Dry film resist and method for forming circuit pattern

Abstract

The present invention is a dry film resist that is obtained by layering, in this order, a substrate film 10, a photosensitive resin layer 20, and a protective film 30. The photosensitive resin layer 20 includes particles 21 containing a metal having a slower etching rate than copper dispersed therein.

Description

Dry film resist and circuit pattern forming method

[0001] The present disclosure relates to a dry film resist and a method for forming a circuit pattern.

[0002] Circuit patterns on printed wiring boards are formed by lithographically processing a copper-clad laminate, which is a laminate of copper foil and a resin substrate. The most common method is the subtractive method, in which copper foil is etched using a photosensitive resist layer (e.g., a dry film) patterned by photolithography as a mask. This method forms a circuit pattern by etching the copper foil, resulting in a trapezoidal shape in which the bottom width of the circuit pattern is greater than the top width in the thickness direction cross section. Therefore, although this method is simple, it is not suitable for forming fine circuit patterns.

[0003] On the other hand, a semi-additive method is also known in which a photosensitive resist layer patterned by photolithography is provided on a resin substrate, and then copper plating is applied to form a circuit pattern. This method is easy to form fine circuit patterns because the shape of the circuit pattern is determined by the precision of the resist pattern. However, this method has the problem of being costly because the circuit pattern must be formed by plating.

[0004] Therefore, development of a method that can form fine circuit patterns like the semi-additive method even with a low-cost subtractive method is underway. For example, Patent Document 1 proposes a technology that suppresses sagging due to etching (i.e., etching that spreads from the surface of the copper foil toward the resin substrate) by providing a layer of a different metal, such as nickel, that has a slower etching rate than the copper foil on the etching surface of the copper foil.

[0005] JP 2011-216528 A

[0006] However, the technology of Patent Document 1 requires the formation of a layer of a different metal, such as nickel, on the surface of the copper foil, which increases the number of steps in forming the circuit pattern, resulting in problems such as increased labor and cost. The embodiments of the present invention have been made to solve the above problems, and an object of the present invention is to provide a dry film resist and a circuit pattern forming method that can reduce the number of steps in forming the circuit pattern and also suppress sagging due to etching.

[0007] The present inventors have conducted extensive research into dry film resists in order to solve the above problems, and have found that sagging due to etching can be easily suppressed by using a dry film resist in which particles containing a metal whose etching rate is slower than that of copper are dispersed in a photosensitive resin layer, thereby completing an embodiment of the present invention.

[0008] That is, an embodiment of the present invention relates to a dry film resist in which a support film, a photosensitive resin layer, and a protective film are laminated in this order, and particles containing a metal having an etching rate slower than that of copper are dispersed in the photosensitive resin layer.

[0009] Furthermore, an embodiment of the present invention relates to a circuit pattern forming method including: a laminating step of peeling off the protective film of the dry film resist and laminating the dry film resist so that the photosensitive resin layer is in contact with a copper foil; an exposing step of exposing the dry film resist to light in a predetermined pattern; a developing step of developing the dry film resist to form a resist pattern layer; an etching step of etching the copper foil to form a circuit pattern; and a resist pattern layer removing step of removing the resist pattern layer.

[0010] According to the embodiments of the present invention, it is possible to provide a dry film resist and a circuit pattern forming method that can reduce the number of steps when forming a circuit pattern and also suppress sagging due to etching.

[0011] 1 is a schematic view of a thickness direction cross section of a dry film resist according to embodiment 1 of the present invention. 2 is a schematic view of a thickness direction cross section of a dry film resist according to embodiment 2 of the present invention. 3 is a schematic cross-sectional view for explaining a soft etching process, a laminating process, an exposure process, a developing process, an etching process, and a resist pattern layer removing process.

[0012] Preferred embodiments of the present invention will be described in detail below, but the present invention should not be construed as being limited thereto, and various modifications and improvements can be made based on the knowledge of those skilled in the art without departing from the gist of the present invention. The multiple components disclosed in the following embodiments can be appropriately combined to form various inventions. For example, some components may be deleted from all the components shown in the following embodiments, or components from different embodiments may be appropriately combined.

[0013] <Embodiment 1> (1. Dry Film Resist) Fig. 1 is a schematic diagram of a cross section in the thickness direction of a dry film resist according to embodiment 1 of the present invention. As shown in Fig. 1, the dry film resist has a structure in which a support film 10, a photosensitive resin layer 20, and a protective film 30 are laminated in this order.

[0014] (1-1. Support Film 10) The support film 10 is a film that supports the photosensitive resin layer 20. In particular, the support film 10 protects the photosensitive resin layer 20 from the time it is laminated on the copper foil surface until it is removed in the development step in the circuit pattern formation step, prevents adhesion between the exposure mask and the photosensitive resin layer 20 in the exposure step, and further suppresses inhibition of photopolymerization due to the penetration and diffusion of oxygen in the air.

[0015] The support film 10 is not particularly limited, and any film known in the art can be used. Furthermore, the support film 10 is preferably a transparent film capable of transmitting light emitted from an exposure light source. Examples of such supports include polyethylene terephthalate (PET) films, polyvinyl alcohol films, polyvinyl chloride films, vinyl chloride copolymer films, polyvinylidene chloride films, vinylidene chloride copolymer films, polymethyl methacrylate copolymer films, polystyrene films, polyacrylonitrile films, styrene copolymer films, polyamide films, cellulose derivative films, and cycloolefin polymer-containing polyolefin films. These films may be used alone or in the form of a laminate film in which two or more types are laminated together.

[0016] The support film 10 preferably has a thickness of 10 to 30 μm, and more preferably 16 to 25 μm, which allows for both supporting the photosensitive resin layer 20 and preventing a decrease in light transmittance.

[0017] (1-2. Photosensitive Resin Layer 20) The photosensitive resin layer 20 has dispersed therein particles 21 containing a metal whose etching rate is slower than that of copper. By providing a photosensitive resin layer 20 having such a configuration, sagging due to etching can be suppressed, similar to the case of providing a layer of a dissimilar metal, such as nickel, whose etching rate is slower than that of copper foil on the surface of copper foil. The technology of providing a layer of a dissimilar metal, such as nickel, whose etching rate is slower than that of copper foil on the surface of copper foil is thought to achieve anisotropic etching by utilizing the contact corrosion effect (galvanic effect) between the copper foil and the dissimilar metal. Therefore, in order to suppress sagging due to etching while eliminating the step of providing a layer of a dissimilar metal, such as nickel, on the surface of the copper foil, this function can be imparted to the dry film resist provided on the surface of the copper foil. Therefore, by dispersing particles 21 containing a metal whose etching rate is slower than that of copper in the photosensitive resin layer 20, anisotropic etching can be achieved by utilizing the contact corrosion effect between the copper foil and the dry film resist (particularly, particles 21 containing a metal whose etching rate is slower than that of copper in the photosensitive resin layer 20).

[0018] Furthermore, if a layer of a dissimilar metal such as nickel, which has an etching rate slower than that of copper foil, is provided on the surface of the copper foil, the adhesion to the dry film resist laminated thereon is low, so the L / S (line width and space width) of the layer formed by the exposure process and development process becomes large, which may make it difficult to form a fine circuit pattern. In contrast, if a dry film resist including a photosensitive resin layer 20 is used, it is not necessary to provide a layer of a dissimilar metal such as nickel, which has an etching rate slower than that of copper foil, on the surface of the copper foil, and the adhesion between the copper foil and the dry film resist is also good, making it possible to form a fine circuit pattern.

[0019] Furthermore, when a dissimilar metal layer, such as nickel, which has a slower etching rate than copper foil, is provided on the surface of copper foil, a pretreatment (soft etching) is generally performed to improve adhesion with the dry film resist. However, this pretreatment may result in excessive dissolution of the dissimilar metal layer. In this case, the contact corrosion effect between the copper foil and the dissimilar metal may not be sufficiently achieved, and sagging due to etching may not be suppressed. In contrast, if a dry film resist including a photosensitive resin layer 20 is used, this problem does not occur because it is not necessary to provide a dissimilar metal layer, such as nickel, which has a slower etching rate than copper foil, on the surface of the copper foil.

[0020] Here, in this specification, a metal having an etching rate slower than that of copper means a metal having an etching rate slower than that of copper in an etching solution (i.e., an etching solution for etching copper) used in an etching step of etching a copper foil to form a circuit pattern. The etching solution is not particularly limited, but examples thereof include an iron chloride-based etching solution such as ferric chloride and a copper chloride-based etching solution such as cupric chloride.

[0021] Metals having an etching rate slower than that of copper are not particularly limited, but examples include nickel, cobalt, platinum group metals, gold, silver, and alloys containing these metals. These may be used alone or in combination of two or more. Among these, the metal having an etching rate slower than that of copper is preferably one or more selected from nickel, cobalt, platinum group metals, gold, and silver, and more preferably nickel. In the case of an alloy, it is preferable that the above metal is the main component. Here, in this specification, "main component" means that the proportion of the total components exceeds 50 mass%. Examples of alloys include Co—P, Ni—P, Co—Ni, Co—Zn, Ni—Zn, Cu—Ni, Pt—Zn, Pt—P, Pt—Mo, Pt—W, Pt—Fe, and Pt—Co. Among these alloys, an alloy containing copper is preferable from the viewpoint of good compatibility with copper foil.

[0022] The thickness of the photosensitive resin layer 20 is not particularly limited, but is preferably 1 to 20 μm, and more preferably 2 to 20 μm. By controlling the thickness within this range, it becomes easier to obtain a desired resist pattern through the exposure step and development step.

[0023] The content of particles 21 in photosensitive resin layer 20 is not particularly limited, but is preferably 1 to 50 volume %, more preferably 10 to 50 volume %, even more preferably 20 to 50 volume %, and particularly preferably 30 to 50 volume %. By setting the content of particles 21 to 1 volume % or more, electrical conductivity can be stably imparted to photosensitive resin layer 20. Furthermore, by setting the content of particles 21 to 50 volume % or less, light scattering by particles 21 in the exposure step can be suppressed, making it easier to obtain a desired resist pattern.

[0024] The content of particles 21 in photosensitive resin layer 20 is calculated from an image obtained by observing a cross section of photosensitive resin layer 20 with a scanning electron microscope (SEM). More specifically, the area occupied by particles 21 and the area of ​​photosensitive resin layer 20 containing particles 21 are calculated using image processing software (ImageJ: open source, developed by the National Institutes of Health), and the ratio of the area occupied by particles 21 to the area of ​​photosensitive resin layer 20 is calculated as the content (volume %) of particles 21 in photosensitive resin layer 20.

[0025] The particles 21 in the photosensitive resin layer 20 do not necessarily need to be exposed on the surface, but it is preferable that the distance from the surface on the protective film 30 side (the surface that comes into contact with the copper foil after the protective film 30 is peeled off in the circuit pattern formation method) to the particles 21 be 0.1 nm or less, and it is preferable that the particles 21 be exposed on the surface on the protective film 30 side. By adopting such a configuration, it is possible to stably obtain anisotropic etching that utilizes the contact corrosion effect between the copper foil and the dry film resist. Furthermore, it is preferable that the particles 21 in the photosensitive resin layer 20 be uniformly dispersed from the viewpoint of suppressing exposure defects.

[0026] The shape of the particles 21 is not particularly limited and may be various shapes such as spherical, cubic, plate-like, flaky, columnar, rod-like, and needle-like, but spherical is preferable. By using spherical particles 21, the particles can be easily dispersed uniformly in the photosensitive resin layer 20 and light is less likely to be scattered during exposure, making it easier to obtain a desired resist pattern.

[0027] The average particle size of the particles 21 is not particularly limited, but is preferably 0.1 to 1.0 μm. By setting the average particle size of the particles 21 to 0.1 μm or more, aggregation between particles is suppressed, making it easier to uniformly disperse the particles 21 in the photosensitive resin layer 20. Furthermore, by controlling the average particle size of the particles 21 to 1.0 μm or less, the surface area of ​​the particles 21 can be increased, thereby efficiently exhibiting conductivity even when the proportion of the particles 21 is reduced. Here, in this specification, the average particle size of the particles 21 refers to the 50% particle size D50 (median diameter) at which the cumulative frequency is 50% in a volume-based particle size histogram obtained by a laser diffraction / scattering method.

[0028] The particles 21 may be surface-treated with an organic substance to enhance their affinity with the photosensitive resin layer 20, in other words, to disperse the particles 21 uniformly in the photosensitive resin layer 20. For example, a dispersion liquid in which the particles 21 are dispersed may contain a compound represented by the general formula: (M)A-(CH) n Surface treatment can be performed by adding, stirring, and drying a silane coupling agent consisting of a compound having a methacryloyl group represented by —Si(OR1)3 and a trialkoxysilane compound having an alkyl group represented by the general formula: R2-Si(OR3)3. In the above general formula, (M)A represents a (meth)acryloyl group, R1 represents an alkyl group having 1 to 4 carbon atoms, n represents an integer from 1 to 4, R2 represents an alkyl group having 10 or less carbon atoms, and R3 represents an alkyl group having 1 to 4 carbon atoms.

[0029] The photosensitive resin constituting the photosensitive resin layer 20 is not particularly limited, and any known photosensitive resin in the art can be used. Photosensitive resins can be either positive-type, in which the exposed (photoexposed) portion dissolves in the developer and the unexposed portion does not, or negative-type, in which the exposed portion does not dissolve in the developer and the unexposed portion does dissolve in the developer. However, negative-type photosensitive resists are often used in the manufacturing process of printed wiring boards. Negative-type photosensitive resins are not particularly limited, but generally contain a binder polymer, a (meth)acrylic compound, and a photopolymerization initiator. The binder polymer is a polymer component added to impart film-forming ability. The polymer component refers to an oligomer or polymer component with a weight-average molecular weight of 5,000 or more. The weight-average molecular weight can be measured using size exclusion chromatography (SEC), for example, an HLC8220GPC manufactured by Tosoh Corporation. The binder polymer used in the present invention is not particularly limited, but is preferably soluble or swellable in an alkaline aqueous solution, and therefore preferably contains an acidic functional group such as a carboxyl group, a hydroxyl group, a sulfonic acid group, or a phosphate group in the polymer chain. Examples of binder polymers having acidic functional groups include carboxyl group-containing vinyl polymers, polyamic acids, and soluble polyimides having carboxyl groups and / or hydroxyl groups, which can be used alone or in combination of two or more. Among these, carboxyl group-containing vinyl polymers can form a photosensitive resin layer 20 that is excellent in flexibility and alkaline solubility.

[0030] Carboxyl group-containing vinyl polymers can be obtained by copolymerizing a carboxyl group-containing monomer and a monomer copolymerizable with the carboxyl group-containing monomer using a known method. Examples of carboxyl group-containing monomers include (meth)acrylic acid, maleic acid, maleic acid monoalkyl esters, vinylbenzoic acid, cinnamic acid, propiolic acid, fumaric acid, crotonic acid, maleic anhydride, and phthalic anhydride. Among these, (meth)acrylic acid is preferred from the standpoints of cost and polymerizability. These can be used alone or in combination of two or more. Examples of monomers copolymerizable with the carboxyl group-containing monomer include (meth)acrylic acid esters, maleic acid diesters, fumaric acid diesters, crotonic acid esters, vinyl esters, (meth)acrylamides, vinyl ethers, vinyl alcohols, styrene, and styrene derivatives. Among these, (meth)acrylic acid esters, styrene, and styrene derivatives are preferred from the standpoints of polymerizability and flexibility. These can be used alone or in combination of two or more.

[0031] The inclusion of a (meth)acrylic compound in a photosensitive resin not only imparts good curing properties, but also reduces the viscoelasticity of the photosensitive dry film resist during thermal processing, thereby imparting fluidity during thermal lamination. In other words, thermal lamination at relatively low temperatures becomes possible, allowing circuit irregularities to be embedded. Examples of (meth)acrylic compounds include, but are not limited to, (meth)acrylic compounds, epoxy (meth)acrylates, polyester (meth)acrylates, urethane (meth)acrylates, and imide (meth)acrylates. These compounds can be used alone or in combination of two or more. In this specification, (meth)acrylic refers to acrylic and / or methacrylic.

[0032] Specific examples of the (meth)acrylic compound include bisphenol F EO-modified (n=2 to 50) diacrylate, bisphenol A EO-modified (n=2 to 50) diacrylate, and bisphenol S EO-modified (n=2 to 50) diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, ethylene glycol diacrylate, pentaerythritol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, tetramethylolpropane tetraacrylate, tetraethylene glycol diacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, ethylene glycol dimethacrylate, pentaerythritol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexamethacrylate, tetramethylolpropane tetramethacrylate, tetraethylene glycol dimethacrylate, methoxydiethylene glycol methacrylate, methoxypolyethylene glycol methacrylate, β-methacryloyloxyethyl hydrogenphthalate acrylate, β-methacryloyloxyethyl hydrogen succinate, 3-chloro-2-hydroxypropyl methacrylate, stearyl methacrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, phenoxypolyethylene glycol acrylate, β-acryloyloxyethyl hydrogen succinate, lauryl acrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 2-hydroxy 1,3 dimethacryloyloxypropane, 2,2-bis[4-(methacryloyloxyethoxy)phenyl]propane, 2,2-bis[4-(methacryloyloxydiethoxy)phenyl]propane, 2,2-bis[4-(methacryloyloxypolyethoxy)phenyl]propane, polyethylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, 2,2-bis[4-(acryloxydiethoxy)phenyl]propane, 2,2-bis[4-(acryloxypolyethoxy)phenyl]propane, 2-hydroxy 1-acryloxy 3-methacryloxypropane, tetramethylolmethane triacrylate, tetramethylolmethane tetraacrylate, methoxydipropylene glycol methacrylate, methoxytriethylene glycol acrylate, nonylphenoxypolyethylene glycol acrylate, nonylphenoxypolypropylene glycol acrylate, 1-acryloyloxypropyl-2 -phthalate, isostearyl acrylate, polyoxyethylene alkyl ether acrylate, nonylphenoxyethylene glycol acrylate, 1,4-butanediol dimethacrylate, 3-methyl-1,5-pentanediol dimethacrylate, 1,9-nonanediol methacrylate, 2,4-diethyl-1,5-pentanediol dimethacrylate, 1,4-cyclohexanedimethanol dimethacrylate, dipropylene glycol diacrylate, tricyclodecane dimethanol diacrylate, 2,2-bis[4-(acryloxy-poly propoxy)phenyl]propane, 2,4-diethyl-1,5-pentanediol diacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, isocyanuric acid tri(ethane acrylate), pentasritol tetraacrylate, ethoxylated pentasritol tetraacrylate, propoxylated pentasritol tetraacrylate, ditrimethylolpropane tetreaacrylate, dipentaerythritol polyacrylate, triallyl isocyanurate, glycidyl methacrylate, Glycidyl allyl ether, 1,3,5-triacryloylhexahydro-s-triazine, triallyl 1,3,5-benzenecarboxylate, triallylamine, triallyl citrate, triallyl phosphate, allobarbital, diallylamine, diallyldimethylsilane, diallyl disulfide, diallyl ether, zallyl sialate, diallyl isophthalate, diallyl terephthalate, 1,3-diallyloxy-2-propanol, diallyl sulfide diallyl maleate, 4,4'-isopropylidenediphenol dimethacrylate, 4,Examples of suitable crosslinking agents include 4'-isopropylidenediphenol diacrylate. In order to improve the crosslink density, it is particularly preferable to use a difunctional or higher functional monomer.

[0033] The amount of the (meth)acrylic compound contained in the photosensitive resin is not particularly limited, but is preferably 1 to 400 parts by mass, more preferably 3 to 300 parts by mass, still more preferably 1 to 200 parts by mass, and particularly preferably 1 to 100 parts by mass, relative to 100 parts by mass of the binder polymer.

[0034] The photopolymerization initiator is a component that generates radicals in the presence of actinic rays during the exposure process and promotes the polymerization reaction. This allows the solubility of the photosensitive dry film resist in the developer to be sufficiently different between the exposed and unexposed regions, thereby enabling the pattern to be developed favorably on the photosensitive dry film resist. While the photopolymerization initiator is not particularly limited, it is preferable that it undergoes a polymerization reaction in the wavelength range of 300 to 400 nm and not in the presence of visible light of 450 nm or more. This is because if the wavelength of light during the exposure process is less than 300 nm, the light may be absorbed by the support film 10 and may not reach the photosensitive resin layer 20. Furthermore, if the photosensitive resin layer 20 is exposed to visible light with a wavelength of 450 nm or more, it is necessary to perform the work in a room that excludes ultraviolet light (a yellow room).

[0035] Examples of the photopolymerization initiator include hexaarylbiimidazole compounds, N-aryl-α-amino acid compounds, quinone compounds, aromatic ketone compounds, acetophenone compounds, acylphosphine oxide compounds, benzoin compounds, benzoin ether compounds, dialkyl ketal compounds, thioxanthone compounds, dialkylaminobenzoic acid ester compounds, oxime ester compounds, acridine compounds, pyrazoline derivatives, N-arylamino acid ester compounds, halogen compounds, etc. These can be used alone or in combination of two or more.

[0036] The amount of the photopolymerization initiator contained in the photosensitive resin is not particularly limited, but is preferably 0.01 to 50 parts by mass relative to 100 parts by mass of the binder polymer.

[0037] In addition to the above components, the negative photosensitive resin may further contain components known in the technical field (e.g., dyes, adhesives, plasticizers, thermal polymerization inhibitors, fillers, flame retardants, storage stabilizers, ion scavengers, etc.) The blending ratio of the known components is not particularly limited as long as it is within a range that does not impair the effects of the present invention.

[0038] The dye is preferably a dye that develops color under ultraviolet light, in order to facilitate pattern inspection after exposure of the photosensitive resin layer 20. Examples of such dyes include leuco dyes and fluoran dyes. The plasticizer is a component that improves the flexibility of the photosensitive resin layer 20 and its fluidity when heated. Examples of plasticizers include phthalate ester compounds, o-toluenesulfonic acid amide, p-toluenesulfonic acid amide, tributyl citrate, triethyl citrate, and acetyl triethyl citrate. The adhesive is a component that improves adhesion to the copper foil. Examples of adhesives include bisphenol A epoxy compounds.

[0039] (1-3. Protective Film 30) The protective film 30 is a film that protects the photosensitive resin layer 20. Therefore, when used in a circuit pattern formation method, the protective film 30 is peeled off from the dry film resist before use. The protective film 30 is not particularly limited, and any film known in the technical field can be used. Furthermore, it is preferable that the protective film 30 has an appropriate adhesive strength to the photosensitive resin layer 20. In other words, it is preferable that the adhesive strength of the protective film 30 to the photosensitive resin layer 20 is sufficiently smaller than the adhesive strength of the support film 10 to the photosensitive resin layer 20, so that the support film 10 can be easily peeled off from the photosensitive resin layer 20.

[0040] Examples of the protective film 30 that can be used include polyethylene film, polypropylene film, polyethylene terephthalate film, and polyester film. The thickness of the protective film 30 is not particularly limited, but is preferably 10 to 100 μm, and more preferably 10 to 50 μm. Note that, from the viewpoint of making the protective film 30 easier to peel off, a known release layer may be provided on the side of the protective film 30 that comes into contact with the photosensitive resin layer 20, as needed.

[0041] (2. Method for Producing Dry Film Resist) The dry film resist can be produced by sequentially laminating the photosensitive resin layer 20 and the protective film 30 on the support film 10. This method can be performed in accordance with methods known in the art. For example, the dry film resist can be produced as follows. First, a photosensitive resin composition containing a binder polymer, a (meth)acrylic compound, a photopolymerization initiator, etc. is mixed with an organic solvent, and then the particles 21 are added and mixed to produce a solution-like photosensitive resin composition preparation liquid (coating liquid). If necessary, the coating liquid may be subjected to a kneading / dispersion treatment, such as passing it through a triple roll. Next, the coating liquid is applied to the support film 10 using a bar coater or roll coater, and then dried, thereby laminating the photosensitive resin layer 20 on the support film 10. Next, the protective film 30 is laminated on the photosensitive resin layer 20 to produce the dry film resist.

[0042] <Embodiment 2> (1. Dry Film Resist) Fig. 2 is a schematic diagram of a cross section in the thickness direction of a dry film resist according to embodiment 2 of the present invention. Note that components having the same reference numerals as those appearing in the description of the dry film resist according to embodiment 2 of the present invention are the same as the components of the dry film resist according to embodiment 2 of the present invention, and therefore description thereof will be omitted.

[0043] As shown in FIG. 2 , the dry film resist has a structure in which a support film 10, a photosensitive resin layer 20, and a protective film 30 are laminated in this order. The photosensitive resin layer 20 has a region A in which particles 21 are dispersed and a region B in which particles 21 are not dispersed. These regions are preferably formed in layers perpendicular to the thickness direction of the dry film resist. The region A in which particles 21 are dispersed is in contact with the protective film 30. Even when the photosensitive resin layer 20 is provided in this manner, when the protective film 30 is peeled off and the resist is applied to the surface of the copper foil, the particles 21 are present in the photosensitive resin layer 20 on the copper foil side, thereby achieving the same effects as the dry film resist of embodiment 1. Furthermore, because the dry film resist of embodiment 1 has particles 21 dispersed throughout the photosensitive resin layer 20, light may be reflected by the particles 21 during the exposure process, resulting in exposure of areas other than the intended area or insufficient exposure. However, by adopting the above-described configuration, these problems can be solved as the amount of particles 21 used can be reduced because it is not necessary to disperse the particles 21 throughout the photosensitive resin layer 20. The photosensitive resins constituting the region A where the particles 21 are dispersed and the region B where the particles 21 are not dispersed may be the same or different.

[0044] 2, in order to facilitate understanding of each region, a region A in which the particles 21 are dispersed and a region B in which the particles 21 are not dispersed are depicted separately, but it should be noted that in an actual photosensitive resin layer 20, the boundary between the regions A and B may be difficult to distinguish. For example, if the resin components constituting the regions A and B are the same or similar, the boundary between the regions A and B may be difficult to distinguish. In this case, the boundary between the regions A and B in the thickness direction cross section of the photosensitive resin layer 20 is defined as the boundary between a portion where a line parallel to the surface of the support film 10 contacts the particles 21 and a portion where a line parallel to the surface of the support film 10 does not contact the particles 21.

[0045] The content of particles 21 in the region where particles 21 are dispersed is not particularly limited, but is preferably 1 to 50 volume %, more preferably 10 to 50 volume %, even more preferably 20 to 50 volume %, and particularly preferably 30 to 50 volume %. By setting the content of particles 21 to 1 volume % or more, it is possible to stably impart conductivity to the region where particles 21 are dispersed. Furthermore, by setting the content of particles 21 to 50 volume % or less, it is possible to suppress light scattering by particles 21 in the exposure step, making it easier to obtain a desired resist pattern.

[0046] The particles 21 in the region where the particles 21 are dispersed do not necessarily need to be exposed on the surface, but it is preferable that the distance from the surface on the protective film 30 side (the surface that comes into contact with the copper foil after the protective film 30 is peeled off in the circuit pattern formation method) to the particles 21 be 0.1 nm or less, and it is preferable that the particles 21 be exposed on the surface on the protective film 30 side. By adopting such a configuration, it is possible to stably obtain anisotropic etching that utilizes the contact corrosion effect between the copper foil and the dry film resist.

[0047] (2. Method for Producing Dry Film Resist) The dry film resist can be produced by sequentially laminating the photosensitive resin layer 20 and the protective film 30 on the support film 10. This method can be performed in accordance with methods known in the art. For example, the dry film resist can be produced as follows. First, a photosensitive resin composition containing a binder polymer, a (meth)acrylic compound, a photopolymerization initiator, etc. is mixed with an organic solvent to produce a solution-like photosensitive resin composition preparation liquid (first coating liquid). Next, the photosensitive resin composition containing a binder polymer, a (meth)acrylic compound, a photopolymerization initiator, etc. is mixed with an organic solvent, and then the particles 21 are added and mixed to produce a solution-like photosensitive resin composition preparation liquid (second coating liquid). Next, the first coating liquid is applied to the support film 10 using a bar coater, a roll coater, or the like, and then dried to form a region on the support film where the particles 21 are not dispersed. Next, a second coating liquid is applied onto the region where the particles 21 are not dispersed using a bar coater, roll coater, or the like, and then dried to form a region where the particles 21 are dispersed above the region where the particles 21 are not dispersed. In this way, a photosensitive resin layer 20 having two regions can be laminated on the support film 10. Next, a protective film 30 is laminated on the photosensitive resin layer 20 to produce a dry film resist.

[0048] <Embodiment 3> A circuit pattern forming method according to an embodiment of the present invention includes a laminating step, an exposing step, a developing step, an etching step, and a resist pattern layer removing step. Furthermore, the circuit pattern forming method according to an embodiment of the present invention may further include a soft etching step before the laminating step, if necessary. Figure 3 is a schematic cross-sectional view (schematic cross-sectional view in the thickness direction) for illustrating the soft etching step, laminating step, exposing step, developing step, etching step, and resist pattern layer removing step. Each step will be described below.

[0049] <Soft Etching Process> As shown in Figure 3(a), the soft etching process involves preparing a copper-clad laminate 100 including a copper foil 110 and a resin substrate 120 bonded to one side of the copper foil 110, and soft-etching the copper foil 110 of the copper-clad laminate 100. By soft-etching the copper foil 110, the surface of the copper foil 110 can be roughened, which can improve adhesion to the dry film resist in the subsequent lamination process due to the anchor effect. Note that Figure 3(a) shows the state of the copper foil 110 after soft etching.

[0050] The soft etching method is not particularly limited, and known methods such as spraying, immersion, and puddling can be used. For example, when using the immersion method, the copper-clad laminate 100 can be immersed in a soft etching solution. The soft etching solution is not particularly limited as long as it is capable of roughening the surface of the copper foil 110. Examples of soft etching solutions that can be used include an aqueous solution containing sulfuric acid and hydrogen peroxide, an aqueous ammonium persulfate solution, and an aqueous sodium persulfate solution. Commercially available soft etching solutions may also be used. The temperature and treatment time of the soft etching solution are not particularly limited and can be adjusted appropriately depending on the type of soft etching solution used.

[0051] The copper-clad laminate 100 used for soft etching is not particularly limited, and can be manufactured by known methods such as pressing, casting, laminating, and metallizing. The copper foil 110 constituting the copper-clad laminate 100 is also not particularly limited, and can be either rolled copper foil or electrolytic copper foil. Furthermore, the resin substrate 120 constituting the copper-clad laminate 100 is also not particularly limited, and can be a known substrate such as a paper-based phenolic resin, a paper-based epoxy resin, a synthetic fiber cloth-based epoxy resin, a glass cloth / paper composite substrate, a glass cloth / glass nonwoven fabric composite substrate, a glass cloth-based epoxy resin, a polyester film, a polyimide resin, a liquid crystal polymer, or a fluororesin.

[0052] <Laminating Process> As shown in Fig. 3(b), the laminating process is a process in which the protective film 30 of the dry film resist is peeled off and the dry film resist is laminated so that the photosensitive resin layer 20 comes into contact with the copper foil 110. Note that Fig. 3(b) shows the state after the laminating process. The particles 21 dispersed in the photosensitive resin layer 20 are omitted. The laminating method is not particularly limited, but it is sufficient to place a dry film on the copper foil 110 and press it together. The conditions for this process are not particularly limited, and may be performed according to conventionally known conditions.

[0053] <Exposure Process> The exposure process is a process of exposing the dry film resist in a predetermined pattern, as shown in Fig. 3(c). Specifically, the photosensitive resin layer 20 is exposed in a predetermined pattern through the support film 10 of the dry film resist to form an exposed portion 50. Here, Fig. 3(c) shows an example in which a dry film resist having a negative photosensitive resin layer 20 is provided, and by exposing it in a predetermined pattern, the exposed portion 50 undergoes a photopolymerization reaction and becomes insoluble in a developer.

[0054] The exposure method is not particularly limited, and any known method can be used, such as a mask exposure method in which a light beam of a required size is irradiated onto the photosensitive resin layer 20 through a mask on which a predetermined pattern is drawn, or a laser direct writing method in which a predetermined pattern is irradiated with laser light using a polygon mirror or a digital mirror device (DMD).

[0055] 3( d ), the development process is a process of developing the dry film resist to form a resist pattern layer 60. Specifically, by developing the dry film resist, the support film 10 and the unexposed portions of the photosensitive resin layer 20 are removed, and the resist pattern layer 60 is formed.

[0056] The developing method is not particularly limited, and any known method can be used. For example, when a dry film resist having a negative photosensitive resin layer 20 is provided, the unexposed portion can be dissolved and removed by treating it with a developer capable of dissolving the unexposed portion. The type of developer may be appropriately selected depending on the type of photosensitive resin layer 20 of the dry film resist used, and is not particularly limited.

[0057] 3( e), the etching process is a process of etching the copper foil 110 to form the circuit pattern 70. Specifically, the circuit pattern 70 is formed by etching the copper foil 110 in the portions where the resist pattern layer 60 is not formed on the surface. In this etching process, a dry film resist having particles 21 dispersed in the photosensitive resin layer 20 is used, so that etching from the surface of the copper foil 110 toward the resin substrate 120 can be prevented from spreading outward, and a circuit pattern 70 with a high etching factor can be formed.

[0058] The etching method is not particularly limited, and known methods such as a spray method, a dipping method, and a puddle method can be used. The etching solution used in the etching step is not particularly limited, and for example, an iron chloride-based etching solution such as ferric chloride, or a copper chloride-based etching solution such as cupric chloride can be used. The etching conditions are not particularly limited and can be adjusted appropriately depending on the type of etching solution used.

[0059] 3(f), the resist pattern layer removal step is a step of removing the resist pattern layer 60. The resist pattern layer 60 remaining on the circuit pattern 70 is an unnecessary layer, and therefore the resist pattern layer 60 is removed in this step. The method for removing the resist pattern layer 60 is not particularly limited, and it is sufficient to dissolve the resist pattern layer 60 using a solution that can dissolve the resist pattern layer 60.

[0060] Therefore, according to the embodiments of the present invention, by adopting the following aspects [1] to [9], it is possible to provide a dry film resist and a circuit pattern forming method that can reduce the number of steps when forming a circuit pattern and also suppress sagging due to etching.

[0061] [1] A dry film resist comprising a support film, a photosensitive resin layer, and a protective film laminated in this order, wherein particles containing a metal having an etching rate slower than that of copper are dispersed in the photosensitive resin layer.

[0062] [2] The dry film resist according to [1], wherein the content of the particles in the photosensitive resin layer is 1 to 50% by volume.

[0063] [3] The dry film resist according to [1], wherein the photosensitive resin layer has a region where the particles are dispersed and a region where the particles are not dispersed, and the region where the particles are dispersed is in contact with the protective film.

[0064] [4] The dry film resist according to [3], wherein the content of the particles in the region where the particles are dispersed is 1 to 50% by volume.

[0065] [5] The dry film resist according to any one of [1] to [4], wherein the metal is at least one selected from nickel, cobalt, platinum group metals, gold, and silver.

[0066] [6] The dry film resist according to any one of [1] to [4], wherein the metal is nickel.

[0067] [7] The dry film resist according to any one of [1] to [6], wherein the particles have an average particle size of 0.1 to 1.0 μm.

[0068] [8] The dry film resist according to any one of [1] to [7], wherein the photosensitive resin layer is a negative photosensitive resin layer.

[0069] [9] A circuit pattern forming method comprising: a laminating step of peeling off the protective film of the dry film resist according to any one of [1] to [8], and laminating the dry film resist so that the photosensitive resin layer is in contact with a copper foil; an exposing step of exposing the dry film resist to light in a predetermined pattern; a developing step of developing the dry film resist to form a resist pattern layer; an etching step of etching the copper foil to form a circuit pattern; and a resist pattern layer removing step of removing the resist pattern layer.

[0070] REFERENCE SIGNS LIST 10 Support film 20 Photosensitive resin layer 21 Particles 30 Protective film 50 Exposed area 60 Resist pattern layer 70 Circuit pattern 100 Copper-clad laminate 110 Copper foil 120 Resin substrate

Claims

1. A dry film resist comprising a support film, a photosensitive resin layer, and a protective film laminated in this order, wherein particles containing a metal having an etching rate slower than that of copper are dispersed in the photosensitive resin layer.

2. The dry film resist according to claim 1, wherein the content of said particles in said photosensitive resin layer is 1 to 50% by volume.

3. The dry film resist according to claim 1, wherein the photosensitive resin layer has an area where the particles are dispersed and an area where the particles are not dispersed, and the area where the particles are dispersed is in contact with the protective film.

4. The dry film resist according to claim 3, wherein the content of said particles in the region where said particles are dispersed is 1 to 50% by volume.

5. The dry film resist according to any one of claims 1 to 4, wherein the metal is at least one selected from the group consisting of nickel, cobalt, platinum group metals, gold, and silver.

6. The dry film resist according to any one of claims 1 to 4, wherein the metal is nickel.

7. The dry film resist according to any one of claims 1 to 4, wherein the particles have an average particle size of 0.1 to 1.0 µm.

8. The dry film resist according to any one of claims 1 to 4, wherein the photosensitive resin layer is a negative photosensitive resin layer.

9. A method for forming a circuit pattern, comprising: a laminating step of peeling off the protective film of the dry film resist according to any one of claims 1 to 4, and laminating the dry film resist so that the photosensitive resin layer comes into contact with a copper foil; an exposing step of exposing the dry film resist to light in a predetermined pattern; a developing step of developing the dry film resist to form a resist pattern layer; an etching step of etching the copper foil to form a circuit pattern; and a resist pattern layer removing step of removing the resist pattern layer.

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