt% sodium hexametaphosphate solution as a dispersion medium so that the sample concentration becomes 0.04 wt%, and an ultrasonic homogenizer. For 3 minutes. The particle size distribution of this alumina dispersion was measured from scattered light obtained by irradiation with a semiconductor laser having a wavelength of 780 nm, using a particle size distribution measuring apparatus Microtrac MT3300EX (manufactured by Nikkiso).

The maximum particle size is a particle size distribution obtained by the above measurement method. When the total particle volume is 100%, the distribution curve of the volume fraction of the particle size has all the particle distribution probabilities above a certain particle size. The minimum value of the particle diameter when 0 is shown.

The average particle diameter D ₅₀ is 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, assuming that the total particle volume is 100%. Show.

The volume average particle size (MV) indicates “average particle size weighted by volume” obtained from the particle size distribution obtained by the measurement method. MV is represented by the formula (1). MV = Σ (d _i * V _i ) (1) However, the particle size distribution is represented by a histogram, d _i is the representative particle size of the i-th section of the histogram, and V _i is in the i-th section. This is the volume fraction of the particle to which it belongs.

The number average particle size (MN) indicates the “average particle size weighted by the number” obtained from the particle size distribution obtained by the measurement method. Here, virtually all the particles are assumed to be spherical, and MN was obtained from Equation (2). MN = Σ (V _i / d _i ² ) / Σ (V _i / d _i ³ ) (2) where d _i is the representative particle diameter of the i-th section of the histogram and Vi is the i-th section Is the volume fraction of particles belonging to.

[Volume average particle size] / [Number average particle size] was used as an index representing the particle size distribution. In general, [volume average particle size] / [number average particle size] ≧ 1, and the smaller this value, the sharper the particle size distribution, and the larger this value, the broader the particle size distribution.

  It mix | blended in the ratio shown to Tables 1-3 using the raw material shown above. First, only the phenoxy resin was stirred and dissolved in methyl isobutyl ketone (MIBK) in a container equipped with a stirrer. (However, when there is an epoxy resin (2), a MIBK solution of only the epoxy resin (2) is prepared separately from the MIBK solution of the phenoxy resin and mixed with the MIBK solution of the phenoxy resin.) Next, this MIBK Into the solution, the epoxy resin (1) (however, when the epoxy resin (3) is blended, the epoxy resin (3) is also blended), the curing agent, and the curing accelerator (1) are mixed, stirred, and dissolved. did. Thereafter, alumina powder was blended into this mixed solution, and stirred and dispersed to prepare a varnish of the adhesive resin composition. By applying this varnish to a 50 μm-thick release-treated PET film (MR-50, manufactured by Mitsubishi Chemical) so that the thickness of the resin layer after drying is 150 μm, and drying at 110 ° C. for 5 minutes. A B-stage adhesive film was prepared.

  The results are shown in Tables 1-3. In the table, the blending amount of epoxy resin, curing agent, curing accelerator, phenoxy resin, alumina powder, and solvent (MIBK) is shown in parts by weight with respect to 100 parts by weight of the solid content of the adhesive resin composition. The alumina content was expressed as% by weight based on the total solid content of the adhesive resin composition.

  From Tables 1 to 3, the adhesive resin compositions of Examples 1 to 6 of the present invention obtained good results in all evaluation items. On the other hand, the hardeners other than the liquid phenol novolak in which the particle size distribution and content of the alumina powder do not satisfy the above-mentioned a) to c) and the hydroxyl group equivalent within the range of 130 to 200 were used. In Comparative Examples 5 to 11, satisfactory evaluation was not obtained for any of the items.

  As described above, the adhesive resin composition of the present invention uses only a liquid phenol novolac having a hydroxyl group equivalent in the range of 130 to 200 as a curing agent, and the amount of ammonium ions in the cured product is 50 ppm by weight or less. Therefore, the adhesive strength and insulation properties are not easily lowered, and the withstand voltage characteristics can be maintained. In addition, the adhesive resin composition of the present invention has excellent thermal conductivity by containing alumina powder having a predetermined particle size distribution, and the flexibility and applicability of the B-stage molded product by the action of liquid phenol novolac. Flexibility is improved and surface cracking can be prevented. Therefore, the adhesive resin composition of the present invention can be preferably applied as an insulating adhesive layer in, for example, circuit boards and electronic components.

As mentioned above, although embodiment of this invention was described in detail for the purpose of illustration, this invention is not restrict | limited to the said embodiment.

Claims (4)

An adhesive resin composition containing the following components (A) and (B), wherein an ammonium ion in a cured product obtained by curing the adhesive resin composition is 50 ppm by weight or less.
(A): Epoxy adhesive resin raw material containing the following components (A) to (D).
(A) epoxy resin,
(B) a curing agent comprising a liquid phenol novolac having a hydroxyl group equivalent in the range of 130 to 200;
(C) a curing accelerator; and (d) a phenoxy resin (B): an alumina powder that satisfies the following conditions a) to c).
a) The maximum particle size is 120 μm or less,
b) The proportion of crystalline spherical alumina in the total alumina powder is 90% by weight or more, and
c) The crystalline spherical alumina particle size distribution satisfies the following conditions i) to iii).
i) An average particle diameter D50 of 35 to ₅₀ μm and a [volume average particle diameter] / [number average particle diameter] in the range of 1.2 to 2.0 is 30 in crystalline spherical alumina. Present in the range of ~ 50% by weight,
ii) An average particle diameter D50 of ₅ to 15 μm and a [volume average particle diameter] / [number average particle diameter] in the range of 2.0 to 3.5 is 30 in crystalline spherical alumina. Present in the range of ~ 50 wt%, and
iii) Those having an average particle diameter D ₅₀ in the range of 0.1 to 2 μm are present in the crystalline spherical alumina in the range of 10 to 30% by weight.   The adhesive resin composition according to claim 1, wherein the content of the component (B) is in the range of 86 to 95 parts by weight with respect to 100 parts by weight of the solid content of the adhesive resin composition.   A cured product obtained by curing the adhesive resin composition according to claim 1. An adhesive film obtained by forming the adhesive resin composition according to claim 1 into a film in a semi-cured state.