JP7540452B2 - Circuit board manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a circuit board.

A known manufacturing technique for multilayer printed wiring boards is the build-up method, in which insulating layers and conductor layers are alternately stacked on an inner layer substrate. The insulating layers are generally formed by curing a resin composition.

For example, Patent Document 1 discloses that an insulating layer in a printed wiring board is formed using a resin composition containing a cyanate ester resin, a specific epoxy resin, and an active ester curing agent, and describes that the insulating layer has both low roughness and high peel strength of the conductor layer formed by plating, and further has a low coefficient of thermal expansion (CTE).

JP 2011-144361 A

In recent years, the need for miniaturization of electronic devices and electronic components has led to a demand for finer and denser wiring in circuit boards. As wiring becomes finer and denser, it becomes more important to reduce warping of the inner layer board, and there is a demand for inner layer boards with a low thermal expansion coefficient to reduce warping.

To achieve a low coefficient of thermal expansion, it is possible to incorporate a high content of inorganic filler such as silica into the insulating layer. However, this reduces the amount of resin component contained in the resin composition, which reduces the adhesion between the conductor layer and the insulating layer in the inner layer board, making delamination more likely to occur.

On the other hand, if the insulating layer is heated after forming the conductor layer on the insulating layer to further increase the hardness of the insulating layer, the adhesion between the conductor layer and the insulating layer can be improved, but there is an issue that the heat hardening makes the material more susceptible to warping.

The present invention was devised in consideration of the above problems, and aims to provide a method for manufacturing a circuit board that suppresses the occurrence of warping and improves adhesion.

In order to achieve the object of the present invention, the inventors conducted extensive research and discovered that by forming a conductor layer on an insulating layer and then carrying out a heating treatment and an annealing treatment so that the heating temperature during the heating treatment and the heating time during the annealing treatment satisfy a specific relationship, it is possible to suppress the occurrence of warping and improve adhesion, which led to the completion of the present invention.

That is, the present invention includes the following.
[1] (A) preparing an insulating resin film including a support and a resin composition layer formed from a resin composition provided on the support;
(B) laminating an insulating resin film on the inner layer substrate such that the resin composition layer is bonded to the inner layer substrate;
(C) a step of thermally curing the resin composition layer to form an insulating layer;
(E) forming a via in the insulating layer and then forming a conductor layer on the insulating layer;
(F) heating the insulating layer at a temperature of 175° C. or more and 205° C. or less; and (G) heating the insulating layer at a temperature of 110° C. or more and less than 175° C.,
The resin composition includes an epoxy resin, a curing agent, and an inorganic filler,
The content of the inorganic filler is 40% by mass or more and 80% by mass or less, when the non-volatile components of the resin composition are 100% by mass,
A method for manufacturing a circuit board, wherein when the heating temperature in step (F) is T3 (°C) and the heating temperature in step (G) is T4 (°C), 20°C≦T3−T4≦70°C is satisfied.
[2] After step (C) and before step (E),
The method for manufacturing a circuit board according to [1], further comprising: (D) a step of heating the insulating layer.
[3] The method for producing a circuit board according to [2], wherein the heating temperature T2 in step (D) is 100° C. or higher and 150° C. or lower.
[4] After step (F) and before step (G),
The method for producing a circuit board according to any one of [1] to [3], further comprising: (F-1) a step of cooling the insulating layer.
[5] The method for producing a circuit board according to any one of [1] to [4], wherein the heating time in step (F) is 10 minutes or longer.
[6] The method for producing a circuit board according to any one of [1] to [5], wherein the heating time in step (G) is 10 minutes or longer.
[7] The method for producing a circuit board according to any one of [1] to [6], wherein the heating temperature T1 in step (C) is 100° C. or higher and 190° C. or lower.

The present invention provides a method for manufacturing a circuit board that suppresses warping and improves adhesion.

The present invention will be described in detail below based on its preferred embodiments. However, the present invention is not limited to the following embodiments and examples, and can be modified as desired without departing from the scope of the claims of the present invention and their equivalents.

Before describing in detail the method for manufacturing the circuit board of the present invention, we will explain the insulating resin film used in the manufacturing method of the present invention.

[Insulating resin film]
The insulating resin film used in the method for producing a circuit board of the present invention includes a support and a resin composition layer formed of a resin composition provided on the support. Each layer constituting the insulating resin film will be described in detail below.

<Support>
The insulating resin film includes a support, for example, a film made of a plastic material, a metal foil, or a release paper, with a film made of a plastic material and a metal foil being preferred.

When a film made of a plastic material is used as the support, examples of the plastic material include polyesters such as polyethylene terephthalate (hereinafter sometimes abbreviated as "PET") and polyethylene naphthalate (hereinafter sometimes abbreviated as "PEN"), polycarbonate (hereinafter sometimes abbreviated as "PC"), acrylics such as polymethyl methacrylate (PMMA), cyclic polyolefins, triacetyl cellulose (TAC), polyether sulfide (PES), polyether ketone, polyimide, etc. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, and inexpensive polyethylene terephthalate is particularly preferred.

When a metal foil is used as the support, examples of the metal foil include copper foil and aluminum foil, with copper foil being preferred. As the copper foil, a foil made of a single metal, copper, or an alloy of copper and another metal (e.g., tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.) may be used.

The support may be subjected to a matte treatment, corona treatment, or antistatic treatment on the surface that is to be bonded to the resin composition layer.

As the support, a support with a release layer having a release layer on the surface of the side bonded to the resin composition layer may be used. Examples of the release agent used in the release layer of the support with a release layer include one or more release agents selected from the group consisting of alkyd resins, polyolefin resins, urethane resins, and silicone resins, and among them, it is preferable to include one or more release agents selected from the group consisting of alkyd resins, polyolefin resins, and urethane resins. The support with a release layer may be a commercially available product, and examples thereof include PET films having a release layer mainly composed of an alkyd resin-based release agent such as "SK-1", "AL-5", and "AL-7" manufactured by Lintec Corporation, "Lumirror T60" manufactured by Toray Industries, Inc., "Purex" manufactured by Teijin Limited, and "Unipeel" manufactured by Unitika Limited; "U2-NR1" manufactured by DuPont Films Co., Ltd., and the like.

The thickness of the support is not particularly limited, but is preferably in the range of 5 μm to 75 μm, and more preferably in the range of 10 μm to 60 μm. When using a support with a release layer, it is preferable that the thickness of the entire support with the release layer is in the above range.

<Resin composition layer>
The insulating resin film includes a resin composition layer made of a resin composition. The resin composition layer is bonded to a support to form an insulating resin film, and in the manufacture of a circuit board, the resin composition layer is laminated on an inner layer substrate and heat-cured to form an insulating layer. The resin composition forming the resin composition layer includes an epoxy resin, a curing agent, and an inorganic filler, and the content of the inorganic filler is 40% by mass or more and 80% by mass or less when the non-volatile components of the resin composition are 100% by mass. The resin composition may further include a thermoplastic resin, a curing accelerator, and other additives as necessary.

-Epoxy resin-
The resin composition contains an epoxy resin. Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol AF type epoxy resin, dicyclopentadiene type epoxy resin, trisphenol type epoxy resin, naphthol novolac type epoxy resin, phenol novolac type epoxy resin, tert-butyl-catechol type epoxy resin, naphthalene type epoxy resin, naphthol type epoxy resin, anthracene type epoxy resin, glycidylamine type epoxy resin, glycidyl ester type epoxy resin, cresol novolac type epoxy resin, biphenyl type epoxy resin, linear aliphatic epoxy resin, epoxy resin having a butadiene structure, alicyclic epoxy resin, heterocyclic epoxy resin, spiro ring-containing epoxy resin, cyclohexane dimethanol type epoxy resin, naphthylene ether type epoxy resin, and trimethylol type epoxy resin. The epoxy resin may be used alone or in combination of two or more.

The epoxy resin preferably contains an epoxy resin having two or more epoxy groups in one molecule. From the viewpoint of obtaining the desired effect of the present invention remarkably, the ratio of the epoxy resin having two or more epoxy groups in one molecule to 100% by mass of the non-volatile components of the epoxy resin is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

Epoxy resins are classified into epoxy resins that are liquid at a temperature of 20°C (hereinafter referred to as "liquid epoxy resins") and epoxy resins that are solid at a temperature of 20°C (hereinafter referred to as "solid epoxy resins"). The resin composition may contain only liquid epoxy resins or only solid epoxy resins as epoxy resins, but from the viewpoint of obtaining the effects of the present invention more significantly, it is preferable to contain a combination of liquid epoxy resins and solid epoxy resins.

Preferably, the liquid epoxy resin has two or more epoxy groups in one molecule.

Preferred liquid epoxy resins are bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AF type epoxy resins, naphthalene type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, phenol novolac type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexane type epoxy resins, cyclohexane dimethanol type epoxy resins, glycidyl amine type epoxy resins, and epoxy resins having a butadiene structure, with bisphenol A type epoxy resins and bisphenol F type epoxy resins being more preferable.

Specific examples of liquid epoxy resins include DIC's "HP4032", "HP4032D", and "HP4032SS" (naphthalene type epoxy resins); Mitsubishi Chemical's "828US", "jER828EL", "825", and "Epicoat 828EL" (bisphenol A type epoxy resins); Mitsubishi Chemical's "jER807" and "1750" (bisphenol F type epoxy resins); Mitsubishi Chemical's "jER152" (phenol novolac type epoxy resin); and Mitsubishi Chemical's "630" and "630LSD" (glycidylamine type epoxy resins). ); "ZX1059" (a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "EX-721" (glycidyl ester type epoxy resin) manufactured by Nagase ChemteX Corporation; "Celloxide 2021P" (alicyclic epoxy resin having an ester skeleton) manufactured by Daicel Corporation; "PB-3600" (epoxy resin having a butadiene structure) manufactured by Daicel Corporation; "ZX1658" and "ZX1658GS" (liquid 1,4-glycidylcyclohexane type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd. may be used alone or in combination of two or more types.

As the solid epoxy resin, a solid epoxy resin having three or more epoxy groups in one molecule is preferable, and an aromatic solid epoxy resin having three or more epoxy groups in one molecule is more preferable.

As solid epoxy resins, bixylenol type epoxy resins, naphthalene type epoxy resins, naphthalene type tetrafunctional epoxy resins, cresol novolac type epoxy resins, dicyclopentadiene type epoxy resins, trisphenol type epoxy resins, naphthol type epoxy resins, biphenyl type epoxy resins, naphthylene ether type epoxy resins, anthracene type epoxy resins, bisphenol A type epoxy resins, bisphenol AF type epoxy resins, and tetraphenylethane type epoxy resins are preferred, with bixylenol type epoxy resins, naphthalene type epoxy resins, naphthylene ether type epoxy resins, and bisphenol AF type epoxy resins being more preferred.

Specific examples of solid epoxy resins include DIC's "HP4032H" (naphthalene type epoxy resin), "HP-4700", and "HP-4710" (naphthalene type tetrafunctional epoxy resin), "N-690" (cresol novolac type epoxy resin), "N-695" (cresol novolac type epoxy resin), "HP-7200", "HP-7200HH", and "HP-7200H" (dicyclopentadiene type epoxy resin). "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP6000", "HP6000L" (naphthylene ether type epoxy resins); "EPPN-502H" (trisphenol type epoxy resin), "NC7000L" (naphthol novolac type epoxy resin), "NC3000H" manufactured by Nippon Kayaku Co., Ltd. Examples of epoxy resins include "NC3000", "NC3000L", and "NC3100" (biphenyl type epoxy resins); "ESN475V" (naphthalene type epoxy resin) and "ESN485" (naphthol novolac type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX4000H", "YL6121" (biphenyl type epoxy resin), "YX4000HK" (bixylenol type epoxy resin), and "YX8800" (anthracene type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "PG-100" and "CG-500" manufactured by Osaka Gas Chemical Co., Ltd., and "YX7760" (bisphenol AF type epoxy resin), "YL7800" (fluorene type epoxy resin), "jER1010" (solid bisphenol A type epoxy resin), and "jER1031S" (tetraphenylethane type epoxy resin) manufactured by Mitsubishi Chemical Corporation. These may be used alone or in combination of two or more.

When a combination of solid epoxy resin and liquid epoxy resin is used as the epoxy resin, the mass ratio thereof (solid epoxy resin:liquid epoxy resin) is preferably 1:0.01 to 1:50, more preferably 1:0.05 to 1:20, and particularly preferably 1:0.1 to 1:10. By setting the mass ratio of the liquid epoxy resin to the solid epoxy resin within this range, the following effects can be obtained: 1) when used in the form of an insulating resin film, appropriate adhesion is achieved; 2) when used in the form of an insulating resin film, sufficient flexibility is obtained and handling is improved; and 3) a cured product having sufficient breaking strength can be obtained.

The epoxy equivalent of the epoxy resin is preferably 50 g/eq. to 5000 g/eq., more preferably 50 g/eq. to 3000 g/eq., even more preferably 80 g/eq. to 2000 g/eq., and even more preferably 110 g/eq. to 1000 g/eq. Within this range, a cured product of the resin composition with sufficient crosslinking density can be obtained. The epoxy equivalent is the mass of an epoxy resin containing one equivalent of epoxy groups. This epoxy equivalent can be measured according to JIS K7236.

From the viewpoint of significantly achieving the desired effects of the present invention, the weight average molecular weight (Mw) of the epoxy resin is preferably 100 to 5000, more preferably 250 to 3000, and even more preferably 400 to 1500. The weight average molecular weight of the epoxy resin is the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

The content of the epoxy resin is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, based on 100% by mass of the non-volatile components in the resin composition, from the viewpoint of obtaining a cured product exhibiting good mechanical strength and insulation reliability. The upper limit of the content of the epoxy resin is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less or 30% by mass or less, based on 100% by mass of the non-volatile components in the resin composition.

- Hardener -
The resin composition contains a curing agent. The curing agent is not particularly limited as long as it has the function of curing the epoxy resin, and examples thereof include phenol-based curing agents, naphthol-based curing agents, active ester-based curing agents, benzoxazine-based curing agents, and cyanate ester-based curing agents. Among them, the curing agent preferably contains one or more selected from phenol-based curing agents and active ester-based curing agents, and more preferably contains a phenol-based curing agent, from the viewpoint of obtaining the effects of the present invention significantly. The curing agent may be used alone or in combination of two or more.

As the phenol-based hardener and naphthol-based hardener, from the viewpoint of heat resistance and water resistance, a phenol-based hardener having a novolac structure or a naphthol-based hardener having a novolac structure is preferred. From the viewpoint of adhesion strength with the conductor layer, a nitrogen-containing phenol-based hardener or a nitrogen-containing naphthol-based hardener is preferred, and a triazine skeleton-containing phenol-based hardener or a triazine skeleton-containing naphthol-based hardener is more preferred. Among them, from the viewpoint of highly satisfying heat resistance, water resistance, and adhesion strength with the conductor layer, a triazine skeleton-containing phenol novolac resin is preferred. These may be used alone or in combination of two or more.

Specific examples of phenol-based and naphthol-based curing agents include "MEH-7700", "MEH-7810", and "MEH-7851" manufactured by Meiwa Kasei Co., Ltd., "NHN", "CBN", and "GPH" manufactured by Nippon Kayaku Co., Ltd., "SN170", "SN180", "SN190", "SN475", "SN485", "SN495", "SN-495V", "SN375", and "SN395" manufactured by Nippon Steel Chemical & Material Co., Ltd., and "TD-2090", "LA-7052", "LA-7054", "LA-1356", "LA-3018-50P", and "EXB-9500" manufactured by DIC Corporation.

There are no particular limitations on the active ester curing agent, but generally compounds having two or more highly reactive ester groups in one molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds, are preferably used. The active ester compound is preferably one obtained by a condensation reaction between a carboxylic acid compound and/or a thiocarboxylic acid compound and a hydroxy compound and/or a thiol compound. In particular, from the viewpoint of improving heat resistance, an active ester compound obtained from a carboxylic acid compound and a hydroxy compound is preferred, and an active ester compound obtained from a carboxylic acid compound and a phenol compound and/or a naphthol compound is more preferred. Examples of carboxylic acid compounds include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and pyromellitic acid. Examples of phenol compounds or naphthol compounds include hydroquinone, resorcin, bisphenol A, bisphenol F, bisphenol S, phenolphthaline, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucin, benzenetriol, dicyclopentadiene-type diphenol compounds, and phenol novolak. Here, "dicyclopentadiene-type diphenol compounds" refer to diphenol compounds obtained by condensing one molecule of dicyclopentadiene with two molecules of phenol.

Specific examples of active ester curing agents include dicyclopentadiene-type active ester compounds, naphthalene-type active ester compounds containing a naphthalene structure, active ester compounds containing an acetylated product of phenol novolac, and active ester compounds containing a benzoylated product of phenol novolac. Of these, at least one selected from dicyclopentadiene-type active ester compounds and naphthalene-type active ester compounds is more preferred. As a dicyclopentadiene-type active ester compound, an active ester compound containing a dicyclopentadiene-type diphenol structure is preferred.

Commercially available active ester curing agents include active ester compounds containing a dicyclopentadiene-type diphenol structure such as "EXB9451", "EXB9460", "EXB9460S", "HPC-8000L-65TM", "HPC-8000-65T", "HPC-8000H", and "HPC-8000H-65TM" (manufactured by DIC Corporation); active ester compounds containing a naphthalene structure such as "HP-B-8151-62T", "EXB-8100L-65T", "EXB-9416-70BK", and "HPC-8150-62T", "EXB-8" (manufactured by DIC Corporation); as an active ester compound containing phosphorus, "EXB9401" (manufactured by DIC Corporation); as an active ester compound which is an acetylated product of phenol novolac, "DC808" (manufactured by Mitsubishi Chemical Corporation); as active ester compounds which are benzoylated products of phenol novolac, "YLH1026", "YLH1030", and "YLH1048" (manufactured by Mitsubishi Chemical Corporation); as an active ester compound containing a styryl group and a naphthalene structure, "PC1300-02-65MA" (manufactured by Air Water Inc.) and the like can be mentioned.

Specific examples of benzoxazine-based curing agents include "HFB2006M" manufactured by Showa Polymer Co., Ltd., and "P-d" and "F-a" manufactured by Shikoku Chemical Industry Co., Ltd.

Examples of cyanate ester curing agents include bifunctional cyanate resins such as bisphenol A dicyanate, polyphenol cyanate, oligo(3-methylene-1,5-phenylene cyanate), 4,4'-methylenebis(2,6-dimethylphenyl cyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanate phenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanate phenyl-1-(methylethylidene))benzene, bis(4-cyanate phenyl)thioether, and bis(4-cyanate phenyl)ether; polyfunctional cyanate resins derived from phenol novolac and cresol novolac; and prepolymers in which these cyanate resins have been partially converted to triazine. Specific examples of cyanate ester-based hardeners include Lonza Japan's "PT30" and "PT60" (phenol novolac-type multifunctional cyanate ester resins), "ULL-950S" (multifunctional cyanate ester resin), "BA230" and "BA230S75" (prepolymers in which part or all of bisphenol A dicyanate has been triazine-converted into a trimer).

A carbodiimide curing agent is a compound that has one or more carbodiimide groups (-N=C=N-) in one molecule, and a carbodiimide curing agent that has two or more carbodiimide groups in one molecule is preferable.

Specific examples of carbodiimide-based curing agents include commercially available carbodiimide-based curing agents such as Carbodilite V-03 (carbodiimide group equivalent: 216), V-05 (carbodiimide group equivalent: 262), and V-07 (carbodiimide group equivalent: 200), all manufactured by Nisshinbo Chemical Co., Ltd.; and Stavaxol P (carbodiimide group equivalent: 302), all manufactured by Rhein Chemie.

The ratio of the amount of epoxy resin to the curing agent is preferably in the range of 1:0.01 to 1:5, more preferably 1:0.1 to 1:3, and even more preferably 1:0.3 to 1:2, in terms of the ratio of [total number of epoxy groups in the epoxy resin] to [total number of active groups in the curing agent]. Here, the "number of epoxy groups in the epoxy resin" refers to the total value obtained by dividing the mass of the non-volatile components of the epoxy resin present in the resin composition by the epoxy equivalent. The "number of active groups in the curing agent" refers to the total value obtained by dividing the mass of the non-volatile components of the curing agent present in the resin composition by the active group equivalent. By setting the ratio of the amount of the epoxy resin to the curing agent within this range, the effects of the present invention can be obtained significantly.

From the viewpoint of obtaining the desired effect of the present invention remarkably, the content of the curing agent is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, assuming that the non-volatile components in the resin composition are 100% by mass. The upper limit is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

- Inorganic filler -
The resin composition contains an inorganic filler. By containing an inorganic filler in the resin composition, it is possible to suppress the occurrence of warping in a cured product of the resin composition.

From the viewpoint of reducing the CTE of the cured resin composition, the content of the inorganic filler is 40% by mass or more, preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more, assuming that the non-volatile components in the resin composition are 100% by mass. The upper limit is 80% by mass or less, preferably 75% by mass or less, more preferably 70% by mass or less, and even more preferably 65% by mass or less.

Inorganic compounds are used as the inorganic filler material. Examples of inorganic filler materials include silica, alumina, glass, cordierite, silicon oxide, barium sulfate, barium carbonate, talc, clay, mica powder, zinc oxide, hydrotalcite, boehmite, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, magnesium oxide, boron nitride, aluminum nitride, manganese nitride, aluminum borate, strontium carbonate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, titanium oxide, zirconium oxide, barium titanate, barium zirconate titanate, barium zirconate, calcium zirconate, zirconium phosphate, and zirconium tungstate phosphate. Among these, calcium carbonate and silica are preferred, and silica is particularly preferred. Examples of silica include amorphous silica, fused silica, crystalline silica, synthetic silica, and hollow silica. In addition, spherical silica is preferred as the silica. The inorganic filler may be used alone or in combination of two or more types.

Commercially available inorganic fillers include, for example, "ST7030-20" manufactured by Nippon Steel Chemical & Material Co., Ltd.; "MSS-6" and "AC-5V" manufactured by Tatsumori Co., Ltd.; "SP60-05" and "SP507-05" manufactured by Nippon Steel & Sumitomo Metal Materials Co., Ltd.; "YC100C", "YA050C", "YA050C-MJE", and "YA010C" manufactured by Admatechs Co., Ltd.; "UFP-30", "SFP-130MC", "FB-7SDC", "FB-5SDC", and "FB-3SDC" manufactured by Denka Co., Ltd.; "Silfill NSS-3N", "Silfill NSS-4N", and "Silfill NSS-5N" manufactured by Tokuyama Corporation; and "SC2500SQ", "SO-C4", "SO-C2", "SO-C1", and "FE9" manufactured by Admatechs Co., Ltd.

The specific surface area of the inorganic filler is preferably 1 m ² /g or more, more preferably 2 m ² /g or more, and particularly preferably 3 m ² /g or more. There is no particular upper limit, but it is preferably 60 m ² /g or less, 50 m ² /g or less, or 40 m ² /g or less. The specific surface area is obtained according to the BET method by adsorbing nitrogen gas onto the surface of a sample using a specific surface area measuring device (Macsorb HM-1210 manufactured by Mountech Co., Ltd.) and calculating the specific surface area using the BET multipoint method.

From the viewpoint of significantly obtaining the desired effects of the present invention, the average particle size of the inorganic filler is preferably 0.01 μm or more, more preferably 0.05 μm or more, even more preferably 0.1 μm or more, and is preferably 20 μm or less, more preferably 15 μm or less, even more preferably 10 μm or less.

The average particle size of the inorganic filler can be measured by a laser diffraction/scattering method based on the Mie scattering theory. Specifically, a particle size distribution of the inorganic filler is created on a volume basis using a laser diffraction/scattering particle size distribution measuring device, and the median diameter is used as the average particle size. The measurement sample can be prepared by weighing 100 mg of inorganic filler and 10 g of methyl ethyl ketone into a vial and dispersing the mixture ultrasonically for 10 minutes. The measurement sample is measured using a laser diffraction particle size distribution measuring device with blue and red light source wavelengths, and the volume-based particle size distribution of the inorganic filler is measured using a flow cell method, and the average particle size can be calculated as the median diameter from the particle size distribution obtained. An example of a laser diffraction particle size distribution measuring device is the "LA-960" manufactured by Horiba, Ltd.

From the viewpoint of improving moisture resistance and dispersibility, the inorganic filler is preferably treated with a surface treatment agent. Examples of the surface treatment agent include vinylsilane coupling agents, (meth)acrylic coupling agents, fluorine-containing silane coupling agents, aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, alkoxysilanes, organosilazane compounds, and titanate coupling agents. Among them, from the viewpoint of obtaining the effects of the present invention significantly, vinylsilane coupling agents, (meth)acrylic coupling agents, aminosilane coupling agents, epoxysilane coupling agents, and silane coupling agents are preferred, and aminosilane coupling agents, epoxysilane coupling agents, and silane coupling agents are more preferred. In addition, the surface treatment agent may be used alone or in any combination of two or more types.

Commercially available surface treatment agents include, for example, Shin-Etsu Chemical Co., Ltd.'s "KBM1003" (vinyltriethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBM503" (3-methacryloxypropyltriethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBM403" (3-glycidoxypropyltrimethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBM803" (3-mercaptopropyltrimethoxysilane), and Shin-Etsu Chemical Co., Ltd.'s "KBE903" (3-aminopropyltriethoxy silane), Shin-Etsu Chemical Co., Ltd.'s "KBM573" (N-phenyl-3-aminopropyltrimethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "SZ-31" (hexamethyldisilazane), Shin-Etsu Chemical Co., Ltd.'s "KBM103" (phenyltrimethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBM-4803" (long-chain epoxy-type silane coupling agent), Shin-Etsu Chemical Co., Ltd.'s "KBM-7103" (3,3,3-trifluoropropyltrimethoxysilane), etc.

From the viewpoint of improving the dispersibility of the inorganic filler, it is preferable that the degree of surface treatment with the surface treatment agent falls within a specified range. Specifically, 100 parts by mass of the inorganic filler is preferably surface-treated with 0.2 parts by mass to 5 parts by mass of the surface treatment agent, more preferably with 0.2 parts by mass to 3 parts by mass, and more preferably with 0.3 parts by mass to 2 parts by mass.

The degree of surface treatment by the surface treatment agent can be evaluated by the amount of carbon per unit surface area of the inorganic filler. From the viewpoint of improving the dispersibility of the inorganic filler, the amount of carbon per unit surface area of the inorganic filler is preferably 0.02 mg/m ² or more, more preferably 0.1 mg/m ² or more, and even more preferably 0.2 mg/m ² or more. On the other hand, from the viewpoint of suppressing the increase in the melt viscosity of the resin varnish and the melt viscosity in the film form, it is preferably 1 mg/m ² or less, more preferably 0.8 mg/m ² or less, and even more preferably 0.5 mg/m ² or less.

The amount of carbon per unit surface area of the inorganic filler can be measured after the surface-treated inorganic filler is washed with a solvent (e.g., methyl ethyl ketone (MEK)). Specifically, a sufficient amount of MEK as a solvent is added to the inorganic filler that has been surface-treated with a surface treatment agent, and ultrasonic cleaning is performed at 25°C for 5 minutes. After removing the supernatant and drying the solids, the amount of carbon per unit surface area of the inorganic filler can be measured using a carbon analyzer. An example of a carbon analyzer that can be used is the "EMIA-320V" manufactured by Horiba, Ltd.

- Thermoplastic resin -
The resin composition may further contain a thermoplastic resin as an optional component in combination with the above-mentioned epoxy resin, curing agent, and inorganic filler. This thermoplastic resin does not include those that correspond to the above-mentioned components.

Examples of thermoplastic resins include phenoxy resins, polyimide resins, polyvinyl acetal resins, polyolefin resins, polybutadiene resins, polyamideimide resins, polyetherimide resins, polysulfone resins, polyethersulfone resins, polyphenylene ether resins, polycarbonate resins, polyetheretherketone resins, and polyester resins. Thermoplastic resins may be used alone or in combination of two or more types.

Examples of phenoxy resins include phenoxy resins having one or more skeletons selected from the group consisting of bisphenol A skeleton, bisphenol F skeleton, bisphenol S skeleton, bisphenolacetophenone skeleton, novolac skeleton, biphenyl skeleton, fluorene skeleton, dicyclopentadiene skeleton, norbornene skeleton, naphthalene skeleton, anthracene skeleton, adamantane skeleton, terpene skeleton, and trimethylcyclohexane skeleton. The terminal of the phenoxy resin may be any functional group such as a phenolic hydroxyl group or an epoxy group. Specific examples of phenoxy resins include "1256" and "4250" manufactured by Mitsubishi Chemical Corporation (both phenoxy resins containing a bisphenol A skeleton); "YX8100" manufactured by Mitsubishi Chemical Corporation (phenoxy resin containing a bisphenol S skeleton); "YX6954" manufactured by Mitsubishi Chemical Corporation (phenoxy resin containing a bisphenol acetophenone skeleton); "FX280" and "FX293" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.; "YL7500BH30", "YX6954BH30", "YX7553", "YX7553BH30", "YX6954", "YL7769BH30", "YL6794", "YL7213", "YL7290", "YL7482" and "YL7891BH30" manufactured by Mitsubishi Chemical Corporation; and the like.

Specific examples of polyimide resins include "SLK-6100" manufactured by Shin-Etsu Chemical Co., Ltd., and "Rikacoat SN20" and "Rikacoat PN20" manufactured by New Japan Chemical Co., Ltd.

Examples of polyvinyl acetal resins include polyvinyl formal resins and polyvinyl butyral resins, with polyvinyl butyral resins being preferred. Specific examples of polyvinyl acetal resins include Denka Butyral 4000-2, Denka Butyral 5000-A, Denka Butyral 6000-C, and Denka Butyral 6000-EP manufactured by Denki Kagaku Kogyo Co., Ltd.; and S-LEC BH series, BX series (e.g. BX-5Z), KS series (e.g. KS-1), BL series, and BM series manufactured by Sekisui Chemical Co., Ltd.

Examples of polyolefin resins include ethylene-based copolymer resins such as low-density polyethylene, very low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methyl acrylate copolymer; polyolefin-based polymers such as polypropylene and ethylene-propylene block copolymer.

Examples of polybutadiene resins include hydrogenated polybutadiene skeleton-containing resins, hydroxyl group-containing polybutadiene resins, phenolic hydroxyl group-containing polybutadiene resins, carboxyl group-containing polybutadiene resins, acid anhydride group-containing polybutadiene resins, epoxy group-containing polybutadiene resins, isocyanate group-containing polybutadiene resins, urethane group-containing polybutadiene resins, polyphenylene ether-polybutadiene resins, etc.

Specific examples of polyamide-imide resins include "Viromax HR11NN" and "Viromax HR16NN" manufactured by Toyobo Co., Ltd. Specific examples of polyamide-imide resins include modified polyamide-imides such as "KS9100" and "KS9300" (polyamide-imide containing a polysiloxane skeleton) manufactured by Hitachi Chemical Co., Ltd.

An example of a polyethersulfone resin is "PES5003P" manufactured by Sumitomo Chemical Co., Ltd.

Specific examples of polysulfone resins include polysulfones "P1700" and "P3500" manufactured by Solvay Advanced Polymers.

A specific example of a polyphenylene ether resin is NORYL SA90 manufactured by SABIC. A specific example of a polyetherimide resin is ULTEM manufactured by GE.

Examples of polycarbonate resins include hydroxyl group-containing carbonate resins, phenolic hydroxyl group-containing carbonate resins, carboxyl group-containing carbonate resins, acid anhydride group-containing carbonate resins, isocyanate group-containing carbonate resins, and urethane group-containing carbonate resins. Specific examples of polycarbonate resins include "FPC0220" manufactured by Mitsubishi Gas Chemical Co., Ltd., "T6002" and "T6001" (polycarbonate diols) manufactured by Asahi Kasei Chemicals Corporation, and "C-1090", "C-2090", and "C-3090" (polycarbonate diols) manufactured by Kuraray Co., Ltd. Specific examples of polyether ether ketone resins include "Sumiploy K" manufactured by Sumitomo Chemical Co., Ltd.

Examples of polyester resins include polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene terephthalate resin, polybutylene naphthalate resin, polytrimethylene terephthalate resin, polytrimethylene naphthalate resin, and polycyclohexane dimethyl terephthalate resin.

The weight average molecular weight (Mw) of the thermoplastic resin is preferably greater than 5,000, more preferably 8,000 or more, even more preferably 10,000 or more, particularly preferably 20,000 or more, and is preferably 100,000 or less, more preferably 70,000 or less, even more preferably 60,000 or less, particularly preferably 50,000 or less.

The amount of thermoplastic resin is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, and is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less, assuming that the non-volatile components in the resin composition are 100% by mass.

- Hardening accelerator -
The resin composition may further contain a curing accelerator as an optional component in combination with the above-mentioned epoxy resin, curing agent, and inorganic filler. This curing accelerator does not include the above-mentioned components. The curing accelerator functions as a curing catalyst that accelerates the curing of the epoxy resin.

Examples of the curing accelerator include phosphorus-based curing accelerators, urea-based curing accelerators, guanidine-based curing accelerators, imidazole-based curing accelerators, metal-based curing accelerators, and amine-based curing accelerators. One type of curing accelerator may be used alone, or two or more types may be used in combination.

Examples of phosphorus-based curing accelerators include aliphatic phosphonium salts such as tetrabutylphosphonium decanoate, tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, tetrabutylphosphonium acetate, tetrabutylphosphonium decanoate, tetrabutylphosphonium laurate, bis(tetrabutylphosphonium)pyromellitate, tetrabutylphosphonium hydrogenhexahydrophthalate, tetrabutylphosphonium 2,6-bis[(2-hydroxy-5-methylphenyl)methyl]-4-methylphenolate, and di-tert-butyldimethylphosphonium tetraphenylborate; methyltriphenylphosphonium bromide, ethyltriphenylphosphonium bromide, propyltriphenylphosphonium bromide, butyltriphenylphosphonium bromide, and benzyltriphenylphosphonium. Aromatic phosphonium salts such as chloride, tetraphenylphosphonium bromide, p-tolyltriphenylphosphonium tetra-p-tolylborate, tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetra-p-tolylborate, triphenylethylphosphonium tetraphenylborate, tris(3-methylphenyl)ethylphosphonium tetraphenylborate, tris(2-methoxyphenyl)ethylphosphonium tetraphenylborate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyltriphenylphosphonium thiocyanate; aromatic phosphine-borane complexes such as triphenylphosphine-triphenylborane; aromatic phosphine-quinone addition products such as triphenylphosphine-p-benzoquinone addition products; tributylphosphine Aliphatic phosphines such as sphines, tri-tert-butylphosphine, trioctylphosphine, di-tert-butyl(2-butenyl)phosphine, di-tert-butyl(3-methyl-2-butenyl)phosphine, and tricyclohexylphosphine; dibutylphenylphosphine, di-tert-butylphenylphosphine, methyldiphenylphosphine, ethyldiphenylphosphine, butyldiphenylphosphine, diphenylcyclohexylphosphine, triphenylphosphine, tri-o-tolylphosphine, tri-m-tolylphosphine, tri-p-tolylphosphine, tris(4-ethylphenyl)phosphine, tris(4-propylphenyl)phosphine, tris(4-isopropylphenyl)phosphine, tris(4-butylphenyl)phosphine, tris(4-tert-butylphenyl)phosphine, tris(2,4-dimethylphenyl)phosphine, tris(2,5-dimethylphenyl)phosphine, tris(2,6-dimethylphenyl)phosphine, tris(3,5-dimethylphenyl)phosphine, tris(2,4,6-trimethylphenyl)phosphine, tris(2,6-dimethyl-4-ethoxyphenyl)phosphine, tris(2-methoxyphenyl)phosphine, tris(4-methoxyphenyl)phosphine, tris(4-ethoxyphenyl)phosphine, tris(4-tert-butoxyphenyl)phosphine, diphenyl-2-pyridylphosphine, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,2-bis(diphenylphosphino)acetylene, 2,2'-bis(diphenylphosphino)diphenyl ether, and other aromatic phosphines.

Examples of urea-based hardening accelerators include 1,1-dimethylurea; aliphatic dimethylureas such as 1,1,3-trimethylurea, 3-ethyl-1,1-dimethylurea, 3-cyclohexyl-1,1-dimethylurea, and 3-cyclooctyl-1,1-dimethylurea; 3-phenyl-1,1-dimethylurea, 3-(4-chlorophenyl)-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 3-(2-methylphenyl)-1,1-dimethylurea, 3-(4-methylphenyl)-1,1-dimethylurea, and 3-(3,4-dimethylphenyl)-1,1-dimethylurea. aromatic dimethylureas such as 3-(4-isopropylphenyl)-1,1-dimethylurea, 3-(4-methoxyphenyl)-1,1-dimethylurea, 3-(4-nitrophenyl)-1,1-dimethylurea, 3-[4-(4-methoxyphenoxy)phenyl]-1,1-dimethylurea, 3-[4-(4-chlorophenoxy)phenyl]-1,1-dimethylurea, 3-[3-(trifluoromethyl)phenyl]-1,1-dimethylurea, N,N-(1,4-phenylene)bis(N',N'-dimethylurea), N,N-(4-methyl-1,3-phenylene)bis(N',N'-dimethylurea) [toluene bisdimethylurea], etc.

Examples of guanidine-based curing accelerators include dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1-methylbiguanide, 1-ethylbiguanide, 1-n-butylbiguanide, 1-n-octadecylbiguanide, 1,1-dimethylbiguanide, 1,1-diethylbiguanide, 1-cyclohexylbiguanide, 1-allylbiguanide, 1-phenylbiguanide, and 1-(o-tolyl)biguanide.

Examples of imidazole-based curing accelerators include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2- Phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl -(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct imidazole compounds such as 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, and 2-phenylimidazoline, as well as adducts of imidazole compounds and epoxy resins. Commercially available imidazole curing accelerators include, for example, "1B2PZ", "2E4MZ", "2MZA-PW", "2MZ-OK", "2MA-OK", "2MA-OK-PW", "2PHZ", "2PHZ-PW", "Cl1Z", "Cl1Z-CN", "Cl1Z-CNS", and "C11Z-A" manufactured by Shikoku Chemical Industry Co., Ltd.; and "P200-H50" manufactured by Mitsubishi Chemical Corporation.

Metal-based curing accelerators include, for example, organometallic complexes or organometallic salts of metals such as cobalt, copper, zinc, iron, nickel, manganese, and tin. Specific examples of organometallic complexes include organocobalt complexes such as cobalt (II) acetylacetonate and cobalt (III) acetylacetonate, organocopper complexes such as copper (II) acetylacetonate, organozinc complexes such as zinc (II) acetylacetonate, organoiron complexes such as iron (III) acetylacetonate, organonickel complexes such as nickel (II) acetylacetonate, and organomanganese complexes such as manganese (II) acetylacetonate. Organometallic salts include, for example, zinc octylate, tin octylate, zinc naphthenate, cobalt naphthenate, tin stearate, and zinc stearate.

Examples of amine-based curing accelerators include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene. Commercially available amine-based curing accelerators may be used, such as "MY-25" manufactured by Ajinomoto Fine-Techno Co., Ltd.

The amount of the curing accelerator is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.05% by mass or more, and is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 0.2% by mass or less, assuming that the non-volatile components in the resin composition are 100% by mass.

-Optional Additives-
The resin composition may further contain any additive as an optional non-volatile component in combination with the above-mentioned components. The optional additives include, for example, flame retardants, polymerization initiators, organometallic compounds such as organic copper compounds, organic zinc compounds, and organic cobalt compounds, colorants such as phthalocyanine blue, phthalocyanine green, iodine green, diazo yellow, crystal violet, titanium oxide, and carbon black, polymerization inhibitors such as hydroquinone, catechol, pyrogallol, and phenothiazine, leveling agents such as silicone-based leveling agents and acrylic polymer-based leveling agents, thickeners such as bentone and montmorillonite, defoamers such as silicone-based defoamers, acrylic defoamers, fluorine-based defoamers, and vinyl resin-based defoamers, ultraviolet absorbers such as benzotriazole-based ultraviolet absorbers, adhesion improvers such as urea silane, adhesion imparters such as triazole-based adhesion imparters, tetrazole-based adhesion imparters, and triazine-based adhesion imparters, and hindered phenol-based antioxidants. antioxidants such as stilbene derivatives; fluorescent brighteners such as stilbene derivatives; surfactants such as fluorine-based surfactants and silicone-based surfactants; flame retardants such as phosphorus-based flame retardants (e.g., phosphate ester compounds, phosphazene compounds, phosphinic acid compounds, red phosphorus), nitrogen-based flame retardants (e.g., melamine sulfate), halogen-based flame retardants, and inorganic flame retardants (e.g., antimony trioxide); dispersants such as phosphate ester-based dispersants, polyoxyalkylene-based dispersants, acetylene-based dispersants, silicone-based dispersants, anionic dispersants, and cationic dispersants; stabilizers such as borate-based stabilizers, titanate-based stabilizers, aluminate-based stabilizers, zirconate-based stabilizers, isocyanate-based stabilizers, carboxylic acid-based stabilizers, and carboxylic anhydride-based stabilizers; photopolymerization initiator assistants such as tertiary amines; and photosensitizers such as pyrarizones, anthracenes, coumarins, xanthones, and thioxanthones. One type of any additive may be used alone, or two or more types may be used in combination.

From the viewpoint of making the circuit board thinner, the thickness of the resin composition layer is preferably 200 μm or less, more preferably 100 μm or less, even more preferably 80 μm or less, even more preferably 60 μm or less, or 50 μm or less. In particular, from the viewpoint of facilitating the formation of small diameter vias, the thickness is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. The lower limit of the thickness of the resin composition layer is not particularly limited, but is usually 3 μm or more.

In the insulating resin film, the resin composition layer may have a multi-layer structure consisting of two or more layers. When using a resin composition layer with a multi-layer structure, it is preferable that the total thickness is within the above range.

The insulating resin film can be produced, for example, by preparing a liquid (varnish-like) resin composition as is or by dissolving the resin composition in a solvent to prepare a liquid (varnish-like) resin composition, applying this onto a support using a coating device such as a die coater, and then drying to form a resin composition layer.

Examples of solvents used in preparing the resin varnish include ketone-based solvents such as acetone, methyl ethyl ketone (MEK), and cyclohexanone; acetate-based solvents such as ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate, and carbitol acetate; carbitol-based solvents such as cellosolve and butyl carbitol; aromatic hydrocarbon-based solvents such as toluene and xylene; and amide-based solvents such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone. The solvents may be used alone or in combination of two or more.

Drying may be performed by known drying methods such as heating or blowing hot air. If a large amount of solvent remains in the resin composition layer, it may cause swelling after curing, so the resin composition is usually dried so that the amount of residual solvent in the resin composition is 10% by mass or less, preferably 5% by mass or less. Although this varies depending on the boiling point of the solvent in the resin varnish, for example, when using a resin varnish containing 30% by mass to 60% by mass of solvent, the resin composition layer can be formed by drying at 50°C to 150°C for 3 to 10 minutes.

In the insulating resin film, a protective film similar to the support can be further laminated on the surface of the resin composition layer that is not bonded to the support (i.e., the surface opposite the support). The thickness of the protective film is not particularly limited and may be, for example, 1 μm to 40 μm. By laminating the protective film, it is possible to prevent the adhesion of dirt and the like to the surface of the resin composition layer and scratches. The insulating resin film can be stored in a roll, and when manufacturing a circuit board, it can be used by peeling off the protective film.

[Method of manufacturing a circuit board]
The method for producing a circuit board of the present invention comprises the steps of:
(A) preparing an insulating resin film including a support and a resin composition layer formed from a resin composition provided on the support;
(B) laminating an insulating resin film on the inner layer substrate so that the resin composition layer is bonded to the inner layer substrate;
(C) a step of thermally curing the resin composition layer to form an insulating layer;
(E) forming a via in the insulating layer and then forming a conductor layer on the insulating layer;
(F) heating the insulating layer at a temperature of 175° C. or more and 205° C. or less; and (G) heating the insulating layer at a temperature of 110° C. or more and less than 175° C.,
When the heating temperature in step (F) is T3 (°C) and the heating temperature in step (G) is T4 (°C), the relationship 20°C≦T3−T4≦70°C is satisfied.

The method for producing a circuit board of the present invention may include the following step (D) as necessary.
(D) heating the insulating layer;
It is preferable that step (D) is carried out after step (C) and before step (E). Therefore, the method for producing a circuit board of the present invention is preferably carried out in the order of steps (A) to (G).

This manufacturing method makes it possible to provide a circuit board with improved adhesion and suppressed warping. By carrying out step (F), the insulating layer can be sufficiently hardened and the adhesion between the conductor layer and the insulating layer can be improved. However, as a result of intensive research by the present inventors, it has been found that by carrying out step (G) after step (F), specifically, by carrying out an annealing treatment after step (F) in which the heating temperature in step (G) is adjusted so that the heating temperature in step (F) and the heating temperature in step (G) satisfy a predetermined relationship, the residual stress accumulated in the insulating layer is alleviated, and as a result, it becomes possible to achieve both adhesion between the conductor layer and the insulating layer and suppression of warping.

Below, we will explain each step in the manufacturing method for the circuit board of the present invention.

<Step (A)>
In step (A), an insulating resin film is prepared as described above.

<Step (B)>
In step (B), an insulating resin film is laminated on the inner layer substrate so that the resin composition layer is bonded to the inner layer substrate, thereby obtaining a laminate.

An inner layer substrate is a member that becomes the substrate of a circuit board or a printed wiring board, and examples thereof include a glass epoxy substrate, a metal substrate, a polyester substrate, a polyimide substrate, a BT resin substrate, and a thermosetting polyphenylene ether substrate. The substrate may have a conductor layer on one or both sides, and the conductor layer may be patterned. In addition, when manufacturing a printed wiring board, an intermediate product on which an insulating layer and/or a conductor layer is to be further formed is also included in the inner layer substrate. When the circuit board is a circuit board with built-in components, an inner layer substrate with built-in components may be used.

The insulating resin film is laminated on the inner layer substrate so that the resin composition layer is bonded to the inner layer substrate to obtain a laminate. In one embodiment, the lamination of the inner layer substrate and the insulating resin film can be performed, for example, by hot pressing the insulating resin film to the inner layer substrate from the support side. Examples of the member for hot pressing the insulating resin film to the inner layer substrate (hereinafter also referred to as the "hot pressing member") include a heated metal plate (such as a SUS plate) or a metal roll (SUS roll). Note that it is preferable to press the hot pressing member through an elastic material such as heat-resistant rubber so that the insulating resin film can sufficiently follow the surface irregularities of the inner layer substrate, rather than directly pressing the insulating resin film with the hot pressing member.

The lamination of the inner layer substrate and the insulating resin film may be performed by a vacuum lamination method. In the vacuum lamination method, the heat-pressure bonding temperature is preferably in the range of 60°C to 160°C, more preferably in the range of 80°C to 140°C, the heat-pressure bonding pressure is preferably in the range of 0.098MPa to 1.77MPa, more preferably in the range of 0.29MPa to 1.47MPa, and the heat-pressure bonding time is preferably in the range of 10 seconds to 400 seconds, more preferably in the range of 20 seconds to 300 seconds. The lamination is preferably performed under reduced pressure conditions of 26.7hPa or less.

Lamination can be performed using a commercially available vacuum laminator. Examples of commercially available vacuum laminators include a vacuum pressure laminator manufactured by Meiki Seisakusho Co., Ltd., a vacuum applicator manufactured by Nikko Materials Co., Ltd., and a batch-type vacuum pressure laminator.

After lamination, the laminated insulating resin film may be smoothed under normal pressure (atmospheric pressure), for example by pressing a thermocompression member from the support side. The pressing conditions for the smoothing treatment may be the same as the thermocompression conditions for the lamination. The smoothing treatment may be performed using a commercially available laminator. Note that lamination and smoothing treatment may be performed consecutively using the commercially available vacuum laminator.

<Step (C)>
In step (C), the resin composition layer is thermally cured to form an insulating layer. Usually, the curing reaction of the resin composition does not proceed completely by the thermal curing in step (C). Therefore, the thermal curing in step (C) is sometimes called "half cure".

The heat curing temperature T1 (°C) of the resin composition layer in step (C) is preferably 100°C or higher, more preferably 150°C or higher, and even more preferably 160°C or higher. The upper limit is preferably 190°C or lower, more preferably 188°C or lower, and even more preferably 185°C or lower.

The heat curing time of the resin composition layer in step (C) varies depending on the type of resin composition, etc., but is preferably 5 minutes or more, more preferably 10 minutes or more, and even more preferably 20 minutes or more. The upper limit is not particularly limited, but is preferably 120 minutes or less, more preferably 100 minutes or less, and even more preferably 90 minutes or less. The heating time of the resin composition layer means the time during which the curing heating temperature of the resin composition layer is maintained. The heat curing is usually performed under a gas atmosphere (e.g., air, argon gas, nitrogen gas, or a mixture thereof), for example, under a pressure of 0.05 MPa to 0.15 MPa, preferably 0.08 to 0.12 MPa.

In the method for manufacturing a circuit board, before step (C), the resin composition layer may be preheated at a temperature lower than the heat curing temperature T1.

The preheating temperature of the resin composition layer is preferably 50°C or higher, more preferably 100°C or higher, and even more preferably 120°C or higher, and is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 140°C or lower. The preheating time of the resin composition layer is preferably 5 minutes or more, more preferably 10 minutes or more, and even more preferably 15 minutes or more, and is preferably 150 minutes or less, more preferably 130 minutes or less, and even more preferably 120 minutes or less. Preheating is usually performed under a gas atmosphere (e.g., air, argon gas, nitrogen gas, or a mixture thereof), for example, under a pressure of 0.05 MPa to 0.15 MPa, preferably 0.08 to 0.12 MPa.

After step (C) and before steps (D) and (E), it is preferable to include a step (C-1) of cooling the insulating layer. The cooling temperature is about room temperature (20°C to 25°C), preferably 35°C or less, more preferably 30°C or less, and even more preferably 25°C or less. The lower limit is preferably 0°C or more, more preferably 5°C or more, and even more preferably 10°C or more. The cooling method is not particularly limited, and the insulating layer may be left to cool, or may be cooled by blowing cold air onto the insulating layer or pressing the insulating layer against a cooled roll. The cooling in this step is usually performed under a gas atmosphere (e.g., air, argon gas, nitrogen gas, or a mixture thereof), for example, under a pressure of 0.05 MPa to 0.15 MPa, preferably 0.08 to 0.12 MPa.

The thickness of the insulating layer formed by thermal curing in step (C) depends on the thickness of the resin composition layer of the prepared insulating resin film, but is, for example, 200 μm or less, preferably 100 μm or less, more preferably 80 μm or less, even more preferably 60 μm or less, and particularly preferably 50 μm or less. The lower limit is not particularly limited, but can usually be 1 μm or more, 5 μm or more, 10 μm or more, etc.

From the viewpoint of improving the adhesion between the conductor layer and the insulating layer, the degree of cure of the insulating layer after step (C) is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. The lower limit of the degree of cure is preferably 95% or less, more preferably 90% or less. The degree of cure can be measured, for example, using a differential scanning calorimeter or a Fourier transform infrared spectrometer.

<Step (D)>
In the step (D), the insulating layer is heated to relieve the stress caused by the curing of the resin composition layer.

The heating temperature T2 (°C) of the insulating layer is preferably lower than the curing heating temperature T1. Specifically, it is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher. The upper limit is preferably 150°C or lower, more preferably 145°C or lower, and even more preferably 140°C or lower.

The heating time of the insulating layer varies depending on the type of resin composition, etc., but is preferably 5 minutes or more, more preferably 10 minutes or more, and even more preferably 15 minutes or more. The upper limit is not particularly limited, but is preferably 120 minutes or less, more preferably 100 minutes or less, and even more preferably 90 minutes or less. The heating time of the insulating layer means the time during which the heating temperature of the insulating layer is maintained. Heating is usually performed under a gas atmosphere (e.g., air, argon gas, nitrogen gas, or a mixture thereof), for example, under a pressure of 0.05 MPa to 0.15 MPa, preferably 0.08 to 0.12 MPa.

Step (D) may be performed once or multiple times. If it is performed multiple times, the heating temperature and heating time may be the same as or different from the first heating temperature and heating time.

After step (D) and before step (E), it is preferable to include a step (D-1) of cooling the insulating layer. The cooling temperature, etc. are the same as in step (C-1).

The difference (T1-T2) between the heat curing temperature T1 in step (C) and the heating temperature T2 in step (D) is preferably 30°C or higher, more preferably 40°C or higher, and even more preferably 45°C or higher, from the viewpoint of obtaining a significant effect of the present invention. The upper limit is preferably 70°C or lower, more preferably 60°C or lower, and even more preferably 50°C or lower.

<Step (E)>
In step (E), a via is formed in the insulating layer, and a conductor layer is further formed on the insulating layer. Step (E) preferably includes the following steps (E-1), (E-2), and (E-3) in this order.
(E-1) forming a via in an insulating layer;
(E-2) a step of roughening the insulating layer; and (E-3) a step of forming a conductor layer on the insulating layer.

In step (E-1), via holes are formed in the surface of the insulating layer by drilling. This usually results in a via hole being formed in the insulating layer, with the conductor layer of the inner substrate being exposed at the bottom of the via hole.

Via holes are usually provided for electrical connection between layers, and can be formed by known methods using drills, lasers, plasma, etc., taking into account the characteristics of the insulating layer, with the use of lasers being preferred.

Examples of laser light sources that can be used to form via holes include _CO2 lasers (carbon dioxide lasers), UV-YAG lasers, UV lasers, YAG lasers, excimer lasers, etc. Among these, from the viewpoints of processing speed and cost, _CO2 lasers and UV-YAG lasers are preferred.

In terms of improving the workability of the via hole, the number of shots when irradiating the laser is preferably 5 or less, more preferably 3 or less. In order to keep the number of shots within the above range, it is preferable to set the laser energy and pulse width to a certain value or more. The laser output is preferably 0.1 W or more, more preferably 0.3 W or more, even more preferably 0.5 W or more, and preferably 30 W or less, more preferably 10 W or less, even more preferably 5 W or less. In addition, the laser pulse width is preferably 0.5 μsec or more, more preferably 1 μsec or more, even more preferably 3 μsec or more, and preferably 35 μsec or less, more preferably 30 μsec or less, even more preferably 25 μsec or less.

The via holes can be formed using a commercially available laser device. Examples of commercially available carbon dioxide gas laser devices include the "LC-2E21B/1C" manufactured by Hitachi Via Mechanics, the "ML605GTWII" manufactured by Mitsubishi Electric, the "605GTWIII(-P)" manufactured by Mitsubishi Electric, and a board drilling laser processing machine manufactured by Matsushita Welding Systems. Examples of UV-YAG laser devices include the "LU-2L212/M50L" manufactured by Via Mechanics.

The shape of the via hole is not particularly limited, but is generally circular (approximately circular). The opening diameter (top diameter) of the via hole that can be formed by carrying out step (E-1) is preferably 5 μm or more, more preferably 10 μm or more, more preferably 20 μm or more, 30 μm or more, 40 μm or more, and preferably 100 μm or less, more preferably 90 μm or less, and even more preferably 80 μm or less, 70 μm or less, 60 μm or less. Here, the opening diameter (top diameter) of the via hole refers to the diameter of the opening of the via hole at the surface of the insulating layer.

In step (E-2), the surface of the insulating layer is roughened (desmeared) to remove smears in the via holes while roughening the surface of the insulating layer. There are no particular limitations on the procedure or conditions of the roughening process, so long as it can roughen the surface of the insulating layer and remove smears in the via holes. For example, the roughening process may include a swelling process using a swelling liquid, a roughening process using an oxidizing agent, and a neutralization process using a neutralizing liquid, in that order.

Examples of the swelling liquid used in the roughening treatment include an alkaline solution, a surfactant solution, and the like, and an alkaline solution is preferred. As the alkaline solution, a sodium hydroxide solution and a potassium hydroxide solution are more preferred. Examples of commercially available swelling liquids include "Swelling Dip Securigans P" and "Swelling Dip Securigans SBU" manufactured by Atotech Japan. The swelling treatment using a swelling liquid is not particularly limited, but can be performed by, for example, immersing the object in a swelling liquid at 30°C to 90°C for 1 to 20 minutes. From the viewpoint of obtaining the effects of the present invention more significantly, it is preferable to immerse the object in a swelling liquid at 40°C to 80°C for 5 to 15 minutes.

The oxidizing agent used in the roughening treatment can be, for example, an alkaline permanganate solution in which potassium permanganate or sodium permanganate is dissolved in an aqueous solution of sodium hydroxide. Roughening treatment using an oxidizing agent such as an alkaline permanganate solution is preferably performed by immersing the target object in an oxidizing agent solution heated to 60°C to 100°C for 10 to 30 minutes. The concentration of permanganate in the alkaline permanganate solution is preferably 5% by mass to 10% by mass. Commercially available oxidizing agents include alkaline permanganate solutions such as "Concentrate Compact CP" and "Dosing Solution Securigans P" manufactured by Atotech Japan.

The neutralizing solution used in the roughening treatment is preferably an acidic aqueous solution, and a commercially available product is, for example, "Reduction Solution Securigant P" manufactured by Atotech Japan. Treatment with a neutralizing solution can be performed by immersing the treated surface that has been desmeared with an oxidizing agent in a neutralizing solution at 30°C to 80°C for 1 to 30 minutes. From the standpoint of workability, etc., a method in which the object that has been desmeared with an oxidizing agent is immersed in a neutralizing solution at 30°C to 70°C for 3 to 20 minutes is preferred.

The arithmetic mean roughness (Ra) of the insulating layer surface after the roughening treatment is preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. The lower limit is not particularly limited, and may be, for example, 1 nm or more, 2 nm or more, etc. The root mean square roughness (Rq) of the insulating layer surface after the desmear treatment is preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. The lower limit is not particularly limited, and may be, for example, 1 nm or more, 2 nm or more, etc. The arithmetic mean roughness (Ra) and root mean square roughness (Rq) of the insulating layer surface can be measured using a non-contact surface roughness meter.

In step (E-3), a conductor layer is formed on the insulating layer. The conductor material used for the conductor layer is not particularly limited. In a preferred embodiment, the conductor layer contains one 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. The conductor layer may be a single metal layer or an alloy layer, and examples of the alloy layer include layers formed from alloys of two or more metals selected from the above group (e.g., nickel-chromium alloy, copper-nickel alloy and copper-titanium alloy). Among these, from the viewpoints of versatility, cost, ease of patterning, etc. of the conductor layer formation, a single metal layer of chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver or copper, or an alloy layer of a nickel-chromium alloy, a copper-nickel alloy, or a copper-titanium alloy is preferred, a single metal layer of chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver or copper, or an alloy layer of a nickel-chromium alloy is more preferred, and a single metal layer of copper is even more preferred.

The conductor layer may be a single-layer structure, or a multi-layer structure in which two or more single metal layers or alloy layers made of different types of metals or alloys are laminated. When the conductor layer has a multi-layer structure, the layer in contact with the insulating layer is preferably a single metal layer of chromium, zinc, or titanium, or an alloy layer of a nickel-chromium alloy.

The thickness of the conductor layer depends on the desired printed wiring board design, but is generally between 3 μm and 35 μm, preferably between 5 μm and 30 μm.

The conductor layer can be formed by any suitable conventional method such as plating, sputtering, or vapor deposition, and is preferably formed by plating. In one suitable embodiment, the surface of the insulating layer is plated by a conventional technique such as a semi-additive method or a full-additive method to form a conductor layer having a desired wiring pattern. Below, an example of forming a conductor layer by a semi-additive method is shown.

A plating seed layer is formed on the surface of the insulating layer by electroless plating. Next, a mask pattern is formed on the formed plating seed layer to expose a portion of the plating seed layer corresponding to the desired wiring pattern. A metal layer is formed on the exposed plating seed layer by electrolytic plating, and the mask pattern is then removed. Thereafter, unnecessary plating seed layer is removed by etching or the like, and a conductor layer having the desired wiring pattern can be formed.

The plating seed layer is formed by electroless plating on the surface of the insulating layer after heat treatment. First, alkaline cleaning is performed to clean the surface of the insulating layer and adjust the charge. Next, a pre-dip process is performed to adjust the charge on the surface of the insulating layer in order to apply Pd (palladium) to the surface of the insulating layer. Next, Pd, an activator, is applied to the surface, and the Pd applied to the insulating layer is reduced. Next, copper (Cu) is precipitated on the surface of the insulating layer to form the plating seed layer.

After forming the plating seed layer, a mask pattern is formed to expose a portion of the plating seed layer. The mask pattern can be formed, for example, by bonding a dry film to the plating seed layer and performing exposure, development, and washing under specified conditions.

As the dry film, a photosensitive dry film made of a photoresist composition can be used. Examples of such dry films include dry films of novolac resin, acrylic resin, and the like. As the dry film, a commercially available product can be used, such as "Photec RY-3600" manufactured by Hitachi Chemical Co., Ltd. or "ALPHO 20A263" manufactured by Nikko Materials Co., Ltd.

Next, an electrolytic plating layer is formed on the exposed plating seed layer by electrolytic plating. If there are via holes, an electrolytic plating layer is formed on the exposed plating seed layer by electrolytic plating, and the via holes may be filled by electrolytic plating to form filled vias.

After the electrolytic plating layer is formed, the mask pattern is removed and the unnecessary plating seed layer is removed by flash etching. Flash etching is performed under any suitable conditions to form a patterned conductor layer. After the mask pattern is removed, an annealing treatment may be performed as necessary.

The mask pattern can be removed using an alkaline remover such as a sodium hydroxide solution.

The annealing process can be carried out, for example, by heating the inner layer substrate at 150 to 200°C for 20 to 90 minutes.

Flash etching is usually performed using an etchant such as an etching solution. For example, when the material of the pattern conductor layer is copper, examples of the etching solution include an etching solution containing hydrogen peroxide as the main component (hydrogen peroxide-based etching solution), an acidic etching solution, an alkaline etching solution, and the like. Among these, hydrogen peroxide-based etching solutions are preferred from the viewpoint of obtaining the effects of the present invention more significantly.

As the hydrogen peroxide-based etching solution, an etching solution containing hydrogen peroxide and an inorganic acid is preferable. Examples of the inorganic acid include sulfuric acid, nitric acid, phosphoric acid, etc., and sulfuric acid and phosphoric acid are preferable. The inorganic acid may be any one type or a combination of two or more types. As the hydrogen peroxide-based etching solution, a commercially available product can be used, for example, the SAC series etching solution (manufactured by Ebara Electric Industries, Ltd.).

Examples of acidic etching solutions include an aqueous solution of ferric chloride, an aqueous solution containing sodium peroxodisulfate and sulfuric acid, and an etching solution whose main components are nitric acid and sulfuric acid. Commercially available acidic etching solutions can be used, such as NH-1865 manufactured by MEC and Melstrip N-950 manufactured by Meltex.

Commercially available alkaline etching solutions can be used, such as CF-6000 manufactured by MEC and E-Process-WL manufactured by Meltex.

Flash etching can be performed by immersing the inner layer substrate in an etching solution or by spraying the etching solution, but immersion in an etching solution is preferred from the viewpoint of obtaining the most significant effects of the present invention.

From the viewpoint of obtaining a significant effect of the present invention, the temperature of the etching solution is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher, and is preferably 60°C or lower, more preferably 50°C or lower, and even more preferably 40°C or lower.

The support of the insulating resin film may be removed between step (B) and step (C), between step (C) and step (D), or between step (D) and step (E), or may be removed in step (E). When removing the support in step (E), it is preferable to remove the support before step (E-2).

If necessary, the formation of the insulating layer and the conductor layer in steps (A) to (E) may be repeated to form a multilayer wiring board.

<Step (F)>
In step (F), the insulating layer is heated at a temperature of 175° C. or more and 205° C. or less to increase the degree of cure of the insulating layer. Usually, the curing reaction of the resin composition proceeds sufficiently by the heat curing in step (F). Therefore, the heat curing in step (F) is sometimes called "full cure". By carrying out step (F), it is possible to improve the adhesion between the insulating layer and the conductor layer.

The heating temperature T3 (°C) of the insulating layer is 175°C or higher, preferably 180°C or higher, more preferably 185°C or higher, and even more preferably 188°C or higher. The upper limit is 205°C or lower, preferably 200°C or lower, more preferably 195°C or lower, and even more preferably 193°C or lower.

The heating time of the insulating layer varies depending on the type of resin composition, etc., but is preferably 10 minutes or more, more preferably 30 minutes or more, and even more preferably 50 minutes or more. The upper limit is not particularly limited, but is preferably 120 minutes or less, more preferably 100 minutes or less, and even more preferably 90 minutes or less. The heating time of the insulating layer means the time for which the heating temperature of the insulating layer is maintained. Heating is usually performed under a gas atmosphere (e.g., air, argon gas, nitrogen gas, or a mixture thereof), for example, under a pressure of 0.05 MPa to 0.15 MPa, preferably 0.08 to 0.12 MPa.

Step (F) may be performed once or multiple times. When performed multiple times, the heating temperature and heating time may be the same as or different from the first heating temperature and heating time. When performing step (F) multiple times, it is preferable that each heating temperature and each heating time are within the above range, and T3-T4 in any one of the multiple steps (F) should satisfy the specified range.

After step (F) and before step (G), it is preferable to include a step (F-1) of cooling the insulating layer. The cooling temperature, etc. are the same as in step (C-1).

<Step (G)>
In step (G), the insulating layer is heated at a temperature of 110° C. or higher and lower than 175° C. to relieve the stress generated by heating the insulating layer in step (F). By carrying out step (G), the stress accumulated inside the insulating layer is relieved, and it becomes possible to suppress the occurrence of warping of the circuit board.

The heating temperature T4 (°C) of the insulating layer is 110°C or higher, preferably 113°C or higher, more preferably 115°C or higher, and even more preferably 118°C or higher. The upper limit is less than 175°C, preferably 170°C or lower, more preferably 165°C or lower, and even more preferably 160°C or lower.

The difference (T3-T4) between the heating temperature T3 in step (F) and the heating temperature T4 in step (G) is 20°C or more, preferably 21°C or more, more preferably 22°C or more, even more preferably 23°C or more, 25°C or more, 30°C or more, or 35°C or more, from the viewpoint of suppressing the occurrence of warping and producing a circuit board with improved adhesion. The upper limit is 70°C or less, preferably 65°C or less, more preferably 60°C or less, and even more preferably 55°C or less.

The heating time of the insulating layer varies depending on the type of resin composition, etc., but is preferably 10 minutes or more, more preferably 20 minutes or more, and even more preferably 30 minutes or more. The upper limit is not particularly limited, but is preferably 60 minutes or less, more preferably 50 minutes or less, and even more preferably 45 minutes or less. The heating time of the insulating layer means the time during which the heating temperature of the insulating layer is maintained. Heating is usually performed under a gas atmosphere (e.g., air, argon gas, nitrogen gas, or a mixture thereof), for example, under a pressure of 0.05 MPa to 0.15 MPa, preferably 0.08 to 0.12 MPa.

Step (G) may be performed once or multiple times. When performed multiple times, the heating temperature and heating time may be the same as or different from the first heating temperature and heating time. When performing step (G) multiple times, it is preferable that each heating temperature and each heating time are within the above range, and T3-T4 in any one of the multiple steps (G) should satisfy the specified range.

After step (G), it is preferable to include a step (G-1) of cooling the insulating layer. The cooling temperature, etc. are the same as in step (C-1).

<Semiconductor Device>
A semiconductor device including a circuit board can be manufactured by using the circuit board obtained by the manufacturing method of the present invention.

Semiconductor devices include various semiconductor devices used in electrical appliances (e.g., computers, mobile phones, digital cameras, televisions, etc.) and vehicles (e.g., motorcycles, automobiles, trains, ships, aircraft, etc.).

A semiconductor device can be manufactured by mounting a component (semiconductor chip) on a conductive part of a circuit board. A conductive part is a part of a circuit board that transmits an electrical signal, and the part may be either on the surface or embedded. In addition, there is no particular limitation on the semiconductor chip, so long as it is an electrical circuit element made of semiconductor material.

The method of mounting semiconductor chips when manufacturing semiconductor devices is not particularly limited as long as the semiconductor chips function effectively, but specific examples include wire bonding mounting method, flip chip mounting method, bumpless build-up layer (BBUL) mounting method, anisotropic conductive film (ACF) mounting method, non-conductive film (NCF) mounting method, etc.

The present invention will be described in detail below with reference to examples. The present invention is not limited to these examples. In the following, the terms "parts" and "%" used to indicate amounts refer to "parts by mass" and "% by mass", respectively, unless otherwise specified. In the following description, the temperature conditions are room temperature (20°C to 25°C) unless otherwise specified, and the pressure conditions are normal pressure (0.1 MPa) unless otherwise specified.

<Production Example 1: Production of Resin Composition 1>
15 parts of a liquid bisphenol A type epoxy resin (epoxy equivalent 180 g/eq., "jER828EL" manufactured by Mitsubishi Chemical Corporation), 30 parts of a biphenyl type epoxy resin (epoxy equivalent 290 g/eq., "NC3000H" manufactured by Nippon Kayaku Co., Ltd.), 5 parts of a naphthalene type tetrafunctional epoxy resin (epoxy equivalent: 162 g/eq., "HP-4700" manufactured by DIC Corporation), and 2 parts of a phenoxy resin ("YX7553" manufactured by Mitsubishi Chemical Corporation, a 1:1 solution of methyl ethyl ketone (hereinafter abbreviated as "MEK") with a non-volatile content of 30 mass% and cyclohexanone) were heated and dissolved in 8 parts of MEK and 8 parts of cyclohexanone with stirring. Thereto, 32 parts of a phenol novolac-based curing agent (DIC Corporation "LA-7054" MEK solution with 60% nonvolatile content, phenolic hydroxyl group equivalent 124 g / eq.), 0.2 parts of tetrabutylphosphonium decanoate salt (Hokuko Chemical Industry Co., Ltd., "TBP-DA") as a curing accelerator, 120 parts of spherical silica (average particle size 0.5 μm, aminosilane-treated "SOC2" Admatechs Co., Ltd.), and 2 parts of a polyvinyl butyral resin solution (Sekisui Chemical Co., Ltd. "KS-1", a mixed solution of 15% nonvolatile content ethanol and toluene in a mass ratio of 1:1) were uniformly dispersed using a high-speed rotating mixer to prepare a varnish-like resin composition 1.

<Production Example 2: Production of Resin Composition 2>
Biphenylaralkyl type epoxy resin ("NC3000H" manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent: about 290/eq.) 5 parts, naphthalene type epoxy resin ("HP4032SS" manufactured by DIC Corporation, epoxy equivalent: about 145 g/eq.) 10 parts, bisphenol A type epoxy resin and bisphenol F type epoxy resin mixture ("ZX1059" manufactured by Nippon Steel Chemical & Material Co., Ltd., epoxy equivalent: 165 g/eq.) 5 parts, active ester type curing agent ("HPC-8150-62T" manufactured by DIC Corporation, active group equivalent: about 229 g/eq., toluene solution with solid content of 61.5% by mass) 30 parts, phenol type curing agent ("HPC-8150-62T" manufactured by DIC Corporation, active group equivalent: about 229 g/eq., toluene solution with solid content of 61.5% by mass) 30 parts, A varnish-like resin composition 2 was prepared by uniformly dispersing 80 parts of spherical silica ("SO-C2" manufactured by Admatechs Co., Ltd., average particle size 0.5 μm) surface-treated with an amine-based alkoxysilane compound ("KBM573" manufactured by Shin-Etsu Chemical Co., Ltd.), 4 parts of 4-dimethylaminopyridine (MEK solution with 5% solids by mass), 30 parts of MEK, and 5 parts of phenoxy resin ("LA3018-50P" manufactured by Mitsubishi Chemical Co., Ltd., active group equivalent of about 151, 2-methoxypropanol solution with 50% solids by mass), 5 parts of phenoxy resin ("YX7553BH30" manufactured by Mitsubishi Chemical Co., Ltd., 1:1 solution of MEK and cyclohexanone with 30% solids by mass), using a mixer.

<Production Example 3: Production of Resin Composition 3>
35 parts of a liquid bisphenol A type epoxy resin (epoxy equivalent 180 g/eq., "jER828EL" manufactured by Mitsubishi Chemical Corporation), 35 parts of a biphenyl type epoxy resin (epoxy equivalent 290 g/eq., "NC3000H" manufactured by Nippon Kayaku Co., Ltd.), and 40 parts of a phenoxy resin (weight average molecular weight 38,000, "YX6954" manufactured by Mitsubishi Chemical Corporation, a 1:1 solution of MEK and cyclohexanone with a nonvolatile content of 30% by mass) were heated and dissolved in 10 parts of MEK and 3 parts of cyclohexanone with stirring. To this was added 45 parts of a phenol novolac curing agent (DIC Corporation's "LA-7054", MEK solution with 60% nonvolatile content by mass, phenolic hydroxyl group equivalent of 124 g/eq.), 2 parts of a curing accelerator (Hokuko Chemical Industry Co., Ltd.'s "TPTP-SCN", dimethylformamide (hereinafter abbreviated as "DMF") solution with 10% nonvolatile content by mass), and 75 parts of spherical silica (average particle size 0.5 μm, aminosilane-treated "SOC2", Admatechs Co., Ltd.) were uniformly dispersed using a high-speed rotating mixer to prepare a varnish-like resin composition 3.

[Example 1]
<Production of Adhesion Evaluation Sample>
-Step (A)-
Resin composition 1 was uniformly applied onto a PET film (thickness 38 μm) serving as a support using a die coater so that the thickness after drying would be 35 μm, and then dried at 80 to 120° C. (average 100° C.) for 5 minutes to obtain an insulating resin film composed of a PET film and a resin composition layer.

-Step (B)-
The obtained resin composition layer of the insulating resin film was laminated on both sides of a copper-clad laminate (Panasonic "R1515A", total thickness 0.8 mm) to prepare a substrate for adhesion evaluation.

The lamination was performed using a vacuum pressure laminator MVLP-500 manufactured by Meiki Seisakusho Co., Ltd., by vacuum suction at a temperature of 100°C for 30 seconds, followed by pressing from above the PET film with heat-resistant rubber for 30 seconds under conditions of a temperature of 100°C and a pressure of 7.0 kg/ ^cm2 . Next, pressing was performed for 60 seconds under atmospheric pressure using a SUS end plate under conditions of a temperature of 100°C and a pressure of 5.5 kg/ ^cm2 .

-Step (C)-
The above-mentioned adhesion evaluation substrate was subjected to thermal curing of the resin composition layer under the temperature and time conditions (T1) shown in the table below using a hot air circulation oven to form an insulating layer, and then cooled to room temperature to obtain adhesion evaluation substrate T1.

-Step (D)-
The substrate T1 for adhesiveness evaluation was subjected to a heat treatment under the temperature and time conditions (T2) shown in the table below, and then cooled to room temperature to obtain a substrate T2 for adhesiveness evaluation.

-Step (E)-
(Formation of via holes)
Without peeling off the PET film, five holes were drilled in the adhesion evaluation substrate T2 using a _CO2 laser processing machine (HITACHI Corporation's "LC-K212") under the following conditions: power: 1.35 W, number of shots: 2, target top diameter: 50 μm. As a result, multiple via holes were formed that opened onto the circuit conductor of the inner layer substrate, and the conductor layer of the inner layer substrate was exposed on the side of each via hole.

(Roughening treatment)
The PET film was peeled off, and the insulating layer surface was immersed in a swelling liquid, Swelling Dip Securiganth P, manufactured by Atotech Japan, at 60° C. for 10 minutes, then in an oxidizing agent, Concentrate Compact CP, manufactured by Atotech Japan, at 80° C. for 15 minutes, and finally in a neutralizing liquid, Reduction Solution Securiganth P, manufactured by Atotech Japan, at 40° C. for 5 minutes. It was then dried at 80° C. for 30 minutes.

(Formation of electroless plating layer)
The roughened adhesion evaluation substrate T2 was immersed in an electroless plating solution containing _PdCl2 , and then in an electroless copper plating solution. The plating seed layer was annealed by heating at 150°C for 30 minutes to form an electroless plating layer.

-Step (F)-
The adhesion evaluation substrate T2 having the electroless plating layer formed thereon was subjected to a heat treatment under the temperature and time conditions (T3) shown in the table below, and then cooled to room temperature to obtain an adhesion evaluation substrate T3.

-Step (G)-
The substrate T3 for adhesiveness evaluation was subjected to a heat treatment under the temperature and time conditions (T4) shown in the table below, and then cooled to room temperature to obtain a sample for adhesiveness evaluation.

<Production of Samples for Evaluating Warpage Behavior>
In manufacturing samples for adhesion evaluation,
1) Step (A) and step (B) are replaced with steps (A) and (B) in the manufacture of a sample for evaluating warpage behavior as follows:
2) Step (E) was not carried out.
Except for the above, the sample for evaluating warpage behavior was produced in the same manner as the sample for evaluating adhesion.

(Step (A) and step (B) in manufacturing a sample for evaluating warpage behavior)
Resin composition 1 was uniformly applied onto a PET film (thickness 38 μm) serving as a support using a die coater so that the thickness after drying would be 35 μm, and then dried at 80 to 120° C. (average 100° C.) for 5 minutes to obtain an insulating resin film composed of a PET film and a resin composition layer.

The insulating resin film was laminated onto one side of a copper-clad laminate substrate (Hitachi Chemical's "MCL-E700G", a copper-etched substrate with a total thickness of 0.2 mm) to prepare a substrate for evaluating warpage behavior.

The lamination was performed using a vacuum pressure laminator MVLP-500 manufactured by Meiki Seisakusho Co., Ltd., by vacuum suction at a temperature of 100°C for 30 seconds, followed by pressing from above the PET film with heat-resistant rubber for 30 seconds under conditions of a temperature of 100°C and a pressure of 7.0 kg/ ^cm2 . Next, pressing was performed for 60 seconds under atmospheric pressure using a SUS end plate under conditions of a temperature of 100°C and a pressure of 5.5 kg/ ^cm2 .

[Examples 2 and 7, Comparative Example 7]
In Example 1, Resin Composition 1 was changed to Resin Composition 2, and further conditions T1 to T4 were changed. Except for the above, a sample for evaluating adhesion and a sample for evaluating warpage behavior were produced in the same manner as in Example 1.

[Example 3]
In Example 1, Resin Composition 1 was changed to Resin Composition 3, and further conditions T1 to T4 were changed. Except for the above, a sample for evaluating adhesion and a sample for evaluating warpage behavior were produced in the same manner as in Example 1.

[Example 4]
Step (D) was not performed in Example 1. Except for the above, a sample for evaluating adhesion and a sample for evaluating warpage behavior were produced in the same manner as in Example 1.

[Example 5]
Step (D) was not performed in Example 2. Except for the above, a sample for evaluating adhesion and a sample for evaluating warpage behavior were produced in the same manner as in Example 2.

[Example 6]
Step (D) was not performed in Example 3. Except for the above, a sample for evaluating adhesion and a sample for evaluating warpage behavior were produced in the same manner as in Example 3.

[Examples 8 and 9, Comparative Examples 8 and 9]
In Example 2, step (D) was not performed, and further conditions T3 and T4 were changed. Except for the above, a sample for evaluating adhesion and a sample for evaluating warpage behavior were produced in the same manner as in Example 2.

[Comparative Example 1]
Step (G) was not performed in Example 1. Except for the above, a sample for evaluating adhesion and a sample for evaluating warpage behavior were produced in the same manner as in Example 1.

[Comparative Example 2]
Step (G) was not performed in Example 2. Except for the above, a sample for evaluating adhesion and a sample for evaluating warpage behavior were produced in the same manner as in Example 2.

[Comparative Example 3]
Step (G) was not performed in Example 3. Except for the above, a sample for evaluating adhesion and a sample for evaluating warpage behavior were produced in the same manner as in Example 3.

[Comparative Example 4]
The steps (F) and (G) were not performed in Example 1. Except for the above, the same procedures as in Example 1 were carried out to produce a sample for evaluating adhesion and a sample for evaluating warpage behavior.

[Comparative Example 5]
Steps (F) and (G) were not performed in Example 2. Except for the above, a sample for evaluating adhesion and a sample for evaluating warpage behavior were produced in the same manner as in Example 2.

[Comparative Example 6]
The steps (F) and (G) were not performed in Example 3. Except for the above, the same procedures as in Example 3 were carried out to produce a sample for evaluating adhesion and a sample for evaluating warpage behavior.

[Evaluation of Adhesion]
The samples for adhesion evaluation prepared in each Example and Comparative Example were subjected to an accelerated test (130°C, 85% RH, 100 hours), and then the samples for adhesion evaluation were cut out at a cross section including the diameter of the via hole using a FIB (focused ion beam). The cut-out cross section was observed under an electron microscope, and the area where delamination occurred was evaluated according to the following criteria to evaluate adhesion.
◯: The length of delamination is less than 5 μm △: The length of delamination is 5 μm or more and less than 10 μm ×: The length of delamination is 10 μm or more

[Warpage evaluation]
The warpage behavior of the samples for evaluating the warpage behavior produced in each of the examples and comparative examples was measured using a shadow moire device (TherMoire AXP manufactured by Akrometrix) and evaluated according to the following criteria.
◯: Warpage behavior is 3.5 mm or less △: Warpage behavior is more than 3.5 mm and less than 7 mm ×: Warpage behavior is 7 mm or more

It can be seen that Examples 1 to 9, in which steps (F) and (G) were performed under specified temperature conditions, were excellent in both the evaluation of warping behavior and the evaluation of adhesion of the conductor layer. In addition, it was confirmed that Examples 1 to 9 had a low coefficient of thermal expansion because the content of the inorganic filler was 40% by mass or more and 80% by mass or less, when the non-volatile components of the resin composition were taken as 100% by mass.

In contrast, Comparative Examples 1 to 9 were inferior to Examples 1 to 9 in at least one of the evaluations of warping behavior and adhesion of the conductor layer, demonstrating the importance of steps (F) and (G). Note that the "content of inorganic filler (mass %)" in the table represents the content when the non-volatile components of the resin composition are taken as 100 mass %.

In Examples 1 to 9, it was confirmed that even when the thermoplastic resin and curing accelerator were not included, the results were similar to those of the above examples, although to a lesser extent.

Claims (7)

(A) preparing an insulating resin film including a support and a resin composition layer formed from a resin composition provided on the support;
(B) laminating an insulating resin film on the inner layer substrate so that the resin composition layer is bonded to the inner layer substrate;
(C) a step of thermally curing the resin composition layer to form an insulating layer;
(E) forming a via in the insulating layer and then forming a conductor layer on the insulating layer;
(F) heating the insulating layer at a temperature of 175° C. or more and 205° C. or less; and (G) heating the insulating layer at a temperature of 110° C. or more and less than 175° C.,
The resin composition includes an epoxy resin, a curing agent, and an inorganic filler,
The content of the inorganic filler is 40% by mass or more and 80% by mass or less, when the non-volatile components of the resin composition are 100% by mass,
A method for manufacturing a circuit board, wherein when the heating temperature in step (F) is T3 (°C) and the heating temperature in step (G) is T4 (°C), 20°C≦T3−T4≦70°C is satisfied. After step (C) and before step (E),
The method for manufacturing a circuit board according to claim 1 , further comprising the step of: (D) heating the insulating layer. The method for manufacturing a circuit board according to claim 2, wherein the heating temperature T2 in step (D) is 100°C or higher and 150°C or lower. After step (F) and before step (G),
The method for producing a circuit board according to any one of claims 1 to 3, further comprising: (F-1) a step of cooling the insulating layer. The method for manufacturing a circuit board according to any one of claims 1 to 4, wherein the heating time in step (F) is 10 minutes or longer. The method for manufacturing a circuit board according to any one of claims 1 to 5, wherein the heating time in step (G) is 10 minutes or longer. The method for manufacturing a circuit board according to any one of claims 1 to 6, wherein the heating temperature T1 in step (C) is 100°C or higher and 190°C or lower.