Printed Wiring Board and Method of Manufacturing the Same

Abstract

To provide a printed wiring board including a via having high conduction reliability.SOLUTION: A printed wiring board 11 includes a first conductor layer 8, a second conductor layer 3, an interlayer insulating layer 7, a via hole 6 penetrating through the interlayer insulating layer 7, and a via conductor 9 arranged in the via hole 6. The interlayer insulating layer 7 is a cured product of a negative type photosensitive resin composition containing a carboxyl group-containing resin (A), an unsaturated compound (B) having at least one ethylenically unsaturated bond in one molecule, and a photopolymerization initiator (C). The via hole 6 has a first end 61 on the side of the first conductor layer 8, a second end 62 on the side of the second conductor layer 3, and a small diameter part 63 that is between the first end 61 and the second end 62 and has a diameter smaller than the second end 62.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure generally relates to printed wiring boards and methods for manufacturing printed wiring boards, and more particularly to printed wiring boards having an interlayer insulating layer with via holes and via conductors, and methods for manufacturing the printed wiring boards.

Background Art

[0002] In a printed wiring board, vias may be formed in an interlayer insulating layer.

[0003] For example, Patent Document 1 discloses a method for manufacturing a multilayer printed wiring board, which includes a step of irradiating a carbon dioxide laser from above a plastic film adhered to the surface of an insulating layer containing 35% by mass or more of an inorganic filler to form blind vias having a top diameter of 100 μm or less.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, according to the findings of the inventors, the invention described in Patent Document 1 has room for improvement in the conduction reliability of vias. Taper-shaped vias are likely to have reduced conduction reliability.

[0006] Through research and development on the material of the interlayer insulating layer, the inventors have obtained the finding that cracks may occur in the conductors of the vias in the interlayer insulating layer, which deteriorates the conduction reliability.

[0007] An object of the present disclosure is to provide a printed wiring board having vias with high conduction reliability and a method for manufacturing the printed wiring board.

Means for Solving the Problems

[0008] A printed wiring board according to one aspect of the present disclosure includes a first conductor layer, a second conductor layer, an interlayer insulating layer interposed between the first conductor layer and the second conductor layer, a via hole penetrating the interlayer insulating layer, and a via conductor disposed in the via hole to electrically connect the first conductor layer and the second conductor layer. The interlayer insulating layer is a cured product of a negative photosensitive resin composition containing a carboxyl group-containing resin (A), an unsaturated compound (B) having at least one ethylenically unsaturated bond in one molecule, and a photopolymerization initiator (C). The via hole has a first end that is an end on the first conductor layer side, a second end that is an end on the second conductor layer side, and a small-diameter portion that is between the first end and the second end and has a diameter smaller than that of the second end.

[0009] A method for manufacturing a printed wiring board according to one aspect of the present disclosure is a method for manufacturing the printed wiring board, and includes preparing a substrate having the negative photosensitive resin composition containing the carboxyl group-containing resin (A), the unsaturated compound (B) having at least one ethylenically unsaturated bond in one molecule, and the photopolymerization initiator (C), and an insulating layer and the second conductor layer overlapping the insulating layer, laminating a film made from the photosensitive resin composition on the substrate so as to cover the second conductor layer, exposing a negative-patterned region of the film including the pattern of the via hole, and then performing development treatment using an alkaline aqueous solution to form the interlayer insulating layer and the via hole penetrating the interlayer insulating layer.

Advantages of the Invention

[0010] According to one aspect of the present disclosure, it is possible to provide a printed wiring board having vias with high conduction reliability and a method for manufacturing the printed wiring board.

Brief Description of the Drawings

[0011]

Figure 1

Mode for Carrying Out the Invention

[0012] (1) Overview An embodiment according to the present disclosure will be described.

[0013] The printed wiring board 11 according to this embodiment includes a first conductor layer 8, a second conductor layer 3, an interlayer insulating layer 7 interposed between the first conductor layer 8 and the second conductor layer 3, a via hole 6 penetrating the interlayer insulating layer 7, and a via conductor 9 disposed in the via hole 6 to conduct the first conductor layer 8 and the second conductor layer 3 (see FIG. 1E). The interlayer insulating layer 7 is a cured product of a negative photosensitive resin composition containing a carboxyl group-containing resin (A), an unsaturated compound (B) having at least one ethylenically unsaturated bond in one molecule, and a photopolymerization initiator (C). The via hole 6 has a first end 61 which is an end on the first conductor layer 8 side, a second end 62 which is an end on the second conductor layer 3 side, and a small-diameter portion 63 which is between the first end 61 and the second end 62 and has a diameter smaller than that of the second end 62.

[0014] In this embodiment, the interlayer insulating layer 7 is formed from a negative photosensitive resin composition containing a carboxyl group-containing resin (A), an unsaturated compound (B) having at least one ethylenically unsaturated bond in one molecule, and a photopolymerization initiator (C). Therefore, by exposing the film 4 made from the photosensitive resin composition in a pattern and then developing it with an alkaline aqueous solution, the interlayer insulating layer 7 can be formed, and the via hole 6 having the small-diameter portion 63 can be easily formed.

[0015] The reason why the small-diameter portion 63 is likely to be formed is presumed as follows. When the film 4 formed from a negative-type photosensitive resin composition is exposed to light on the surface where the first end 61 of the via hole 6 is formed, the light scatters inside the film 4, making it easier for a wider portion closer to the deep part of the film 4 to be cured. As a result, the uncured portion 5 that becomes the via hole 6 gradually becomes smaller, and the small-diameter portion 63 with a diameter smaller than that of the first end 61 is likely to be formed. Further, on the deeper side inside the film 4, since the light is absorbed by the film 4, it becomes difficult for the light to reach, and thereby the influence of light scattering becomes smaller, making it difficult for the film 4 to progress in curing. Therefore, the diameter of the second end 62 becomes larger than the diameter of the small-diameter portion 63, and the via hole 6 is likely to have a shape that expands from the small-diameter portion 63 to the second end 62.

[0016] In particular, when a film 4 with a film thickness of 5 μm or more and 100 μm or less is produced from a photosensitive resin composition, and ultraviolet light having a spectral intensity at at least one wavelength in the wavelength range of 365 nm ± 65 nm is irradiated onto the region excluding the circular portion with a diameter of 5 μm or more and 100 μm or less in the film 4, and then the film 4 is subjected to development treatment with an alkaline aqueous solution, it is preferable that the photosensitive resin composition has the property that a via hole 6 is formed in the circular portion and the via hole 6 has a small-diameter portion 63. In this case, the diameter of the small-diameter portion 63 of the via hole 6 is 65% or more and less than 100% of the diameter of the second end 62, the diameter of the first end 61 is 65% or more of the diameter of the second end 62, and it is preferable that the diameter of the first end 61 is 100 μm or less. Such characteristics can be realized within the range of the composition of the photosensitive resin composition, which will be described in detail later. Note that the method of irradiating the film 4 with ultraviolet light may be an exposure method using a negative mask or a direct drawing method. Examples of specific test methods and conditions are described in the Examples section.

[0017] Further, in the present embodiment, since the via hole 6 has such a shape, even if stress is generated in the via conductor 9 due to a thermal load being applied to the via conductor 9, cracks are less likely to occur at the interface between the via conductor 9 and the second conductor layer 3. Therefore, a good conduction reliability between the first conductor layer 8 and the second conductor layer 3 is easily obtained by the via. This is presumably because, in the present embodiment, as described above, the inner surface of the via hole 6 of the interlayer insulating layer 7 has a shape in which the diameter increases from the small-diameter portion 63 to the second end 62, so that even if stress is generated in the via conductor 9, the stress is more likely to concentrate on the small-diameter portion 63 than at the second end 62 of the via.

[0018] It is preferable that the minimum diameter of the small-diameter portion 63 is 65% or more and less than 100% of the diameter of the second end 62. In this case, conduction reliability by the via is particularly easily obtained. More preferably, the minimum diameter of the small-diameter portion 63 is 95% or less of the diameter of the second end 62, and even more preferably 90% or less. Also, more preferably, the minimum diameter of the small-diameter portion 63 is 67% or more of the diameter of the second end 62, and even more preferably 79% or more.

[0019] It is preferable that the diameter of the first end 61 is 65% or more with respect to the diameter of the second end 62. In this case, by allowing the plating solution to penetrate into the via hole 6, it becomes easier to fabricate the via conductor 9. That is, it is easy to fabricate the via conductor 9 by the plating method. Therefore, better conduction reliability is more easily obtained. From the viewpoint of obtaining good resolution when fabricating the via hole 6, it is more preferable that the diameter of the first end 61 is 70% or more with respect to the diameter of the second end 62, even more preferably 75% or more, and particularly preferably 80% or more. Also, it is preferable that the diameter of the first end 61 is less than 130% with respect to the diameter of the second end 62, more preferably less than 120%, even more preferably less than 110%, and particularly preferably less than 100%.

[0020] Also, it is preferable that the diameter of the first end 61 is 100 μm or less. In this case, it becomes easier to fabricate the via conductor 9 in the via hole 6 by the plating method or the like. Therefore, better conduction reliability is more easily obtained. Also, the diameter of the first end 61 is, for example, 5 μm or more.

[0021] (2) Photosensitive resin composition Hereinafter, the details of the photosensitive resin composition of this embodiment will be specifically described. In the following description, "(meth)acryl" means at least one of "acryl" and "methacryl". For example, (meth)acrylate means at least one of acrylate and methacrylate.

[0022] The photosensitive resin composition according to this embodiment contains a carboxyl group-containing resin (A), an unsaturated compound (B) having at least one ethylenically unsaturated bond in one molecule, and a photopolymerization initiator (C).

[0023] The carboxyl group-containing resin (A) preferably contains a carboxyl group-containing resin (A1) having a bisphenol fluorene skeleton represented by the following formula (1). When the carboxyl group-containing resin (A) has a bulky bisphenol fluorene skeleton, when ultraviolet rays are irradiated on the film 4 formed from the photosensitive resin composition, light scattering hardly occurs in the deep part. Further, since the carboxyl group-containing resin (A1) has a bisphenol fluorene skeleton, high heat resistance and insulation reliability can be imparted to the cured product of the photosensitive resin composition.

[0024] [Chemical formula]

[0025] In formula (1), R1 to R8 are each independently hydrogen, an alkyl group having 1 to 5 carbon atoms, or a halogen. That is, each of R1 to R8 in formula (1) may be hydrogen, but may also be an alkyl group having 1 to 5 carbon atoms or a halogen. Even if the hydrogen in the aromatic ring is substituted with a low molecular weight alkyl group or a halogen, it does not adversely affect the physical properties of the carboxyl group-containing resin (A1). On the contrary, in some cases, the heat resistance or flame retardancy of the cured product of the photosensitive resin composition containing the carboxyl group-containing resin (A1) is improved by the substitution.

[0026] The carboxyl group-containing resin (A1) is synthesized, for example, by reacting an epoxy compound (a1) having a bisphenol fluorene skeleton represented by the formula (1) with an unsaturated group-containing carboxylic acid (a2), and then reacting the resulting intermediate with an acid anhydride (a3).

[0027] The epoxy compound (a1) has, for example, a structure represented by the following formula (2). In the formula (2), n is an integer, for example, in the range of 0 to 20. In order to appropriately control the molecular weight of the carboxyl group-containing resin (A1), it is more preferable that the average of n is in the range of 0 to 1. If the average of n is in the range of 0 to 1, an excessive increase in the molecular weight of the carboxyl group-containing resin (A1) is likely to be suppressed. Further, in the formula (2), R1 to R8 are each independently hydrogen, an alkyl group having 1 to 5 carbon atoms, or a halogen.

[0028]

Chemical formula

[0029] The unsaturated group-containing carboxylic acid (a2) contains, for example, a compound having only 1 ethylenically unsaturated group in one molecule. More specifically, the unsaturated group-containing carboxylic acid (a2) is, for example, acrylic acid, methacrylic acid, ω-carboxy-polycaprolactone (n≈2) monoacrylate, crotonic acid, cinnamic acid, 2-acryloyloxyethyl succinic acid, 2-methacryloyloxyethyl succinic acid, 2-acryloyloxyethyl phthalic acid, 2-methacryloyloxyethyl phthalic acid, 2-acryloyloxypropyl phthalic acid, 2-methacryloyloxypropyl phthalic acid, 2-acryloyloxyethyl maleic acid, 2-methacryloyloxyethyl maleic acid, β-carboxyethyl acrylate, 2-acryloyloxyethyl tetrahydrophthalic acid, 2-methacryloyloxyethyl tetrahydrophthalic acid, 2-acryloyloxyethyl hexahydrophthalic acid, and 2-methacryloyloxyethyl hexahydrophthalic acid. Preferably, the unsaturated group-containing carboxylic acid (a2) contains acrylic acid. When the unsaturated group-containing carboxylic acid (a2) contains acrylic acid, it is preferably contained in an amount of 50 mol% or more, more preferably 80 mol% or more, still more preferably 85 mol% or more, and particularly preferably 90 mol% or more in the unsaturated group-containing carboxylic acid (a2).

[0030] When reacting the epoxy compound (a1) with the unsaturated group-containing carboxylic acid (a2), an appropriate method can be adopted. For example, the unsaturated group-containing carboxylic acid (a2) is added to a solvent solution of the epoxy compound (a1), and further a thermal polymerization inhibitor and a catalyst are added as necessary and stirred and mixed to obtain a reactive solution. This reactive solution is reacted by a conventional method, preferably at a temperature of 60°C or higher and 150°C or lower, more preferably 80°C or higher and 120°C or lower, to obtain an intermediate. The solvent in this case can contain at least one component selected from the group consisting of ketones such as methyl ethyl ketone and cyclohexanone, aromatic hydrocarbons such as toluene and xylene, acetic acid esters such as ethyl acetate, butyl acetate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, and propylene glycol monomethyl ether acetate, and dialkyl glycol ethers. The thermal polymerization inhibitor can contain at least one component selected from the group consisting of hydroquinone, methyl hydroquinone, and hydroquinone monomethyl ether. The catalyst can contain at least one component selected from the group consisting of tertiary amines such as benzyldimethylamine and triethylamine, quaternary ammonium salts such as trimethylbenzylammonium chloride and methyltriethylammonium chloride, triphenylphosphine, and triphenylstibine.

[0031] It is particularly preferable that the catalyst contains triphenylphosphine. That is, in the presence of triphenylphosphine, it is preferable to react the epoxy compound (a1) with the unsaturated group-containing carboxylic acid (a2). In this case, the ring-opening addition reaction between the epoxy group in the epoxy compound (a1) and the unsaturated group-containing carboxylic acid (a2) is particularly promoted, and a reaction rate (conversion rate) of 95% or more, or 97% or more, or almost 100% can be achieved.

[0032] It is also preferable to react the epoxy compound (a1) with the unsaturated group-containing carboxylic acid (a2) under air bubbling. In this case, the addition polymerization reaction of the unsaturated group can be suppressed, the increase in the molecular weight of the intermediate and the gelation of the solution of the intermediate can be suppressed. Further, excessive coloring of the carboxyl group-containing resin (A1) as the final product can be suppressed.

[0033] When reacting the epoxy compound (a1) with the unsaturated group-containing carboxylic acid (a2), the amount of the unsaturated group-containing carboxylic acid (a2) relative to 1 mol of the epoxy group of the epoxy compound (a1) is preferably 0.8 mol or more and 1.2 mol or less. In this case, a photosensitive resin composition having excellent photosensitivity and stability can be obtained.

[0034] The intermediate thus obtained has a hydroxyl group formed by the reaction of the epoxy group of the epoxy compound (a1) and the carboxyl group of the unsaturated group-containing carboxylic acid (a2).

[0035] Next, the intermediate is reacted with the acid anhydride (a3). The acid anhydride (a3) contains, for example, an acid dianhydride (a4).

[0036] The acid dianhydride (a4) is a compound having two acid anhydride groups. The acid dianhydride (a4) can contain an anhydride of a tetracarboxylic acid. The acid dianhydride (a4) is, for example, 1,2,4,5-benzenetetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride, methylcyclohexene tetracarboxylic dianhydride, tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, ethylene tetracarboxylic dianhydride, 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride, glycerin bisanhydrotrimellitate monoacetate, ethylene glycol bisanhydrotrimellitate, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 1,3,3a,4,5,9b-hexahydro-5(tetrahydro-2,5-dioxo-3-furanyl)naphtho[1,2-c]furan-1,3-dione, 1,2,3,4-butanetetracarboxylic dianhydride, and at least one compound selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride. In particular, it is preferable that the acid dianhydride (a4) contains 3,3',4,4'-biphenyltetracarboxylic dianhydride. In this case, while ensuring good developability of the photosensitive resin composition, the tackiness of the film 4 produced from the photosensitive resin composition can be suppressed, and the insulation reliability and plating resistance of the cured product can be improved.

[0037] The acid anhydride (a3) may contain a monoacid anhydride (a5). The monoacid anhydride (a5) is a compound having one acid anhydride group. The monoacid anhydride (a5) can contain an anhydride of a dicarboxylic acid. The monoacid anhydride (a5) contains, for example, one or more compounds selected from the group consisting of phthalic anhydride, 1,2,3,6-tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, succinic anhydride, methylsuccinic anhydride, maleic anhydride, citraconic anhydride, glutaric anhydride, cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride, and itaconic anhydride. In particular, it is preferable that the monoacid anhydride (a5) contains 1,2,3,6-tetrahydrophthalic anhydride. That is, it is preferable that the acid anhydride (a3) contains 1,2,3,6-tetrahydrophthalic anhydride. In this case, while ensuring good developability of the photosensitive resin composition, the tackiness of the film 4 formed from the photosensitive resin composition can be further suppressed, and the insulation reliability and plating resistance of the cured product can be further improved. With respect to the whole monoacid anhydride (a5), 1,2,3,6-tetrahydrophthalic anhydride is preferably in the range of 20 mol% or more and 100 mol% or less, more preferably in the range of 40 mol% or more and 100 mol% or less, but is not limited thereto.

[0038] When reacting the intermediate with the acid anhydride (a3), an appropriate method can be adopted. For example, the acid anhydride (a3) is added to a solvent solution of the intermediate, and further, a thermal polymerization inhibitor and a catalyst are added as necessary and stirred and mixed to obtain a reactive solution. By reacting this reactive solution by a conventional method, preferably at a temperature of 60°C or higher and 150°C or lower, particularly preferably 80°C or higher and 120°C or lower, a carboxyl group-containing resin (A1) having a bisphenol fluorene skeleton is obtained. As the solvent, catalyst, and polymerization inhibitor, appropriate ones can be used, and the solvent, catalyst, and polymerization inhibitor used in the synthesis of the intermediate can also be used as they are.

[0039] The catalyst preferably contains triphenylphosphine in particular. That is, in the presence of triphenylphosphine, it is preferable to react the intermediate with the acid anhydride (a3). In this case, the reaction between the intermediate and the acid anhydride (a3) is particularly promoted, and a reaction rate (conversion rate) of 90% or more, 95% or more, 97% or more, or almost 100% can be achieved.

[0040] When the acid anhydride (a3) contains the diacid anhydride (a4), the amount of the diacid anhydride (a4) is preferably 0.05 mol or more and 0.24 mol or less with respect to 1 mol of the epoxy groups of the epoxy compound (a1). In this case, a carboxyl group-containing resin (A1) having a bisphenol fluorene skeleton with the acid value and molecular weight appropriately adjusted can be easily obtained.

[0041] Further, when the acid anhydride (a3) further contains the monoacid anhydride (a5), the amount of the monoacid anhydride (a5) is preferably 0.3 mol or more and 0.7 or less with respect to 1 mol of the epoxy groups of the epoxy compound (a1). In this case, a carboxyl group-containing resin (A1) having a bisphenol fluorene skeleton with the acid value and molecular weight appropriately adjusted can be easily obtained.

[0042] It is also preferable to react the intermediate with the acid anhydride (a3) under air bubbling. In this case, excessive increase in the molecular weight of the carboxyl group-containing resin (A1) having a bisphenol fluorene skeleton to be produced is suppressed, so that the developability of the photosensitive resin composition with an alkaline aqueous solution is particularly improved.

[0043] The components other than the carboxyl group-containing resin (A1) having a bisphenol fluorene skeleton in the photosensitive resin composition will be described.

[0044] As described above, the photosensitive resin composition contains a carboxyl group-containing resin (A), an unsaturated compound (B) having at least one ethylenically unsaturated bond in one molecule, and a photopolymerization initiator (C).

[0045] The carboxyl group-containing resin (A) may contain only the carboxyl group-containing resin (A1) having a bisphenol fluorene skeleton, or may contain only a carboxyl group-containing resin other than the carboxyl group-containing resin (A1) having a bisphenol fluorene skeleton. Alternatively, it may contain both the carboxyl group-containing resin (A1) having a bisphenol fluorene skeleton and a carboxyl group-containing resin other than the carboxyl group-containing resin (A1). The carboxyl group-containing resin other than the carboxyl group-containing resin (A1) having a bisphenol fluorene skeleton includes a carboxyl group-containing resin having no bisphenol fluorene skeleton (hereinafter also referred to as the carboxyl group-containing resin (A2)).

[0046] The carboxyl group-containing resin (A2) can contain, for example, a compound having a carboxyl group and no photopolymerizability (hereinafter referred to as the component (A2-1)). The component (A2-1) contains, for example, a polymer of an ethylenically unsaturated monomer containing an ethylenically unsaturated compound having a carboxyl group. The ethylenically unsaturated compound having a carboxyl group can contain compounds such as acrylic acid, methacrylic acid, ω-carboxy-polycaprolactone (n≈2) monoacrylate. The ethylenically unsaturated compound having a carboxyl group can also contain a reaction product of pentaerythritol triacrylate, pentaerythritol trimethacrylate, etc. with a dibasic acid anhydride. The ethylenically unsaturated monomer may further contain an ethylenically unsaturated compound having no carboxyl group, such as 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, a linear or branched aliphatic or alicyclic (however, it may have a partial unsaturated bond in the ring) (meth)acrylate ester, etc.

[0047] The carboxyl group-containing resin (A2) may contain a compound having a carboxyl group and an ethylenically unsaturated group (hereinafter referred to as component (A2-2)). Further, the carboxyl group-containing resin (A2) may contain only component (A2-2). Component (A2-2) is, for example, a resin (referred to as the first resin (x)) which is a reaction product of an intermediate which is a reaction product of an epoxy compound (x1) having two or more epoxy groups in one molecule and an ethylenically unsaturated compound (x2), and at least one compound (x3) selected from the group consisting of polyvalent carboxylic acids and their anhydrides. The first resin (x) is obtained, for example, by adding compound (x3) to an intermediate obtained by reacting an epoxy group in epoxy compound (x1) with a carboxyl group in ethylenically unsaturated compound (x2). The epoxy compound (x1) can contain an appropriate epoxy compound such as a cresol novolak type epoxy compound, a phenol novolak type epoxy compound, a biphenyl novolak type epoxy compound, etc. In particular, the epoxy compound (x1) preferably contains at least one compound selected from the group consisting of biphenyl novolak type epoxy compounds and cresol novolak type epoxy compounds. The epoxy compound (x1) may contain only a biphenyl novolak type epoxy compound, or may contain only a cresol novolak type epoxy compound. In this case, since the main chain of the epoxy compound (x1) contains an aromatic ring, the degree to which the cured product of the photosensitive resin composition is significantly corroded by an oxidizing agent containing, for example, potassium permanganate can be reduced. The epoxy compound (x1) may contain a polymer of an ethylenically unsaturated compound (z). The ethylenically unsaturated compound (z) contains, for example, a compound (z1) having an epoxy group such as glycidyl (meth)acrylate, or further contains a compound (z2) having no epoxy group such as 2-(meth)acryloyloxyethyl phthalate. The ethylenically unsaturated compound (x2) preferably contains at least one of acrylic acid and methacrylic acid. The compound (x3) contains one or more compounds selected from the group consisting of polyvalent carboxylic acids such as phthalic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, etc., and anhydrides of these polyvalent carboxylic acids.In particular, the compound (x3) preferably contains at least one polyvalent carboxylic acid selected from the group consisting of phthalic acid, tetrahydrophthalic acid, and methyltetrahydrophthalic acid.

[0048] (Component (A2-2) may contain a resin (referred to as the second resin (y)), which is a reaction product of a polymer of an ethylenically unsaturated monomer containing an ethylenically unsaturated compound having a carboxyl group and an ethylenically unsaturated compound having an epoxy group. The ethylenically unsaturated monomer may further contain an ethylenically unsaturated compound having no carboxyl group. The second resin (y) is obtained by reacting an ethylenically unsaturated compound having an epoxy group with a part of the carboxyl groups in the polymer. The ethylenically unsaturated monomer may further contain an ethylenically unsaturated compound having no carboxyl group. The ethylenically unsaturated compound having a carboxyl group contains compounds such as acrylic acid, methacrylic acid, ω-carboxy-polycaprolactone (n≈2) monoacrylate, pentaerythritol triacrylate, and pentaerythritol trimethacrylate. The ethylenically unsaturated compound having no carboxyl group contains compounds such as 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, and linear or branched aliphatic or alicyclic (wherein the ring may have a partial unsaturated bond) (meth)acrylic acid esters. The ethylenically unsaturated compound having an epoxy group preferably contains glycidyl (meth)acrylate.

[0049] The carboxyl group-containing resin (A) contains only the carboxyl group-containing resin (A1), only the carboxyl group-containing resin (A2), or both the carboxyl group-containing resin (A1) and the carboxyl group-containing resin (A2). The carboxyl group-containing resin (A) preferably contains 25% by mass or more of the carboxyl group-containing resin (A1), more preferably 40% by mass or more, still more preferably 60% by mass or more, and particularly preferably 100% by mass. In this case, excellent photosensitivity and developability with an alkaline aqueous solution of the photosensitive resin composition can be ensured. Further, the heat resistance and insulation reliability of the cured product of the photosensitive resin composition can be particularly improved. Furthermore, the tackiness of the film 4 formed from the photosensitive resin composition can be sufficiently reduced.

[0050] The weight average molecular weight of the carboxyl group-containing resin (A) is preferably 700 or more and 100,000 or less. When the weight average molecular weight of the carboxyl group-containing resin (A) is 700 or more, the tackiness of the film 4 formed from the photosensitive resin composition is easily suppressed, and the insulation reliability and plating resistance of the cured product of the photosensitive resin composition can be improved. When the weight average molecular weight of the carboxyl group-containing resin (A) is 100,000 or less, the developability of the photosensitive resin composition with an alkaline aqueous solution tends to be good. The weight average molecular weight of the carboxyl group-containing resin (A) is more preferably 900 or more and 60,000 or less, still more preferably 1,200 or more and 10,000 or less, and particularly preferably 1,400 or more and 5,000 or less. The weight average molecular weight of the carboxyl group-containing resin (A) is calculated, for example, from the measurement results under the following conditions by gel permeation chromatography.

[0051] GPC apparatus: SHODEX SYSTEM 11 manufactured by Showa Denko KK, Columns: Four columns of SHODEX KF-800P, KF-005, KF-003, and KF-001 in series, Mobile phase: THF, Flow rate: 1 ml / min, Column temperature: 45°C, Detector: RI, Conversion: Polystyrene.

[0052] The carboxyl group-containing resin (A) preferably contains a component having an acid value of 65 mgKOH / g or more and 150 mgKOH / g or less. In this case, the developability of the photosensitive resin composition with an alkaline aqueous solution is particularly improved, and by developing the film 4 after exposure with an alkaline aqueous solution, the via hole 6 having the small-diameter portion 63 is particularly easily produced. It is more preferable that the acid value is 70 mgKOH / g or more and 145 mgKOH / g or less, still more preferable that it is 75 mgKOH / g or more and 140 mgKOH / g or less, and particularly preferable that it is 85 mgKOH / g or more and 135 mgKOH / g or less.

[0053] The unsaturated compound (B) can impart photocurability to the photosensitive resin composition. The unsaturated compound (B) includes, for example, monofunctional (meth)acrylates such as 2-hydroxyethyl (meth)acrylate; and polyfunctional (meth)acrylates such as diethylene glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ε-caprolactone-modified pentaerythritol hexaacrylate, tricyclodecane dimethanol di(meth)acrylate, and can contain at least one compound selected from the group consisting of these.

[0054] In particular, it is preferable that the unsaturated compound (B) contains a trifunctional compound, that is, a compound having three unsaturated bonds in one molecule. In this case, the resolution when the film 4 formed from the photosensitive resin composition is exposed and developed is improved, and the developability of the photosensitive resin composition with an alkaline aqueous solution is particularly improved. The trifunctional compound can contain, for example, at least one compound selected from the group consisting of trimethylolpropane tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ethoxylated isocyanuric acid tri(meth)acrylate, ε-caprolactone-modified tris-(2-acryloxyethyl)isocyanurate, and ethoxylated glycerin tri(meth)acrylate.

[0055] It is also preferable that the unsaturated compound (B) contains a phosphorus-containing compound (phosphorus-containing unsaturated compound). In this case, the flame retardancy of the cured product of the photosensitive resin composition is improved. The phosphorus-containing unsaturated compound can contain, for example, at least one compound selected from the group consisting of 2-methacryloyloxyethyl acid phosphate (specific examples include product numbers Light Ester P-1M and Light Ester P-2M manufactured by Kyoeisha Chemical Co., Ltd.), 2-acryloyloxyethyl acid phosphate (specific example: product number Light Acrylate P-1A manufactured by Kyoeisha Chemical Co., Ltd.), diphenyl-2-methacryloyloxyethyl phosphate (specific example: product number MR-260 manufactured by Daihachi Chemical Industry Co., Ltd.), and the HFA series manufactured by Showa Highpolymer Co., Ltd. (specific examples include product numbers HFA-6003 and HFA-6007, which are addition reaction products of dipentaerythritol hexaacrylate and HCA (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), product numbers HFA-3003 and HFA-6127, which are addition reaction products of caprolactone-modified dipentaerythritol hexaacrylate and HCA (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), etc.).

[0056] The unsaturated compound (B) may contain a prepolymer. The prepolymer can contain at least one compound selected from the group consisting of, for example, prepolymers obtained by polymerizing monomers having ethylenically unsaturated bonds and then adding ethylenically unsaturated groups, and oligo(meth)acrylate prepolymers. The oligo(meth)acrylate prepolymers can contain at least one component selected from the group consisting of, for example, epoxy(meth)acrylate, polyester(meth)acrylate, urethane(meth)acrylate, alkyd resin(meth)acrylate, silicone resin(meth)acrylate, and spiran resin(meth)acrylate.

[0057] The photopolymerization initiator (C) preferably contains a photopolymerization initiator (C1) selected from the group consisting of acylphosphine oxide-based photopolymerization initiators, α-aminoalkylphenone-based photopolymerization initiators, and oxime ester-based photopolymerization initiators. In this case, when the photosensitive resin composition is exposed to ultraviolet light, high light absorbency can be imparted to the photosensitive resin composition. When the photosensitive resin composition has good light absorbency, when the film 4 formed from the photosensitive resin composition is exposed, light is easily absorbed, so photocuring proceeds easily. Furthermore, by the absorption of light within the film 4, the amount of light reaching the deep part is reduced. For this reason, the influence due to light scattering is particularly unlikely to occur in the deep part, and photocuring of the film 4 is particularly unlikely to proceed in the deep part compared to the surface. For this reason, when producing the via hole 6 by the photolithography method, the small-diameter part 63 is particularly likely to be formed.

[0058] More preferably, the photopolymerization initiator (C1) contains an acylphosphine oxide-based photopolymerization initiator. In this case, higher light absorbency can be imparted to the photosensitive resin composition.

[0059] The acylphosphine oxide-based photoinitiator can contain at least one component selected from the group consisting of monoacylphosphine oxide-based photoinitiators such as 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2,4,6-trimethylbenzoyl-ethyl-phenyl-phosphinate, and bisacylphosphine oxide-based photoinitiators such as bis-(2,6-dichlorobenzoyl)phenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis-(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,4,6-trimethylbenzoyl)phenylphosphine oxide, (2,5,6-trimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide. The acylphosphine oxide-based photoinitiator preferably contains at least one of 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis-(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and more preferably contains 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide.

[0060] The α-aminoalkylphenone-based photoinitiator can contain at least one component selected from the group consisting of 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone.

[0061] The oxime ester-based photoinitiator can contain at least one component selected from the group consisting of, for example, 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime)], and ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetoxime).

[0062] In addition to the photoinitiator (C1) containing the above components, the photoinitiator (C) may contain a photoinitiator (C2) containing components other than the above. The photoinitiator (C2) preferably contains at least one of an α-hydroxyacetophenone-based photoinitiator and a thioxanthone-based photoinitiator. In this case, particularly high light absorbency can be imparted to the photosensitive resin composition. More preferably, the photoinitiator (C2) contains an α-hydroxyacetophenone-based photoinitiator.

[0063] The α-hydroxyacetophenone-based photoinitiator preferably contains, for example, 1-hydroxycyclohexyl-phenyl ketone.

[0064] The thioxanthone-based photoinitiator preferably contains, for example, 2,4-diethylthioxanthen-9-one.

[0065] It is also preferable that the photoinitiator (C) contains 4,4-bis(diethylamino)benzophenone (C3). That is, it is also preferable that the photosensitive resin composition contains the photoinitiator (C1) and 4,4-bis(diethylamino)benzophenone (C3), or the photoinitiator (C1), the photoinitiator (C2), and 4,4-bis(diethylamino)benzophenone (C3). In this case, when the film 4 formed from the photosensitive resin composition is partially exposed and then developed, the curing of the unexposed portion is particularly easily suppressed. Therefore, it becomes particularly easy to form the via hole 6 having the small diameter portion 63.

[0066] 4,4-bis(diethylamino)benzophenone (C3) is preferably in the range of 0.5% by mass or more and 20% by mass or less with respect to the photopolymerization initiator (C1). When 4,4-bis(diethylamino)benzophenone (C3) is 0.5% by mass or more, the curing of the unexposed portion is particularly likely to be suppressed. Also, when 4,4-bis(diethylamino)benzophenone (C3) is 20% by mass or less, the electrical insulation of the cured product of the photosensitive resin composition is less likely to be inhibited by 4,4-bis(diethylamino)benzophenone (C3). 4,4-bis(diethylamino)benzophenone (C3) is particularly preferably in the range of 1% by mass or more and 18% by mass or less with respect to the photopolymerization initiator (C1). When the photosensitive resin composition contains an organic filler (E), the organic filler (E) may cause light scattering within the photosensitive resin composition during exposure. In this case, there may arise a problem that good resolution cannot be obtained with the photosensitive resin composition. For this reason, there is a possibility that it becomes difficult to form the small-diameter portion 63 in the via hole 6. However, if 4,4-bis(diethylamino)benzophenone (C3) is within the above range, the photosensitive resin composition is likely to have good resolution, and thus the small-diameter portion 63 is particularly likely to be formed in the via hole 6.

[0067] The photosensitive resin composition preferably contains an epoxy resin (D). The epoxy resin (D) can impart thermosetting properties to the photosensitive resin composition. The epoxy resin (D) preferably contains a crystalline epoxy resin. In this case, the developability of the photosensitive resin composition can be improved. Also, the epoxy resin (D) may further contain an amorphous epoxy resin. Here, the "crystalline epoxy resin" is an epoxy resin having a melting point, and the "amorphous epoxy resin" is an epoxy resin having no melting point.

[0068] The crystalline epoxy resin preferably contains one or more components selected from the group consisting of, for example, 1,3,5-tris(2,3-epoxypropyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, hydroquinone-type crystalline epoxy resin (specific example: product name YDC-1312 manufactured by Nippon Steel Chemical & Material Co., Ltd.), biphenyl-type crystalline epoxy resin (specific example: product name YX-4000 manufactured by Mitsubishi Chemical Corporation), diphenyl ether-type crystalline epoxy resin (specific example: product number YSLV-80DE manufactured by Nippon Steel Chemical & Material Co., Ltd.), bisphenol-type crystalline epoxy resin (specific examples: product names YSLV-70XY and YSLV-80XY manufactured by Nippon Steel Chemical & Material Co., Ltd.), tetrakisphenol ethane-type crystalline epoxy resin (specific example: product number GTR-1800 manufactured by Nippon Kayaku Co., Ltd.), and bisphenol fluorene-type crystalline epoxy resin.

[0069] The crystalline epoxy resin preferably has two or more epoxy groups in one molecule. In this case, during repeated temperature changes, cracks are less likely to occur in the cured product of the photosensitive resin composition.

[0070] The crystalline epoxy resin preferably has an epoxy equivalent of 150 g / eq or more and 300 g / eq or less. This epoxy equivalent is the gram weight of the crystalline epoxy resin containing one gram equivalent of epoxy groups. The crystalline epoxy resin has a melting point. Examples of the melting point of the crystalline epoxy resin include 70°C or higher and 180°C or lower.

[0071] In particular, it is preferable that the epoxy compound (D) contains a crystalline epoxy resin having a melting point of 110 °C or lower. In this case, the developability of the photosensitive resin composition with an alkaline aqueous solution is particularly improved. The crystalline epoxy resin having a melting point of 110 °C or lower can contain at least one component selected from the group consisting of, for example, a biphenyl type epoxy resin (specific example: product number YX-4000 manufactured by Mitsubishi Chemical Corporation), a diphenyl ether type epoxy resin (specific example: product number YSLV-80DE manufactured by Nippon Steel Chemical & Material Co., Ltd.), a bisphenol type epoxy resin (specific examples: product numbers YSLV-70XY and YSLV-80XY manufactured by Nippon Steel Chemical & Material Co., Ltd.), and a bisphenol fluorene type crystalline epoxy resin.

[0072] Amorphous epoxy resins include, for example, phenol novolac type epoxy resins (specific example: product number EPICLON N-775 manufactured by DIC Corporation), cresol novolac type epoxy resins (specific example: product number EPICLON N-695 manufactured by DIC Corporation), bisphenol A novolac type epoxy resins (specific example: product number EPICLON N-865 manufactured by DIC Corporation), bisphenol A type epoxy resins (specific example: product number jER1001 manufactured by Mitsubishi Chemical Corporation), bisphenol F type epoxy resins (specific example: product number jER4004P manufactured by Mitsubishi Chemical Corporation), bisphenol S type epoxy resins (specific example: product number EPICLON EXA-1514 manufactured by DIC Corporation), bisphenol AD type epoxy resins, biphenyl novolac type epoxy resins (specific example: product number NC-3000 manufactured by Nippon Kayaku Co., Ltd.), hydrogenated bisphenol A type epoxy resins (specific example: product number ST-4000D manufactured by Nippon Steel Chemical & Material Co., Ltd.), naphthalene type epoxy resins (specific examples: product numbers EPICLON HP-4032, EPICLON HP-4700, EPICLON HP-4770 manufactured by DIC Corporation), tertiary butyl catechol type epoxy resins (specific example: product number EPICLON HP-820 manufactured by DIC Corporation), dicyclopentadiene type epoxy resins (specific example: product number EPICLON HP-7200 manufactured by DIC), adamantane type epoxy resins (specific example: product number ADAMANTATEX-E-201 manufactured by Idemitsu Kosan Co., Ltd.), special bifunctional type epoxy resins (specific examples: product numbers YL7175-500 and YL7175-1000 manufactured by Mitsubishi Chemical Corporation; product numbers EPICLON TSR-960, EPICLON TER-601, EPILON TSR-250-80BX, EPICLON 1650-75MPX, EPICLON EXA-4850, EPICLON EXA-4816, EPICLON EXA-4822, and EPICLON EXA-9726 manufactured by DIC Corporation;It is preferable to contain at least one component selected from the group consisting of a rubber-like core-shell polymer-modified bisphenol A type epoxy resin (product number YSLV-120TE manufactured by Nippon Steel Chemical & Material Co., Ltd.), a rubber-like core-shell polymer-modified bisphenol F type epoxy resin (product number MX-156 manufactured by Kaneka Corporation as a specific example), a rubber-like core-shell polymer-modified bisphenol F type epoxy resin (product number MX-136 manufactured by Kaneka Corporation as a specific example), and a rubber particle-containing bisphenol F type epoxy resin (product number Kaneka Ace MX-130 manufactured by Kaneka Corporation as a specific example).;

[0073] When the photosensitive resin composition contains an epoxy resin (D), the photosensitive resin composition preferably contains both a crystalline epoxy resin and an amorphous epoxy resin. In this case, the plating resistance and insulation properties of the cured product produced from the photosensitive resin composition can be further improved.

[0074] The epoxy resin (D) may contain a phosphorus-containing epoxy resin. In this case, the flame retardancy of the cured product of the photosensitive resin composition is improved. The phosphorus-containing epoxy resin may be contained in the crystalline epoxy resin or may be contained in the amorphous epoxy resin. Examples of the phosphorus-containing epoxy resin include a phosphoric acid-modified bisphenol F type epoxy resin (product numbers EPICLON EXA-9726 and EPICLON EXA-9710 manufactured by DIC Corporation), product number Epotote FX-305 manufactured by Nippon Steel Chemical & Material Co., Ltd., and the like.

[0075] The photosensitive resin composition preferably does not contain a filler. In this case, by suppressing the scattering of light in the deep part of the film 4, the via hole 6 having the small diameter part 63 is particularly likely to be formed. When the photosensitive resin composition contains a filler, it is preferable that the material, particle size, and blending amount of the filler are appropriately set so that light scattering hardly occurs appropriately in the film 4.

[0076] The photosensitive resin composition may contain an organic filler (E). Note that the organic filler (E) does not contain melamine. In this case, it is preferable that the material, particle size, and blending amount of the organic filler (E) are appropriately set as described above. The organic filler (E) imparts thixotropy to the photosensitive resin composition, thereby improving the storage stability of the photosensitive resin composition. Also, the adhesion of the cured product to the plating layer is improved. The organic filler (E) preferably has a reactive group. By having a reactive group, the organic filler (E) has high compatibility in the photosensitive resin composition and imparts a stronger thixotropy to the photosensitive resin composition, thereby further improving the storage stability of the photosensitive resin composition. Also, the adhesion between the cured product and the plating layer is further improved. The reactive group of the organic filler (E) more preferably contains at least one group selected from the group consisting of a carboxyl group, an amino group, an epoxy group, a vinyl group, and a hydroxyl group, and even more preferably contains at least one of a carboxyl group and an amino group. In this case, the storage stability of the photosensitive resin composition is further improved. Also, the adhesion of the cured product to the plating layer is further improved. It is particularly preferable that the reactive group of the organic filler (E) contains a carboxyl group. In this case, the developability of the photosensitive resin composition is improved. At the same time, the carboxyl group of the organic filler (E) can react with the epoxy resin (D) in the photosensitive resin composition during thermosetting. Thereby, the cured product after thermosetting can contain the organic filler (E) uniformly dispersed therein. Furthermore, the unreacted carboxyl groups of the organic filler (E) can also be modified at the stage of roughening the surface of the cured product. That is, among the organic fillers (E) contained in the cured product, the organic fillers (E) located near the surface of the cured product are liable to be altered at the stage of roughening the surface of the cured product. The thus-altered organic filler (E) is liable to be removed from the cured product when imparting a rough surface to the cured product. Thereby, a rough surface can be imparted to the surface of the cured product to improve the adhesion between the cured product and the plating layer. Moreover, since the organic filler (E) contains a carboxyl group, the non-uniformity of the coating film due to the fluidity of the photosensitive resin composition can be reduced. Thereby, it becomes easy to make the film thickness of the layer formed of the photosensitive resin composition uniform.In addition, it becomes easier to form via holes 6 having small-diameter portions 63 in the interlayer insulating layer 7 formed from the photosensitive resin composition.

[0077] When the organic filler (E) contains a carboxyl group, the carboxyl group is formed as a side chain in the product, for example, by polymerizing or crosslinking carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid. The carboxylic acid monomer has a carboxyl group and a polymerizable unsaturated double bond. The organic filler (E) enhances the thixotropy of the photosensitive resin composition and improves the stability (especially storage stability) of the photosensitive resin composition. Further, when the organic filler (E) contains a carboxyl group, the developability of the cured product can be improved, and the compatibility with the crystalline epoxy resin can be improved to prevent crystallization in the photosensitive resin composition. The carboxyl group content of the organic filler (E) is not particularly limited, but the acid value of the organic filler (E) is preferably 1 mgKOH / g or more and 60 mgKOH / g or less in terms of the acid value by acid-base titration. If the acid value is less than 1 mgKOH / g, the stability of the photosensitive resin composition and the developability of the cured product may decrease. If the acid value is greater than 60 mgKOH / g, the moisture resistance reliability of the cured product may decrease. The acid value of the organic filler (E) is more preferably 3 mgKOH / g or more and 40 mgKOH / g or less.

[0078] The organic filler (E) preferably has an average primary particle diameter of 1 μm or less. When the average primary particle diameter of the organic filler (E) is 1 μm or less, the developability of the photosensitive resin composition becomes good. In addition, the roughness of the rough surface formed on the cured product can be made finer, and as the surface area of the cured product increases, the anchor effect becomes larger, and the adhesion between the rough surface and the plating layer can be improved.

[0079] The lower limit of the average primary particle diameter of the organic filler (E) is not particularly limited, but is preferably, for example, 0.001 μm or more. The average primary particle diameter is measured by a laser diffraction particle size distribution analyzer, D 50It is measured as such. It is more preferable that the average primary particle diameter of the organic filler (E1) is 0.4 μm or less, and it is even more preferable that it is 0.1 μm or less. In this case, light scattering in the photosensitive resin composition during exposure can be suppressed, whereby the resolution of the photosensitive resin composition is further improved, and it becomes easier to form the via hole 6 having the small diameter portion 63 in the interlayer insulating layer 7. In addition, the roughness of the rough surface formed on the cured product can be made particularly fine.

[0080] The organic filler (E) is preferably dispersed in the photosensitive resin composition with a maximum particle diameter of less than 1.0 μm, and more preferably less than 0.5 μm. The maximum particle diameter is measured by a laser diffraction particle size distribution measuring device as D 50 It is measured as such. Alternatively, the maximum particle diameter is measured by observing the cured product with a transmission electron microscope (TEM). The organic filler (E) may aggregate in the photosensitive resin composition (for example, secondary particles may be formed), but in that case, the maximum particle diameter means the size of the aggregated particles. When the maximum particle diameter of the organic filler (E) in the dispersed state is within the above range, scattering during exposure is suppressed in the photosensitive resin composition, whereby the resolution of the photosensitive resin composition is further improved, and it becomes even easier to form the via hole 6 having the small diameter portion 63 in the interlayer insulating layer 7. In addition, the roughness of the rough surface formed on the cured product can be made even finer. Note that when particle aggregation occurs, the maximum particle diameter is usually larger than the average primary particle diameter.

[0081] The organic filler (E) preferably contains a rubber component. Further, the organic filler (E) preferably contains only the rubber component. The rubber component can impart flexibility to the cured product of the photosensitive resin composition. The rubber component can be composed of a resin. The rubber component preferably contains at least one polymer selected from crosslinked acrylic rubber, crosslinked NBR, crosslinked MBS, and crosslinked SBR. In this case, the rubber component can impart excellent flexibility to the cured product of the photosensitive resin composition. Further, a more appropriate rough surface can be imparted to the surface of the cured product. Here, the rubber component contains a crosslinked structure formed when copolymerizing the monomers constituting the polymer. NBR is generally a copolymer of butadiene and acrylonitrile and is classified as nitrile rubber. MBS is generally a copolymer composed of three components of methyl methacrylate, butadiene, and styrene and is classified as butadiene-based rubber. SBR is generally a copolymer of styrene and butadiene and is classified as styrene rubber. Specific examples of the organic filler (E) include product number XER-91-MEK manufactured by JSR Corporation, product number XER-32-MEK manufactured by JSR Corporation, product number XSK-500 manufactured by JSR Corporation, etc. XER-91-MEK is a crosslinked rubber (NBR) having a carboxyl group with an average primary particle diameter of 0.07 μm, and is provided as a methyl ethyl ketone dispersion with a content ratio of this crosslinked rubber of 15% by weight, and its acid value is 10.0 mgKOH / g. XER-32-MEK is a dispersion in which a polymer (linear particles) of carboxyl group-modified hydrogenated nitrile rubber is dispersed in methyl ethyl ketone at a content of 17% by weight based on the total amount of the dispersion. Further, XSK-500 is a crosslinked rubber (SBR) having a carboxyl group and a hydroxyl group with an average primary particle diameter of 0.07 μm, and is provided as a methyl ethyl ketone dispersion with a content ratio of this crosslinked rubber of 15% by weight. Thus, the organic filler (E) may be blended with the photosensitive resin composition in the form of a dispersion. That is, the rubber component can be blended with the photosensitive resin composition in the form of a dispersion. Further, specific examples of the organic filler (E) include, in addition to the above, product number XER-92 manufactured by JSR Corporation, etc.

[0082] The photosensitive resin composition can contain a silane coupling agent. In this case, the dispersibility of the organic filler (E) can be improved. Furthermore, the resolution of the photosensitive resin composition can also be improved.

[0083] The silane coupling agent is, for example, a compound containing a silicon atom and two to four hydrolyzable groups selected from the group consisting of -OCH3 group, -OC2H5 group, and -OCOCH3 group. In addition to the hydrolyzable groups, the silane coupling agent may contain a reactive group such as an amino group, an epoxy group, a vinyl (allyl) group, a methacryl group, a mercapto group, an isocyanate group, a sulfide group, or a methyl group.

[0084] Examples of the silane coupling agent include amino compounds such as 3-(2-aminoethylamino)propyldimethoxymethylsilane, 3-(2-aminoethylamino)propyltriethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-aminopropyldiethoxymethylsilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane; epoxies such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidyloxypropyl(dimethoxy)methylsilane, diethoxy(3-glycidyloxypropyl)methylsilane; (meth)acrylates such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane; vinyl compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, p-styryltrimethoxysilane, diethoxymethylvinylsilane, vinyltris(2-methoxyethoxy)silane; allyl compounds such as allyltriethoxysilane, allyltrimethoxysilane; styryl compounds such as p-styryltrimethoxysilane; isocyanates such as 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane; ureides such as 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane; mercapto compounds such as (3-mercaptopropyl)triethoxysilane, (3-mercaptopropyl)trimethoxysilane; sulfides such as bis(triethoxysilylpropyl)tetrasulfide; tetraethyl orthosilicate, methyltrimethoxysilane, and the like.

[0085] The photosensitive resin composition can contain melamine. In this case, the degree of significant corrosion of the cured product of the photosensitive resin composition can be reduced by an oxidizing agent containing, for example, potassium permanganate. That is, when the photosensitive resin composition contains melamine, when roughening the surface of the cured product of the photosensitive resin composition in the pre-step of the plating process, it becomes difficult to reduce the thickness of the layer containing the cured product. By imparting a rough surface to the cured product in this way, the adhesion between the cured product of the photosensitive resin composition and the plating layer made of copper, gold, etc. can be improved. Melamine is 2,4,6-triamino-1,3,5-triazine and is generally available from commercially available compounds. Melamine preferably has an average particle size of 20 μm or less, preferably 15 μm or less, and is preferably dispersed in the photosensitive resin composition. When melamine is uniformly dispersed in the photosensitive resin composition, melamine is more likely to form a coordination bond with metal elements. Thereby, the adhesion of the photosensitive resin composition can be further improved. The lower limit of the average particle size of melamine is not particularly limited, but can be 0.01 μm or more. The average particle size of melamine is measured by a laser diffraction particle size distribution measuring device in a state where melamine is dispersed in the uncured photosensitive resin composition, D 50 is measured as.

[0086] The photosensitive resin composition may contain an inorganic filler. In this case, the curing shrinkage of the film formed from the photosensitive resin composition is reduced. Also, the dielectric tangent can be lowered. The inorganic filler can contain one or more materials selected from the group consisting of, for example, barium sulfate, silica, carbon nanotubes, talc, bentonite, aluminum hydroxide, magnesium hydroxide, and titanium oxide.

[0087] The photosensitive resin composition according to this embodiment may contain an organic solvent. The organic solvent is used for purposes such as liquefying or varnishing the photosensitive resin composition, adjusting the viscosity, adjusting the coatability, and adjusting the film-forming property.

[0088] The organic solvent can contain one or more compounds selected from the group consisting of linear, branched, secondary or polyhydric alcohols such as ethanol, propyl alcohol, isopropyl alcohol, hexanol, ethylene glycol, etc.; ketones such as methyl ethyl ketone, cyclohexanone, etc.; aromatic hydrocarbons such as toluene, xylene, etc.; petroleum-based aromatic mixed solvents such as the Swazol series (manufactured by Maruzen Petrochemical Co., Ltd.), the Solvesso series (manufactured by Exxon Chemical Co., Ltd.), etc.; cellosolves such as cellosolve, butyl cellosolve, etc.; carbitols such as carbitol, butyl carbitol, etc.; propylene glycol alkyl ethers such as propylene glycol methyl ether, etc.; polypropylene glycol alkyl ethers such as dipropylene glycol methyl ether, etc.; acetate esters such as ethyl acetate, butyl acetate, cellosolve acetate, carbitol acetate, etc.; and dialkyl glycol ethers.

[0089] The carboxyl group-containing resin (A) is preferably in the range of 5% by mass or more and 85% by mass or less, more preferably in the range of 10% by mass or more and 75% by mass or less, and still more preferably in the range of 30% by mass or more and 60% by mass or less with respect to the solid content of the photosensitive resin composition. The solid content refers to the total amount of all components excluding volatile components such as solvents from the photosensitive resin composition.

[0090] The unsaturated compound (B) having at least one ethylenically unsaturated bond in one molecule is preferably in the range of 5% by mass or more and 45% by mass or less with respect to the carboxyl group-containing resin (A). When the unsaturated compound (B) is within this range, the via hole 6 having the small diameter portion 63 is particularly easily produced. The unsaturated compound (B) is more preferably in the range of 10% by mass or more and 42% by mass or less, and still more preferably in the range of 21% by mass or more and 40% by mass or less with respect to the carboxyl group-containing resin (A).

[0091] The photoinitiator (C) is preferably within the range of 1% by mass or more and 30% by mass or less with respect to the carboxyl group-containing resin (A). When the proportion of the photoinitiator (C) is 1% by mass or more with respect to the carboxyl group-containing resin (A), the photosensitive resin composition is likely to have good light absorbency. By having good light absorbency, the degree of curing on the surface of the interlayer insulating layer 7 can be easily increased, and the water absorbency of the interlayer insulating layer 7 can be reduced. Also, it is easier to form the via hole 6 having the small-diameter portion 63 in the interlayer insulating layer 7. When the photoinitiator (C) is 30% by mass or less with respect to the carboxyl group-containing resin (A), the cured film of the photosensitive resin composition is likely to have good electrical insulation.

[0092] The photoinitiator (C) is more preferably within the range of 1.5% by mass or more and 25% by mass or less, still more preferably within the range of 2% by mass or more and 20% by mass or less, and particularly preferably within the range of 3% by mass or more and 10% by mass or less with respect to the carboxyl group-containing resin (A).

[0093] When the photosensitive resin composition contains an epoxy resin (D), it is preferable that the total equivalent of the epoxy groups contained in the epoxy resin (D) is 0.1 or more and 5 or less with respect to 1 equivalent of the carboxyl groups of the carboxyl group-containing resin (A). By the equivalent of the epoxy groups of the epoxy resin (D) being 0.1 or more with respect to 1 equivalent of the carboxyl groups of the carboxyl group-containing resin (A), thermosetting properties can be imparted to the photosensitive resin composition. By the equivalent of the epoxy groups of the epoxy resin (D) being 5 or less with respect to 1 equivalent of the carboxyl groups of the carboxyl group-containing resin (A), the photosensitive resin composition has good developability. The equivalent of the epoxy groups of the epoxy resin (D) is more preferably 0.3 or more and 4 or less, still more preferably 0.5 or more and 3 or less, and particularly preferably 0.7 or more and 2 or less with respect to 1 equivalent of the carboxyl groups of the carboxyl group-containing resin (A).

[0094] The content of the organic filler (E) is preferably 1% by mass or more and 100% by mass or less with respect to the carboxyl group-containing resin (A). When the content of the organic filler (E) is 1% by mass or more, the surface of the cured product of the photosensitive resin composition can be moderately roughened, thereby improving the adhesion between the rough surface of the cured product and the plating layer. When the content of the organic filler (E) is 100% by mass or less, the photosensitive resin composition is likely to have good developability. The content of the organic filler (E) is more preferably 1.5% by mass or more and 50% by mass or less, still more preferably 2% by mass or more and 30% by mass or less, and particularly preferably 3% by mass or more and 20% by mass or less with respect to the carboxyl group-containing resin (A). In this case, the via hole 6 having the small-diameter portion 63 is particularly easily formed.

[0095] When the photosensitive resin composition contains a silane coupling agent, the content of the silane coupling agent is preferably 0.01% by mass or more and 7% by mass or less with respect to the organic filler (E). When the ratio of the silane coupling agent is within this range, aggregation of the organic filler (E) in the photosensitive resin composition is prevented, and the dispersibility is improved. The ratio of the silane coupling agent is more preferably 0.05% by mass or more and 5% by mass or less with respect to the organic filler (E). When the ratio of the silane coupling agent is within this range, aggregation of the organic filler (E1) in the photosensitive resin composition is more efficiently prevented, and the dispersibility is more effectively improved.

[0096] When the photosensitive resin composition contains melamine, the content of melamine is preferably 0.1% by mass or more and 10% by mass or less with respect to the carboxyl group-containing resin (A). In this case, it shows good developability with respect to the alkaline aqueous solution, and the via hole 6 having the small-diameter portion 63 is more likely to be formed in the interlayer insulating layer 7. The content of melamine is more preferably 0.3% by mass or more and 9% by mass or less, still more preferably 0.5% by mass or more and 8% by mass or less, and particularly preferably 1% by mass or more and 6% by mass or less with respect to the carboxyl group-containing resin (A).

[0097] The ratio of the inorganic filler in the photosensitive resin composition is appropriately set, and the content of the inorganic filler is preferably 0% by mass or more and 200% by mass or less with respect to the carboxyl group-containing resin (A). In this case, good resolution can be obtained, and vias 6 having small-diameter portions 63 are more likely to be formed in the interlayer insulating layer 7. The content of the inorganic filler is more preferably 0% by mass or more and 150% by mass or less, still more preferably 0% by mass or more and 100% by mass or less, even more preferably 0% by mass or more and 50% by mass or less, and particularly preferably 0% by mass or more and 20% by mass or less with respect to the carboxyl group-containing resin (A).

[0098] When the photosensitive resin composition contains an organic solvent, the amount of the organic solvent is preferably adjusted so that the organic solvent volatilizes promptly when drying the coating film formed from the photosensitive resin composition, that is, so that the organic solvent does not remain in the dry film. In particular, the ratio of the organic solvent is preferably 0% by mass or more and 99.5% by mass or less, and more preferably 15% by mass or more and 60% by mass or less with respect to the entire photosensitive resin composition. Note that the suitable ratio of the organic solvent varies depending on the coating method and the like, and it is preferably adjusted appropriately according to the coating method.

[0099] As long as the effects of this embodiment are not inhibited, the photosensitive composition may further contain components other than the above components.

[0100] The photosensitive resin composition may contain at least one resin selected from the group consisting of blocked isocyanates such as tolylene diisocyanate-based, morpholine diisocyanate-based, isophorone diisocyanate-based, and hexamethylene diisocyanate-based blocked with caprolactam, oxime, malonic ester, etc.; butylated urea resin; various thermosetting resins other than the above; ultraviolet curable epoxy (meth)acrylate; resins obtained by adding (meth)acrylic acid to epoxy resins such as bisphenol A type, phenol novolak type, cresol novolak type, and alicyclic type; and high molecular compounds such as diallyl phthalate resin, phenoxy resin, urethane resin, melamine resin, and fluororesin.

[0101] The photosensitive resin composition may contain a curing agent for curing the epoxy compound (D). Examples of the curing agent include imidazole derivatives such as imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole; amine compounds such as dicyandiamide, benzyldimethylamine, 4-(dimethylamino)-N,N-dimethylbenzylamine, 4-methoxy-N,N-dimethylbenzylamine, 4-methyl-N,N-dimethylbenzylamine; hydrazine compounds such as adipic acid hydrazide, sebacic acid hydrazide; phosphorus compounds such as triphenylphosphine; acid anhydrides; phenols; mercaptans; Lewis acid amine complexes; and onium salts. Commercially available products of these components are, for example, 2MZ-A, 2MZ-OK, 2PHZ, 2P4BHZ, 2P4MHZ (all are trade names of imidazole-based compounds) manufactured by Shikoku Kasei Co., Ltd., U-CAT3503N, UCAT3502T (both are trade names of dimethylamine-blocked isocyanate compounds) manufactured by San-Apro Ltd., DBU, DBN, U-CATSA102, U-CAT5002 (all are bicyclic amidine compounds and their salts).

[0102] The photosensitive resin composition may contain an adhesion promoter. Examples of the adhesion promoter include guanamine derivatives such as acetoguanamine (2,4-diamino-6-methyl-1,3,5-triazine) and benzoguanamine (2,4-diamino-6-phenyl-1,3,5-triazine), and S-triazine derivatives such as 2,4-diamino-6-methacryloyloxyethyl-S-triazine, 2-vinyl-4,6-diamino-S-triazine, 2-vinyl-4,6-diamino-S-triazine·isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-S-triazine·isocyanuric acid adduct, silane coupling agents, melamine derivatives, and the like.

[0103] The photosensitive resin composition may contain a rheology control agent. The rheology control agent can easily optimize the viscosity of the photosensitive resin composition. Examples of the rheology control agent include urea-modified medium-polar polyamides (product numbers BYK-430 and BYK-431 manufactured by Big Chemie Japan Co., Ltd.), polyhydroxycarboxylic acid amides (product number BYK-405 manufactured by Big Chemie Japan Co., Ltd.), modified urea (product numbers BYK-410, BYK-411, and BYK-420 manufactured by Big Chemie Japan Co., Ltd.), high molecular weight urea derivatives (product number BYK-415 manufactured by Big Chemie Japan Co., Ltd.), urea-modified urethanes (product number BYK-425 manufactured by Big Chemie Japan Co., Ltd.), polyurethanes (product number BYK-428 manufactured by Big Chemie Japan Co., Ltd.), castor oil wax, polyethylene wax, polyamide wax, bentonite, kaolin, and clay.

[0104] The photosensitive resin composition may contain at least one component selected from the group consisting of a curing accelerator; a colorant; a copolymer such as silicone and acrylate; a leveling agent; a thixotropy agent; a polymerization inhibitor; an anti-halation agent; a flame retardant; an antifoaming agent; an antioxidant; a surfactant; and a polymer dispersant.

[0105] In preparing the photosensitive resin composition of the present embodiment, it may be adjusted by an appropriate method. For example, the photosensitive resin composition can be adjusted by mixing and stirring the raw materials of the photosensitive resin composition. Also, for example, the photosensitive resin composition may be prepared by kneading using an appropriate kneading method such as a three-roll mill, a ball mill, or a sand mill. When the raw materials contain liquid components, low-viscosity components, etc., a part or all of the liquid components, low-viscosity components, etc. are first excluded from the raw materials, and the remaining part is kneaded to prepare a mixture, and then the liquid components, low-viscosity components, etc. are added to the obtained mixture and mixed to prepare the photosensitive resin composition. When the photosensitive resin composition contains a solvent (E), first, a part or all of the solvent may be mixed among the raw materials and then mixed with the rest of the raw materials.

[0106] The photosensitive resin composition preferably has a property such that even a film 4 with a thickness of 25 μm can be developed with an aqueous sodium carbonate solution. In this case, since a sufficiently thick electrically insulating layer can be produced from the photosensitive resin composition by photolithography, the photosensitive resin composition can be widely applied to produce the interlayer insulating layer 7 in the printed wiring board 11. Of course, it is also possible to produce an electrically insulating layer thinner than 25 μm from the photosensitive resin composition.

[0107] Whether or not the film 4 with a thickness of 25 μm can be developed with an aqueous sodium carbonate solution can be confirmed by the following method. A wet coating film is produced by applying the photosensitive resin composition on a suitable substrate 1, and the film 4 with a thickness of 25 μm is formed by heating this wet coating film at 80 °C for 40 minutes. With a negative mask having an exposed portion that transmits ultraviolet light and a non-exposed portion that shields ultraviolet light directly applied to this film 4, the film 4 is irradiated with ultraviolet light at 500 mJ / cm 2 under the above conditions for exposure. After exposure, a 1% Na2CO3 aqueous solution at 30 °C is sprayed onto the film 4 at an injection pressure of 0.2 MPa for 90 seconds, and then pure water is sprayed at an injection pressure of 0.2 MPa for 90 seconds. As a result of observing the film 4 after this treatment, when the portion corresponding to the non-exposed portion in the film 4 is removed and no residue is observed, it can be determined that the film 4 with a thickness of 25 μm can be developed with an aqueous sodium carbonate solution. Incidentally, for films 4 with other thicknesses (for example, 30 μm), it is similarly possible to confirm whether they can be developed with an aqueous sodium carbonate solution.

[0108] (2.2) Manufacture of the printed wiring board 11 The manufacturing method of the printed wiring board 11 according to this embodiment will be described in detail with reference to FIGS. 1A to 1E.

[0109] In manufacturing the printed wiring board 11, for example, a photosensitive resin composition and a substrate are prepared. The substrate has an insulating layer 2 and a second conductor layer 3 overlapping the insulating layer 2. A film 4 made from the photosensitive resin composition is overlaid on the substrate so as to cover the second conductor layer 3, and after exposing a negative-patterned region of the film 4 including the pattern of the via holes 6, development processing is performed using an alkaline aqueous solution. Thereby, an interlayer insulating layer 7 and via holes 6 penetrating the interlayer insulating layer 7 are produced.

[0110] Specifically, for example, first, as shown in FIG. 1A, a base material 1 is prepared. The base material 1 includes an insulating layer 2 and a second conductor layer 3. The second conductor layer 3 is a conductor wiring.

[0111] The photosensitive resin composition is applied onto the substrate, and further dried if necessary, thereby producing a film 4 covering the second conductor layer 3 as shown in FIG. 1B. The application method of the photosensitive resin composition is selected from the group consisting of known methods, for example, dipping method, spraying method, spin coating method, roll coating method, curtain coating method, and screen printing method. When drying the photosensitive resin composition, the photosensitive resin composition is heated at a temperature of, for example, 60°C or higher and 130°C or lower.

[0112] The film 4 may be produced by overlaying a dry film made from the photosensitive resin composition on the substrate. The dry film is formed on a suitable support, for example, by applying the photosensitive resin composition on a support such as a polyester support and then drying. Thereby, a dry film with a support including the dry film and the support supporting the dry film is obtained. After overlaying the dry film in this dry film with a support on the base material 1 so as to cover the second conductor layer 3, pressure is applied to the dry film and the base material 1. Thereby, a film 4 made from the dry film is overlaid on the base material 1.

[0113] Next, the film 4 is exposed. For example, the negative-patterned region of the film 4 that includes the pattern of the via holes 6 is exposed. In this case, for example, the film 4 is irradiated with ultraviolet light through a negative mask. The negative mask includes an exposure portion that transmits ultraviolet light and a non-exposure portion that shields ultraviolet light, and the pattern of the non-exposure portion includes the pattern of the via holes 6. The negative mask is a phototool such as a mask film or a dry plate, for example. The light source of the ultraviolet light is selected from the group consisting of, for example, a chemical lamp, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a xenon lamp, and a metal halide lamp.

[0114] When the film 4 is made from a dry film, when exposing the film 4, for example, the support is peeled off from the film 4 in advance and then the film 4 is exposed. Note that the film 4 may be exposed by irradiating the film 4 with ultraviolet light through the support while the support overlaps the film 4, and then the support may be peeled off from the exposed film 4.

[0115] As the exposure method, a method other than the method using a negative mask may be adopted. For example, the film 4 may be exposed by a direct drawing method in which ultraviolet light emitted from a light source is irradiated only on the portion to be exposed on the film 4. The light source applied to the direct drawing method is selected from the group consisting of, for example, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, g-line (436 nm), h-line (405 nm), i-line (365 nm), and a combination of two or more of g-line, h-line, and i-line.

[0116] The ultraviolet light irradiating the film 4 preferably has a spectral intensity at at least one wavelength in the wavelength range of 365 nm ± 65 nm. Further, it is preferable that the ultraviolet light irradiating the film 4 does not have a spectral intensity at wavelengths of 435 nm or more. When the ultraviolet light irradiating the film 4 has a spectral intensity at at least one wavelength in the wavelength range of 365 nm ± 65 nm, the film 4 is likely to be cured. Further, when the ultraviolet light contains light having a wavelength of 435 nm or more, the diameter of the second end 62 of the via hole 6 formed in the interlayer insulating layer 7 is likely to become small after development. This is presumably because light having a long wavelength of 435 nm or more is less likely to be absorbed by the photosensitive resin composition and thus easily reaches the deep part of the film 4, and light scattering is likely to occur in the deep part of the film 4. More preferably, the ultraviolet light irradiating the film 4 has a spectral intensity at at least one wavelength in the wavelength range of 365 nm ± 45 nm and does not have a spectral intensity at 415 nm or more. Even more preferably, it has a spectral intensity at at least one wavelength in the wavelength range of 365 nm ± 30 nm and does not have a spectral intensity at 400 nm or more. Particularly preferably, it has a spectral intensity at at least one wavelength in the wavelength range of 365 nm ± 15 nm and does not have a spectral intensity at 385 nm or more.

[0117] Next, by developing the film 4 with an alkaline aqueous solution, an interlayer insulating layer 7 having via holes 6 is formed. At this time, as already described, via holes 6 having small-diameter portions 63 are likely to be formed. By subjecting the film 4 to a developing process, the uncured portion 5 of the film 4 shown in FIG. 1C is removed, and thereby, via holes 6 are provided as shown in FIG. 1D. In the developing process, an appropriate developer corresponding to the composition of the photosensitive resin composition can be used. The developer is, for example, an alkaline aqueous solution containing at least one of an alkali metal salt and an alkali metal hydroxide, or an organic amine. More specifically, the alkaline aqueous solution contains, for example, at least one component selected from the group consisting of sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, sodium hydroxide, potassium hydroxide, ammonium hydroxide, tetramethylammonium hydroxide, and lithium hydroxide. The solvent in the alkaline aqueous solution may be only water or a mixture of water and a hydrophilic organic solvent such as lower alcohols. The organic amine contains, for example, at least one component selected from the group consisting of monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, and triisopropanolamine.

[0118] The alkaline aqueous solution preferably contains at least one of an alkali metal salt and an alkali metal hydroxide, and particularly preferably contains sodium carbonate. In this case, improvement of the working environment and reduction of the burden of waste treatment can be achieved.

[0119] Since the photosensitive resin composition according to the present embodiment has good developability, residues of the uncured photosensitive resin composition are less likely to remain at the bottom of the via holes 6 after development. Therefore, via holes 6 having small-diameter portions 63 are likely to be formed.

[0120] Subsequently, the developed film 4 may be heat-cured by heating. The heating conditions are, for example, within a range of a heating temperature of 120°C or higher and 200°C or lower and a heating time of 20 minutes or longer and 180 minutes or shorter. When the film 4 is heat-cured in this manner, the performance such as the strength, hardness, and chemical resistance of the interlayer insulating layer 7 is improved.

[0121] If necessary, the film 4 may be further irradiated with ultraviolet rays either before or after heating, or both. In this case, the photocuring of the film 4 can be further advanced.

[0122] As described above, an interlayer insulating layer 7 made of a cured product of a photosensitive resin composition is provided on the base material 1. Subsequently, a first conductor layer 8, which is a conductor wiring, can be formed on the interlayer insulating layer 7 by a known method such as an additive method, and a via conductor 9 can be formed in the via hole 6. Thereby, as shown in FIG. 1E, a printed wiring board 11 including the first conductor layer 8, the second conductor layer 3, the interlayer insulating layer 7, the via hole 6, and the via conductor 9 is obtained. In FIG. 1E, the via conductor 9 fills the entire inside of the via hole 6, but the via conductor 9 may be a film covering the inner surface of the via hole 6.

[0123] Also, before forming the via conductor 9, the entire inner surface of the via hole 6 and a part of the outer surface of the interlayer insulating layer 7 may be roughened. In this case, the adhesion between the base material 1 and the via conductor 9 can be improved.

[0124] The roughening of a part of the outer surface of the interlayer insulating layer 7 and the entire inner surface of the via hole 6 can be performed by the same procedure as a general desmear treatment using an oxidizing agent. For example, an oxidizing agent is brought into contact with the outer surface of the interlayer insulating layer 7 to roughen the outer surface of the interlayer insulating layer 7. However, it is not limited to this, and an appropriate roughening method such as plasma treatment, UV treatment, or ozone treatment may be employed.

[0125] The oxidizing agent may be an oxidizing agent available as a desmear solution. Such an oxidizing agent can contain at least one permanganate selected from the group consisting of sodium permanganate and potassium permanganate, for example.

[0126] When providing the via conductor 9, an electroless metal plating treatment can be performed on a part of the roughened outer surface and the inner surface of the via hole 6 to form an initial conductor. Thereafter, the via conductor 9 can be formed by depositing a metal in the electrolytic plating solution on the initial conductor by an electrolytic metal plating treatment.

Example

[0127] Hereinafter, the present disclosure will be specifically described by way of examples. However, the present disclosure is not limited to the following examples, and various modifications can be made according to the design as long as the object of the present disclosure can be achieved.

[0128] 1. Synthesis of carboxyl group-containing resin [Synthesis Examples 1 to 6: Bisphenol fluorene skeleton-containing resin] In a four-necked flask equipped with a reflux condenser, a thermometer, an air blowing tube, and a stirrer, the components shown in the "First Reaction" column in Table 1 were added, and these were stirred under air bubbling to prepare a mixture. This mixture was heated in the flask at the reaction temperature and reaction time shown in the "Reaction Conditions" column while stirring under air bubbling. Thereby, a solution of the intermediate was prepared.

[0129] Subsequently, the components shown in the "Second Reaction" column of Table 1 were added to the solution of the intermediate in the flask, and it was heated at the reaction temperature and reaction time shown in the "Reaction Conditions (1)" column while stirring under air bubbling. Subsequently, it was heated at the reaction temperature and reaction time shown in the "Reaction Conditions (2)" column while stirring under air bubbling. Thereby, a 65% by mass solution of the carboxyl group-containing resin was obtained. The weight average molecular weight and acid value of the carboxyl group-containing resin are as shown in Table 1.

[0130] The details of the components shown in column (a1) in Table 1 are as follows. ·Epoxy compound 1: A bisphenol fluorene type epoxy compound represented by formula (2) with an epoxy equivalent of 250 g / eq, where all of R1 to R8 in formula (2) are hydrogen. ·Epoxy compound 2: A bisphenol fluorene type epoxy compound represented by formula (2) with an epoxy equivalent of 279 g / eq, where both R1 and R5 in formula (2) are methyl groups, and all of R2 to R4 and R6 to R8 are hydrogen.

[0131] [Synthesis Example 7: Biphenyl novolak skeleton-containing resin] Into a four-necked flask equipped with a reflux condenser, a thermometer, an air inlet tube, and a stirrer, 288 parts by mass of a biphenyl novolak type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., product number NC-3000-H, epoxy equivalent 288 g / eq), 155 parts by mass of diethylene glycol monoethyl ether acetate, 0.2 parts by mass of methylhydroquinone, 72 parts by mass of acrylic acid, and 3 parts by mass of triphenylphosphine were added to prepare a mixture. This mixture was heated at a temperature of 115 °C for 12 hours while stirring under air bubbling in the flask. Thereby, a solution of the intermediate was prepared.

[0132] Subsequently, 85 parts by mass of tetrahydrophthalic anhydride and 86.3 parts by mass of diethylene glycol monoethyl ether acetate were added to the solution of the intermediate in the flask, and the mixture was heated at 90 °C for 4 hours while stirring under air bubbling. Thereby, a 65% by mass solution of carboxyl group-containing resin B-1 was obtained. The weight average molecular weight of the carboxyl group-containing resin B-1 was 8026, and the acid value was 69 mgKOH / g.

[0133] 2. Preparation of the Composition The components shown in Tables 2 to 3 below were kneaded with a three-roll mill and then stirred and mixed in a flask to obtain a composition. The details of the components shown in Tables 2 to 3 are as follows. · Unsaturated compound A: Trimethylolpropane triacrylate. · Photoinitiator A: 2,4,6-Trimethylbenzoyl-diphenyl-phosphine oxide, manufactured by BASF, product number Irgacure TPO. · Photoinitiator B: 1-Hydroxy-cyclohexyl-phenyl-ketone, manufactured by BASF, product number Irgacure 184. · Photoinitiator C: 4,4’-Bis(diethylamino)benzophenone. · Photoinitiator D: 2,4-Diethylthioxanthone-9-one. · Crystalline epoxy resin A: Bisphenol type crystalline epoxy resin, product number YSLV-80XY manufactured by Nippon Steel Chemical & Material Co., Ltd., melting point 75 to 85 °C, epoxy equivalent 192 g / eq. · Amorphous epoxy resin solution A: A bisphenol A type epoxy resin containing long-chain carbon chains, manufactured by DIC Corporation, product number EPICLON EXA-4816, a liquid resin, a solution in which the epoxy equivalent of 410 g / eq is dissolved in diethylene glycol monoethyl acetate at a solid content of 90%. · Organic filler A dispersion: Crosslinked rubber (NBR) with an average primary particle size of 0.07 μm, with a content of 15% by weight based on the total amount of the dispersion, dispersed in methyl ethyl ketone (manufactured by JSR Corporation, product number XER-91-MEK; acid value 10.0 mgKOH / g). · Organic filler B: Glycidyl-modified acrylonitrile-butadiene rubber with an average primary particle size of 0.3 μm. · Additive A: 3-glycidoxypropyltrimethoxysilane. · Additive B: Melamine. · Solvent A: Methyl ethyl ketone.

[0134] 3. Evaluation of the composition (1) Preparation of test pieces Test pieces were prepared as follows using the compositions of each composition example.

[0135] The composition of each composition example was applied onto a polyethylene terephthalate film using an applicator, then heated at 80 °C for 5 minutes and then dried by heating at 95 °C for 20 minutes to form a dry film with a thickness of 35 μm on the film.

[0136] A glass epoxy copper-clad laminate (FR-4 type) with a copper foil thickness of 17.5 μm was prepared. The surface portion of about 1 μm thickness in this glass epoxy copper-clad laminate was roughened by treating it with an etching agent (product number CZ-8101 manufactured by Meck Co., Ltd.). The above dry film was heat-laminated on the entire surface of one side of this glass epoxy copper-clad laminate using a vacuum laminator. The conditions for heat lamination were set at 0.5 MPa, 80 °C, and 1 minute. As a result, a film made of the above dry film was formed on the glass epoxy copper-clad laminate. Through a negative mask having a non-exposed portion with a pattern including a circular shape with a diameter of 80 μm and a film made of polyethylene terephthalate, ultraviolet rays with a wavelength of 365 nm were irradiated under the condition of an integrated light quantity of 250 mJ / cm 2 2. Subsequently, the polyethylene terephthalate film was peeled off from the film.

[0137] Subsequently, an alkaline aqueous solution (1% Na2CO3 aqueous solution) at 30 °C was injected onto the film at an injection pressure of 0.2 MPa for 90 seconds, and then pure water was injected at an injection pressure of 0.2 MPa for 90 seconds to develop the film. Subsequently, the film was heated at 180 °C for 120 minutes. As a result, an interlayer insulating layer and via holes penetrating this interlayer insulating layer were formed on the printed wiring board. Thus, a test piece was obtained.

[0138] The following evaluations were performed on this test piece. In Composition Example 11, development was not possible and no evaluation was performed. In addition, in Composition Example 14, there were portions where film peeling due to insufficient curing was observed during development, so no evaluation was performed.

[0139] (2) Measurement of the diameter of the first end and the diameter of the second end The test piece was cut so as to bisect the via hole in a plane parallel to the axis of the via hole, and the cross section was photographed using an electron microscope (SEM). From the image thus obtained, the diameter of the first end and the diameter of the second end of the via hole were measured. Also, the value of (diameter of the first end ÷ diameter of the second end) × 100 (%) was obtained.

[0140] (3) Presence or absence of a small diameter portion From the image obtained in the above “(2) Measurement of the diameter of the first end and the diameter of the second end”, it was confirmed whether there was a small-diameter portion between the first end and the second end of the via hole, and the evaluation was made as follows. A: There is a small-diameter portion between the first end and the second end, and the minimum diameter of the small-diameter portion is 65% or more and less than 100% of the diameter of the second end. B: There is a small-diameter portion between the first end and the second end, and the minimum diameter of the small-diameter portion is less than 65% of the diameter of the second end. C: There is no small-diameter portion between the first end and the second end.

[0141] (4) Via shape evaluation From the image obtained in the above “(2) Measurement of the diameter of the first end and the diameter of the second end”, the shape of the via hole was evaluated as follows. A: The value of (diameter of the first end ÷ diameter of the second end) × 100 (%) is 80% or more, and there is a small-diameter portion between the first end and the second end that is 65% or more and less than 100% of the diameter of the second end. B: The value of (diameter of the first end ÷ diameter of the second end) × 100 (%) is 75% or more and less than 80%, and there is a small-diameter portion between the first end and the second end that is 65% or more and less than 100% of the diameter of the second end. C: The value of (diameter of the first end ÷ diameter of the second end) × 100 (%) is 65% or more and less than 75%, and there is a small-diameter portion between the first end and the second end that is 65% or more and less than 100% of the diameter of the second end. D: The value of (diameter of the first end ÷ diameter of the second end) × 100 (%) is less than 65%, and there is a small-diameter portion between the first end and the second end. E: There is no small-diameter portion.

[0142] The results of the above evaluation tests are shown in Tables 2 to 3 below.

[0143] 4. Evaluation of printed circuit board (1) Preparation of test piece The test pieces were prepared by the method described in "(1) Preparation of test pieces" in the above "1. Evaluation of the composition", except that the film formation method, film thickness, diameter of the circular pattern, wavelength and integrated light amount of ultraviolet rays, and injection time of the alkaline aqueous solution during development of the film during film production were as shown in Tables 4 to 6. When a plurality of numerical values are described in the wavelength column, ultraviolet rays having the wavelengths of the respective numerical values were irradiated simultaneously.

[0144] The following evaluations were performed on this test piece. Note that in Comparative Example 1, development was not possible and no evaluation was performed. Also, in Comparative Example 3, evaluation was not performed because there were portions where film peeling due to insufficient curing was observed during development.

[0145] (2) Measurement of the diameter of the first end and the diameter of the second end The test piece was cut so as to bisect the via hole on a plane parallel to the axis of the via hole, and the cross section was observed with an electron microscope (SEM). From the image thus obtained, the diameter of the first end and the diameter of the second end of the via hole were measured. Also, the value of (diameter of the first end ÷ diameter of the second end) × 100 (%) was obtained.

[0146] (3) Presence or absence of a small diameter portion From the image obtained in the above "(2) Measurement of the diameter of the first end and the diameter of the second end", it was confirmed whether a small diameter portion exists between the first end and the second end of the via hole, and the evaluation was performed as follows. A: A small diameter portion exists between the first end and the second end, and the minimum diameter of the small diameter portion is 65% or more and less than 100% of the diameter of the second end. B: A small diameter portion exists between the first end and the second end, and the minimum diameter of the small diameter portion is less than 65% of the diameter of the second end. C: No small diameter portion exists between the first end and the second end.

[0147] (4) Via shape evaluation From the image obtained in the above "(2) Measurement of the diameter of the first end and the diameter of the second end", the shape of the via hole was evaluated as follows. A: The value of (diameter of the first end ÷ diameter of the second end) × 100 (%) is 80% or more, and there is a small-diameter portion between the first end and the second end that is 65% or more and less than 100% of the diameter of the second end. B: The value of (diameter of the first end ÷ diameter of the second end) × 100 (%) is 75% or more and less than 80%, and there is a small-diameter portion between the first end and the second end that is 65% or more and less than 100% of the diameter of the second end. C: The value of (diameter of the first end ÷ diameter of the second end) × 100 (%) is 65% or more and less than 75%, and there is a small-diameter portion between the first end and the second end that is 65% or more and less than 100% of the diameter of the second end. D: The value of (diameter of the first end ÷ diameter of the second end) × 100 (%) is less than 65%, and there is a small-diameter portion between the first end and the second end. E: There is no small-diameter portion.

[0148] (5) Via connection reliability For the test piece, the outer surface of the interlayer insulating layer was roughened by the following general desmear treatment as a pre-process of the plating treatment.

[0149] The interlayer insulating layer was swollen at 70 °C for 10 minutes using a swelling liquid for desmear (Swelling Dip Security Gunth P manufactured by Atotech Japan Co., Ltd.) to swell the surface of the interlayer insulating layer, and then the interlayer insulating layer was rinsed with hot water. Subsequently, the surface of the interlayer insulating layer was roughened by treating it with a desmear liquid (an oxidizing agent containing potassium permanganate, Concentrate Compact CP manufactured by Atotech Japan Co., Ltd.) at 70 °C for 10 minutes, and then the interlayer insulating layer was rinsed with hot water. Next, the surface of the interlayer insulating layer was treated with a neutralizing liquid (Reduction Solution Security Gunth P manufactured by Atotech Japan Co., Ltd.) at 40 °C for 5 minutes to remove the residue, and then the interlayer insulating layer was washed with water.

[0150] Next, an initial conductor was fabricated by performing electroless copper plating on the interlayer insulating layer, and then heated at 150 °C for 1 hour. Next, on the initial conductor, a current density of 2 A / dm 2After performing an electrolytic copper plating treatment under the given conditions, it was heated at 180°C for 30 minutes. As a result, a first conductor layer with a thickness of 33 μm was formed on the interlayer insulating layer, and via conductors were formed in the via holes.

[0151] Next, a temperature cycle test was conducted in which the test piece was exposed under the condition of -55°C for 15 minutes and then exposed under the condition of 125°C for 15 minutes for 500 cycles. The electrical resistance value between the first conductor layer and the second conductor layer through the via conductor before and after the test was measured, and the change rate was evaluated as follows. A: The change rate of the resistance value before and after the temperature cycle test is less than 8%. B: The change rate of the resistance value before and after the temperature cycle test is 8% or more and less than 10%. C: The change rate of the resistance value before and after the temperature cycle test is 10% or more.

[0152] The results of the above evaluation tests are shown in Tables 4 to 6 below.

[0153]

Table 1

[0154]

Table 2

[0155]

Table 3

[0156]

Table 4

[0157]

Table 5

[0158]

Table 6

Description of Symbols

[0159] 3 Second Conductor Layer 4 Film 6 Via Hole 61 First End 62 Second End 63 Small-Diameter Portion 7 Interlayer Insulation Layer 8 First Conductor Layer 9 Via Conductor

Claims

1. A first conductor layer, a second conductor layer, an interlayer insulating layer interposed between the first conductor layer and the second conductor layer, a via hole penetrating the interlayer insulating layer, and a via conductor disposed in the via hole and electrically connecting the first conductor layer and the second conductor layer, wherein the interlayer insulating layer is a cured product of a negative photosensitive resin composition containing a carboxyl group-containing resin (A), an unsaturated compound (B) having at least one ethylenically unsaturated bond in one molecule, and a photopolymerization initiator (C), wherein the via hole has a first end which is an end on the first conductor layer side, a second end which is an end on the second conductor layer side, and a small-diameter portion which is between the first end and the second end and has a diameter smaller than that of the second end, wherein the minimum diameter of the small-diameter portion is 65% or more and less than 100% of the diameter of the second end, wherein the diameter of the first end is 65% or more and less than 130% of the diameter of the second end, A printed wiring board.

2. The diameter of the first end is 100 μm or less, The printed wiring board according to Claim 1.

3. The carboxyl group-containing resin (A) contains a carboxyl group-containing resin (A1) having a bisphenol fluorene skeleton, The printed wiring board according to Claim 1 or 2.

4. The weight average molecular weight of the carboxyl group-containing resin (A) is 700 or more and 100,000 or less, The printed wiring board according to any one of Claims 1 to 3.

5. The carboxyl group-containing resin (A) contains a component having an acid value of 65 mgKOH / g or more and 150 mgKOH / g or less, The printed wiring board according to any one of Claims 1 to 4.

6. The percentage of the unsaturated compound (B) is 5% by mass or more and 45% by mass or less with respect to the carboxyl group-containing resin (A), The printed wiring board according to any one of Claims 1 to 5.

7. The percentage of the photoinitiator (C) is 1% by mass or more and 30% by mass or less with respect to the carboxyl group-containing resin (A). The printed wiring board according to any one of claims 1 to 6.

8. The photoinitiator (C) contains at least one selected from the group consisting of acylphosphine oxide-based photoinitiators, α-aminoalkylphenone-based photoinitiators, and oxime ester-based photoinitiators. The printed wiring board according to any one of claims 1 to 7.

9. The photosensitive resin composition further contains an epoxy resin (D). The printed wiring board according to any one of claims 1 to 8.

10. The equivalent of the epoxy group of the epoxy resin (D) is 0.1 or more and 5 or less with respect to 1 equivalent of the carboxyl group of the carboxyl group-containing resin (A). The printed wiring board according to claim 9.

11. The photosensitive resin composition further contains an organic filler (E). The printed wiring board according to any one of claims 1 to 10.

12. The organic filler (E) has a reactive group. The printed wiring board according to claim 11.

13. The reactive group includes at least one group selected from the group consisting of a carboxyl group, an amino group, an epoxy group, a vinyl group, and a hydroxyl group. The printed wiring board according to claim 12.

14. The ratio of the organic filler (E) with respect to the carboxyl group-containing resin (A) is 1% by mass or more and 100% by mass or less. The printed wiring board according to any one of claims 11 to 13.

15. A method for manufacturing the printed wiring board according to any one of claims 1 to 14. A negative photosensitive resin composition containing the carboxyl group-containing resin (A), the unsaturated compound (B) having at least one ethylenically unsaturated bond in one molecule, and the photopolymerization initiator (C), and a substrate having an insulating layer and the second conductor layer overlapping the insulating layer are prepared. A film made from the photosensitive resin composition is superposed on the substrate so as to cover the second conductor layer. After exposing a negative pattern-like region of the film including the pattern of the via holes, development treatment is performed using an alkaline aqueous solution to form the interlayer insulating layer and the via holes penetrating the interlayer insulating layer. A method for manufacturing a printed wiring board.

16. The method for manufacturing a printed wiring board according to claim 15, including forming the film by superposing a dry film made from the photosensitive resin composition on the substrate. The method for manufacturing a printed wiring board according to claim 15.

17. When exposing the film, the film is irradiated with light having a spectral intensity at at least one wavelength in the wavelength range of 365 nm ± 65 nm and not having a spectral intensity at a wavelength of 435 nm or more. The method for manufacturing a printed wiring board according to claim 15 or 16.

Images