Patent Description:
With a recent increase in the demand of reduction in size and thinning of electronic equipment, a circuit substrate to be used in the electronic equipment is also demanded to have a reduced size and an increased wiring density. In the circuit substrate of this type, a through hole is formed. This through hole is sometimes filled with a resin composition including magnetic powder thereby forming a magnetic layer to form an inductor substrate.

For example, in <CIT>, a resin composition including a thermosetting resin and magnetic powder such as iron oxide (III) or cobalt ferrite is described as a material to form the magnetic layer inside the through hole in the inductor substrate.

<CIT> discloses a through hole filling paste, comprising: a magnetic powder (A); an epoxy resin (B); and a curing agent (C), wherein the magnetic powder (A) is surface treated with a surface treating agent containing at least one element selected from Si, Al, and Ti.

To increase a relative permeability of a cured product of a resin composition including magnetic powder so as to enhance performance of an inductor, a method may be conceived in which the amount of the magnetic powder in the resin composition is increased. The inventor of the present invention increased the amount of ferrite therein as the magnetic powder; however, it was found that not only a viscosity of the resin composition increased but also a mechanical strength and an elongation property of a cured product of the resin composition were deteriorated. The increase in the viscosity of the resin composition can cause deterioration in a handling property and a printing property thereof; and the deterioration in the mechanical strength and the elongation property can cause generation of a crack due to a shear force and so forth.

The present invention was made under the circumstances described above; and thus, an object thereof is to provide: a resin composition that is excellent in a relative permeability of a cured product thereof, low in a viscosity, and excellent in a mechanical strength and an elongation property of the cured product; and a magnetic sheet, a circuit substrate, and an inductor substrate, all being obtained by using this resin composition.

The inventors of the present invention carried out an extensive investigation to solve the problems described above; and as a result, it was found that when a carbon amount included in the ferrite in the resin composition including a thermosetting resin is made to less than a prescribed level, not only the cured product thereof was excellent in its relative permeability, but also the resin composition was low in its viscosity and the cured product thereof was excellent in its mechanical strength and elongation property. The present invention could be completed on the basis of these findings.

Namely, the present invention is defined in the independent claims <NUM> and <NUM>-<NUM> and optional features are covered by the dependent claims.

According to the present invention, provided are: the resin composition that is excellent in the relative permeability of the cured product thereof, low in the viscosity, and excellent in the mechanical strength and the elongation property of the cured product thereof; and the magnetic sheet, the circuit substrate, and the inductor substrate, all being obtained by using this resin composition.

Hereinafter, with referring to the drawings, embodiments of the present invention will be explained. In these drawings, the shape, size, and arrangement of the composition elements are roughly illustrated so as to merely help to understand the present invention. The present invention is limited by the appended claims.

The resin composition of the present invention includes (A) a ferrite and (B) a thermosetting resin, in which a carbon amount included in the (A) component is <NUM>% or less by mass relative to <NUM>% by mass of the (A) component, a relative permeability (<NUM>) of a cured product obtained by thermally curing the resin composition at <NUM> for <NUM> minutes is <NUM> or more, and a maximum point strength (<NUM>) of a cured product obtained by thermally curing the resin composition at <NUM> for <NUM> minutes is <NUM> MPa or more. In the present invention, when the resin composition is made to include the ferrite whose carbon amount is lower than the prescribed level, the resin composition that is excellent in a relative permeability of the cured product thereof, low in a viscosity, and excellent in a mechanical strength and an elongation property of the cured product can be obtained.

In the resin composition, the (A) component and the (B) component are combined; and in addition, the composition may further include an arbitrary component. Illustrative examples of the arbitrary component include (C) a dispersant, (D) a curing accelerator, and (E) other additives. Hereinafter, each component included in the resin composition of the present invention will be explained in detail.

The resin composition includes (A) a ferrite as the (A) component. A carbon amount included in the (A) component is <NUM>% or less by mass relative to <NUM>% by mass of the (A) component. When the carbon amount included in the (A) component is made to <NUM>% or less by mass relative to <NUM>% by mass of the (A) component, the resin composition can have a low viscosity as well as excellent printing and handling properties. In general, the ferrite is produced by mixing a granulated raw material thereof with a sintering adjuvant followed by sintering this mixture. The inventors of the present invention found that the carbon derived from this sintering adjuvant remained in the ferrite even after sintering and that this carbon caused an increase in the viscosity of the resin composition. As far as the inventors of the present invention know, it can be said that the technological idea to lower the viscosity of the resin composition by bringing the carbon amount included in the ferrite to below a prescribed level has not been proposed at all in the past. The carbon amount in a surface modifying agent is not included in the carbon amount mentioned here. The carbon amount included in the (A) component may be controlled, for example, by controlling the amount of the sintering adjuvant such as lauric acid.

The carbon amount included in the (A) component is <NUM>% or less by mass, and preferably <NUM>% or less by mass, while more preferably <NUM>% or less by mass, relative to <NUM>% by mass of the (A) component. The lower limit of the carbon amount is not particularly restricted; it can be <NUM>% or more by mass, <NUM>% or more by mass, or the like, relative to <NUM>% by mass of the (A) component.

The carbon amount included in the (A) component may be measured by using a carbon analyzer. In the carbon analyzer, for example, a ferrite to be measured is burnt by a high frequency induction furnace, and then, the carbon amount therein can be obtained by measuring amounts of carbon monoxide and carbon dioxide thus produced by an infrared light absorption method. Specifically, in the carbon analyzer, an oxygen gas pressure is made to <NUM>/cm<NUM>, and a nitrogen gas pressure is made to <NUM>/cm<NUM>. First, the carbon amount in a standard sample whose carbon amount is known and almost in the same level as that of the ferrite to be measured is measured. Next, a blank test is carried out without using the ferrite. Then, a conversion coefficient is calculated by using the following equation.

Next, the ferrite to be measured is measured by using the carbon analyzer, and the carbon amount therein is calculated by using the following equation.

When the (A) component is surface-modified with a surface treating agent to be described later, the ferrite to be measured is heated at <NUM> for <NUM> hours in an electric furnace with flowing nitrogen at the flow rate of <NUM>/minute to remove the surface treating agent on the ferrite surface; and then, the carbon amount is calculated by the method described above. The carbon derived from the sintering adjuvant cannot be removed even about <NUM>, <NUM>, but usually the surface treating agent can be completely removed by heating at the temperature of <NUM> to <NUM>.

Illustrative examples of the ferrite include a Mg-Zn type ferrite, a Fe-Mn type ferrite, a Mn-Zn type ferrite, a Mn-Mg type ferrite, a Cu-Zn type ferrite, a Mg-Mn-Sr type ferrite, a Ni-Zn type ferrite, a Ba-Zn type ferrite, a Ba-Mg type ferrite, a Ba-Ni type ferrite, a Ba-Co type ferrite, a Ba-Ni-Co type ferrite, a Y type ferrite, iron oxide (III) powder, and triiron tetraoxide. Among these, a ferrite including at least one element selected from Ni, Cu, Mn, and Zn is preferable, and the Fe-Mn type ferrite is more preferable. The (A) component may be used singly or as a combination of two or more of these ferrites.

As for the ferrite, a commercially available ferrite may be used. Specific examples of the usable and commercially available ferrite include "M05S" (carbon amount of less than <NUM>% by mass) and "E10s" (carbon amount of less than <NUM>% by mass), both being manufactured by Powdertech Co.

As for the ferrite, a spherical ferrite is preferable. The value that is obtained by dividing a long axis with a short axis of the ferrite (namely, aspect ratio) is preferably <NUM> or less, more preferably <NUM> or less, still more preferably <NUM> or less, and far still more preferably <NUM> or less, while especially preferably <NUM>. In general, the ferrite in a flat shape can have a higher relative permeability than the ferrite in a spherical shape. On the other hand, especially the spherical ferrite can usually have a low magnetic loss; and from a viewpoint to obtain the resin composition having a preferable viscosity, the spherical ferrite is preferably used. The aspect ratio may be measured by the method to be described later.

The average particle diameter of the (A) component may be measured with a laser diffraction/scattering method based on the Mie scattering theory. Specifically, the particle diameter distribution of the magnetic powder on the volume basis is prepared by using a laser diffraction scattering type particle diameter distribution measurement apparatus, and the median diameter thus obtained is taken as the average particle diameter thereof. The measurement sample that is obtained by dispersing the magnetic powders in water by means of an ultrasonic wave is preferably used. Illustrative examples of the laser diffraction and scattering type particle diameter distribution measurement apparatus that can be used include "LA-<NUM>" manufactured by Horiba Ltd. and "SALD-7500nano" and "SALD-<NUM>" manufactured by Shimadzu Corp.

The <NUM>% diameter (D10) in a particle diameter distribution is a volume-average particle diameter at the time when a cumulative amount of the volume that is accumulated from the side of a small particle diameter reaches <NUM>% in a particle diameter distribution curve obtained by measurement of the particle diameter distribution with the method described above. The <NUM>% diameter (D50) is a volume-average particle diameter at the time when a cumulative amount of the volume that is accumulated from the side of a small particle diameter reaches <NUM>% in a particle diameter distribution curve obtained by measurement of the particle diameter distribution with the method described above. In addition, the <NUM>% diameter (D90) is a volume-average particle diameter at the time when a cumulative amount of the volume that is accumulated from the side of a small particle diameter reaches <NUM>% in a particle diameter distribution curve obtained by measurement of the particle diameter distribution with the method described above.

From a viewpoint to obtain the cured product that is excellent in the relative permeability, the <NUM>% diameter (D10) in the particle diameter distribution is preferably <NUM> or more, and more preferably <NUM> or more, while still more preferably <NUM> or more. The upper limit thereof is preferably <NUM> or less, preferably less than <NUM>, and more preferably <NUM> or less, while still more preferably <NUM> or less.

From a viewpoint to obtain the cured product that is excellent in the relative permeability, the <NUM>% diameter (D50) in the particle diameter distribution is preferably <NUM> or more, and more preferably <NUM> or more, while still more preferably <NUM> or more. The upper limit thereof is preferably <NUM> or less, preferably less than <NUM>, and more preferably <NUM> or less, while still more preferably <NUM> or less.

From a viewpoint to obtain the cured product that is excellent in the relative permeability, the <NUM>% diameter (D90) in the particle diameter distribution is preferably <NUM> or more, and more preferably <NUM> or more, while still more preferably <NUM> or more. The upper limit thereof is preferably <NUM> or less, and more preferably <NUM> or less, while still more preferably <NUM> or less.

From a viewpoint to obtain the cured product that is excellent in a magnetic characteristic, a specific surface area of the (A) component is preferably <NUM><NUM>/g or more, and more preferably <NUM><NUM>/g or more, while still more preferably <NUM><NUM>/g or more. Also the specific surface area is preferably <NUM><NUM>/g or less, and more preferably <NUM><NUM>/g or less, while still more preferably <NUM><NUM>/g or less. The specific surface area of the (A) component may be measured by a BET method.

From a viewpoint to enhance the humidity resistance and the dispersion property, the (A) component may be treated with a surface treating agent. Illustrative examples of the surface treating agent include a vinylsilane type coupling agent, a (meth) acryl type coupling agent, a fluorine-containing silane coupling agent, an aminosilane type coupling agent, an epoxy silane type coupling agent, a mercapto silane type coupling agent, a silane type coupling agent, an alkoxy silane, an organosilazane compound, and a titanate type coupling agent. These surface treating agents may be used singly or as an arbitrary combination of two or more of them.

Illustrative examples of the commercially available surface treating agent include "KBM1003" (vinyl triethoxy silane; manufactured by Shin-Etsu Chemical Co. ) ; "KBM503" (<NUM>-methacryloxy propyl triethoxy silane; manufactured by Shin-Etsu Chemical Co. ); "KBM403" (<NUM>-glycidoxy propyl trimethoxy silane; manufactured by Shin-Etsu Chemical Co. ), "KBM803" (<NUM>-mercaptopropyl trimethoxy silane; manufactured by Shin-Etsu Chemical Co. ); "KBE903" (<NUM>-aminopropyl triethoxy silane; manufactured by Shin-Etsu Chemical Co. ); "KBM573" (N-phenyl-<NUM>-aminopropyl trimethoxy silane; manufactured by Shin-Etsu Chemical Co. ); "SZ-<NUM>" (hexamethyl disilazane; manufactured by Shin-Etsu Chemical Co. ); "KBM103" (phenyl trimethoxy silane; manufactured by Shin-Etsu Chemical Co. ); "KBM-<NUM>" (long chain epoxy type silane coupling agent; manufactured by Shin-Etsu Chemical Co. ); and "KBM-<NUM>" (<NUM>,<NUM>,<NUM>-trifluoropropyl trimethoxy silane; manufactured by Shin-Etsu Chemical Co.

From a viewpoint to enhance the dispersion property of the (A) component, the degree of the surface treatment by means of the surface treating agent is preferably within a prescribed range. Specifically, the (A) component is surface-treated by the surface treating agent with the amount of preferably <NUM> to <NUM> parts by mass, preferably <NUM> to <NUM> parts by mass, and preferably <NUM> to <NUM> parts by mass, relative to <NUM> parts by mass of the (A) component.

From a viewpoint to obtain the cured product that is excellent in a magnetic characteristic, the content (% by volume) of the (A) component is, on the basis of <NUM>% by volume as the non-volatile components in the resin composition, preferably <NUM>% or more by volume, and more preferably <NUM>% or more by volume, while still more preferably <NUM>% or more by volume. Also the content is preferably <NUM>% or less by volume, and more preferably <NUM>% or less by volume, while still more preferably <NUM>% or less by volume.

From a viewpoint to obtain the cured product that is excellent in a magnetic characteristic, the content (% by mass) of the (A) component is, on the basis of <NUM>% by mass as the non-volatile components in the resin composition, preferably <NUM>% or more by mass, and more preferably <NUM>% or more by mass, while still more preferably <NUM>% or more by mass. Also the content is preferably <NUM>% or less by mass, and more preferably <NUM>% or less by mass, while still more preferably <NUM>% or less by mass. In the present invention, the content of each component in the resin composition is the value based on <NUM>% by mass as the non-volatile components in the resin composition unless specifically mentioned otherwise.

The resin composition includes a thermosetting resin as the (B) component. As for (B) the thermosetting resin, for example, a thermosetting resin that is used at the time when an insulating layer of a wiring board is formed can be used. Illustrative examples of the thermosetting resin like this include an epoxy resin, a phenol type resin, a naphthol type resin, a benzoxazine type resin, an active ester type resin, a cyanate ester type resin, a carbodiimide type resin, an amine type resin, and an acid anhydride type resin. Among these, the resin composition including the epoxy resin is preferable.

(B) These thermosetting resin may be used singly, or as a combination of two or more of those mentioned above. Note that the components capable of curing the resin composition by reacting with an epoxy resin, i.e., the components such as the phenol type resin, the naphthol type resin, the benzoxazine type resin, the active ester type resin, the cyanate ester type resin, the carbodiimide type resin, the amine type resin, and the acid anhydride type resin, are sometimes collectively called "curing agent".

Illustrative examples of the epoxy resin include: a glycyrol type epoxy resin; a bisphenol A type epoxy resin; a bisphenol F type epoxy resin; a bisphenol S type epoxy resin; a bisphenol AF type epoxy resin; a dicyclopentadiene type epoxy resin; a trisphenol type epoxy resin; a phenol novolak type epoxy resin; a tert-butyl-catechol type epoxy resin; epoxy resins having a condensed cyclic structure such as a naphthol novolak type epoxy resin, a naphthalene type epoxy resin, a naphthol type epoxy resin, and an anthracene type epoxy resin; a glycidyl amine type epoxy resin; a glycidyl ester type epoxy resin; a cresol novolak type epoxy resin; a biphenyl type epoxy resin; a linear aliphatic epoxy resin; an epoxy resin having a butadiene structure; an alicyclic epoxy resin; a heterocyclic epoxy resin; an epoxy resin having a spiro ring; a cyclohexane dimethanol type epoxy resin; a trimethylol type epoxy resin; and a tetraphenylethane type epoxy resin. These epoxy resins may be used singly or as a combination of two or more of them. The epoxy resin is preferably one or more epoxy resins selected from the bisphenol A type epoxy resin and the bisphenol F type epoxy resin.

It is preferable that the epoxy resin include an epoxy resin having two or more epoxy groups in one molecule. In addition, the epoxy resin having an aromatic structure is preferable. When two or more of the epoxy resins are used, it is more preferable that at least one of them have an aromatic structure. The aromatic structure means a chemical structure generally defined as aromatic, and this includes a polycyclic aromatic and an aromatic heterocycle. The ratio of the epoxy resin having two or more epoxy groups in one molecule relative to <NUM>% by mass of the non-volatile components in the epoxy resin is preferably <NUM>% or more by mass, and more preferably <NUM>% or more by mass, while especially preferably <NUM>% or more by mass.

As for the epoxy resin, there are an epoxy resin that is in a liquid state at <NUM> (hereinafter, this is also called "liquid epoxy resin") and an epoxy resin that is in a solid state at <NUM> (hereinafter, this is also called "solid epoxy resin"). When the resin composition includes the epoxy resin as the (B) component, the resin composition may include, as the epoxy resin, only the liquid epoxy resin, or only the solid epoxy resin, or a combination of the liquid epoxy resin and the solid epoxy resin, though from a viewpoint to lower the viscosity of the resin composition, only the liquid epoxy resin is preferably included therein.

The liquid epoxy resin is preferably a glycyrol type epoxy resin, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a bisphenol AF type epoxy resin, a naphthalene type epoxy resin, a glycidyl ester type epoxy resin, a glycidyl amine type epoxy resin, a phenol novolak type epoxy resin, an alicyclic epoxy resin having an ester skeleton, a cyclohexane dimethanol type epoxy resin, and an epoxy resin having a butadiene structure. Among these, the glycyrol type epoxy resin, the bisphenol A type epoxy resin, and the bisphenol F type epoxy resin are more preferable. Specific examples of the liquid epoxy resin include: "HP4032", "HP4032D", and "HP4032SS" (all are naphthalene type epoxy resins) manufactured by DIC Corp. ; "<NUM>" and "jER828EL" (both are bisphenol A type epoxy resins), "jER807" (a bisphenol F type epoxy resin), and "jER152" (a phenol novolak type epoxy resin), all of these resins being manufactured by Mitsubishi Chemical Corp. ; "<NUM>" and "630LSD" both being manufactured by Mitsubishi Chemical Corp. ; "ED-523T" (a glycyrol type epoxy resin (Adeka glycyrol)), "EP-<NUM>" (a glycidyl amine type epoxy resin), and "EP-<NUM>" (a dicyclopentadiene type epoxy resin), all of these resins being manufactured by ADEKA Corp. ; "ZX1059" (a mixture of a bisphenol A type epoxy resin and a bisphenol F type epoxy resin) manufactured by Nippon Steel Chemical & Material Co. ; "EX-<NUM>" (a glycidyl ester type epoxy resin) manufactured by Nagase ChemteX Corp. ; "Celloxide-2021P" (an alicyclic epoxy resin having an ester skeleton) and "PB-<NUM>" (an epoxy resin having a butadiene structure), both resins being manufactured by Daicel Corp. ; and "ZX1658" and "ZX1658GS" (liquid <NUM>,<NUM>-glycidyl cyclohexane) both being manufactured by Nippon Steel Chemical & Material Co. These may be used singly or as a combination of two or more of them.

The solid epoxy resin is preferably a naphthalene type <NUM>-functional epoxy resin, a cresol novolak type epoxy resin, a dicyclopentadiene type epoxy resin, a trisphenol type epoxy resin, a naphthol type epoxy resin, a biphenyl type epoxy resin, a naphthylene ether type epoxy resin, an anthracene type epoxy resin, a bisphenol A type epoxy resin, and a tetraphenylethane type epoxy resin. Among them, the naphthalene type <NUM>-functional epoxy resin, the naphthol type epoxy resin, and the biphenyl type epoxy resin are more preferable. Specific examples of the solid epoxy resin include: "HP4032H" (a naphthalene type epoxy resin), "HP-<NUM>" and "HP-<NUM>" (both are naphthalene type four-functional epoxy resins) ; "N-<NUM>" (a cresol novolak type epoxy resin), "N-<NUM>" (a cresol novolak type epoxy resin), "HP-<NUM>", "HP-7200HH", and "HP-<NUM>" (all are dicyclopentadiene type epoxy resins), "EXA-<NUM>", "EXA-<NUM>-G3", "EXA-<NUM>-G4", "EXA-<NUM>-G4S", and "HP6000" (all are naphthalene ether type epoxy resins), all of these resins being manufactured by DIC Corp. ; "EPPN-<NUM>" (a trisphenol type epoxy resin), "NC7000L" (naphthol novolak type epoxy resin), and "NC3000H", "NC3000", "NC3000L", and "NC3100" (all are biphenyl type epoxy resins), all of these resins being manufactured by Nippon Kayaku Co. ; "ESN475V" (a naphthalene type epoxy resin) and "ESN485" (a naphthol novolak type epoxy resin), both being manufactured by Nippon Steel Chemical & Material Co. ; "YX4000H" and "YL6121" (both are biphenyl type epoxy resins), "YX4000HK" (a bixylenol type epoxy resin), and "YX8800" (an anthracene type epoxy resin), all of them being manufactured by Mitsubishi Chemical Corp. ; "PG-<NUM>" and "CG-<NUM>", both being manufactured by Osaka Gas Chemicals Co. ; and "YL7760" (a bisphenol AF type epoxy resin), "YL7800" (a fluorene type epoxy resin), "jER1010" (a solid bisphenol A type epoxy resin), and "jER1031S" (a tetraphenylethane type epoxy resin), all of them being manufactured by Mitsubishi Chemical Corp. These may be used singly or as a mixture of two or more of them.

When the liquid epoxy resin and the solid epoxy resin are concurrently used as the (B) component, the ratio of them (liquid epoxy resin: solid epoxy resin) is, as the mass ratio, preferably in the range of <NUM>:<NUM> to <NUM>:<NUM>, and more preferably in the range of <NUM>:<NUM> to <NUM>:<NUM>, while still more preferably in the range of <NUM>:<NUM> to <NUM>:<NUM>. When the ratio of the liquid epoxy resin and the solid epoxy resin is within this range, the intended advantageous effects of the present invention can be clearly obtained.

The epoxy equivalent of the epoxy resin as the (B) component is preferably in the range of <NUM> to <NUM>,<NUM>/eq. , more preferably in the range of <NUM> to <NUM>,<NUM>/eq. , and still more preferably in the range of <NUM> to <NUM>,<NUM>/eq. , while far still more preferably in the range of <NUM> to <NUM>,<NUM>/eq. Within this range, the crosslinking density of a cured product is sufficient, so that a magnetic layer having a low surface roughness can be obtained. The epoxy equivalent, which is a mass of the resin including one equivalent of the epoxy group, can be measured with a method in accordance with JIS K7236.

The weight-average molecular weight of the epoxy resin as the (B) component is preferably in the range of <NUM> to <NUM>, <NUM>, and more preferably in the range of <NUM> to <NUM>, <NUM>, while still more preferably in the range of <NUM> to <NUM>,<NUM>. Note that the weight-average molecular weight of the epoxy resin is the weight-average molecular weight in terms of polystyrene measured with a gel permeation chromatography (GPC) method.

As the active ester type resin, resins having one or more active ester groups in one molecule thereof can be used. Among the active ester type resins like this, resins having two or more highly reactive ester groups in one molecule thereof are preferable as the active ester curing agent, these including a phenol ester type, a thiophenol ester type, an N-hydroxyamine ester type, and a heterocyclic hydroxy compound ester type. The active ester type resin is preferably the compound that is obtained by condensation reaction of a carboxylic acid compound and/or a thiocarboxylic acid compound with a hydroxy compound and/or a thiol compound. Especially, in view of enhancement of a heat resistance, an active ester type resin obtained from a carboxylic acid compound and a hydroxy compound is preferable, while an active ester type resin obtained from a carboxylic acid compound and a phenol compound and/or a naphthol compound is more preferable.

Illustrative examples of the carboxylic acid include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and pyromellitic acid.

Illustrative examples of the phenol compound or the naphthol compound include hydroquinone, resorcin, bisphenol A, bisphenol F, bisphenol S, phenolphthalin, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, <NUM>,<NUM>-dihydroxynaphthalene, <NUM>,<NUM>-dihydroxynaphthalene, <NUM>,<NUM>-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucin, benzene triol, a dicyclopentadiene type diphenol compound, and phenol novolak. Here, "dicyclopentadiene type diphenol compound" means the diphenol compound obtained by condensation of one dicyclopentadiene molecule with two phenol molecules.

Specific examples of the preferable active ester type resin include an active ester type resin containing a dicyclopentadiene type diphenol structure, an active ester type resin containing a naphthalene structure, an active ester type resin containing an acetylated phenol novolak, and an active ester type resin containing a benzoylated phenol novolak. Among them, the active ester type resin containing a naphthalene structure and the active ester type resin containing a dicyclopentadiene type diphenol structure are preferable. Here, "dicyclopentadiene type diphenol structure" means the divalent structure unit formed of phenylene-dicyclopentylene-phenylene.

Illustrative examples of the commercially available active ester type resin include active ester type resins containing a dicyclopentadiene type diphenol structure, such as "EXB9451", "EXB9460", "EXB9460S", "HPC-<NUM>-65T", "HPC-<NUM>-65TM", and "EXB-<NUM>-65TM" (all are manufactured by DIC Corp. ) ; active ester type resins containing a naphthalene structure, such as "EXB9416-70BK", "EXB-<NUM>-65T", "EXB-<NUM>-65T", and "EXB-<NUM>-62T" (all are manufactured by DIC Corp. ); active ester type resins containing an acetylated phenol novolak, such as "DC808" (manufactured by Mitsubishi Chemical Corp. ); active ester type resins containing a benzoylated phenol novolak, such as "YLH1026" (manufactured by Mitsubishi Chemical Corp. ); and active ester type resins as a benzoylated phenol novolak, such as "YLH1026" (manufactured by Mitsubishi Chemical Corp. ), "YLH1030" (manufactured by Mitsubishi Chemical Corp. ), and "YLH1048" (manufactured by Mitsubishi Chemical Corp.

In view of the heat resistance and the water resistance, as the phenol type resin and the naphthol type resin, both having a novolak structure are preferable. In view of adhesion with a conductive layer, a nitrogen-containing phenol curing agent is preferable, while a phenol type resin having a triazine skeleton is more preferable.

Specific examples of the phenol type resin and the naphthol type resin include "MEH-<NUM>", "MEH-<NUM>", and "MEH-<NUM>" all being manufactured by Meiwa Plastic Industries, Ltd. ; "NHN", "CBN", and "GPH" all being manufactured by Nippon Kayaku Co. ; "SN170", "SN180", "SN190", "SN475", "SN485", "SN495", "SN-495V", "SN375", and "SN395" all being manufactured by Nippon Steel Chemical & Material Co. ; and "TD-<NUM>", "LA-<NUM>", "LA-<NUM>", "LA-<NUM>", "LA-<NUM>-50P", and "EXB-<NUM>" all being manufactured by DIC Corp.

Specific examples of the benzoxazine type resin include "JBZ-OD100" (benzoxazine ring equivalent of <NUM>/eq. ), "JBZ-OP100D" (benzoxazine ring equivalent of <NUM>/eq. ), and "ODA-BOZ" (benzoxazine ring equivalent of <NUM>/eq. ) all being manufactured by JFE Chemical Corp. ; "P-d" (benzoxazine ring equivalent of <NUM>/eq. ) and "F-a" (benzoxazine ring equivalent of <NUM>/eq. ), both being manufactured by Shikoku Chemicals Corp. ; and "HFB2006M" (benzoxazine ring equivalent of <NUM>/eq. ) manufactured by Showa Highpolymer Co.

Illustrative examples of the cyanate ester type resin include bifunctional cyanate resins such as bisphenol A dicyanate, polyphenol cyanate, oligo(<NUM>-methylene-<NUM>,<NUM>-phenylenecyanate), <NUM>,<NUM>'-methylenebis(<NUM>,<NUM>-dimethylphenylcyanate), <NUM>,<NUM>'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, <NUM>,<NUM>-bis(<NUM>-cyanate)phenylpropane, <NUM>,<NUM>-bis(<NUM>-cyanatephenylmethane), bis(<NUM>-cyanate-<NUM>,<NUM>-dimethylphenyl)methane, <NUM>,<NUM>-bis(<NUM>-cyanatephenyl-<NUM>-(methylethylidene) )benzene, bis(<NUM>-cyanatephenyl) thioether, and bis(<NUM>-cyanatephenyl) ether; polyfunctional cyanate resins derived from a phenol novolak, a cresol novolak, and the like; and a prepolymer in which these cyanate resins are partially made to triazine. Specific examples of the cyanate ester type resin include "PT30" and "PT60" (both are phenol novolak type polyfunctional cyanate ester resins); "ULL-<NUM>" (polyfunctional cyanate ester); "BA230" and "BA230S75" (prepolymers in which part or all of bisphenol A dicyanate is made to triazine so as to be a trimer), all of these being manufactured by Lonza Japan Ltd.

Specific examples of the carbodiimide type resin include Carbodilite (registered trade mark) V-<NUM> (carbodiimide equivalent of <NUM>/eq. ), V-<NUM> (carbodiimide equivalent of <NUM>/eq. ), V-<NUM> (carbodiimide equivalent of <NUM>/eq. ), and V-<NUM> (carbodiimide equivalent of <NUM>/eq. ) all being manufactured by Nisshinbo Chemical, Inc. ; and Stabaxol (registered trade mark) P (carbodiimide equivalent of <NUM>/eq. ) manufactured by Rhein Chemie GmbH.

The amine type resin can be the resin having one or more amino groups in one molecule thereof. Illustrative examples thereof include an aliphatic amine, a polyether amine, an alicyclic amine, and an aromatic amine. Among them, in view of expressing the intended effects of the present invention, an aromatic amine is preferable. The amine type resin is preferably a primary amine and a secondary amine, while a primary amine is more preferable. Specific examples of the amine curing agent include <NUM>,<NUM>'-methylene bis(<NUM>,<NUM>-dimethylaniline), diphenyl diaminosulfone, <NUM>,<NUM>'-diaminodiphenylmethane, <NUM>,<NUM>'-diaminodiphenyl sulfone, <NUM>,<NUM>'-diaminodiphenyl sulfone, m-phenylene diamine, m-xylylene diamine, diethyltoluene diamine, <NUM>,<NUM>'-diaminodiphenyl ether, <NUM>,<NUM>'-dimethyl-<NUM>,<NUM>'-diaminobiphenyl, <NUM>,<NUM>'-dimethyl-<NUM>,<NUM>'-diaminobiphenyl, <NUM>,<NUM>'-dihydroxybenzidine, <NUM>,<NUM>-bis(<NUM>-amino-<NUM>-hydroxyphenyl)propane, <NUM>,<NUM>-dimethyl-<NUM>,<NUM>-diethyl-<NUM>,<NUM>-diphenylmethane diamine, <NUM>,<NUM>-bis(<NUM>-aminophenyl)propane, <NUM>,<NUM>-bis(<NUM>-(<NUM>-aminophenoxy)phenyl)propane, <NUM>,<NUM>-bis(<NUM>-aminophenoxy)benzene, <NUM>,<NUM>-bis(<NUM>-aminophenoxy)benzene, <NUM>,<NUM>-bis(<NUM>-aminophenoxy)benzene, <NUM>,<NUM>'-bis(<NUM>-aminophenoxy)biphenyl, bis(<NUM>-(<NUM>-aminophenoxy)phenyl) sulfone, and bis(<NUM>-(<NUM>-aminophenoxy)phenyl) sulfone. Commercially available amine type resins may be used. Illustrative examples thereof include "KAYABOND C-<NUM>", "KAYABOND C-<NUM>", "KAYAHARD A-A", "KAYAHARD A-B", and "KAYAHARD A-S" all being manufactured by Nippon Kayaku Co. , as well as "Epicure W" manufactured by Mitsubishi Chemical Corp.

The acid anhydride type resin may be those having one or more acid anhydride groups in one molecule thereof. Specific examples of the acid anhydride type resin include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyl tetrahydrophthalic anhydride, methyl hexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyl tetrahydrophthalic anhydride, dodecenyl succinic anhydride, <NUM>-(<NUM>,<NUM>-dioxotetrahydro-<NUM>-furanyl)-<NUM>-methyl-<NUM>-cyclohexene-<NUM>, <NUM>-dicarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic dianhydride, biphenyl tetracarboxylic dianhydride, naphthalene tetracarboxylic dianhydride, oxydiphthalic dianhydride, <NUM>,<NUM>'-<NUM>,<NUM>'-diphenylsulfone tetracarboxylic dianhydride, <NUM>,<NUM>,3a,<NUM>,<NUM>,9b-hexahydro-<NUM>-(tetrahydro-<NUM>,<NUM>-dioxo-<NUM>-furanyl)-naphto[<NUM>,<NUM>-C]furan-<NUM>,<NUM>-dione, ethylene glycol bis(anhydrotrimellitate), and a polymer type acid anhydride such as a styrene-maleic acid resin, which is a copolymer of styrene and maleic acid.

When the epoxy resin and a curing agent are included in the (B) component, the ratio of the epoxy resin to all the curing agents, in terms of the ratio of [total number of the epoxy groups in the epoxy resin] to [total number of the reactive groups in the curing agent], is preferably in the range of <NUM>:<NUM> to <NUM>:<NUM>, and more preferably in the range of <NUM>:<NUM> to <NUM>:<NUM>, while still more preferably in the range of <NUM>:<NUM> to <NUM>:<NUM>. Note that, "the number of the epoxy groups in the epoxy resin" means the total value of the values obtained by dividing the mass of the non-volatile components of the epoxy resin that is present in the resin composition with the epoxy equivalent. "The number of the reactive groups in the curing agent" means the total value of the values obtained by dividing the mass of the non-volatile components of the curing agent that is present in the resin composition with the equivalent of the reactive group.

From a viewpoint to obtain the cured product having excellent mechanical and magnetic characteristics, the content of (B) the thermosetting resin is, on the basis of <NUM>% by mass as the non-volatile components in the resin composition, preferably <NUM>% or more by mass, and more preferably <NUM>% or more by mass, while still more preferably <NUM>% or more by mass. Although the upper limit thereof is not particularly restricted so far as the advantageous effects of the present invention can be expressed, the upper limit is preferably <NUM>% or less by mass, and more preferably <NUM>% or less by mass, while still more preferably <NUM>% or less by mass.

In (B) the thermosetting resin, the content of the solid thermosetting resin is, on the basis of <NUM>% by mass as (B) the thermosetting resin in the resin composition, preferably <NUM>% or less by mass, and more preferably <NUM>% or less by mass, while still more preferably <NUM>% or less by mass, <NUM>% or less by mass, or <NUM>% or less by mass, and preferably <NUM>% or more by mass, and more preferably <NUM>% or more by mass, while still more preferably <NUM>% or more by mass. "The solid thermosetting resin" means a thermosetting resin that is in a solid state in which the viscosity thereof at <NUM> is <NUM> Pa·s or more. When the content of the solid thermosetting resin is controlled within this range, the viscosity of the resin composition can be lowered.

The resin composition may further include (C) a dispersant as the arbitrary component.

Illustrative examples of (C) the dispersant include: phosphate ester type dispersants such as a polyoxyethylene alkyl ether phosphate; anion type dispersants such as sodium dodecylbenzene sulfonate, sodium laurate, and an ammonium polyoxyethylene alkyl ether sulfate; and nonionic dispersants such as an organosiloxane type dispersant, a polyoxyalkylene type dispersant, an acetylene glycol, a polyoxyethylene alkyl ether, a polyoxyethylene alkyl ester, a polyoxyethylene sorbitan fatty acid ester, a polyoxyethylene alkyl phenyl ether, a polyoxyethylene alkylamine, and a polyoxyethylene alkylamide. Among these, the nonionic dispersants are preferable. (C) The dispersant may be used singly, or as a mixture of two or more of those mentioned above.

As for the phosphate ester type dispersant, a commercially available dispersant may be used. Illustrative examples of the commercially available phosphate ester type dispersant include "RS-<NUM>", "RS-<NUM>", and "RS-<NUM>" of the "Phosphanol" series manufactured by Toho Chemical Industry Co.

As for the organosiloxane type dispersant, illustrative examples of this type that is commercially available include "BYK <NUM>" and "BYK <NUM>" manufactured by BYK Chemie GmbH.

As for the polyoxyalkylene type dispersant, illustrative examples of this type that is commercially available include "AKM-<NUM>", "AFB-<NUM>", "SC-<NUM>", "SC-1015F", "SC-0708A", and "HKM-50A" of the "Mariarim" series manufactured by NOF Corp. The polyoxyalkylene type dispersant is the general term of the polyoxyethylene alkyl ether, the polyoxyethylene alkyl ester, the polyoxyethylene sorbitan fatty acid ester, the polyoxyethylene alkyl phenyl ether, the polyoxyethylene alkylamine, the polyoxyethylene alkylamide, and the like.

As for the acetylene glycol, illustrative examples of this type that is commercially available include "<NUM>", "<NUM>", "<NUM>", "<NUM>", "<NUM>", and "Olefin Y" of the "Surfynol" series manufactured by Air Products and Chemicals Inc.

When the resin composition includes (C) the dispersant, from a viewpoint to clearly express the advantageous effects of the present invention, the content of (C) the dispersant is, on the basis of <NUM>% by mass as the non-volatile components in the resin composition, preferably <NUM>% or more by mass, and more preferably <NUM>% or more by mass, while still more preferably <NUM>% or more by mass. The upper limit thereof is preferably <NUM>% or less by mass, and more preferably <NUM>% or less by mass, while still more preferably <NUM>% or less by mass.

The resin composition can further include, as an arbitrary component, (D) a curing accelerator. Illustrative examples of (D) the curing accelerator include a phosphorous type curing accelerator, an amine type curing accelerator, an imidazole type curing accelerator, a guanidine type curing accelerator, and a metal type curing accelerator. Among these, the phosphorous type curing accelerator, the amine type curing accelerator, the imidazole type curing accelerator, and the metal type curing accelerator are preferable. The amine type curing accelerator, the imidazole type curing accelerator, and the metal type curing accelerator are more preferable, while the imidazole type curing accelerator is still more preferable. (D) The curing accelerator may be used singly, or as a combination of two or more of those mentioned above.

Illustrative examples of the phosphorous type curing accelerator include triphenyl phosphine, a phosphonium borate compound, tetraphenyl phosphonium tetraphenyl borate, n-butyl phosphonium tetraphenyl borate, a tetrabutyl phosphonium decanoate salt, (<NUM>-methylphenyl) triphenyl phosphonium thiocyanate, tetraphenyl phosphonium thiocyanate, and butyl triphenyl phosphonium thiocyanate. Among these, triphenyl phosphine and a tetrabutyl phosphonium decanoate salt are preferable.

Illustrative examples of the amine type curing accelerator include: trialkyl amines such as triethyl amine and tributyl amine; and <NUM>-dimethylaminopyridine, benzyl dimethyl amine, <NUM>,<NUM>,<NUM>-tris(dimethylaminomethyl)phenol, and <NUM>,<NUM>-diazabicyclo(<NUM>,<NUM>,<NUM>)-undecene. Among these, <NUM>-dimethylaminopyridine and <NUM>,<NUM>-diazabicyclo(<NUM>,<NUM>,<NUM>)-undecene are preferable.

Illustrative examples of the imidazole type curing accelerator include imidazole compounds such as <NUM>-methyl imidazole, <NUM>-undecyl imidazole, <NUM>-heptadecyl imidazole, <NUM>,<NUM>-dimethyl imidazole, <NUM>-ethyl-<NUM>-methyl imidazole, <NUM>,<NUM>-dimethyl imidazole, <NUM>-ethyl-<NUM>-methyl imidazole, <NUM>-phenyl imidazole, <NUM>-phenyl-<NUM>-methyl imidazole, <NUM>-bezyl-<NUM>-methyl imidazole, <NUM>-benzyl-<NUM>-phenyl imidazole, <NUM>-cyanoethyl-<NUM>-methyl imidazole, <NUM>-cyanoethyl-<NUM>-undecyl imidazole, <NUM>-cyanoethyl-<NUM>-ethyl-<NUM>-methyl imidazole, <NUM>-cyanoethyl-<NUM>-phenyl imidazole, <NUM>-cyanoethyl-<NUM>-undecyl imidazolium trimellitate, <NUM>-cyanoethyl-<NUM>-phenyl imidazolium trimellitate, <NUM>,<NUM>-diamino-<NUM>-[<NUM>'-methylimidazolyl-(<NUM>')]-ethyl-s-triazine, <NUM>,<NUM>-diamino-<NUM>-[<NUM>'-undecylimidazolyl-(<NUM>')]-ethyl-s-triazine, <NUM>,<NUM>-diamino-<NUM>-[<NUM>'-ethyl-<NUM>'-metylimidazolyl-(<NUM>')]-ethyl-s-tr iazine, <NUM>,<NUM>-diamino-<NUM>-[<NUM>'-methylimidazolyl-(<NUM>')]-ethyl-s-triazine isocyanuric acid adduct, <NUM>-phenylimidazole isocyanuric acid adduct, <NUM>-phenyl-<NUM>,<NUM>-dihydroxymethyl imidazole, <NUM>-phenyl-<NUM>-methyl-<NUM>-hydroxymethyl imidazole, <NUM>,<NUM>-dihydro-<NUM>-pyrro[<NUM>,<NUM>-a]benzimidazole, <NUM>-dodecyl-<NUM>-methyl-<NUM>-benzyl imidazolium chloride, <NUM>-methyl imidazoline, and <NUM>-phenyl imidazoline; and adducts of these imidazole compounds with an epoxy resin. Among these, <NUM>-ethyl-<NUM>-methyl imidazole and <NUM>-benzyl-<NUM>-phenyl imidazole are preferable.

As for the imidazole type curing accelerator, commercially available products thereof may be used. Illustrative examples thereof include "2P4MZ" manufactured by Shikoku Chemicals Corp. and "P200-H50" manufactured by Mitsubishi Chemical Corp.

Illustrative examples of the guanidine type curing accelerator include dicyan diamide, <NUM>-methyl guanidine, <NUM>-ethyl guanidine, <NUM>-cyclohexyl guanidine, <NUM>-phenyl guanidine, <NUM>-(o-tolyl) guanidine, dimethyl guanidine, diphenyl guanidine, trimethyl guanidine, tetramethyl guanidine, pentamethyl guanidine, <NUM>,<NUM>,<NUM>-triazabicyclo[<NUM>. <NUM>]deca-<NUM>-ene, <NUM>-methyl-<NUM>,<NUM>,<NUM>-triazabicyclo[<NUM>. <NUM>]deca-<NUM>-ene, <NUM>-methyl biguanide, <NUM>-ethyl biguanide, <NUM>-n-butyl biguanide, <NUM>-n-octadecyl biguanide, <NUM>,<NUM>-dimethyl biguanide, <NUM>,<NUM>-diethyl biguanide, <NUM>-cyclohexyl biguanide, <NUM>-allyl biguanide, <NUM>-phenyl biguanide, and <NUM>-(o-tolyl) biguanide. Among these, dicyan diamide and <NUM>,<NUM>,<NUM>-triazabicyclo[<NUM>. <NUM>]deca-<NUM>-ene are preferable.

Illustrative examples of the metal type curing accelerator include organometallic complexes or organometallic salts of metals such as cobalt, copper, zinc, iron, nickel, manganese, and tin. Specific examples of the organometallic complex include organic cobalt complexes such as cobalt (II) acetylacetonate and cobalt (III) acetylacetonate; organic copper complexes such as copper (II) acetylacetonate; organic zinc complexes such as zinc (II) acetylacetonate; organic iron complexes such as iron (III) acetylacetonate; organic nickel complexes such as nickel (II) acetylacetonate; and organic manganese complexes such as manganese (II) acetylacetonate. Illustrative examples of the organometallic salt include zinc octylate, tin octylate, zinc naphthenate, cobalt naphthenate, tin stearate, and zinc stearate.

When the resin composition includes (D) the curing accelerator, from a viewpoint to obtain the cured product having further enhanced mechanical characteristics, the content of (D) the curing accelerator is, on the basis of <NUM>% by mass as the non-volatile components in the resin composition, preferably <NUM>% or more by mass, and more preferably <NUM>% or more by mass, while still more preferably <NUM>% or more by mass, and preferably <NUM>% or less by mass, and more preferably <NUM>% or less by mass, while still more preferably <NUM>% or less by mass.

The resin composition of the present invention may further include an arbitrary additive as necessary. Illustrative examples of the other additive like this include thermoplastic resins such as a phenoxy resin, a flame retardant, organometallic compounds such as an organic copper compound, an organic zinc compound, and an organic cobalt compound, as well as resin additives such as a thickener, an antifoaming agent, a leveling agent, an adhesion assisting agent, and a colorant.

The resin composition may be produced, for example, with a method in which blended components are agitated by using an agitator such as three rollers and a rotation mixer.

The resin composition has the characteristic of a low viscosity. Accordingly, the resin composition can have a characteristic that the resin composition is in a paste-like form (paste-like resin composition). Thus, the resin composition can be suitably used as a filling material of a through hole. Specifically, the viscosity of the resin composition at <NUM> is preferably <NUM> Pa·s or less, and more preferably <NUM> Pa·s or less, while still more preferably <NUM> Pa·s or less. Although there is no particular restriction with regard to the lower limit thereof, the lower limit is preferably <NUM> Pa·s or more, while more preferably <NUM> Pa·s or more. The viscosity may be measured by using an E-type viscometer while keeping the temperature of the resin composition at <NUM>±<NUM>. Specifically, the viscosity may be measured by the method described in Examples to be described later.

Usually, the resin composition can be in a paste-like form, which is the characteristic that the resin composition has a low viscosity even without including a solvent. Therefore, the content of the solvent in the resin composition is preferably <NUM>% or less by mass, more preferably <NUM>% or less by mass, and still more preferably <NUM>% or less by mass, while especially preferably <NUM>% or less by mass, relative to the total mass of the resin composition. Although the lower limit thereof is not particularly restricted, the lower limit is preferably <NUM>% or more by mass, or preferably the solvent is not included therein. When a liquid thermosetting resin or the like is used, usually, the viscosity of the resin composition can be lowered even when the solvent is not included therein. When the amount of the solvent in the resin composition is small, not only generation of a void due to evaporation of the solvent can be suppressed, but also application to a vacuum printing becomes possible.

The cured product obtained by thermally curing the resin composition at <NUM> for <NUM> minutes has a characteristic that the relative permeability thereof at the frequency of <NUM> is high. The relative permeability at the frequency of <NUM> is <NUM> or more, and preferably <NUM> or more, while more preferably <NUM> or more. Although The upper limit thereof is not particularly restricted, it can be <NUM> or less, or the like. The relative permeability may be measured by the method described in Examples to be described later.

It is preferable that the cured product obtained by thermally curing the resin composition at <NUM> for <NUM> minutes be high in the relative permeability at the frequency of <NUM>. The relative permeability at the frequency of <NUM> is preferably <NUM> or more, and more preferably <NUM> or more, while still more preferably <NUM> or more. Although the upper limit thereof is not particularly restricted, it can be <NUM> or less, or the like. The relative permeability may be measured by the method described in Examples to be described later.

The cured product obtained by thermally curing the resin composition at <NUM> for <NUM> minutes has a characteristic that the magnetic loss thereof at the frequency of <NUM> is low. The magnetic loss at the frequency of <NUM> is preferably <NUM> or less, and more preferably <NUM> or less, while still more preferably <NUM> or less. Although the upper limit thereof is not particularly restricted, it can be <NUM> or more, or the like. The magnetic loss may be measured by the method described in Examples to be described later.

It is preferable that the cured product obtained by thermally curing the resin composition at <NUM> for <NUM> minutes be low in the magnetic loss at the frequency of <NUM>. The magnetic loss at the frequency of <NUM> is preferably <NUM> or less, and more preferably <NUM> or less, while still more preferably <NUM> or less. Although the lower limit thereof is not particularly restricted, it can be <NUM> or more, or the like. The magnetic loss may be measured by the method described in Examples to be described later.

The cured product obtained by thermally curing the resin composition at <NUM> for <NUM> minutes has a characteristic that the maximum point strength thereof is high. The maximum point strength at <NUM> is <NUM> MPa or more, and preferably <NUM> MPa or more, while more preferably <NUM> MPa or more. Although the upper limit thereof is not particularly restricted, it can be <NUM> MPa or less, or the like. The maximum point strength may be measured by the method described in Examples to be described later.

It is preferable that the cured product obtained by thermally curing the resin composition at <NUM> for <NUM> minutes be high in elongation thereof. The elongation at <NUM> is preferably <NUM>% or more, and more preferably <NUM>% or more, while still more preferably <NUM>% or more. Although the upper limit thereof is not particularly restricted, it can be <NUM>% or less, or the like. The elongation may be measured by the method described in Examples to be described later.

The magnetic sheet includes a support and a resin composition layer formed on the support, the resin composition layer being formed of the resin composition of the present invention.

In view of thinning, thickness of the resin composition layer is preferably <NUM> or less, and more preferably <NUM> or less. Although the lower limit of the thickness of the resin composition layer is not particularly restricted, it can be usually <NUM> or more, <NUM> or more, or the like.

Illustrative examples of the support include a film formed of a plastic material, metal foil, and a releasing paper. Among them, a film formed of a plastic material and metal foil are preferable.

When the film formed of a plastic material is used as the support, illustrative examples of the plastic material include polyesters such as polyethylene terephthalate (hereinafter, sometimes this is simply called "PET") and polyethylene naphthalate (hereinafter, sometimes this is simply called "PEN"); polycarbonate (hereinafter, sometimes this is simply called "PC") ; acrylic polymers such as polymethyl methacrylate (PMMA); a cyclic polyolefin; triacetyl cellulose (TAC) ; polyether sulfide (PES); polyether ketone; and polyimide. Among them, polyethylene terephthalate and polyethylene naphthalate are preferable, while cheap polyethylene terephthalate is especially preferable.

When the metal foil is used as the support, illustrative examples of the metal foil include copper foil and aluminum foil, while copper foil is preferable. As to the copper foil, the foil formed of a copper single metal or an alloy of copper with other metal (for example, tin, chromium, silver, magnesium, nickel, zirconium, silicon, and titanium) may be used.

The support may be subjected to a treatment such as a mat treatment, or a corona treatment on the surface to be bonded with the resin composition layer.

As for the support, a releasing layer-attached support having a releasing layer on the surface to be bonded to the resin composition layer may be used. The releasing agent used in the releasing layer of the releasing layer-attached support may be one or more releasing agents selected from the group consisting of, for example, an alkyd resin, a polyolefin resin, a urethane resin, and a silicone resin. Commercially available products may be used as the releasing layer-attached support, such as for example, a PET film having a releasing layer formed of the alkyd resin type releasing agent as a main ingredient. Illustrative examples thereof include "PET501010", "SK-<NUM>", "AL-<NUM>", and "AL-<NUM>" all being manufactured by Lintech Corp. ; "Lumirror T60" manufactured by Toray Industries; "Purex" manufactured by Teijin Ltd. ; and "Unipeel" manufactured by Unitika Ltd.

Although thickness of the support is not particularly restricted, this is preferably in the range of <NUM> to <NUM>, while more preferably in the range of <NUM> to <NUM>. When the releasing layer-attached support is used, total thickness of the releasing layer-attached support is preferably within this range.

In the magnet sheet, a protection film similar to the support may be further laminated on the surface of the resin composition layer not bonded to the support (namely, on the surface opposite to the support). Although thickness of the protection film is not particularly restricted, for example, this is in the range of <NUM> to <NUM>. By laminating the protection film, the surface of the resin composition layer may be prevented from attachment of dirt and the like as well as from a scar. The magnetic sheet can be rolled up so as to be stored. When the magnetic sheet has the protection film, the magnetic sheet can be used by removing the protection film.

The circuit substrate according to a first embodiment includes a substrate having a through hole and a cured product of the resin composition of the present invention that is filled in the through hole. The circuit substrate according to a second embodiment includes a magnetic layer of the magnetic sheet formed of a cured product of the resin composition layer. Hereinafter, the first embodiment and the second embodiment with regard to the production method of the circuit substrate will be explained. Note that the production method of the circuit substrate relating to the present invention is not limited to the first embodiment or the second embodiment exemplified below.

The circuit substrate according to the first embodiment is produced, for example, by the production method including following processes (<NUM>) to (<NUM>). In the first embodiment, it is preferable to form the magnetic layer by using the resin composition, and it is more preferable to form the magnetic layer by using the resin composition in a paste-like form.

The production method of the circuit substrate according to the present invention may be carried out in the order of the processes (<NUM>) to (<NUM>), or the process (<NUM>) may be carried out after the process (<NUM>).

Hereinafter, the processes (<NUM>) to (<NUM>) upon producing the circuit substrate will be explained in detail.

Upon carrying out the process (<NUM>), the process may include a preparation process of the resin composition. The resin composition has already been explained above.

Upon carrying out the process (<NUM>), as illustrated in <FIG> as one example, the process may include a process to prepare a core substrate <NUM> having a supporting substrate <NUM>, and a first metal layer <NUM> and a second metal layer <NUM> that are formed of a metal such as copper foil on both surfaces of the supporting substrate <NUM>. Illustrative examples of the material of the supporting substrate <NUM> include an insulating substrate such as a glass epoxy substrate, a metal substrate, a polyester substrate, a polyimide substrate, a BT resin substrate, and a thermosetting type polyphenylene ether substrate. Illustrative examples of the material of the first and the second metal layers include carrier-attached copper foil and a material of the conductive layer to be described later.

In addition, as illustrated in <FIG> as one example, the process may include a process to form a through hole <NUM> in the core substrate <NUM>. The through hole <NUM> may be formed, for example, by a drill, a laser irradiation, or a plasma irradiation. Specifically, the through hole <NUM> may be formed by forming a penetrating hole in the core substrate <NUM> by using a drill or the like.

Formation of the through hole <NUM> may be carried out by using a drilling machine that is commercially available. Illustrative examples of the commercially available drilling machine include "ND-1S211" manufactured by Hitachi Via Mechanics, Ltd.

After the through hole <NUM> is formed in the core substrate <NUM>, as illustrated in <FIG> as one example, the process may include a process to carry out a roughening treatment to the core substrate <NUM> followed by formation of a plated layer <NUM> in the through hole <NUM>, on the surface of the first metal layer <NUM>, and on the surface of the second metal layer <NUM>.

The roughening treatment may be carried out with any of a dry roughening treatment and a wet roughening treatment. Illustrative examples of the dry roughening treatment include a plasma treatment. Illustrative examples of the wet roughening treatment include a method in which a swelling treatment by a swelling liquid, a roughening treatment by an oxidant, and a neutralizing treatment by a neutralizing solution are carried out in this order.

The plated layer <NUM> is formed by a plating method. The procedure to form the plated layer <NUM> by the plating method is the same as that in formation of a conductive layer at the process (<NUM>) to be described later.

After the core substrate <NUM> having the plated layer <NUM> formed in the through hole <NUM> is prepared, as illustrated in <FIG> as one example, a resin composition 30a is filled into the through hole <NUM>. The filling may be carried out, for example, by a printing method. Illustrative examples of the printing method include a method in which the resin composition 30a is printed to the through hole <NUM> via a squeegee, a method in which the resin composition 30a is printed via a cartridge, a method in which the resin composition 30a is printed by a mask printing, a roll coating method, and an inkjet method.

After the resin composition 30a is filled into the through hole <NUM>, at the process (<NUM>), the resin composition 30a is thermally cured to form a cured product layer (magnetic layer) <NUM> in the through hole <NUM>, as illustrated in <FIG> as one example. The thermal curing condition of the resin composition 30a is different depending on the composition and kind of the resin composition 30a. The curing temperature is preferably <NUM> or higher, and more preferably <NUM> or higher, while still more preferably <NUM> or higher, and preferably <NUM> or lower, and more preferably <NUM> or lower, while still more preferably <NUM> or lower. The curing time of the resin composition 30a is preferably <NUM> minutes or longer, and more preferably <NUM> minutes or longer, while still more preferably <NUM> minutes or longer, and preferably <NUM> minutes or shorter, and more preferably <NUM> minutes or shorter, while still more preferably <NUM> minutes or shorter.

The curing degree of the magnetic layer <NUM> at the process (<NUM>) is preferably <NUM>% or more, and more preferably <NUM>% or more, while still more preferably <NUM>% or more. The curing degree may be measured, for example, by using a differential scanning calorimeter.

Before the resin composition 30a is thermally cured, the resin composition 30a may be subjected to a preliminary heat treatment by heating at the temperature lower than the curing temperature. For example, prior to the thermal curing of the resin composition 30a, the resin composition 30a may be preliminary heated usually in the temperature range of <NUM> or higher to lower than <NUM> (preferably in the range of <NUM> or higher and <NUM> or lower, while more preferably in the range of <NUM> or higher and <NUM> or lower), and for the period of usually <NUM> minutes or longer (preferably in the range of <NUM> to <NUM> minutes, while more preferably in the range of <NUM> to <NUM> minutes).

At the process (<NUM>), as illustrated in <FIG> as one example, an excess amount of the magnetic layer <NUM> that is projected from or attached to the core substrate <NUM> is removed by polishing to flatten the surface thereof. The polishing method that can polish the excess amount of the magnetic layer <NUM> that is projected from or attached to the core substrate <NUM> may be used. Illustrative examples of the polishing method like this include a buff polishing method and a belt polishing method. Illustrative examples of the buff polishing equipment that is commercially available include "NT-700IM" manufactured by Ishii hyoki Co.

From a viewpoint to enhance the plating adhesion, the arithmetic average roughness (Ra) of the polished surface of the magnetic layer is preferably <NUM> or more, and more preferably <NUM> or more, while still more preferably <NUM> or more. The upper limit thereof is preferably <NUM>,<NUM> or less, and more preferably <NUM> or less, while still more preferably <NUM> or less. The surface roughness (Ra) may be measured, for example, by using a non-contact type surface roughness meter.

When the process (<NUM>) is carried out after the process (<NUM>), among other purposes, with a purpose to further increase the curing degree of the magnetic layer, a heat treatment may be carried out, as needed, after the process (<NUM>) and before the process (<NUM>). The temperature at the heating process may be similar to the curing temperature described before. Therefore, the temperature is preferably <NUM> or higher, and more preferably <NUM> or higher, while still more preferably <NUM> or higher, and preferably <NUM> or lower, and more preferably <NUM> or lower, while still more preferably <NUM> or lower. The time for the heat treatment is preferably <NUM> minutes or longer, and more preferably <NUM> minutes or longer, while still more preferably <NUM> minutes or longer, and preferably <NUM> minutes or shorter, and more preferably <NUM> minutes or shorter, while still more preferably <NUM> minutes or shorter.

When the process (<NUM>) is carried out before the process (<NUM>), a preliminary heat treatment may be carried out before the process (<NUM>) by heating at the temperature lower than the curing temperature of the resin composition. The temperature at the preliminary heat treatment is preferably <NUM> or higher, and more preferably <NUM> or higher, while still more preferably <NUM> or higher, and preferably <NUM> or lower, and more preferably <NUM> or lower, while still more preferably <NUM> or lower. The time for the heat treatment is preferably <NUM> minutes or longer, and more preferably <NUM> minutes or longer, while still more preferably <NUM> minutes or longer, and preferably <NUM> minutes or shorter, and more preferably <NUM> minutes or shorter, while still more preferably <NUM> minutes or shorter.

At the process (<NUM>), as illustrated in <FIG> as one example, a conductive layer <NUM> is formed on the polished surface of the magnetic layer <NUM> and on the plated layer <NUM>. Then, after the conductive layer <NUM> is formed, as illustrated in <FIG> as one example, by carrying out a treatment such as etching, a patterned conductive layer <NUM> may be formed by removing part of the conductive layer <NUM>, the first metal layer <NUM>, the second metal layer <NUM>, and the plated layer <NUM>. In the example illustrated here, because the cured product has already been polished at the process (<NUM>), a process of a roughening treatment of the magnetic layer is not included. In <FIG>, the conductive layer <NUM> is formed on both surfaces of the core substrate <NUM>, but the conductive layer <NUM> may be formed on only one surface of the core substrate <NUM>.

Illustrative examples of the method for forming the conductive layer include a plating method, a sputtering method, and a vacuum evaporation method. Among them, the plating method is preferable. In the preferable embodiment, the surface of the cured product is plated with an appropriate method such as a semi-additive method or a full additive method to form the patterned conductive layer having an intended wiring pattern. Illustrative examples of the material of the conductive layer include: a single metal such as gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium; and metal alloys of two or more metals selected from the group consisting of gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium. Among these, from viewpoints of general applicability, cost, easiness in patterning, and the like, preferable to be used are chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, and copper, as well as a nickel-chromium alloy, a copper-nickel alloy, and a copper-titanium alloy. More preferable to be used are chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, and copper, as well as a nickel-chromium alloy. Copper is still more preferable.

Here, an example of the embodiment to form the patterned conductive layer on the polished surface of the cured product will be explained in detail. A plated seed layer is formed on the polished surface of the cured product by electroless plating. Next, onto the plated seed layer thus formed, an electroplated layer is formed by electroplating; and as needed, an unnecessary plated seed layer is removed by a treatment such as etching, whereby the conductive layer having an intended wiring pattern can be formed. After the conductive layer is formed, among other purposes, with a purpose to enhance the peel strength of the conductive layer, an annealing treatment may be carried out, as necessary. The annealing treatment may be carried out, for example, by heating the circuit substrate in the temperature range of <NUM> to <NUM> for the period of <NUM> to <NUM> minutes.

From a viewpoint of thinning, the thickness of the patterned conductive layer is preferably <NUM> or less, more preferably <NUM> or less, still more preferably <NUM> or less, and far still more preferably <NUM> or less, while especially preferably <NUM> or less, <NUM> or less, <NUM> or less, or <NUM> or less. The lower limit thereof is preferably <NUM> or more, and more preferably <NUM> or more, while still more preferably <NUM> or more.

The circuit substrate according to the second embodiment includes a magnetic layer formed of a cured product of the resin composition. In the second embodiment, it is preferable to form the magnetic layer by using a magnetic sheet. Hereinafter, the second embodiment with regard to the production method of a product substrate will be explained. Explanation overlapped with the first embodiment will be omitted as appropriate.

The circuit substrate of the second embodiment is produced, for example, by the production method including the following processes (A) to (D):.

Hereinafter, upon producing the circuit substrate, the processes (A) to (D) will be explained in detail.

The process (A) is the process at which a magnetic sheet is laminated to an inner substrate such that a resin composition layer may be bonded to the inner substrate to form a magnetic layer. In one embodiment of the process (A), the magnetic sheet is laminated to the inner substrate such that the resin composition layer may be bonded to the inner substrate, and then, the resin composition layer is thermally cured to form the magnetic layer.

At the process (A), as illustrated in <FIG> as one example, a magnetic sheet <NUM> having a support <NUM> and a resin composition layer 320a formed on the support <NUM> is laminated to an inner substrate <NUM> such that the resin composition layer 320a may be bonded to the inner substrate <NUM>.

The inner substrate <NUM> is an insulating substrate. Illustrative examples of the material of the inner substrate <NUM> include insulating substrates such as a glass epoxy substrate, a metal substrate, a polyester substrate, a polyimide substrate, a BT resin substrate, and a thermosetting type polyphenylene ether substrate. The inner substrate <NUM> may be an inner layer circuit substrate having a wiring or the like incorporated in the thickness thereof.

As illustrated in <FIG> as one example, the inner substrate <NUM> has a first conductive layer <NUM> formed on a first main surface 200a and an outside terminal <NUM> formed on a second main surface 200b. The first conductive layer <NUM> may include a plurality of wirings. In the example illustrated by the drawing, only a wiring that constitutes a coil-like conductive structural body <NUM> of an inductor element is illustrated. The outside terminal <NUM> is a terminal to electrically connect to an outside device or the like that is not illustrated in the drawing. The outside terminal <NUM> may be constructed as part of a conductive layer formed on the second main surface 200b.

Conductive materials that are capable of constructing the first conductive layer <NUM> and the outside terminal <NUM> are the same as the materials of the conductive layer that have been explained in the paragraphs of "Process (<NUM>)" of the first embodiment.

The first conductive layer <NUM> and the outside terminal <NUM> may be any of a monolayer structure and a multilayer structure in which two or more layers formed of single metal layers formed of different metals or of alloy layers are laminated. Thicknesses of the first conductive layer <NUM> and of the outside terminal <NUM> are the same as those of a second conductive layer <NUM> to be described later.

The line (L)/space (S) ratios of the first conductive layer <NUM> and of the outside terminal <NUM> are not particularly restricted. From a viewpoint to reduce irregularity of the surface thereby obtaining the magnetic layer that is excellent in the smoothness, the ratio is usually <NUM>/<NUM> or less, preferably <NUM>/<NUM> or less, more preferably <NUM>/<NUM> or less, and still more preferably <NUM>/<NUM> or less, while far still more preferably <NUM>/<NUM> or less. Although the lower limit of the line/space ratio is not particularly restricted, from a viewpoint to enhance an embedding property of the resin composition layer into the space, the ratio is preferably <NUM>/<NUM> or more.

The inner substrate <NUM> may have a plurality of through holes <NUM> such that these may penetrate the inner substrate <NUM> from the first main surface 200a to the second main surface 200b. In the through hole <NUM>, an inside-the-through-hole wiring 220a is formed. The inside-the-through-hole wiring 220a electrically connects the first conductive layer <NUM> with the outside terminal <NUM>.

Bonding of the resin composition layer 320a to the inner layer substrate <NUM> may be carried out, for example, by hot-press bonding of the magnet sheet <NUM> to the inner layer substrate <NUM> from the side of the support <NUM>. Illustrative examples of the component for hot-press bonding of the magnetic sheet <NUM> to the inner layer substrate <NUM> (hereinafter, this component is also called "hot-pressing component") include a heated metal plate (stainless steel (SUS) mirror plate or the like) and a heated metal roll (SUS roll). At this time, it is preferable that the hot-pressing component be not pressed directly to the magnetic sheet <NUM> but pressed via a sheet or the like formed of an elastic material such as a heat-resistant rubber so that the magnetic sheet <NUM> may well follow the surface irregularity of the inner layer substrate <NUM>.

The temperature at the time of the hot-press bonding is preferably in the range of <NUM> to <NUM>, and more preferably in the range of <NUM> to <NUM>, while still more preferably in the range of <NUM> to <NUM>. The pressure at the time of the hot-press bonding is preferably in the range of <NUM> to <NUM> MPa, while more preferably in the range of <NUM> to <NUM> MPa. The period at the time of the hot-press bonding is preferably in the range of <NUM> to <NUM> seconds, while more preferably in the range of <NUM> to <NUM> seconds. The bonding of the magnetic sheet to the inner substrate is carried out preferably under an evacuated condition with the pressure of <NUM> hPa or less.

Bonding of the resin composition layer 320a of the magnetic sheet <NUM> to the inner layer substrate <NUM> may be carried out by using a commercially available vacuum laminator. Illustrative examples of the commercially available vacuum laminator include a vacuum and pressure laminator manufactured by Meiki Co. and a vacuum applicator manufactured by Nikko-Materials Co.

After bonding of the resin sheet <NUM> to the inner layer substrate <NUM>, under a normal pressure (under an atmospheric pressure), for example, the laminated magnetic sheet <NUM> may be flattened by pressing the hot-pressing component from the side of the support thereof. The pressing conditions of the flattening process can be the same as the hot-press bonding conditions in the before-mentioned lamination. The flattening process may be carried out by using a commercially available laminator. Note that the lamination and the flattening processes may be carried out continuously by using the commercially available vacuum laminator described above.

After the magnetic sheet is laminated to the inner substrate, the resin composition layer is thermally cured to form a magnetic layer. As illustrated in <FIG> as one example, the resin composition layer 320a that is bonded to the inner substrate <NUM> is thermally cured to form a first magnetic layer <NUM>.

Conditions of the thermal curing of the resin composition layer 320a are different depending on the composition and kind of the resin composition. The curing temperature is preferably <NUM> or higher, and more preferably <NUM> or higher, while still more preferably <NUM> or higher, and preferably <NUM> or lower, and more preferably <NUM> or lower, while still more preferably <NUM> or lower. The curing period of the resin composition layer 320a is preferably <NUM> minutes or longer, and more preferably <NUM> minutes or longer, while still more preferably <NUM> minutes or longer, and preferably <NUM> minutes or shorter, and more preferably <NUM> minutes or shorter, while still more preferably <NUM> minutes or shorter.

The support <NUM> may be removed between after thermal curing at the (A) process and the (B) process, or after the (B) process.

At the (B) process, as illustrated in <FIG> as one example, a via hole <NUM> is formed by carrying out the hole-making process in the first magnetic layer <NUM>. The via hole <NUM> will be a channel to electrically connect the first magnetic layer <NUM> with the second conductive layer <NUM> to be described later. Formation of the via hole <NUM> may be carried out by using a drill, a laser, a plasma, or the like in accordance with composition and the like of the resin composition used to form the magnetic layer. The size and shape of the hole may be arbitrarily determined in accordance with a design of the printed wiring board.

At the (C) process, the surface of the magnetic layer formed with the via hole is polished. Polishing at the (C) process may be carried out with the same polishing method as the method already explained in the paragraphs of "Process (<NUM>)" in the first embodiment.

At the (D) process, as illustrated in <FIG> as one example, the second conductive layer <NUM> is formed on the first magnetic layer <NUM>.

The conductive materials that are capable of constituting the second conductive layer <NUM> are the same as those of the conductive layer explained in the paragraphs of "Process (<NUM>)" in the first embodiment.

From a viewpoint of thinning, the thickness of the second conductive layer <NUM> is preferably <NUM> or less, more preferably <NUM> or less, still more preferably <NUM> or less, and far still more preferably <NUM> or less, while especially preferably <NUM> or less, <NUM> or less, <NUM> or less, or <NUM> or less. The lower limit thereof is preferably <NUM> or more, and more preferably <NUM> or more, while still more preferably <NUM> or more.

The second conductive layer <NUM> may be formed by plating. For example, the second conductive layer <NUM> is preferably formed by a wet plating method such as a semi-additive method including an electroless plating process, a mask patterning process, an electroplating process, and a flash etching process, as well as a full additive method. When the second conductive layer <NUM> is formed by the wet plating method, the second conductive layer <NUM> having an intended wiring pattern can be formed. Note that, at this process, an inside-the-via-hole wiring 360a is concurrently formed in the via hole <NUM>.

The first conductive layer <NUM> and the second conductive layer <NUM> may be formed, for example, spirally, as illustrated in <FIG> to be described later as one example. In one example, one end in the center side of the spiral wiring of the second conductive layer <NUM> is electrically connected through the inside-the-via-hole wiring 360a to one end in the center side of the spiral wiring of the first conductive layer <NUM>. Other end in the circumferential side of the spiral wiring of the second conductive layer <NUM> is electrically connected through the inside-the-via-hole wiring 360a to a land 420a of the first conductive layer <NUM>. Therefore, the other end in the circumferential side of the spiral wiring of the second conductive layer <NUM> is electrically connected to the outside terminal <NUM> through the inside-the-via-hole wiring 360a, the land 420a, and the inside-the-through-hole wiring 220a.

The coil-like conductive structural body <NUM> is composed of the spiral wiring that is part of the first conductive layer <NUM>, the spiral wiring that is part of the second conductive layer <NUM>, and the inside-the-via-hole wiring 360a that electrically connects between the spiral wiring of the first conductive layer <NUM> and the spiral wiring of the second conductive layer <NUM>.

After the (D) process, a process to further form a magnetic layer on the conductive layer may be carried out. Specifically, as illustrated in <FIG> as one example, a second magnetic layer <NUM> is formed on the first magnetic layer <NUM> that has the second conductive layer <NUM> and the inside-the-via-hole wiring 360a formed therein. The second magnetic layer may be formed with the same process as the process that has already been explained.

The inductor substrate includes the circuit substrate of the present invention. When the inductor substrate includes the circuit substrate obtained by the production method of the circuit substrate according to the first embodiment, the inductor substrate has an inductor pattern that is formed by a conductor at least in part around the cured product of the resin composition. The inductor substrate like this may be, for example, the one that is described in <CIT>.

When the inductor substrate includes the circuit substrate obtained by the production method of the circuit substrate according to the second embodiment, the inductor substrate has a magnetic layer and a conductive structural body having at least part thereof been embedded into the magnetic layer. The inductor substrate includes this conductive structural body and an inductor element that is extendedly present in a thickness direction of the magnetic layer and is composed of part of the magnetic layer surrounded with the conductive structural body. Note that, <FIG> is a schematic plane view from one direction in a thickness direction of the inductor substrate, which includes the inductor element therein. <FIG> is a schematic plane view illustrating a cut end face of the inductor substrate that is cut at the place indicated by the II-II one dot chain line illustrated in <FIG>. <FIG> is a schematic plane view to explain a composition of the first conductive layer in the inductor substrate.

As illustrated in <FIG> as one example, a inductor substrate <NUM> has a plurality of the magnetic layers (the first magnetic layer <NUM> and the second magnetic layer <NUM>) and a plurality of the conductive layers (the first conductive layer <NUM> and the second conductive layer <NUM>). Namely, this is a build-up wiring board having a build-up magnetic layer and a build-up conductive layer. Also, the inductor substrate <NUM> has an inner substrate <NUM>.

From <FIG>, the first magnetic layer <NUM> and the second magnetic layer <NUM> constitute a magnetic member <NUM>, which can be regarded as an integrated magnetic layer of these magnetic layers. Therefore, the coil-like conductive structural body <NUM> is formed such that at least part thereof may be embedded into the magnetic member <NUM>. Namely, in the inductor substrate <NUM> according to this embodiment, the inductor element is composed of the coil-like conductive structural body <NUM> and a core part, which is extendedly present in the thickness direction of the magnetic member <NUM> and is part of the magnetic member <NUM> that is surrounded with the coil-like conductive structural body <NUM>.

As illustrated in <FIG> as one example, the first conductive layer <NUM> includes the spiral wiring to constitute the coil-like conductive structure <NUM> and the land 420a in a square shape that is electrically connected to the inside-the-through-hole wiring 220a. In the example illustrated by the drawing, the spiral wiring includes a linear portion, a bent portion that is bent at a right angle to the linear portion, and a detour portion that detours the land 420a. In the example illustrated by the drawing, outline of the entire spiral wiring of the first conductive layer <NUM> is substantially in a square shape and has a shape that the wiring is whirled in the anticlockwise direction from a center side to an outer side.

Similarly, the second conductive layer <NUM> is formed on the first magnetic layer <NUM>. The second conductive layer <NUM> includes the spiral wiring to constitute the coil-like conductive structural body <NUM>. In <FIG>, the spiral wiring includes a linear portion and a bent portion that is bent at a right angle to the linear portion. In <FIG>, outline of the entire spiral wiring of the second conductive layer <NUM> is substantially in a square shape and has a shape that the wiring is whirled clockwise from a center side to an outer side.

The inductor substrate can be used as the wiring board to mount an electronic part such as a semiconductor chip, and can also be used as a (multi-layered) printed wiring board that uses this wiring board as the inner substrate. In addition, this can be used as a chip inductor substrate obtained by dicing the wiring board, and can also be used as a printed wiring board that is surface-mounted with the chip inductor substrate.

In addition, by using this wiring board, semiconductor devices with various embodiments may be produced. The semiconductor device having the wiring board can be suitably used in electric products (for example, a computer, a mobile phone, a digital camera, and a television), vehicles (for example, a motor bike, an automobile, a train, a marine ship, and an airplane), and so forth.

Hereinafter, the present invention will be specifically explained, but the present invention is not limited to these Examples. Note that, in the description below, "part" and "%" that describe quantity mean "part by mass" and "% by mass", respectively, unless otherwise specifically mentioned.

Iron oxide and manganese oxide were weighed such that the mole ratio of iron to manganese might be <NUM>:<NUM>; then, water was added to these, and then they were mixed and crushed to prepare the slurry with a solid concentration of <NUM>% by mass. The crushed average particle diameter (primary particle diameter of raw material) at this moment was <NUM>. The slurry thus prepared was granulated by means of a spray dryer, and then the granules were classified to obtain the granules having an average particle diameter of about <NUM>. Then, <NUM> parts by mass of lauric acid in a powder form was mixed with <NUM> parts by mass of the granules thus obtained to obtain a raw material for thermal spraying.

Next, the raw material for thermal spraying thus obtained was supplied into a flammable gas flare (propane/oxygen=<NUM>/<NUM>) in the thermal spraying equipment to carry out thermal spraying (ferrite formation). Subsequently, with supplying an air, this was transported by an air stream while being rapidly cooled. The ferrite thus formed was collected by means of the air stream classification equipment (cyclone) that was installed in the downstream side of the thermal spray equipment. Then, this ferrite was classified so as to give an intended particle diameter distribution to obtain the spherical ferrite particle A (aspect ratio of <NUM>).

A mixture of <NUM> parts by mass of the ferrite particle A, <NUM> parts by mass of an epoxy resin ("ZX-<NUM>"; a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin; manufactured by Nippon Steel & Sumikin Materials Co. ), <NUM> part by mass of a curing facilitator ("2P4MZ"; imidazole type curing facilitator; manufactured by Shikoku Chemicals Corp. ), and <NUM> part by mass of a dispersant ("SC-1015F"; polyoxyalkylene type dispersant; manufactured by NOF Corp. ) was uniformly dispersed by using a high-speed rotation mixer to obtain the resin composition <NUM> in a paste-like form.

In Example <NUM>, the amount of lauric acid was changed from <NUM> parts by mass to <NUM> parts by mass. The spherical ferrite particle B was prepared with the same manner as Example <NUM> except for the above-mentioned change; and then, the resin composition <NUM> in a paste-like form was obtained. The aspect ratio of the spherical ferrite particle B was <NUM>.

In Example <NUM>, the amount of lauric acid was changed from <NUM> parts by mass to <NUM> parts by mass. The spherical ferrite particle C was prepared with the same manner as Example <NUM> except for the above-mentioned change; and then, the resin composition <NUM> in a paste-like form was obtained. The aspect ratio of the spherical ferrite particle C was <NUM>.

In Example <NUM>, lauric acid was not used. The spherical ferrite particle D was prepared with the same manner as Example <NUM> except for the above-mentioned change; and then, the resin composition <NUM> in a paste-like form was obtained. The aspect ratio of the spherical ferrite particle D was <NUM>.

In Example <NUM>, the ferrite particle D was surface-modified with a silane coupling agent by the method described below to obtain the spherical ferrite particle E. The ferrite particle E was prepared with the same manner as Example <NUM> except for the above-mentioned change; and then, the resin composition <NUM> in a paste-like form was obtained.

The ferrite particle D (<NUM> parts by mass) was treated with <NUM> part by mass of a silane coupling agent ("KBM-<NUM>"; manufactured by Shin-Etsu Silicon Co. ) to obtain the ferrite particle E. The aspect ratio of the spherical ferrite particle E was <NUM>.

In Example <NUM>, the amount of the spherical ferrite particle D was changed from <NUM> parts by mass to <NUM> parts by mass. The resin composition <NUM> in a paste-like form was prepared with the same manner as Example <NUM> except for the above-mentioned change.

In Example <NUM>, the amount of lauric acid was changed from <NUM> parts by mass to <NUM> parts by mass. The ferrite particle F was prepared with the same manner as Example <NUM> except for the above-mentioned change; and then, the resin composition <NUM> in a paste-like form was obtained. The aspect ratio of the spherical ferrite particle F was <NUM>.

The ferrite particle was measured with a scanning electron microscope (SEM), and the lengths of the image were measured by using image analysis software. The SEM pictures of each particle were obtained with the condition of <NUM> kV and with the magnification of <NUM>,<NUM>. The value dividing the maximum diameter length with the width that is perpendicular to the maximum diameter length was taken as the aspect ratio. The aspect ratio of the particle was the average value of <NUM> particles.

Ferrite particles (<NUM>) and <NUM> of water were taken into a <NUM>-mL beaker, and then, <NUM> of sodium hexamethaphosphate as the dispersant was added to it. Next, this mixture was dispersed by using an ultrasonic homogenizer (UH-<NUM> type; manufactured by SMT Co. The dispersion was carried out for <NUM> seconds with setting the ultrasonic homogenizer at the output level of <NUM>. Then, after the foam formed on the surface of the beaker was removed, the dispersion solution was introduced into a laser diffraction type particle diameter distribution analyzer (SALD-7500nano; manufactured by Shimadzu Corp. ) for measurement. From this measurement, the <NUM>% diameter (D10), the <NUM>% diameter (D50), and the <NUM>% diameter (D90) in the volume-based particle diameter distribution were obtained. At this time, the pump speed of <NUM>, the built-in ultrasonic wave irradiation time of <NUM> seconds, and the refractive index of <NUM>-050i were used as the measurement conditions.

The carbon amount in the ferrite particles A to D and F were measured by using a carbon analyzer (C-<NUM>; manufactured by LECO Corp. ) with the oxygen gas pressure of <NUM>/cm<NUM> and the nitrogen gas pressure of <NUM>/cm<NUM>. First, the standard sample whose carbon amount is known and almost in the same level as that of the ferrite particle was measured with this analyzer. In addition, the measurement was carried out without using the sample itself (blank test). Then, the conversion coefficient was calculated from the measured values by using the following equation.

Next, the ferrite particle was measured by using the carbon analyzer, and the carbon amount therein was calculated by using the following equation.

The ferrite particle E (<NUM>) was heated at <NUM> for <NUM> hours in an electric furnace ("FP <NUM>"; manufactured by Yamato-net Co. ) with flowing nitrogen at the flow rate of <NUM>/minute to remove the silane coupling agent on the surface of the ferrite particle. After the silane coupling agent was removed, the carbon amount therein was measured by the same method as that of the ferrite particle whose surface was not treated.

The particle diameter distributions and the carbon amounts in the ferrite particles A to F measured by the respective methods described above are summarized in Table below.

With keeping the temperature of the resin composition of each of Examples and Comparative Example at <NUM>±<NUM>, the viscosity thereof was measured by using an E-type viscometer ("RE-80U"; <NUM>° x R9. <NUM> rotor; manufactured by Toki Sangyo Co. ) with the measurement sample volume of <NUM> and the rotation number of <NUM> rpm as the measurement conditions.

A polyethylene terephthalate (PET) film that was treated with a silicone type releasing agent ("PET <NUM>"; thickness of <NUM>; manufactured by Lintec Corp. ) was prepared as a support. Each of the resin compositions <NUM> to <NUM> was uniformly applied onto the release-treated surface of the PET film by using a doctor blade such that the thickness of the resin composition layer after dried might become <NUM> to obtain a magnetic sheet. The magnetic sheet thus obtained was heated at <NUM> for <NUM> minutes to thermally cure the resin composition layer; and then, the support was removed to obtain a cured product in a sheet form. The cured product in the sheet form thus obtained was cut to a specimen having the width of <NUM> and the length of <NUM>; and this was used as a sample for evaluation. The relative permeability (µ') and the magnetic loss (tanδ (=µ"/µ')) of the sample for evaluation thus obtained were measured at room temperature (<NUM>) with the <NUM>-turn coil method and the measurement frequency of <NUM> by using Agilent Technologies ("HP 8362B"; manufactured by Agilent Technologies, Inc. By using the same method with the measurement frequency of <NUM>, the relative permeability (µ') and the magnetic loss (tanδ ) were measured at room temperature (<NUM>).

A polyethylene terephthalate (PET) film that was treated with a silicone type releasing agent ("PET <NUM>"; thickness of <NUM>; manufactured by Lintec Corp. ) was prepared as a support. Each of the resin compositions <NUM> to <NUM> was uniformly applied onto the release-treated surface of the PET film by using a doctor blade such that the thickness of the resin composition layer after dried might become <NUM> to obtain a magnetic sheet. The magnetic sheet thus obtained was heated at <NUM> for <NUM> minutes to thermally cure the resin composition layer; and then, the support was removed to obtain a cured product in a sheet form. The cured product in the sheet form thus obtained was subjected to the tensile test in accordance with Japanese Industrial Standard (JIS K7127) by using Tensilon Universal Testing Machine (manufactured by A&D Co. ) to obtain the maximum point strength and the elongation at <NUM>.

Claim 1:
A resin composition comprising:
(A) a ferrite; and
(B) a thermosetting resin,
wherein the content of the (A) component is <NUM>% or more by mass and <NUM>% or less by mass, on the basis of <NUM>% by mass as nonvolatile components in the resin composition, and
the content of the (B) component is <NUM>% or more by mass and <NUM>% or less by mass, on the basis of <NUM>% by mass as nonvolatile components in the resin composition, and wherein the resin is
characterized in that:
a carbon amount included in the (A) component is <NUM>% or less by mass relative to <NUM>% by mass of the (A) component, wherein
the carbon amount included in the (A) component is measured using a carbon analyzer; in the carbon analyzer, a ferrite to be measured is burnt by a high frequency induction furnace, and then, the carbon amount therein can be obtained by measuring amounts of carbon monoxide and carbon dioxide thus produced by an infrared light absorption method; in the carbon analyzer, an oxygen gas pressure is made to <NUM>/cm<NUM>, and a nitrogen gas pressure is made to <NUM>/cm<NUM>; first, the carbon amount in a standard sample whose carbon amount is known and almost in the same level as that of the ferrite to be measured is measured; next, a blank test is carried out without using the ferrite; then, a conversion coefficient is calculated; next, the ferrite to be measured is measured by using the carbon analyzer, and the carbon amount therein is calculated; when the (A) component is surface-modified with a surface treating agent, the ferrite to be measured is heated at <NUM> for <NUM> hours in an electric furnace with flowing nitrogen at the flow rate of <NUM>/minute to remove the surface treating agent on the ferrite surface prior to measurement of the carbon amount,
a relative permeability (<NUM>) of a cured product obtainable by thermally curing the resin composition at <NUM> for <NUM> minutes is <NUM> or more, and
a maximum point strength (<NUM>) of a cured product obtainable by thermally curing the resin composition at <NUM> for <NUM> minutes is <NUM> MPa or more.